HLA-MATCHED RELATED allogeneic stem cell transplantation has been successfully used as the treatment of choice in selected high-risk or recurrent hematologic malignancies, marrow failure syndromes, severe congenital immunodeficiency states, and selected metabolic disorders.1 Recently, the use of matched related allogeneic peripheral blood stem cells as a source of transplantable stem cells has been reported by a variety of groups.2-4 Initial studies have suggested that the risk of graft rejection and the risk of developing severe acute graft-versus-host disease (GVHD) are similar when using matched related allogeneic peripheral blood stem cells as compared with matched related allogeneic bone marrow (BM) stem cells. However, the major limitation of using HLA-matched related sibling donors in BM transplantation (BMT) has been that only 30% to 40% of potential recipients in need of such therapy have an HLA-matched related family donor.1 The recent use of either related or unrelated donor umbilical cord blood stem cells for allogeneic stem cell transplantation has been secondary to a number of factors, most important of which have been (1) the attempt to reduce transplant-related complications and (2) augmentation of the donor pool. Gluckman et al5 first reported the successful use of HLA-matched sibling umbilical cord blood stem cells to reconstitute a child with severe Fanconi anemia. Since 1988, there have been an estimated 500 related and unrelated donor umbilical cord blood transplants.

To increase the pool of potential donors for allogeneic BMT, the National Marrow Donor Program (NMDP) was established in 1987 to develop a registry of available BM donors, promote cooperation with other international BM donor pools, and develop clinical and basic research relative to unrelated donor BMT. As of May 1997, more than 2.7 million donors in the United States have been registered by the NMDP. These potential allogeneic donors have been typed for HLA A and B antigens and approximately one third have additionally been typed for HLA DR. To date, more than 5,700 unrelated donor BMTs have been facilitated by the NMDP (personal communication, May 1997). Despite the recent success in using unrelated donor matched BM, there continue to be limitations and obstacles in using this form of therapy. The average length of time from donor search to transplant is approximately 135 days, and the cost for donor search and marrow procurement ranges from $25,000 to $50,000 dollars.6 

It has been shown in early studies by Broxmeyer et al7 and others that both term and preterm umbilical cord blood contains a significantly higher number of early and committed progenitor cells when compared with adult peripheral blood. The number of colony-forming unit–granulocyte-macrophage (CFU-GM) is greatly increased in umbilical cord blood obtained from term neonates compared with peripheral blood obtained from adults (Fig 1A).8-14 The CFU-GM proliferative rate, as assayed by thymidine suicide studies, is also significantly higher in term umbilical cord blood (Fig 1B).15 The number of circulating colony-forming unit granulocyte, erythroid, monocyte, megakaryocyte (CFU-GEMM) also appears to be significantly increased in term umbilical cord blood (Fig 1A)9 and the CFU-GEMM proliferative rate is also significantly higher in term umbilical cord blood compared with that of adult peripheral blood (Fig 1B).10 Lastly, committed megakaryocytic progenitor cells as identified by circulating colony-forming unit megakaryocyte (CFU-Meg) are also enriched in term umbilical cord blood compared with adult peripheral blood but to a much less degree than CFU-GM and CFU-GEMM (Fig 1A).11 

Fig. 1.

Comparison of the fold increase of circulating committed progenitor cells (A) and proliferative rates (B) in term unrelated cord blood versus adult peripheral blood. Data are a compilation of previous studies.8-15 

Fig. 1.

Comparison of the fold increase of circulating committed progenitor cells (A) and proliferative rates (B) in term unrelated cord blood versus adult peripheral blood. Data are a compilation of previous studies.8-15 

Close modal

Recently, Broxmeyer et al13 showed that umbilical cord blood contains numbers of CFU-GM well within the range of marrow CFU-GM previously shown to allow successful engraftment after autologous BMT. It has recently been demonstrated that umbilical cord blood contains sufficient numbers of hematopoietic progenitor cells to engraft larger size children and adults.14 Others have suggested that ex vivo expansion of umbilical cord blood progenitor cells may be necessary to engraft larger patients.16 In vitro studies have shown that ex vivo expansion is possible; the addition of stem cell factor (SCF ) and granulocyte-macrophage colony-stimulating factor (GM-CSF ) increases umbilical cord blood CFU-GM progenitor cells by 8- to 11-fold in short-term liquid culture.14 Umbilical cord blood progenitor cells also appear to be more sensitive to ex vivo expansion with both lineage-specific and lineage-nonspecific hematopoietic growth factors.7,17,18 In long-term hematopoietic in vitro cultures, umbilical cord progenitor cell production and culture life span are significantly increased compared with progenitor cells from normal adult BM.19 

We and others have demonstrated that CD34+ stem cells can be isolated from umbilical cord blood and adult human BM.18,20-22 Fourteen-day expansion of CD34+ cells isolated from umbilical cord blood stimulated with interleukin-11 (IL-11) + granulocyte colony-stimulating factor (G-CSF ) was significantly greater than that from stimulated CD34+ cells isolated from human adult BM (80-fold).21 Additionally, IL-11 + G-CSF also significantly increased the expansion of day-14 CFU-GM and CFU-Meg from umbilical cord blood compared with adult BM.21 Single nonadherent low-density T-lymphocyte–depleted CD34+ cells expanded ex vivo with SCF, GM-CSF, G-CSF, IL-3, and erythropoietin results in an eightfold increase in colony formation from umbilical cord blood CD34+ cells compared with that from adult BM.22 Additionally, single CD34+ cells isolated from umbilical cord blood are capable of at least five serial in vitro replatings, demonstrating a significant level of self-renewal capacity for single-sorted CD34+ umbilical cord blood stem cells.22 Future clinical trials might incorporate ex vivo expansion of umbilical cord blood progenitor cells to accelerate hematopoietic reconstitution.

The CD34+ CD38 immunophenotype reportedly defines a primitive subpopulation of progenitor cells23-28 and continues to be an area of ongoing study. Hao et al23 showed that CD34+ CD38 cells in umbilical cord blood have a higher cloning efficiency than the same immunophenotype in adult BM. CD34+ CD38 cells in umbilical cord blood also proliferate more rapidly in response to cytokine stimulation with IL-3, IL-6, and SCF and generate seven times more progeny than do BM cells.23 Cardoso et al24 found that isolated umbilical cord blood CD34+ CD38 cells yield approximately the same number of CFU-GEMM, twice the CFU-GM, and three times the burst-forming unit-erythroid (BFU-E) as similar cell populations isolated from BM.

Hematopoiesis and host defense in the neonate is developmentally immature compared with the adult.29 Dysregulation of neonatal hematopoiesis and the immune response is a significant contributing factor to the increased susceptibility of the neonate to overwhelming infection.30,31 Cairo et al32-38 have recently demonstrated significant dysregulation of a number of hematopoietic cytokines and lymphokines from umbilical cellular sources compared with adult peripheral blood. Lineage-specific hematopoietic cytokines, such as G-CSF, GM-CSF, IL-3, and macrophage colony-stimulating factor (M-CSF ), and negative hematopoietic regulators, including transforming growth factor-β1 (TGF-β1) and macrophage inhibitory protein-1α (MIP-1α), are significantly decreased from activated umbilical cells compared with adult cell sources. There is a significant reduction in mRNA expression from activated umbilical cord blood mononuclear cells (MNC) compared with adult peripheral blood MNC as well as decreased protein production with regards to G-CSF, GM-CSF, IL-3, M-CSF, TGF-β1, and MIP-1α (10% to 40% adult values).33-36 In comparison, expression and protein production of IL-11, SCF, and thrombopoietin (TPO) are significantly increased from umbilical cord blood sources compared with adult fibroblasts and endothelial cells (200% to 400% adult values).37-39 Recent studies examining the complex regulatory mechanisms associated with GM-CSF mRNA expression and protein production have suggested a significant decrease in posttranscriptional stability in umbilical cord blood compared with adult peripheral blood MNC.40 It has additionally been shown that both IL-2 and IL-12, two critically important lymphokines regulating cellular immunity, are significantly decreased in gene expression and protein production from activated umbilical cord versus adult peripheral blood MNC.41 42 Dysregulation of hematopoietic growth factors and cytokines could potentially predispose the recipient of umbilical cord blood to delays in immune or hematopoietic reconstitution.

The immunoreactivity of umbilical cord blood effector cells (monocytes and lymphocytes) appears to be normal to slightly decreased compared with that of adult peripheral blood. Phenotypic comparisons of umbilical cord blood and adult peripheral blood have shown umbilical cord blood total B-cell numbers to be comparable to adult peripheral blood; however, approximately half the population has the immature (CD5+/CD19+) phenotype thought to be involved in anti-self reactions. Lower absolute numbers of CD4+, CD8+, and CD3+ T cells but a higher CD4+/CD8+ ratio have been demonstrated in umbilical cord versus adult peripheral blood. Additionally, umbilical cord blood T cells have an increased number of unprimed (ie, naive) T cells (CD45 RA+) and decreased populations of mature or primed T cells (CD45 RO+) compared with that of adult peripheral blood T cells (Table 1).43 Decreased CD3 expression in umbilical cord blood T cells has also been reported, suggesting the presence of maturational intermediate T cells that may not be fully functional. A unique T-lymphocyte population (CD3/CD8) has also been observed in umbilical cord blood but not in adult peripheral blood. These umbilical cord blood T-cell subsets are postulated to be lymphopoietic precursors for the T-cell lineage (Table 1).43 These decreases in mature or primed T cells and subpopulations of T cells also lead to decreased release of certain mediators during activation, including γ interferon and tumor necrosis factor-α (TNF-α) from umbilical cord versus adult peripheral blood T cells (Table 1).41,43,44 Despite the fact that umbilical cord blood T cells have altered subpopulations and decreased mediator release, they appear to have similar natural killer (NK) activity and similar lymphokine-activated killer activity compared with that of adult peripheral blood T cells (Table 1).45-47 

Table 1.

Comparison of Unrelated Cellular Immunity (T or Mononuclear Cells) Isolated From Cord Blood Versus Adult Peripheral Blood

ImmunophenotypeMediators
CD45 RA+CD45 RO+CD3+CD3 CD8+γIFNTNFαIL-4IL-6
 
Umbilical cord blood MNC versus adult MNC Increased Decreased Decreased Present in cord only Decreased Decreased Decreased Decreased 
         
ImmunophenotypeMediators
CD45 RA+CD45 RO+CD3+CD3 CD8+γIFNTNFαIL-4IL-6
 
Umbilical cord blood MNC versus adult MNC Increased Decreased Decreased Present in cord only Decreased Decreased Decreased Decreased 
         
 Functional Responses 
 NK Activity LAK Activity Primary T-Cell Proliferation Secondary T-Cell Alloantigen Proliferation Alloantigen Cytotoxicity 
      
 
Umbilical cord blood MNC versus adult MNC Normal Normal Normal Decreased Decreased 
 Functional Responses 
 NK Activity LAK Activity Primary T-Cell Proliferation Secondary T-Cell Alloantigen Proliferation Alloantigen Cytotoxicity 
      
 
Umbilical cord blood MNC versus adult MNC Normal Normal Normal Decreased Decreased 

Data are from previous studies.39-47 

Abbreviations: γIFN, γ interferon; TNFα, tumor necrosis factor α; NK, natural killer; LAK, lymphokine activated killer.

The proliferative response after allogeneic stimulation of E-rosetted T cells is similar in umbilical cord blood compared with adult peripheral blood.48 However, in contrast, allogeneic cytolytic activity in mixed leukocyte cultures of umbilical cord blood T cells is significantly decreased compared with that in adult peripheral blood (Table 1).48 Umbilical cord blood has been shown to be 10 to 1,000 times less alloreactive in terms of proliferative T cells and cytotoxic T cells as measured by limiting dilution analyses (Table 1).48 Umbilical cord blood T cells are also significantly decreased in secondary proliferative responses to alloantigens compared with that of adult peripheral blood T cells. The unresponsiveness of umbilical cord blood T cells to allogeneic restimulation appears to be long-lasting and sustained by the induction of anergy and the activity of CD8+ suppressor cells.49 Cytotoxic activity in secondary and tertiary mixed leukocyte cultures of umbilical cord blood T cells has also been shown to be typically less than 20% (Table 1).48 However, the graft-versus-leukemia and GVHD properties of umbilical cord blood remain to be defined.

Properties of the neonatal immune system that might account for umbilical cord blood mediating GVHD reaction are currently being explored. However, some recent reports suggest that the frequencies of helper lymphocyte precursor (HTLp) and cytotoxic T lymphocyte precursor (CTLp) cells in umbilical cord blood are similar to or exceed those of adult peripheral blood50,51 and activation by alloantigen is normal.51 However, other reports suggest that the cytotoxic activity of umbilical cord blood is not mediated by CTLs but primarily by NK cells.52 

Successful hematologic reconstitution after myeloablative therapy and umbilical cord blood transplantation has resulted in considerable interest in the techniques of umbilical cord and placental blood collection and storage. Using an open collection procedure,53 a variety of obstetricians have collected umbilical cord blood for purposes of hematopoietic stem cell transplantation and shipped the specimens to Indiana University for storage. The volume of umbilical cord blood collected ranged from 42 to 240 mL, with a median volume of 103 ± 49 mL (n = 38). Needle aspirations of the placental veins produced an additional 8 to 85 mL, with a median volume of 31 ± 16 mL (n = 31). Of specimens (n = 38) sent by overnight courier express mail, the total number of nucleated cells contained in a single collection has ranged from 4.7 × 108 to 4.6 × 109 cells with a median value of 1.4 × 109 ± 0.96 × 109. The nucleated cell concentration varied significantly between umbilical cords (range, 3.1 × 106 to 24.3 × 106 cells/mL). The numbers of day-14 CFU-GM (colonies and clusters) ranged from 5.4 × 105 to 59.2 × 105 (median, 21.5 × 105 ± 3.1 × 105 [SEM]).

A variety of collection methods have subsequently been proposed to optimize the collection volume and reduce the risks of microbial and maternal cell contamination.54-56 Closed collection systems have been principally used by designated umbilical cord blood collection centers with trained staff. Although the open collection system may be technically easier, the most important disadvantage is the greater potential of microbial and maternal cell contamination, yet maternal cell contamination of the umbilical cord blood at the time of collection appears to be of limited clinical importance. Kurtzberg et al (presented by Broxmeyer et al13 ), Wagner et al,57 and Vilmer et al58 failed to demonstrate maternal cells in the umbilical cord blood grafts used for transplantation by cytogenetic or DNA techniques. However, more recent data by Socie et al,59 Hall et al,60 Scaradavou et al,61 and Kugler et al62 suggest that maternal cells are detectable in all umbilical cord blood specimens at a frequency of 1 in 10,000 to 100,000. Although maternal cell contamination might therefore be present in all grafts, the very low incidence of GVHD observed in unrelated sibling donor umbilical cord blood transplant recipients suggests that carefully collected umbilical cord blood has either too little maternal T-cell contamination to be clinically significant or that maternal T cells are not immunologically active in this context.

Different procedures for umbilical cord blood collection, separation, and cryopreservation have been evaluated and reported in anticipation of large-scale banking projects proposed in the United States and Europe. Bertolini et al56 have reported on one of the most extensive evaluations of umbilical cord blood collection procedures thus far, comparing open and closed collection systems, the effect of vaginal versus Caesarian section delivery, and the recoveries of colony-forming cells (CFC) and high proliferative potential-CFC (HPP-CFC) after density gradient centrifugation and gelatin sedimentation of both fresh and cryopreserved cell samples. Bertolini et al56 failed to show any statistical differences in the collection volumes of umbilical cord blood recovered during vaginal delivery (in utero, n = 445) or after Caesarian section deliveries (ex utero, n = 82). The median volume of blood collected was 72 ± 34 mL and 62 ± 19 mL, respectively. Furthermore, no significant difference in collection volume could be discerned between open and closed collection systems. As expected, there appeared to be a lower risk of bacterial contamination for samples collected by venipuncture into a blood collection bag as compared with the open collection method (4% v 14%, respectively).

In the instance in which there are already limited numbers of nucleated cells and hematopoietic progenitors, manipulations that might further reduce the number of these cells in the umbilical cord blood graft must be avoided. Broxmeyer et al13 first reported significant losses in progenitor recovery with umbilical cord blood after density gradient centrifugation (Ficoll-Hypaque, 1.077 g/mL; Sigma, St Louis, MO). They found that CFC were lost by a variety of red blood cell (RBC) separation techniques, suggesting that RBC depletion before clinical transplantation, even if the recipient and donor were ABO-incompatible, should be carefully reconsidered. However, Harris et al,55 Newton et al,63 and Bertolini et al56 failed to observe the same substantial losses of progenitor cells as assessed by in vitro colony-forming assays. Harris et al55 described a double Ficoll-Hypaque procedure in which the final preparation was virtually devoid of RBC and polymorphonuclear leukocytes but contained virtually all CFC. Bertolini et al56 compared the double Ficoll-Hypaque method proposed by Harris et al55 and a 3% gelatin sedimentation method proposed by Nagler et al.64 Umbilical cord blood separation using either Ficoll-hypaque or gelatin sedimentation resulted in only 8% to 14% loss of CFC and HPP-CFC. However, Bertolini et al56 also found that the effectiveness of either separation procedure was markedly reduced when umbilical cord blood was stored for more than 12 hours before the procedure. Although the gelatin procedure took less time relative to the Ficoll-Hypaque method (1.5 v 2.5 hours), in one third of instances, the gelatin procedure failed to result in RBC depletion when performed at room temperature. However, this technical issue was corrected simply by performing the procedure at 4°C. Rubinstein et al65 developed an RBC separation method using hydroxyethylstarch (HES; Hespan; McGaw, Inc, Irvine, CA) sedimentation. This procedure resulted in recovery of 98% of CFC.

These data suggest that RBC depletion by either density-gradient centrifugation, gelatin sedimentation, or HES results in only modest losses of hematopoietic progenitor cells.13 Rubinstein et al65 currently recommend that the frozen umbilical cord blood graft be placed in a sterile bag and then thawed in a 38°C waterbath with gentle agitation. With an equal volume of dextran/albumin solution added after thawing, the cells are centrifuged gently and the supernatant is removed. The cell pellet is then resuspended in dextran/albumin. This procedure removes the bulk of RBC ghosts, free hemoglobin, and dimethyl sulfoxide (DMSO), thus reducing some of the risks associated with the transplant procedure. At the University of Minnesota, this method routinely has provided greater than 90% recovery and greater than 90% viability (n = 35) of nucleated cells (J.E.W., unpublished data).

Patient population. Data on 62 patients receiving sibling donor umbilical cord blood transplants for malignant and nonmalignant disorders (Table 2) between October 1988 and November 1995 were reported by 22 transplant teams to the International Cord Blood Transplant Registry. Data on the first 44 were previously reported57 (update by Wagner et al, personal communication, May 1997). Patients were aged 0.5 to 16 years. Eleven patients received HLA 1-3-antigen mismatched grafts; all others were matched. Prophylaxis for acute GVHD (aGVHD) consisted of cyclosporine A alone or in combination with methylprednisolone or an anti–T-cell antibody (n = 40), cyclosporine A with short-course methotrexate (n = 18), or methotrexate alone or in combination with methylprednisolone (n = 2); 2 patients received no prophylaxis. Hematopoietic growth factors were used early after the infusion of umbilical cord blood in 37 patients by study design; 20 received GM-CSF, 14 received G-CSF, and 3 received both simultaneously.

Table 2.

Diseases Treated by Umbilical Cord Blood Transplantation Using Either Sibling or Unrelated Donors

Malignant DiseasesNonmalignant Diseases
 
Acute lymphocytic leukemia Fanconi anemia 
Acute myelocytic leukemia Idiopathic aplastic anemia 
Juvenile chronic myelogenous leukemia Thalassemia 
Chronic myelogeneous leukemia Sickle cell anemia 
Neuroblastoma Amegakaryocytic thrombocytopenia 
Myelodysplastic syndrome Kostman syndrome 
 Blackfan-Diamond syndrome 
 Severe combined immunodeficiency 
 X-linked lymphoproliferative syndrome 
 Wiskott-Aldrich syndrome 
 Hurler syndrome 
 Hunter syndrome 
 Gunther disease 
 Osteopetrosis 
 Globoid cell leukodystrophy 
 Adrenoleukodystrophy 
 Lesch-Nyhan syndrome 
Malignant DiseasesNonmalignant Diseases
 
Acute lymphocytic leukemia Fanconi anemia 
Acute myelocytic leukemia Idiopathic aplastic anemia 
Juvenile chronic myelogenous leukemia Thalassemia 
Chronic myelogeneous leukemia Sickle cell anemia 
Neuroblastoma Amegakaryocytic thrombocytopenia 
Myelodysplastic syndrome Kostman syndrome 
 Blackfan-Diamond syndrome 
 Severe combined immunodeficiency 
 X-linked lymphoproliferative syndrome 
 Wiskott-Aldrich syndrome 
 Hurler syndrome 
 Hunter syndrome 
 Gunther disease 
 Osteopetrosis 
 Globoid cell leukodystrophy 
 Adrenoleukodystrophy 
 Lesch-Nyhan syndrome 

Umbilical cord blood graft characteristics. The method of umbilical cord blood collection varied significantly between institutions; however, the majority of collections were performed by obstetricians or nurse midwives without any prior experience in the large-scale collection of umbilical cord and placental blood. The median volume of umbilical cord blood collected was 98 mL (range, 42.1 to 282 mL). The median number of nucleated cells and CFU-GM in the graft on the basis of the patient's body weight was 4.7 × 107/kg (range, 1.0 to 33.0 × 107/kg) and 1.7 × 104/kg (range, <0.1 to 25.6 × 104/kg), respectively. Despite the diversity of collection systems and inexperience of collectors, the majority of samples were sterile. In 6 of 44 reported cases, the umbilical cord blood was contaminated with bacteria. However, bacterial contamination of the umbilical cord blood graft did not have any demonstrable impact on the posttransplant morbidity in any of these patients.

Hematopoietic recovery and engraftment. Patients (n = 56) surviving greater than 30 days after transplantation were considered evaluable for engraftment. For recipients of HLA-matched or HLA-1-antigen mismatched umbilical sibling donor cord blood grafts, the actuarial probability of hematopoietic recovery at 60 days after transplantation was 0.91 ± 0.08 (Fig 2). Median time to neutrophil recovery (defined as time to achieve an absolute neutrophil count [ANC] ≥500/μL) and platelet recovery (defined as platelet count ≥50,000/μL untransfused for 7 days) was 22.0 days (range, 12 to 46 days) and 51 days (range, 15 to 117 days) after transplantation, respectively. Four patients never had signs of hematopoietic recovery and 1 patient had early recovery but cells were entirely host in origin. Of the 5 patients without donor cell engraftment, 4 had undergone umbilical cord blood transplantation for the treatment of a BM failure syndrome and one for the treatment of Hunter syndrome.

Fig. 2.

Time to neutrophil recovery (ANC ≥500/μL) for recipients of HLA-matched or HLA-1-antigen mismatched sibling donor umbilical cord blood.

Fig. 2.

Time to neutrophil recovery (ANC ≥500/μL) for recipients of HLA-matched or HLA-1-antigen mismatched sibling donor umbilical cord blood.

Close modal

No correlation could be discerned between nucleated cell count or hematopoietic progenitor cell content of the graft and time to neutrophil recovery or probability of engraftment (Fig 3). Although the use of hematopoietic growth factors in 37 of 62 patients did not appreciably shorten the time to neutrophil recovery, the variables of patient and growth factor selection prevent definitive conclusion.

Fig. 3.

Comparison between the number of nucleated cells per kilogram of recipient body weight and time to neutrophil recovery (ANC ≥500/μL) after sibling related cord blood transplantation. (▪) The nucleated cell count for patients achieving an ANC ≥500/μL (n = 56). (♦) Cell doses in patients failing to engraft.

Fig. 3.

Comparison between the number of nucleated cells per kilogram of recipient body weight and time to neutrophil recovery (ANC ≥500/μL) after sibling related cord blood transplantation. (▪) The nucleated cell count for patients achieving an ANC ≥500/μL (n = 56). (♦) Cell doses in patients failing to engraft.

Close modal

GVHD. Patients (n = 51) surviving greater than 30 days after transplantation and demonstrating evidence of donor-derived hematopoiesis were evaluable for aGVHD. The actuarial probability of grade II-IV GVHD at 100 days after transplantation was 0.02 ± 0.02 for recipients with an HLA 0-1-antigen mismatched umbilical cord blood donor. Notably, no patient was reported to have grade III-IV aGVHD. Of the entire cohort of patients, chronic GVHD has been reported in only 3 patients to date, with no patient having extensive disease.

Interestingly, moderate to severe GVHD was infrequently observed in 8 evaluable patients with 1-3 HLA-antigen mismatched haploidentical sibling donors (Table 3). Of these 8 patients, 3 were mismatched at one antigen, 1 was mismatched at two antigens, and 4 were mismatched at three antigens. As shown in Table 3, donor-recipient pairs mismatched at a maternal allele appeared to be less likely to develop grade II-IV GVHD than donor-recipient pairs mismatched at a paternal allele. This observation supports the hypothesis that partial tolerance develops to the noninherited maternal allele during the donor's gestation, but small patient numbers at this time prevent any conclusion.

Table 3.

GVHD Outcome in Recipients of HLA Mismatched Sibling Donor Umbilical Cord Blood Transplants

Patient UPNDonor HLA TypeRecipient HLA TypeGVHD Grade
(no. disparate HLA antigens)
4 (1 antigen) A2 B35 DR1 (M)3-150 A11 B35 DR4 (M)3-150 Grade I 
 A2 B16 DR4 (P) A2 B16 DR4 (P) 
23 (1 antigen) A2 B18 DR11 (M)3-150 A2 B27 DR11 (M)3-150 Grade I 
 A2 B44 DR7 (P) A2 B44 DR7 (P) 
27 (1 antigen) A29 B44 DR14 (M) A29 B44 DR14 (M) Grade 0 
 A11 B14 DR13 (P)3-150 A3 B14 DR13 (P)3-150 
15 (2 antigen) A24 B60 DR15 (M)3-150 A24 B55 DR11 (M)3-150 Grade I 
 A1 B49 DR1 (P) A1 B49 DR1 (P) 
21 (3 antigen) A2 B8 DR3 (M) A2 B8 DR3 (M) Grade III 
 A10 B35 DR14 (P)3-150 A29 B5 DR7 (P)3-150 
22 (3 antigen) A2 B44 DR1 (M)3-150 A3 B7 DR2 (M)3-150 Grade I 
 A26 B8 DR3 (P) A26 B8 DR3 (P) 
24 (3 antigen) A24 B44 DR7 (M) A24 B44 DR7 (M) Grade II 
 A24 B70 DR2 (P)3-150 A30 B39 DR6 (P)3-150 
52 (3 antigen) A2 B40 DR4 (M)3-150 A33 B39 DR13 (M)3-150 Grade I 
 A23 B14 DR2 (P) A23 B14 DR2 (P) 
Patient UPNDonor HLA TypeRecipient HLA TypeGVHD Grade
(no. disparate HLA antigens)
4 (1 antigen) A2 B35 DR1 (M)3-150 A11 B35 DR4 (M)3-150 Grade I 
 A2 B16 DR4 (P) A2 B16 DR4 (P) 
23 (1 antigen) A2 B18 DR11 (M)3-150 A2 B27 DR11 (M)3-150 Grade I 
 A2 B44 DR7 (P) A2 B44 DR7 (P) 
27 (1 antigen) A29 B44 DR14 (M) A29 B44 DR14 (M) Grade 0 
 A11 B14 DR13 (P)3-150 A3 B14 DR13 (P)3-150 
15 (2 antigen) A24 B60 DR15 (M)3-150 A24 B55 DR11 (M)3-150 Grade I 
 A1 B49 DR1 (P) A1 B49 DR1 (P) 
21 (3 antigen) A2 B8 DR3 (M) A2 B8 DR3 (M) Grade III 
 A10 B35 DR14 (P)3-150 A29 B5 DR7 (P)3-150 
22 (3 antigen) A2 B44 DR1 (M)3-150 A3 B7 DR2 (M)3-150 Grade I 
 A26 B8 DR3 (P) A26 B8 DR3 (P) 
24 (3 antigen) A24 B44 DR7 (M) A24 B44 DR7 (M) Grade II 
 A24 B70 DR2 (P)3-150 A30 B39 DR6 (P)3-150 
52 (3 antigen) A2 B40 DR4 (M)3-150 A33 B39 DR13 (M)3-150 Grade I 
 A23 B14 DR2 (P) A23 B14 DR2 (P) 

Data reported to the International Cord Blood Transplant Registry.

Abbreviations: UPN, unique patient no.; M, maternal; P, paternal.

F3-150

Disparate allele.

Table 4.

Unrelated Donor Umbilical Cord Blood Transplantation: Review of Reports in the Literature (n = 43)

Median AgeMedian WeightMedian VolumeMedian Nuc/kg (range) × 107Median ANC ≥500/μL (range) in DaysMedian Platelets ≥50K/μL (range) in DaysNonmyeloid Engraftment (%)
(range) in yrs(range) in kg(range) in mL
4.1 18.7 83.0 3.7 23 75 9% 
(0.1-23.5) (3.3-79.0) (35-214) (0.7-40.0) (14-41) (67->120*) 
      
Median AgeMedian WeightMedian VolumeMedian Nuc/kg (range) × 107Median ANC ≥500/μL (range) in DaysMedian Platelets ≥50K/μL (range) in DaysNonmyeloid Engraftment (%)
(range) in yrs(range) in kg(range) in mL
4.1 18.7 83.0 3.7 23 75 9% 
(0.1-23.5) (3.3-79.0) (35-214) (0.7-40.0) (14-41) (67->120*) 
      
HLA A, B, DRB1 Match4-151 HLA A, B, DRB1 1-antigen HLA, A, B, DRB1 2 or 3 All HLA Parity (n = 43) (n = 35) 
(n = 8) (n = 6) (n = 16) (n = 14) (n = 19) (n = 15) Grade II-IV aGVHD Grade III-IV aGVHD 
Grade II-IV aGVHD Grade III-IV aGVHD Grade II-IV aGVHD Grade III-IV aGVHD Grade II-IV aGVHD Grade III-IV aGVHD   
33% 16% 43% 7% 73% 7% 57% 9% 
HLA A, B, DRB1 Match4-151 HLA A, B, DRB1 1-antigen HLA, A, B, DRB1 2 or 3 All HLA Parity (n = 43) (n = 35) 
(n = 8) (n = 6) (n = 16) (n = 14) (n = 19) (n = 15) Grade II-IV aGVHD Grade III-IV aGVHD 
Grade II-IV aGVHD Grade III-IV aGVHD Grade II-IV aGVHD Grade III-IV aGVHD Grade II-IV aGVHD Grade III-IV aGVHD   
33% 16% 43% 7% 73% 7% 57% 9% 

Data are from previous studies.64-66 

F4-150

Some patients did not platelet engraft by day 120.

F4-151

HLA A, B, DR by serology and DRB1 by high resolution DNA typing.

Evaluable for aGVHD.

Patient population. At the present time, more than 450 unrelated donor umbilical cord blood transplants are known to have been performed worldwide. However, thus far few published manuscripts exist summarizing the experiences with unrelated donor umbilical cord blood transplantation.66-68 In these reports, 32 patients received an unrelated donor umbilical cord blood transplant for malignant disorders and 11 patients for nonmalignant disorders (Table 4). The median age and weight of patients were 4.1 years (range, 0.1 to 23.5 years) and 18.7 kg (range, 3.3 to 79.0 kg), respectively (Table 4).66 67 Eight patients received unrelated donor umbilical cord blood transplants that were matched at all three HLA loci (A, B, and DRB1) by serology and molecular typing, and 16 patients received unrelated donor umbilical cord blood transplants that were disparate at 1 HLA locus. Fourteen patients were disparate at 2 HLA loci and 5 patients were disparate at three HLA loci (Table 4).

Umbilical cord blood graft characteristics and hematologic recovery. Unrelated donor umbilical cord blood grafts were provided by the New York Blood Center. In these two reports, the time between search request and donor confirmation ranged between 12 and 291 days.66,67 The median volume of umbilical cord blood collected was 83.0 mL (range, 35 to 214 mL) and the median number of nucleated cells/kg recipient weight was 3.7 × 107 (range, 0.7 to 40 × 107; Table 4).66,67 The median time to ANC ≥500/μL and platelet count ≥50,000/μL was 23 days (range, 14 to 41 days) and 75 days (range, 50 to >120 days), respectively.66 67 

GVHD. For the patients in the two reports, the overall incidence of grade II-IV and grade III-IV aGVHD by day 100 was 57% and 9%, respectively (Table 4). In patients fully matched at HLA A, B, DR by serology and DRB1 by high resolution DNA typing, the incidence of grade II-IV and III-IV aGVHD was 33% and 16%, respectively; for a 1-antigen mismatch, 43% and 7%, respectively; and for a 2- or 3-antigen mismatch, 73% and 7%, respectively. The combined groups of fully matched and 1-antigen mismatched (6/5 and 5/6) had an incidence of grade II-IV and III-IV aGVHD of 40% and 5%, respectively, compared with the group with either 2- or 3-antigen mismatch of 73% and 7%, respectively (Table 4).66 67 

Survival. Twenty-four patients survived to day 100, 16 patients with malignant disease (16 of 32 [50%]) and 8 patients with nonmalignant disease (8 of 11 [72%]).66 67 

Two recent abstracts have reported the preliminary results of larger numbers of recipients of unrelated donor umbilical cord blood transplantation. Gluckman et al69 reported the result of 65 unrelated donor umbilical cord blood transplants reported to the European Cord Blood Transplant Registry. The median nucleated cell dose per kilogram was 3.7 × 107 /kg, and there was a 21% incidence of grade III-IV aGVHD and a 1-year survival rate of 29% in this population undergoing unrelated donor cord blood transplantation. Rubinstein et al70 recently reported the preliminary results of unrelated donor umbilical cord blood transplants that received their unrelated donor umbilical cord blood grafts from the New York Blood Center. Two hundred seventy-two unrelated donor umbilical cord blood transplants (220 from the United States and 52 foreign) were performed with umbilical cord blood from the New York Blood Center, and the incidence of severe grade III-IV aGVHD was 23% and the median time to platelet recovery ≥50,000/μL was 72 days.

These initial results suggest that unrelated donor umbilical cord blood transplantation is feasible in children, is associated with a decreased time of search, and has comparable myeloid engraftment but delayed platelet reconstitution when compared with unrelated donor BMT. It is too early to conclusively determine whether the incidence of severe aGVHD will be decreased compared with unrelated donor BM or whether there is the potential of using more disparate grafts from unrelated donor umbilical cord blood compared with unrelated donor BM. Although there are several reports on the use of umbilical cord blood for adult recipients,71 72 more data are needed. Preliminary results in 19 adult patients undergoing unrelated donor cord blood transplantation at Duke University suggest that the incidence of nonengraftment is similar to that reported in children (J. Kurtzberg, personal communication, May 1997). Carefully designed, future prospective randomized trials will be necessary to answer these important questions.

Comparison to unrelated donor unmanipulated BMT in children. To date, the largest series of unrelated donor BMT in children (n = 88) was reported by Balduzzi et al73 (Table 5). Although the age range of the recipients was similar, the median age was almost twice as high in the unrelated donor BM recipients (9.1 v 4.1 years) and the median number of nucleated cells per kilogram was more than 1 log higher (42 v 3.7 × 107/kg) in the children receiving unrelated donor BM (Table 5). Despite a 1 log higher number of nucleated cells per kilogram, the median time to myeloid engraftment was similar in both groups. However, the median days to platelet recovery was significantly delayed in the children receiving unrelated donor umbilical cord blood versus BM (75 v 23 days; Table 5). The median time of 23 days to recover the platelet count ≥50,000/μL after unmanipulated unrelated donor BMT in children may be somewhat misleading, because 17 patients were not included in the analysis because of discharge before platelet recovery and another 27 patients were eliminated from the analysis because of relapse or death before platelet recovery. This discrepancy between myeloid and platelet engraftment may reflect a 100-fold increase in CFU-GM compared with only a onefold or twofold increase in CFU-Meg in umbilical cord blood versus adult peripheral blood (Fig 1). Additionally, the number of CD34/41+ cells in umbilical cord blood grafts is 1 log less than seen under optimal conditions of platelet reconstitution after mobilized autologous peripheral blood stem cell transplantation.74 

Table 5.

Comparison of Unrelated Donor Umbilical Cord Blood and Unmanipulated Unrelated BM Stem Cell Transplantation in Children

Demographics
Median Age (range) in yrHLA A, B, DR, B1 Match5-150HLA A, B, DR, B1 1-Antigen MismatchHLA A, B, DR, B1 2- or 3-Antigen MismatchGrade II-IV aGVHDGrade III-IV aGVHD
 
Unrelated donor umbilical cord blood transplantation 4.1 (0.1-23.5) 8 (19%) 16 (73%) 19 (24%) 57% 9% 
Unrelated donor unmanipulated BMT 9.1 (0.5-17.8) 46 (54%) 41 (45%) 1 (1%) 90% 49% 
       
Demographics
Median Age (range) in yrHLA A, B, DR, B1 Match5-150HLA A, B, DR, B1 1-Antigen MismatchHLA A, B, DR, B1 2- or 3-Antigen MismatchGrade II-IV aGVHDGrade III-IV aGVHD
 
Unrelated donor umbilical cord blood transplantation 4.1 (0.1-23.5) 8 (19%) 16 (73%) 19 (24%) 57% 9% 
Unrelated donor unmanipulated BMT 9.1 (0.5-17.8) 46 (54%) 41 (45%) 1 (1%) 90% 49% 
       
 Search and Engraftment 
 Median ANC ≥500/μL (days) Median Platelet ≥50,000/μL Median Nuc Cells/kg Infused (range) × 107 
  (days)  
Unrelated donor umbilical cord blood transplantation 23 75 3.7 (0.7-40.0) 
Unrelated donor unmanipulated BMT 21 235-151 42 (12-460) 
    
 Search and Engraftment 
 Median ANC ≥500/μL (days) Median Platelet ≥50,000/μL Median Nuc Cells/kg Infused (range) × 107 
  (days)  
Unrelated donor umbilical cord blood transplantation 23 75 3.7 (0.7-40.0) 
Unrelated donor unmanipulated BMT 21 235-151 42 (12-460) 
    
 HLA Disparity and Incidence of Acute GvHD 
 HLA A, B, DR, B1 Match5-152 Grade II-IV aGVHD (%) Grade III-IV aGVHD (%) HLA A, B, DR, B1 1-Antigen Mismatch Grade II-IV aGVHD (%) Grade III-IV aGVHD (%) 
       
 
Unrelated donor umbilical cord blood transplantation n = 6 33% 16% n = 14 43% 7% 
Unrelated donor unmanipulated BMT n = 46 83% 37% n = 41 98% 62% 
 HLA Disparity and Incidence of Acute GvHD 
 HLA A, B, DR, B1 Match5-152 Grade II-IV aGVHD (%) Grade III-IV aGVHD (%) HLA A, B, DR, B1 1-Antigen Mismatch Grade II-IV aGVHD (%) Grade III-IV aGVHD (%) 
       
 
Unrelated donor umbilical cord blood transplantation n = 6 33% 16% n = 14 43% 7% 
Unrelated donor unmanipulated BMT n = 46 83% 37% n = 41 98% 62% 

Data are from previous studies.64,65 67 

F5-150

HLA A, B, DR by serology. HLA DR B1 by high resolution DNA typing.

F5-151

Forty-four patients excluded from analysis because of earlier discharge, relapse, or death before platelet recovery.

F5-152

Evaluable for aGVHD.

The incidence of both grade II-IV and grade III-IV aGVHD appeared to be less after unrelated donor umbilical cord blood versus unrelated donor BMT in children (Table 5). Similarly, matched (6/6) grafts using unrelated donor umbilical cord blood compared with unrelated donor BM in children have a decreased incidence of grade II-IV and III-IV aGVHD (33% v 83% and 16% v 37%, respectively; Table 5). In comparison, the incidence of grade II-IV aGVHD after T-cell–depleted unrelated donor BMT in children was 33%, with similar survival rates.75 Additionally, for HLA 1-antigen mismatched grafts, the incidence of grade II-IV and III-IV aGVHD is less in children after unrelated donor umbilical cord blood versus unmanipulated unrelated donor BM (43% v 98% and 7% v 62%, respectively; Table 5). Although this lower incidence of severe aGVHD after unrelated donor umbilical cord blood could reflect an immaturity in umbilical cord blood effector cells, a decrease in the number of nucleated cells per kilogram in the graft and/or a lower age of the recipient after unrelated donor umbilical cord blood transplant could account for the differences in the incidence of severe aGVHD.

BMT has been used successfully to treat a variety of genetic diseases. Parkman76 suggested more than a decade ago that BMT could be used to treat a variety of conditions that were secondary to a single genetic deletion. Hematopoietic stem cells are ideal cells for gene transduction because of their ability to renew themselves and differentiate into progeny cells and generate a self-perpetuating cell population that contains the transduced gene for the lifetime of the patient.77 Specific diseases that could be candidates for gene therapy following gene transduction into hematopoietic stem cells include thalassemia, sickle cell anemia, Fanconi anemia, severe combined immune deficiency secondary to adenosine deaminase deficiency (ADA) or purine nucleoside phosphorylase (PNP) deficiency, chronic granulomatous disease, leukocyte adhesion deficiency, Gaucher's disease, and a variety of other metabolic/storage deficiencies.77 Autologous umbilical cord blood hematopoietic stem cells potentially could be used to correct genetic deficiencies at birth after successful gene transduction and autologous umbilical cord blood stem cell transplantation.

There have been recent reports of treatment using gene therapy after autologous lymphocyte and stem cell transductions.78-84 T lymphocytes transduced ex vivo using a retroviral vector containing the normal human ADA gene and infused have been shown to express the transduced ADA gene and partially improve the immune status of patients with severe combined immune deficiency.78 Additionally, the neomycin-resistance gene (NeoR) has been successfully transduced into tumor-infiltrating lymphocytes, reinfused into 5 patients with advanced melanoma using retroviral gene transduction,79 and transduced into human BM mononuclear cells subsequently transplanted into adult cancer patients, using the retroviral vector, N2.80,85 Recently, several genes, including the human multiple drug resistance gene (MDR) and the murine ADA, were successfully transduced into isolated CD34+ BM stem cells by retroviral-mediated gene transfer.81,82 Human CD34+ stem cells isolated from peripheral blood have also been successfully used as targets for retroviral gene transduction with gene transfer of two genes encoding the components of the superoxide-generating NADPH oxidase (gp91phox and gp22phox).83 

Recently, there was noted an increase in the efficiency of gene transfer after retroviral transduction in neonatal (umbilical cord) compared with adult progenitor cells.84 Incubation of hematopoietic stem cells (CD34+) ex vivo with a variety of cytokines, including SCF, IL-3, IL-6, etc, and cotransplantation of marrow stroma expressing human IL-3 has been shown to enhance sustained human hematopoiesis and gene transduction.86 Subsequently, Kohn et al87 transplanted autologous umbilical cord blood CD34+ stem cells that had been transduced with an ADA-containing retrovirus (LASN) into three neonates with severe combined immune deficiency secondary to ADA deficiency. Although all 3 patients are currently being treated with PEG-ADA, reverse transcription polymerase chain reaction (RT-PCR) analysis has shown successful expression of the ADA gene. An analysis of the efficiency of LASN-ADA transduction has demonstrated a transduction frequency of 1/3,000 to 1/100,000 peripheral blood leukocytes and 1/10,000 BM mononuclear cells.84 This pilot study has suggested that autologous umbilical cord blood stem cells can be successfully transduced with long-term expression. Notably, the frequency of transduced T cells has increased to the range of 3% to 10%. with graded reduction in PEG-ADA dose (Parkman and Kohn, personal communication, December 1996). However, the transduction efficiency is still low and may not translate into significant clinical activity. Future studies will be required to determine the clinical success of this form of gene therapy and to develop new and better approaches to obtain a higher degree of gene expression and protein production after gene transduction.

The collection of umbilical cord blood poses a number of ethical issues that remain to be resolved. If umbilical cord blood is considered to be like any other organ or tissue, then consent by the tissue donor must be obtained. In the case of umbilical cord blood, the donor is always a minor, leaving it to the infant's mother to provide consent. Other issues include timing of the consent. For obvious reasons, consent should not be obtained when the infant's mother is in active labor or immediately after delivery. Other questions include whether consent should also be obtained from the infant's father. Presuming the umbilical cord blood remains stored for decades, what rights will the infant donor have at 21 years of age? Will the donor have any rights to umbilical cord blood that was previously given to the unrelated donor umbilical cord blood bank? To make the matter more complex, who gives consent if there is a surrogate mother? Although some of this may seem far-fetched, umbilical cord blood is being collected at an increasing frequency. At some point, many of these issues will likely surface.

Alternatively, umbilical cord blood could be considered as discarded tissue. As such, consent would not be required. Although the collection of umbilical cord blood from the delivered placenta poses no risk to mother or infant, this classification would also raise some difficult questions. What would we do about the issue of human immunodeficiency virus (HIV) testing? How do we protect the rights of individuals whose religious and cultural practices would not allow the collection and transplantation of placental blood? What if a genetic disease (eg, sickle cell disease, thalassemia, G6PD deficiency, hereditary spherocytosis) is detected upon subsequent testing? Although some would argue that a link between donor and umbilical cord blood graft should be maintained, this may be costly and logistically very difficult. Moreover, it should be recalled that such tests were only performed because the umbilical cord blood was collected for future use in an allogeneic recipient; if it were not intended for that use, no tests would have been performed and it would have been discarded. Nonetheless, earlier identification of a disease might benefit some children.

However, ethical issues are not limited to the area of consent and disease screening; other issues include (1) the potential of deliberate conception and embryo cloning for the purpose of producing an HLA-identical tissue donor and (2) commercialization. These are emotionally charged issues that are beyond the scope of these investigators. Clearly, these issues need to be considered by medical ethicists and various members of the medical community so that a consensus opinion might be made available to help guide clinicians and storage services in their practices.

Over the past 5 years, umbilical cord blood has moved from the status of biologic waste to a potentially important source of hematopoietic stem cells. Clinical experience has already shown that placental and umbilical cord blood contains sufficient numbers of hematopoietic stem cells to engraft at least small recipients consistently. As a result, banks of umbilical cord blood have been developed or are being considered throughout the United States and Europe as well as many countries in South America and Asia. Moreover, the potential of storing the child's own umbilical cord blood for future use as a form of biologic insurance has also been considered, resulting in the establishment of commercial banks. Hence, there has been an explosion of banking activity, making the need for standard policies and procedures particularly acute.

Although there will be debate on the optimal procedures for handling umbilical cord blood, there is already extensive experience in handling blood and marrow. Many of the procedures for obtaining consent, collection, testing, cryopreservation, RBC depletion, histocompatibility testing, and sample labeling are likely to be extracted from existing operating manuals for blood. However, a major problem will be in the definition of suitable product. Moreover, the definition of suitable product may vary depending on the type of recipient — self, sibling, or unrelated donor.

Table 6.

Comparison of Unrelated and Sibling Donor Umbilical Cord Blood Transplantation

Median Age (range) in yrMedian Volume (range) in mLMedian Nuc/kg (range) × 107Median ANC ≥500/μL (range) in Days
Sibling donor CBT (n = 44) 4.1 (0.1-21.3) 98 (42-282) 4.7 (1-33) 22 (12-46) 
Unrelated donor CBT (n = 43) 2.7 (0.1-23.5) 83.0 (35-214) 3.7 (10.7-40.0) 23 (14-41) 
     
Median Age (range) in yrMedian Volume (range) in mLMedian Nuc/kg (range) × 107Median ANC ≥500/μL (range) in Days
Sibling donor CBT (n = 44) 4.1 (0.1-21.3) 98 (42-282) 4.7 (1-33) 22 (12-46) 
Unrelated donor CBT (n = 43) 2.7 (0.1-23.5) 83.0 (35-214) 3.7 (10.7-40.0) 23 (14-41) 
     
 Median Platelet Grade II-IV* aGVHD (%) Grade III-IV* aGVHD (%) Survival (%) 
 ≥50K/μL (range)    
 in Days    
Sibling donor CBT (n = 44) 51 (15-77) 2 ± 2 61 ± 126-151 
Unrelated donor CBT (n = 43) 75 (50->120) 57 8.6 556-150 
 Median Platelet Grade II-IV* aGVHD (%) Grade III-IV* aGVHD (%) Survival (%) 
 ≥50K/μL (range)    
 in Days    
Sibling donor CBT (n = 44) 51 (15-77) 2 ± 2 61 ± 126-151 
Unrelated donor CBT (n = 43) 75 (50->120) 57 8.6 556-150 

Data are from previous studies.55,64 65 

F6-150

100 days (median follow-up).

F6-151

2.2 years (median follow-up).

In February 1997, the US Food and Drug Administration (FDA) announced a Proposed Approach to Regulation of Cellular and Tissue-Based Products that includes hematopoietic stem and progenitor cells derived from placental/umbilical cord blood and peripheral blood.88 The proposed approach focuses on five major considerations for such products, which include (1) prevention of the transmission of communicable diseases, (2) process controls necessary to preserve the integrity and function of products so that they will work as they are intended, (3) assurance of clinical safety and effectiveness, (4) necessary labeling and permissible promotion for proper use of the product, and (5) a means to monitor and communicate with the cell and tissue industry. The specific regulations to implement the FDA's proposed approach will be phased in during the next several years through a public rule and comment process.

Although it is clear that umbilical cord blood should be considered as a viable source of hematopoietic stem cells for transplantation, we are still in the learning phase. Just as the transplant physician requires assurances that the umbilical cord blood graft product has been processed and stored properly, the director of umbilical cord blood banks may require assurances that the transplant team will use the graft properly. Clinical outcome data may impact upon the bank's methods of processing and graft characterization. Policies for defining the qualifications of transplant teams and the appropriate use of umbilical cord blood should not be overlooked. Similar issues had to be addressed by the NMDP. Perhaps existing societies, such as the International Society of Hematotherapy and Graft Engineering (ISHAGE) and The American Society of Blood and Marrow Transplantation (ASBMT), will aid in addressing these difficult issues.

The large-scale collection and storage of umbilical cord blood stem cells is no longer just a concept. Pilot programs for the banking of unrelated donor umbilical cord blood have already begun in the United States and Europe and are being considered in Asia, Canada, and South America.89-91 Not only is there the potential for reducing the time from search initiation to the time of donor stem cell acquisition, but also the potential for reducing the risks associated with unrelated donor BMT and the hope of remedying the shortage of donors from ethnic and racial backgrounds that are currently underrepresented in most unrelated donor programs. Even with the creation of such banks, the collection of umbilical cord blood should certainly still be considered when a child with leukemia, lymphoma, neuroblastoma, marrow failure syndrome, immunodeficiency state, or inborn error of metabolism has a mother who is pregnant.

A multi-institutional cooperative trial is currently being designed by the National Heart, Lung, and Blood Institute (NHLBI) to determine the safety and efficacy of HLA-matched and mismatched unrelated donor umbilical cord blood transplantation in pediatric and adult recipients. Even in instances in which a preliminary search of the unrelated donor marrow registry identifies a potential unrelated BM donor, the use of immediately available, cryopreserved, HLA-compatible umbilical cord blood over BM may be justified in specific patients, such as those with high-risk leukemia, myelodysplastic syndrome, severe aplastic anemia, severe combined immune deficiency, and metabolic disease, because these patients are at high risk of early death due to disease progression or overwhelming infection. Although there have been considerable efforts to shorten the time of marrow acquisition from unrelated donors, the median interval from initial search request to BM harvest remains at 3.5 months. Furthermore, patients with diseases expected to remain stable over a 3- to 5-month period of a donor search without relapse or overwhelming infection (eg, chronic myelogenous leukemia, acute myelogenous leukemia, Wiskott-Aldrich syndrome) might be considered ineligible for umbilical cord blood transplantation unless the marrow donor registry fails to identify a suitable donor in a fixed period of time. As more is learned about the safety of umbilical cord blood transplantation, these restrictive criteria are likely to be modified.

Although the clinical results thus far have been very encouraging, there are potential disadvantages with umbilical cord blood as well: (1) lower risk of GVHD might translate into a higher risk of relapse (ie, absence of graft-versus-leukemia effect); (2) higher risk of genetic disorder transmission due to inability to observe growth and development of stem cell donor; and (3) an insufficient number of stem and progenitor cells in umbilical cord blood for larger recipients, limiting this stem cell source to pediatric patients. Although these risks have yet to be realized, they cannot be excluded.

Despite these limitations, the use of unrelated donor umbilical cord blood has several known advantages, including (1) immediate availability (minimum of 2 weeks for confirmatory HLA testing); (2) absence of donor risk; (3) absence of donor attrition; and (4) a very low risk of transmissible infectious diseases, such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV).92-94 Other advantages potentially include (1) lower risk of aGVHD and (2) the ability to expand available donor pools in targeted ethnic and racial minorities currently underrepresented in all marrow donor registries.

This review of sibling and unrelated donor umbilical cord blood transplants (Table 6) suggests that (1) the rate of neutrophil recovery after umbilical cord blood transplantation is comparable to that observed after allogeneic BMT; (2) there is a potentially higher risk of graft failure in recipients of sibling umbilical cord blood transplants with nonmalignant states; and (3) platelet reconstitution (≥50,000/μL) appears delayed compared with matched related allogeneic BMT.

There are several unresolved issues that will need to be addressed in the future: optimal methods for harvesting, processing, and storing umbilical cord blood units; minimum number of banked umbilical cord blood units necessary to support the needs of recipients who lack matched family member donors; the ethical and regulatory issues of collecting and storing umbilical cord blood units; the minimum number of stem/progenitor cells required for hematopoietic engraftment in larger recipients; the risks of acute and chronic GVHD with mismatched unrelated donor umbilical cord blood transplants; the malignant relapse rate after umbilical cord blood transplantation; the potential for gene therapy with autologous umbilical cord blood transplantation; ex vivo expansion of umbilical cord blood stem/progenitor cells; and immunologic reconstitution after umbilical cord blood transplantation.

Recently, the NHLBI has approved the development of three regional umbilical cord blood banks and a consortium of seven transplant centers to study many of the above-mentioned issues. Additionally, a consortium in Europe and several single-center studies are currently underway to answer many of the questions that still remain regarding this potential form of therapy. Over the next several years, many answers will be forthcoming to provide us with guidance on how to appropriately use this new and exciting form of alternate stem cell therapy.

The authors thank Linda Rahl for her assistance in the preparation of this manuscript. We also thank Jeff Buzby, PhD, Vicki Slone, PhD, Yu Suen, PhD, Carmella van de Ven, MA, Robin Ellis, RN, and Leonard Sender, MD, for their critical review of this manuscript.

Supported by grants from the Pediatric Cancer Research Foundation, the CHOC PSF Research and Education Foundation, the Walden W. and Jean Young Shaw Foundation (M.S.C.), The Childrens Cancer Research Fund, Bone Marrow Transplant Research Fund, and the National Institutes of Health Grants No. P01-CA65493 and P01-CA21737 (J.E.W.).

Address reprint requests to Mitchell S. Cairo, MD, Director of Hematology/Oncology Research, Children's Hospital of Orange County, 455 S Main St, Orange, CA 92868.

1
Armitage
J
Bone marrow transplantation.
N Engl J Med
330
1994
827
2
Bensinger
WI
Weaver
CH
Appelbaum
FR
Rowley
S
Demirer
T
Sanders
J
Storb
R
Buckner
CD
Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony-stimulating factor.
Blood
85
1995
1655
3
Korbling
M
Przepiorka
D
Huh
Y
Engel
H
van Besien
K
Giralt
S
Andersson
B
Kleine
HD
Seong
D
Deisseroth
AB
Andreeff
M
Champlin
R
Allogeneic blood stem cell transplantation for refractory leukemia and lymphoma: Potential advantage of blood over marrow allografts.
Blood
85
1995
1659
4
Schmitz
N
Dreger
P
Suttorp
M
Rohwedder
EB
Haferlach
T
Loffler
H
Hunter
A
Russell
NH
Primary transplantation of allogeneic peripheral blood progenitor cells mobilized by filgrastim (granulocyte colony-stimulating factor).
Blood
85
1995
1666
5
Gluckman
E
Broxmeyer
H
Auerbach
A
Friedman
H
Douglas
G
Devergie
A
Esperou
H
Thierry
D
Socie
G
Lehn
P
Cooper
S
English
D
Kurtzberg
J
Bard
J
Boyse
E
Hematopoietic reconstitution in a patient with Fanconi's anemia by means of umbilical-cord blood from an HLA-identical sibling.
N Engl J Med
321
1989
1174
6
Kernan
NA
Bartsch
G
Ash
RC
Beatty
PG
Champlin
R
Filipovich
A
Gajewski
J
Hansen
JA
Henslee-Downey
J
McCullough
J
McGlave
P
Perkins
HA
Phillips
GL
Sanders
J
Stroncek
D
Thomas
ED
Blume
KG
Analysis of 462 transplantations from unrelated donors facilitated by the National Marrow Donor Program.
N Engl J Med
328
1993
593
7
Broxmeyer
HE
Gluckman
E
Auerbach
AD
Douglas
GW
Friedman
H
Cooper
S
Hangoc
G
Kurtzberg
J
Bard
J
Boyse
EA
Human umbilical cord blood: A clinically useful source of transplantable hematopoietic stem/progenitor cells.
Int J Cell Cloning
8
1990
76
8
Emerson
SG
Sieff
CA
Wang
EA
Wong
GG
Clark
SC
Nathan
DG
Purification of fetal hematopoietic progenitors and demonstration of recombinant multipotential colony-stimulating activity.
J Clin Invest
76
1985
1286
9
Haneline
LS
Marshall
KP
Clapp
DW
The highest concentration of primitive hematopoietic progenitor cells in cord blood is found in extremely premature infants.
Pediatr Res
39
1996
820
10
Christensen
RD
Harper
TE
Rothstein
G
Granulocyte-macrophage progenitor cells in term and preterm neonates.
J Pediatr
109
1986
1047
11
Olson
T
Levine
R
Mazur
E
Wright
D
Salvado
A
Megakaryocytes and megakaryocyte progenitors in human cord blood.
Am J Pediatr Hematol Oncol
14
1992
241
12
Deutsch
VR
Olson
TA
Nagler
A
Slavin
S
Levine
RF
Eldor
A
The response of cord blood megakaryocyte progenitors to IL-3, IL-6 and aplastic canine serum varies with gestational age.
Br J Haematol
89
1995
8
13
Broxmeyer
H
Douglas
G
Hangoc
G
Cooper
S
Bard
J
English
D
Arny
M
Thomas
L
Boyse
E
Human umbilical cord blood as a potential source of transplantable hematopoietic stem/progenitor cells.
Proc Natl Acad Sci USA
86
1989
3828
14
Broxmeyer
H
Hangoc
G
Cooper
S
Ribeiro
R
Graves
V
Yoder
M
Wagner
J
Vadhan-Raj
S
Benninger
L
Rubinstein
P
Broun
E
Growth characteristics and expansion of human umbilical cord blood and estimation of its potential for transplantation in adults.
Proc Natl Acad Sci USA
89
1992
4109
15
Christensen
R
Circulating pluripotent hematopoietic progenitor cells in neonates.
J Pediatr
110
1987
622
16
Abboud
M
Xu
F
LaVia
M
Laver
J
Study of early hematopoietic precursors in human cord blood.
Exp Hematol
20
1992
1043
17
Thierry
D
Hervatin
F
Traineau
R
Brossard
Y
Stark
R
Benbunan
M
Gluckman
E
Hematopoietic progenitor cells in cord blood.
Bone Marrow Transplant
9
1992
101
18
Traycoff
CM
Kosak
ST
Grigsby
S
Srour
EF
Evaluation of ex vivo expansion potential of cord blood and bone marrow hematopoietic progenitor cells using cell tracking and limiting dilution analysis.
Blood
85
1995
2059
19
Hows
J
Bradley
B
Marsh
J
Luft
T
Coutinho
L
Testa
N
Dexter
T
Growth of human umbilical-cord blood in longterm haemopoietic cultures.
Lancet
340
1992
73
20
Cairo
M
Law
P
van de Ven
C
Plunkett
J
Williams
D
Ishizawa
L
Gee
A
The in vitro effects of stem cell factor and PIXY321 on myeloid progenitor formation (CFU-GM) from immunomagnetic separated CD34+ cord blood.
Pediatr Res
32
1992
277
21
van de Ven
C
Ishizawa
L
Law
P
Cairo
M
IL-11 in combination with steel factor and G-CSF or GM-CSF significantly increases expansion of isolated CD34+ cell population from cord blood versus adult bone marrow.
Exp Hematol
23
1995
1289
22
Lu
L
Xiao
M
Shen
R-N
Grigsby
S
Broxmeyer
H
Enrichment, characterization, and responsiveness of single primitive CD34+++ human umbilical cord blood hematopoietic progenitors with high proliferative and replating potential.
Blood
81
1993
41
23
Hao
Q-L
Shah
AJ
Thiemann
FT
Smogorzewska
EM
Crooks
GM
A functional comparison of CD34+CD38− cells in cord blood and bone marrow.
Blood
86
1995
3745
24
Cardoso
AA
Li
M-L
Batard
P
Hatzfeld
A
Brown
EL
Levesque
J-P
Sookdeo
H
Panterne
B
Sansilvestri
P
Clark
SC
Hatzfeld
J
Release from quiescence of CD34+ CD38− human umbilical cord blood cells reveals their potentiality to engraft adults.
Proc Natl Acad Sci USA
90
1993
8707
25
Waller
EK
Huang
S
Terstappen
L
Changes in the growth properties of CD34+, CD38− bone marrow progenitors during human fetal development.
Blood
86
1995
710
26
Payne
TA
Traycoff
CM
Laer
J
Xu
F
Srour
EF
Abboud
MR
Phenotypic analysis of early hematopoietic progenitors in cord blood and determination of their correlation with clonogenic progenitors: Relevance to cord blood stem cell transplantation.
Bone Marrow Transplant
15
1995
187
27
Randall
TD
Lund
FE
Howard
MC
Weissman
IL
Expression of murine CD38 defines a population of long-term reconstituting hematopoietic stem cells.
Blood
87
1996
4057
28
Shah
AJ
Smogorzewska
EM
Hannum
C
Crooks
GM
Flt3 ligand induces proliferation of quiescent human bone marrow CD34+CD38− cells and maintains progenitor cells in vitro.
Blood
87
1996
3563
29
Christensen
R
Hematopoiesis in the fetus and neonate.
Pediatr Res
26
1989
531
30
Hill
H
Biochemical, structural and functional abnormalities of polymorphonuclear leukocytes in the neonate.
Pediatr Res
22
1987
375
31
Wilson
C
Immunologic basis for increased susceptibility of the neonate to infection.
J Pediatr
108
1986
1
32
Cairo
M
Therapeutic implications of dysregulated colony-stimulating factor expression in neonates.
Blood
82
1993
2269
33
Cairo
M
Suen
Y
Knoppel
E
Dana
R
Park
L
Clark
S
van de Ven
C
Sender
L
Decreased G-CSF and IL-3 production and gene expression from mononuclear cells of newborn infants.
Pediatr Res
31
1992
574
34
Cairo
M
Suen
Y
Knoppel
E
van de Ven
C
Nguyen
A
Sender
L
Decreased stimulated GM-CSF production and GM-CSF gene expression but normal numbers of GM-CSF receptors in human term newborns compared to adults.
Pediatr Res
30
1991
362
35
Suen
Y
Lee
S
Schreurs
J
Knoppel
E
Cairo
MS
Decreased macrophage colony-stimulating factor mRNA expression from activated cord versus adult mononuclear cells: Altered post transcriptional stability.
Blood
84
1994
4269
36
Chang
M
Suen
Y
Lee
S
Baly
D
Buzby
J
Knoppel
E
Wolpe
S
Cairo
MS
Transforming growth factor-β1, macrophage inflammatory protein-1α, and interleukin-8 gene expression is lower in stimulated human neonatal compared to adult mononuclear cells.
Blood
84
1994
118
37
Buzby
J
Knoppel
E
Cairo
M
Coordinate regulation of Steel factor, its receptor (Kit), and cytoadhesion molecule (ICAM-1 and ELAM-1) mRNA expression in human vascular endothelial cells of differing origins.
Exp Hematol
22
1994
122
38
Suen
Y
Chang
M
Lee
S
Buzby
J
Cairo
M
Regulation of interleukin-11 protein and mRNA expression in neonatal and adult fibroblasts and endothelial cells.
Blood
84
1994
4125
39
Chang M, Suen Y, Buzby J, Williams S, Sadick M, Cairo M: Thrombopoietin (TPO) mRNA expression by RT-PCR in neonatal endothelial cells and fibroblasts is increased compared to adults: Implications in the regulation of neonatal thrombopoiesis. Pediatr Res 37:280a, 1995 (abstr)
40
Buzby
J
Lee
SM
Van Winkle
P
DeMaria
CT
Brewer
G
Cairo
MS
Increased GM-CSF mRNA instability in cord vs adult mononuclear cells is translation dependent and associated with increased levels of A+U-rich element binding factor (AUF1).
Blood
88
1996
2889
41
Lee
SM
Suen
Y
Chang
L
Bruner
V
Qian
J
Indes
J
Knoppel
E
van de Ven
C
Cairo
MS
Decreased interleukin-12 from activated cord vs adult peripheral blood mononuclear cells and upregulation of interferon-γ, natural killer, and lymphokine-activated killer activity by IL-12 in cord blood MNC.
Blood
88
1996
945
42
Bertotto
A
Gerli
R
LanFrancone
L
Crupi
S
Arcangeli
C
Cernetti
C
Spinozzi
F
Rambotti
P
Cellular and molecular analysis of the defective response induced by anti-CD3 monoclonal antibody.
Cell Immunol
127
1990
247
43
Harris
D
Schumacher
M
Locascio
J
Besencon
F
Olson
G
DeLuca
D
Shenker
L
Bard
J
Boyse
E
Phenotypic and functional immaturity of human umbilical cord blood T lymphocytes.
Proc Natl Acad Sci USA
89
1992
10006
44
Lee
S
Suen
Y
Knoppel
E
Cairo
MS
Decreased interleukin-12 mRNA expression and protein production from activated cord vs. adult mononuclear cells: Possible role in the decreased incidence of graft-vs-host disease post cord blood transplant.
Blood
86
1995
163
45
Chin
TW
Ank
BJ
Murakami
D
Gill
M
Spina
C
Strom
S
Stiehm
E
Cytotoxic studies in human newborns: Lessened allogeneic cell-induced (augmented) cytotoxicity but strong lymphokine-activated cytotoxicity of cord monunuclear cells.
Cell Immunol
103
1986
241
46
Chin
T
Cairo
M
Lymphokine activated killer cytotoxicity in neonatal mononuclear cells: In vitro responses to tumor cell lines from pediatric solid tumors.
Pediatr Res
25
1989
156
47
Harris
DT
LoCascio
J
Besencon
FJ
Analysis of the alloreactive capacity of human umbilical cord blood: Implications for graft-versus-host disease.
Bone Marrow Transplant
14
1994
545
48
Risdon
G
Gaddy
J
Stehman
FB
Broxmeyer
HE
Proliferative and cytotoxic responses of human cord blood T lymphocytes following allogeneic stimulation.
Cell Immunol
154
1994
14
49
Risdon
G
Gaddy
J
Horie
M
Broxmeyer
HE
Alloantigen priming induces a state of unresponsiveness in human umbilical cord blood T cells.
Proc Natl Acad Sci USA
92
1995
2413
50
Deacock
SJ
Schwarer
AP
Bridge
J
Batchelor
JR
Goldman
JM
Lechler
RI
Evidence that umbilical cord blood contains a higher frequency of HLA class II specific alloreactive T cells than adult peripheral blood: A limiting dilution analysis.
Transplant
53
1992
1128
51
Roncarolo
MG
Bigler
M
Ciuti
E
Martino
S
Tovo
P-A
Immune responses by cord blood cells.
Blood Cells
20
1994
573
52
Bensussan
A
Gluckman
E
El Marsafy
S
Schiavon
V
Mansur
I-G
Dausset
J
Boumsell
L
Carosella
E
BY55 monoclonal antibody delineates within human cord blood and bone marrow lymphocytes distinct subsets mediating cytotoxic activity.
Proc Natl Acad Sci USA
91
1994
9136
53
Wagner
WE
Broxmeyer
HE
Cooper
S
Umbilical cord and placental blood hematopoietic stem cells: Collection, cryopreservation, and storage.
J Hematother
1
1992
167
54
Turner
CW
Luzins
J
Hutcheson
C
A modified harvest technique for cord blood hematopoietic stem cells.
Bone Marrow Transplant
10
1992
89
55
Harris
DT
Schumacher
MJ
Rychlik
S
Booth
A
Acevedo
A
Rubinstein
P
Bard
J
Boyse
EA
Collection, separation and cryopreservation of umbilical cord blood for use in transplantation.
Bone Marrow Transplant
13
1994
135
56
Bertolini
F
Lazzari
L
Lauri
E
Corsini
C
Castelli
C
Gorini
F
Sirchia
G
A comparative study of different procedures for the collection and banking of umbilical cord blood.
J Hematother
4
1995
29
57
Wagner
JE
Kernan
NA
Steibuch
M
Broxmeyer
HE
Gluckman
E
Allogeneic sibling umbilical-cord-blood transplantation in children with malignant and non-malignant disease.
Lancet
346
1995
214
58
Vilmer
E
Sterkers
G
Rahimy
C
Denamur
E
Elion
J
Broyart
A
Lescoeur
B
Tiercy
JM
Gerota
J
Blot
P
HLA-mismatched cord blood transplantation in a patient with advanced leukemia.
Transplantation
53
1992
1155
59
Socie
G
Gluckman
E
Carosella
E
Brossard
Y
Lafon
C
Brison
O
Search for maternal cells in human umbilical cord blood by polymerase chain reaction by amplification of two minisatellite sequences.
Blood
83
1994
340
60
Hall
JM
Lingenfelter
P
Adams
SL
Lasser
D
Hansen
JA
Bean
MA
Detection of maternal cells in human umbilical cord blood using florescence in situ hybridization.
Blood
86
1995
2829
61
Scaradavou
A
Carrier
C
Mollen
N
Stevens
C
Rubinstein
P
Detection of maternal DNA in placental/umbilical cord blood by locus specific amplification of the non-inherited maternal HLA gene.
Blood
88
1996
1494
62
Kogler
G
Gobel
U
Sombille
T
Enczmann
J
Arkestein
G
Wernet
P
Simultaneous genotypic and immunophenotypic analysis of interphase cells for the detection of contaminating maternal cells in cord blood and their respective CFU-GM and BFU-E.
J Hematother
2
1992
235
63
Newton
I
Charbord
P
Schaal
JP
Herve
P
Toward cord blood banking: Density-separation and cryopreservation of cord blood progenitors.
Exp Hematol
21
1993
671
64
Nagler
A
Peacock
M
Tantoco
M
Lamons
D
Okarma
TB
Okrongly
DA
Separation of hematopoietic progenitor cells from human umbilical cord blood.
J Hematother
2
1993
243
65
Rubinstein
P
Dobrila
L
Rosenfield
RE
Adamson
JW
Migliaccio
G
Migliaccio
AR
Taylor
PE
Stevens
CE
Processing and cryopreservation of placental/umbilical cord blood for unrelated bone marrow reconstitution.
Proc Natl Acad Sci USA
92
1995
10119
66
Wagner
JE
Rosenthal
J
Sweetman
R
Shu
XO
Davies
SM
Ramsay
NKC
Sender
L
Cairo
M
Successful transplantation of HLA-identical and HLA-1 and 2-antigen mismatched unrelated umbilical cord blood: Analysis of engraftment and acute graft-versus-host disease.
Blood
88
1996
795
67
Kurtzberg
J
Laughlin
M
Graham
ML
Smith
C
Olson
JF
Halperin
EC
Ciocci
G
Carrier
C
Stevens
CE
Rubinstein
P
Placental blood as a source of hematopoietic stem cells for transplantation into unrelated recipients.
N Engl J Med
335
1996
157
68
Laporte
J-P
Gorin
N-C
Rubinstein
P
Lesage
S
Portnoi
M-F
Barbu
V
Lopez
M
Douay
L
Najman
A
Cord-blood transplantation from an unrelated donor in an adult with chronic myelogenous leukemia.
N Engl J Med
335
1996
167
69
Gluckman E, Rocha V, Boyer Chammard A, Locatelli F, Arcese W, Souillet G: Results of cord blood transplants in Europe. Blood 88:485a, 1996 (abstr, suppl 1)
70
Rubinstein P, Carrier C, Adamson J, Migliaccio A, Berkowitz R, Kurtzberg J, Scaradavou A, Stevens C: New York Blood Center's program for unrelated placental/umbilical cord blood (PCB) transplantation: 243 transplants in the first 3 years. Blood 88:142a, 1996 (abstr, suppl 1)
71
Lambertenghi
Deliliers G
Soligo
D
Della Volpe
A
Bertolini
F
Poli
F
Romitti
L
Tagliaferri
E
Ibatici
A
Onida
F
Annaloro
C
Gattinoni
L
Sirchia
G
Unrelated mismatched cord blood transplantation in an adult with secondary AML.
Bone Marrrow Transplant
18
1996
469
72
Fernandez
MN
Regidor
C
Diez
JL
Fores
R
Sanjuan
I
Briz
M
Cabrera
R
HLA haploidentical cord blood cell transplant in a 15-year-old, 50 kg weight patient: Successful treatment for chronic myeloid leukemia after myeloid blastic transformation.
Bone Marrow Transplant
17
1996
1175
73
Balduzzi
A
Gooley
T
Anasetti
C
Sanders
JE
Martin
PJ
Petersdorf
EW
Appelbaum
FR
Buckner
CD
Matthews
D
Storb
R
Sullivan
KM
Hansen
JA
Unrelated donor marrow transplantation in children.
Blood
86
1995
3247
74
Slone V, Abu-Ghosh A, Goldman S, Murphy L, Sender LS, van de Ven C, Cairo MS: Delayed platelet, but comparable myeloid engraftment following unrelated cord blood transplantation: Decreased megakaryocytic lineage (CD34+/CD41+) stem cells in cord blood. Blood 88:114a, 1996 (abstr, suppl 1)
75
Casper J, Camitta B, Baxter-Lowe L, Bunin N, Lawton C, Murray K, Hunter J, Pietryga D, Garbrecht F, Keever Taylor C, Drobyski W, Horowitz M, Flomenberg N, Ash R: Unrelated bone marrow door transplants for children with leukemia or myelodysplasia. Blood 85:2354a, 1995 (abstr, suppl 1)
76
Parkman
R
The application of bone marrow transplantation to the treatment of genetic diseases.
Science
232
1986
1373
77
Karlsson
S
Treatment of genetic defects in hematopoietic cell function by gene transfer.
Blood
78
1991
2481
78
Culver
KW
Anderson
WF
Blaese
RM
Lymphocyte gene therapy.
Hum Gene Ther
2
1991
107
79
Rosenberg
SA
Aebersold
P
Cornetta
K
Kasid
A
Morgan
RA
Moen
R
Karson
EM
Lotze
MT
Yang
JC
Topalian
SL
Merino
MJ
Culver
K
Miller
AD
Blaese
RM
Anderson
WF
Gene transfer into humans — Immunotherapy of patients with advanced melanoma, using tumor-infiltrating lymphocytes modified by retroviral gene transduction.
N Engl J Med
323
1990
570
80
Ekhterae
D
Crumbleholme
T
Karson
E
Harrison
MR
Anderson
WF
Zanjani
ED
Retroviral vector-mediated transfer of the bacterial neomycin resistance gene into fetal and adult sheep and human hematopoietic progenitors in vitro.
Blood
75
1990
365
81
Bodine
DM
Moritz
T
Donahue
RE
Luskey
BD
Kessler
SW
Martin
DIK
Orkin
SH
Nienhuis
AW
Williams
DA
Long-term in vivo expression of a murine adenosine deaminase gene in Rhesus monkey hematopoietic cells of multiple lineages after retroviral mediated gene transfer into CD34+ bone marrow cells.
Blood
82
1993
1975
82
Ward
M
Richardson
C
Pioli
P
Smith
L
Podda
S
Goff
S
Hesdorffer
C
Bank
A
Transfer and expression of the human multiple drug resistance gene in human CD34+ cells.
Blood
84
1994
1408
83
Li
F
Linton
GF
Sekhsaris
S
Whiting-Theobald
N
Katkin
JP
Gallin
JI
Malech
HL
CD34+ peripheral blood progenitors as a target for genetic correction of the two flavocytochrome b558 defective forms of chronic granulomatous disease.
Blood
84
1994
53
84
Al-Lebban
ZS
Henry
JM
Jones
JB
Eglitis
MA
Anderson
WF
Lothrop
CD Jr
Increased efficiency of gene transfer with retroviral vectors in neonatal hematopoietic progenitor cells.
Exp Hematol
18
1990
180
85
Brenner
MK
Rill
DR
Holladay
MS
Heslop
HE
Moen
RC
Buschle
M
Krance
RA
Santana
VM
Anderson
WF
Ihle
JN
Gene marking to determine whether autologous marrow infusion restores long-term haemopoiesis in cancer patients.
Lancet
342
1993
1134
86
Nolta
JA
Hanley
MB
Kohn
DB
Sustained human hematopoiesis in immunodeficient mice by cotransplantation of marrow stroma expressing human interleukin-3: Analysis of gene transduction of long-lived progenitors.
Blood
83
1994
3041
87
Kohn
DB
Weinberg
KI
Nolta
JA
Heiss
LN
Lenarsky
C
Crooks
GM
Hanley
ME
Annett
G
Brooks
JS
El-Khoureiy
A
Lawrence
K
Wells
S
Moen
RC
Bastian
J
Williams-Herman
DE
Elder
M
Wara
D
Bowen
T
Hershfield
MS
Mullen
CA
Blaese
RM
Parkman
R
Engraftment of gene-modified umbilical cord blood cells in neonates with adenosine deaminase deficiency.
Nat Med
1
1995
1017
88
Proposed Approach to Regulation of Cellular and Tissue-Based Products. United States Food and Drug Administration, Docket No. 97N-0068, February 28, 1997
89
Rubinstein
P
Rosenfield
RE
Adamson
JW
Stevens
CE
Stored placental blood for unrelated bone marrow reconstitution.
Blood
81
1993
1679
90
Gluckman
E
Wagner
J
Hows
J
Kernan
N
Bradley
B
Broxmeyer
HE
Cord blood banking for haematopoietic stem cell transplantation: An International Cord Blood Transplant Registry.
Bone Marrow Transplant
11
1993
199
91
Gluckman E: European organization for cord blood banking, in Bull BS (ed): Blood Cells, vol 20. New York, NY, Springer-Verlag, 1995, p 601
92
Bertolini
F
Battaglia
M
de Iulio
C
Sirchia
G
Rosti
L
Placental blood collection: Effects on newborns.
Blood
86
1995
3361
93
Chang
RS
Seto
DSY
Perinatal infection by Epstein-Barr virus.
Lancet
2
1979
201
94
Stagno
S
Pass
RF
Cloud
G
Britt
WJ
Henderson
RE
D WP
Veren
DA
Page
F
Alford
CA
Primary cytomegalovirus infection in pregnancy. Incidence, transmission to fetus and clinical outcome.
JAMA
256
1986
1904
Sign in via your Institution