• Pregnancy recalls short-lived immunity against TAAs mimicking antileukemic responses after allogeneic stem cell transplantation.

Donor-derived immunity against tumor-associated antigens (TAAs) may exert selective antileukemic activity reprieving the allogeneic recipient from graft-versus-host disease. As TAAs are highly expressed in placental tissues we hypothesized that pregnancy could drive respective immunity in healthy individuals. Thus, we investigated the frequency and level of immune responses against clinically relevant TAAs in 114 blood donors and 44 women during their first pregnancy. Quantitative reverse-transcription polymerase chain reaction was employed to detect low levels of interferon-γ after primary peptide stimulation of CD8+ T lymphocytes. In blood donors, primary immune responses of low and/or high avidity were found against WT1 (15%), MUC1 (14%), PRAME (7%), and HER2/neu (5%) and exerted killing functions against leukemic cells. Men had higher responses than women, likely due to gonadal cancer-testis-antigen expression. Interestingly, a history of prior delivery was not associated with increased responses, whereas the strongest responses during pregnancy were found in early trimesters to disappear after delivery. This boost and loss of TAA-specific immunity suggests that virtually every donor harbors the potential to mount antileukemic immune responses in a recipient. However, in the absence of the driving target and a permissive environment, they are short-lived and thus require supplemental strategies such as vaccination or immunomodulation to facilitate their persistence.

The graft-versus-leukemia (GVL) effect is the central component of the hematopoietic stem cell allograft’s ability to cure hematologic malignancies.1-3  Donor-derived T lymphocytes targeting minor histocompatibility antigens such as Y-chromosomal antigens in female-into-male transplants are well known to contribute largely to this strong immunologic effect, which may also cause graft-versus-host disease (GVHD) when the target antigen’s expression is not restricted to the hematologic site.4-9  Meanwhile, it has become evident that in addition to recognition of hematologically restricted minor histocompatibility antigens, donor T lymphocytes can exert selective GVL effects by recognition of tumor-associated antigens (TAAs) on leukemic tissues.10-12  The efficacy of these TAA-specific immune responses particularly depends on the level of antigen expression in the target tissue and the presence of a proinflammatory immune environment allowing donor-derived T lymphocytes of lower avidity to overcome peripheral tolerance and to attack the malignant cells in a selective manner.13,14 

Rezvani et al first described the detection of immune responses against Wilms tumor protein 1 (WT1) in a smaller group of healthy stem cell donors and the expansion of WT1-specific T lymphocytes in the host.12  However, so far little is known about the exact frequency, origin, and functionality of TAA-directed immune responses in healthy donors awaiting their transfer into the host where an optimal immunologic environment and proper target expression facilitate their therapeutic potential.11,15,16  As it is evident that women can be immunized by pregnancies with male infants17,18  and transfer this immunity against Y-chromosomal–encoded antigens to male allograft recipients,19,20  we wanted to explore the possibility of pregnancy inducing immune responses against TAAs in healthy women, too. Indeed, several TAAs with clinical relevance in tumor and/or transplant immunotherapy such as human epidermal growth factor receptor 2 (HER2/neu), mucin 1 (MUC1), preferentially expressed antigen of melanoma (PRAME), and WT1 are highly expressed in placental tissues.21-24  Thus, we investigated the effects of pregnancy and gender on the frequency of immune responses against these TAAs in a large, prospectively designed cross-sectional study in 114 volunteer blood donors completed by longitudinal analyses in 44 first-time pregnant women.

Study design and subjects

Based on the preliminary experience from Rezvani et al,12  we hypothesized that 20% (p = 0.2) of HLA-A*02:01-positive healthy individuals could carry positive immune responses against WT1 and assumed that pregnancy increases this frequency.

In a cross-sectional analysis in volunteer blood donors (study group I), 3 subgroups should be analyzed including nulligravidous women, primi- or multiparous women, and men. Taking the potential effects of pregnancy into account, we hypothesized that nulligravidous women and men have a lower frequency (p1 = 0.1) and women with a history of delivery have a higher frequency (p2 = 0.4) of positive immune responses. Using a 2-sided χ2 test with a power of 80% (β = 0.2) and a level of significance of 95% (α = 0.05), at least 38 volunteers needed to be included for each subgroup to be able to show significant differences.

In a longitudinal analysis in healthy women during their first pregnancy (study group II), 3 time points were to be analyzed including the baseline at the first to second trimester, 1 to 4 days after delivery, and 2 to 3 months after delivery. To show significant differences between the time points, a paired χ2 test according to McNemar was applied to test the hypothesis that a conversion of immune responses from negative to positive results appears in the course of pregnancy. Using the parameters as stated above, at least 38 volunteers needed to be included for this study group. To compensate for expected loss of follow-up or the fact that sampling may not be possible at every time point, we decided to recruit at least 44 women at baseline. After an ethical amendment, additional blood samples should be drawn after completion of nursing where possible to extend the time period after pregnancy and consider the effects of alterations in peripheral blood counts as well as hormonal changes after delivery and nursing.

The original scientific study protocol and further amendments were approved by the local Ethical Committee of the Medical Faculty, University of Würzburg, Germany. All volunteers provided their written informed consent, in accordance with the Declaration of Helsinki.

Cell processing

Peripheral blood mononuclear cells (PBMCs) from healthy platelet donors were isolated from leukoreduction system chambers (Trima Accel apheresis apparatus, Terumo BCT, Lakewood, CO)25  or directly from venous blood by density-gradient centrifugation using LSM 1077 lymphocyte separation medium (PAA Laboratories GmbH, Cölbe, Germany). Additionally, 10 mL venous blood was drawn from pregnant women to obtain serum.

Peptide synthesis

Peptides were prepared by JPT Peptide Technologies (Berlin, Germany) to a minimum purity of 95%. The identity of each peptide was confirmed by mass spectral analysis. The following HLA-A*02:01–restricted peptides were used in this study as described elsewhere12,26-28 : CMV-pp65495-503 (NLVPMVATV), gp100209-217(210M) (IMDQVPFSV), HER2/neu369-377 (KIFGSLAFL), MUC1950-958 (STAPPVHNV), PRAME300-309 (ALYVDSLFFL), and WT1126-134 (RMFPNAPYL).

Restimulation of antigen-specific T lymphocytes

CD8+ T lymphocytes were purified from PBMCs using a commercially available kit (Dynabeads CD8 Positive Isolation Kit; Life Technologies, Darmstadt, Germany). For every condition, 1 × 106 CD8+ T lymphocytes were resuspended in RPMI 1640 (Life Technologies) supplemented with 10% (vol/vol) heat-inactivated human AB serum (HABS; PAA Laboratories) and rested overnight in 96-well round bottom plates in a humidified incubator at 37°C and 5% CO2. The next day, 1 × 106 T2 cells (ATCC CRL-199229 ) were pulsed with the respective peptides (peptide concentration of 0.1 and 10 µmol/L, as described elsewhere12 ) and incubated for 2 hours in serum-free RPMI 1640. After irradiation with a total dose of 30 Gy, peptide-pulsed T2 cells were washed once and coincubated with CD8+ T lymphocytes for 3 hours.

qRT-PCR

Interferon-γ (IFN-γ) messenger RNA (mRNA) expression upon antigen-specific stimulation was analyzed using quantitative reverse-transcription polymerase chain reaction (qRT-PCR). IFN-γ mRNA expression was normalized to CD8 mRNA levels and expressed as relative expression as compared with the stimulation with the irrelevant melanoma antigen Glycoprotein 100 (gp100). Total RNA was isolated using TRIzol reagent according to the manufacturer’s recommendations (Life Technologies). RNA integrity was verified using the Experion automated electrophoresis station from Bio-Rad Laboratories (Munich, Germany). Complementary DNA was synthesized from 1 µg total RNA using the iScript cDNA synthesis kit (Bio-Rad Laboratories). The following protocol was run on the thermal cycler Primus 96 (Peqlab Biotechnologie, Erlangen, Germany): 5 minutes at 25°C, 30 minutes at 42°C, and 5 minutes at 85°C. The qRT-PCR reactions were performed on a CFX96 real-time PCR system (Bio-Rad Laboratories) operated by CFX Manager Software 2.0 (Bio-Rad Laboratories). Thermal cycler parameters included 5 minutes at 95°C, 40 cycles at 95°C for 15 seconds, 60°C for 1 minute, and 72°C for 5 minutes. Reactions were prepared using the iScript Supermix ready-to-use solution (Bio-Rad Laboratories) with optimal concentration of reaction components. Primers and probes were synthesized by Eurofins MWG Operon, Ebersberg, Germany. Primer and probe sequences were used as described by Rezvani et al.12  Purified PCR products were sequenced to confirm their accuracy (SeqLab, Göttingen, Germany). All PCR reactions were performed in duplicates and reported as mean ± standard deviation.

Dextramer staining

PBMCs were stained using commercially available allophycocyanin (APC)-conjugated HLA-A*02:01 dextramer molecules (Immudex, Copenhagen, Denmark) loaded with the respective antigens. Briefly, cells were incubated in phosphate-buffered saline (Life Technologies) supplemented with 10% (vol/vol) heat-inactivated fetal calf serum (Sigma-Aldrich Chemie, Schnelldorf, Germany) for 20 minutes on ice. Cells were washed once and stained with the respective APC-conjugated dextramer for 30 minutes at room temperature (RT). Cells were washed and additionally stained with fluorescein isothiocyanate–conjugated anti-CD3 (SK7) and PerCP-conjugated anti-CD8 (SK1; both from BD Biosciences, Heidelberg, Germany) antibodies for 15 minutes at RT. Cells with the forward and side light scatter properties of lymphocytes were analyzed using a FACSCalibur flow cytometer (Becton-Dickinson, Heidelberg, Germany). Data analysis was performed using FlowJo 7.6.1 software (Tree Star, Ashland, OR).

Expansion of antigen-specific T lymphocytes

For each condition, thawed or freshly isolated 1 × 107 PBMCs were seeded on day −1 in 24-well plates at a density of 2.5 × 106 cells/mL in cytotoxic T lymphocyte (CTL) medium containing RPMI 1640 supplemented with 10% (vol/vol) heat-inactivated HABS, penicillin (100 U/mL; Life Technologies), streptomycin (100 µg/mL; Life Technologies), 2 mmol/L l-glutamine (Sigma-Aldrich), 12.5 mmol/L HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; Sigma-Aldrich), and 50 µmol/L 2-mercaptoethanol (Sigma-Aldrich). On day 0, cells were peptide-pulsed (0.1 and 10 µmol/L, respectively) and dextramer staining was performed as described above. On day 3, PBMCs were seeded in 12-well plates at a density of 2.5 × 106 cells/mL and restimulated with autologous peptide-pulsed, irradiated PBMCs and interleukin-2 (IL-2), IL-7, and IL-15 (all from Miltenyi Biotec, Bergisch Gladbach, Germany) at a final concentration of 30 U/mL (IL-2) and 5 ng/mL (IL-7 and IL-15), respectively. On days 6 and 9, PBMCs were stimulated with autologous peptide-pulsed, irradiated PBMCs and the cytokines mentioned above. On day 14, 1 batch of the cells was restimulated with Dynabeads Human T-Activator CD3/CD28 (Life Technologies) according to the manufacturer’s instructions. On days 16 (7 days after last peptide stimulation) and 21 (7 days after bead restimulation), cells were harvested, stained with dextramers, and functionally analyzed using CD107a/b degranulation assay.

CD107a/b degranulation assay

A total of 1 × 106 T2 cells or K562-A2 cells (kindly provided by Professor Wolfgang Herr, University of Regensburg, Germany30 ) were peptide-pulsed and incubated for 2 hours in serum-free RPMI 1640. Cells were washed once and transferred to 96-well round bottom plates containing 1 × 106 expanded antigen-specific T lymphocytes in 200 µL RPMI 1640 supplemented with 10% (vol/vol) heat-inactivated HABS. Positive control wells were stimulated with 250 ng/mL phorbol 12-myristate 13-acetate (Sigma-Aldrich) and 10 µg/mL ionomycin (Sigma-Aldrich). Fluorescein isothiocyanate–conjugated anti-CD107a (H4A3) and anti-CD107b (H4B4; both from BD Biosciences) antibodies were added simultaneously to all wells. After 1 hour, monensin (BD GolgiStop, BD Biosciences) was added to all wells and the cells were incubated for 4 hours. Cells were stained with APC-conjugated anti-CD3 (SK7) and PerCP-conjugated anti-CD8 (SK1; both from BD Biosciences) antibodies for 15 minutes at RT and analyzed by flow cytometry.

IFN-γ ELISPOT assay

Freshly isolated or thawed PBMCs were resuspended in CTL medium and seeded in 24-well plates at a density of 1 × 107 cells/mL for 48 hours according to the “Restore” protocol.31  IFN-γ enzyme-linked immunosorbent spot assay (ELISPOT) assay was performed using the ELISpotPLUS for Human IFNγ Kit (Mabtech, Hamburg, Germany) according to the manufacturer’s instructions.

Peptide-pulsed and irradiated T2 cells served as stimulator cells. Positive control wells were stimulated with phorbol 12-myristate 13-acetate (250 ng/mL) and ionomycin (10 µg/mL), and negative control wells were mock stimulated with medium. Spots were counted using ImmunoSpot Series 4.0 analyzer and ImmunoSpot 4.0.16 software (CTL-Europe, Bonn, Germany).

Peripheral blood counts

For basic hematologic blood analysis, fractions of drawn whole-blood samples were analyzed using the KX-21N apparatus (Sysmex Germany, Norderstedt, Germany) used for clinical purposes as well.

Determination of hormone levels

Quantitative hormone levels for β human chorionic gonadotropin (β-hCG), estradiol, progesterone, and prolactin were measured by our central laboratory using an automated electrochemiluminescence immunoassay method.

Statistical analysis

Normal distribution was evaluated using the D’Agostino-Pearson omnibus K2 normality test. Continuous variables with normal distribution are presented as means with standard deviation and continuous variables with non-Gaussian distribution as median values with ranges. Categorical variables are presented as absolute numbers and respective percentage. Two groups with normal distribution were compared using nonpaired t tests and 2 groups with skew distribution using the Mann-Whitney U test. Fisher’s exact test was applied for evaluation of differences in frequencies between subgroups. Kruskal-Wallis 1-way analysis of variance with Dunn’s multiple comparison was performed to compare >2 subgroups. Spearman’s rank correlation test was employed for correlation analyses. P < .05 was considered significant. Statistical analyses and graphs were conducted applying Prism 5.04 software (GraphPad Software, San Diego, CA).

Cross-sectional analysis in volunteer blood donors

Subject characteristics.

Between March 2010 and June 2011, 193 volunteer blood donors (118 women and 75 men) with a known A*02 HLA subtype were screened for eligibility in the cross-sectional study group I after providing written informed consent. Of these, 180 were confirmed to be HLA-A*02:01 positive. Finally, PBMCs were collected from 124 consecutively recruited donors, of whom 10 dropped out due to the quality of collected PBMCs being below the required level, leaving 114 donors in total and 38 per subgroup for final analysis as originally planned. Their characteristics are displayed in Table 1. Sample acquisition was closed in December 2011.

Table 1

Characteristics of 114 HLA-A*02:01+ volunteer blood donors (cross-sectional study group I)

All donors (n = 114)Nulligravidous women (n = 38)Primi-/ multiparous women* (n = 38)Men (n = 38)
Age, y     
 Median 39 28 46 41 
 Range 21-63 21-53 28-63 21-56 
Serologic CMV status     
 Positive 33 10 14 
 Negative 73 27 17 29 
 Not available 
Receipt of a prior blood transfusion     
 Yes 
 No 112 38 37 37 
Number of pregnancies (women only)     
 0 38 38 — 
 1 10 10 — 
 2 18 18 — 
 3 — 
 4 — 
 5 — 
Current oral contraception (women only)     
 Yes 28 21 — 
 No 48 17 31 — 
Postmenopause (women only)     
 Yes — 
 No 69 37 32 — 
All donors (n = 114)Nulligravidous women (n = 38)Primi-/ multiparous women* (n = 38)Men (n = 38)
Age, y     
 Median 39 28 46 41 
 Range 21-63 21-53 28-63 21-56 
Serologic CMV status     
 Positive 33 10 14 
 Negative 73 27 17 29 
 Not available 
Receipt of a prior blood transfusion     
 Yes 
 No 112 38 37 37 
Number of pregnancies (women only)     
 0 38 38 — 
 1 10 10 — 
 2 18 18 — 
 3 — 
 4 — 
 5 — 
Current oral contraception (women only)     
 Yes 28 21 — 
 No 48 17 31 — 
Postmenopause (women only)     
 Yes — 
 No 69 37 32 — 
*

Women were not pregnant at time of blood donation.

Postmenopause was defined as last menstrual bleeding at least 12 months before study inclusion.

Immune levels and frequencies against TAAs.

Of the analyzed 114 healthy volunteer donors 32% (n = 37; 11 nulligravidous women, 12 primi- or multiparous women, and 14 men) showed positive immune responses against at least 1 TAA including HER2/neu, MUC1, PRAME, and WT1 in their CD8+ T lymphocytes using a qRT-PCR–based IFN-γ detection assay. This included both low and high avidity immune responses as suggested by the IFN-γ production following stimulation using 2 different peptide concentrations (0.1 and 10 µmol/L). The exact frequencies in the different subgroups are displayed in Table 2, whereas individual immune levels of each donor are displayed in Figure 1. Comparing nulligravidous and primi- or multiparous women, there was no significant difference regarding the levels of immune responses. However, men showed more frequent positive and higher levels of immune responses as compared with women (Figure 1; Table 2). Using the Mann-Whitney U test, this difference in immune levels between women and men was significant for HER2/neu and WT1 solely when using 10 µmol/L peptide concentrations for stimulation as depicted in Figure 2.

Table 2

Frequency of CD8+ T-cell IFN-γ immune responses against TAAs and CMV in 114 HLA-A*02:01+ volunteer blood donors (cross-sectional study group I)

All donorsNulligravidous womenPrimi-/multiparous womenMen
n%n%n%n%
HER2/neu         
 0.1 µmol/L 3/112 0/37 1/38 2/37 
 10 µmol/L 4/110 0/37 1/36 3/37 
 0.1 and/or 10 µmol/L 6/114 0/38 2/38 4/38 11 
MUC1         
 0.1 µmol/L 8/109 3/37 3/37 2/35 
 10 µmol/L 9/110 3/37 3/36 3/37 
 0.1 and/or 10 µmol/L 16/114 14 6/38 16 6/38 16 4/38 11 
PRAME         
 0.1 µmol/L 3/113 0/37 0/38 3/38 
 10 µmol/L 7/111 2/37 0/36 5/38 13 
 0.1 and/or 10 µmol/L 8/114 2/38 0/38 6/38 16 
WT1         
 0.1 µmol/L 11/114 10 4/38 11 4/38 11 3/38 
 10 µmol/L 9/112 3/38 2/36 4/38 11 
 0.1 and/or 10 µmol/L 17/114 15 5/38 13 6/38 16 6/38 16 
CMV         
 10 µmol/L 42/111 38 8/37 22 20/37 54 14/37 38 
All donorsNulligravidous womenPrimi-/multiparous womenMen
n%n%n%n%
HER2/neu         
 0.1 µmol/L 3/112 0/37 1/38 2/37 
 10 µmol/L 4/110 0/37 1/36 3/37 
 0.1 and/or 10 µmol/L 6/114 0/38 2/38 4/38 11 
MUC1         
 0.1 µmol/L 8/109 3/37 3/37 2/35 
 10 µmol/L 9/110 3/37 3/36 3/37 
 0.1 and/or 10 µmol/L 16/114 14 6/38 16 6/38 16 4/38 11 
PRAME         
 0.1 µmol/L 3/113 0/37 0/38 3/38 
 10 µmol/L 7/111 2/37 0/36 5/38 13 
 0.1 and/or 10 µmol/L 8/114 2/38 0/38 6/38 16 
WT1         
 0.1 µmol/L 11/114 10 4/38 11 4/38 11 3/38 
 10 µmol/L 9/112 3/38 2/36 4/38 11 
 0.1 and/or 10 µmol/L 17/114 15 5/38 13 6/38 16 6/38 16 
CMV         
 10 µmol/L 42/111 38 8/37 22 20/37 54 14/37 38 
Figure 1

Immune responses against TAAs in 114 HLA-A*02:01+ volunteer blood donors (cross-sectional study group I). CD8+ isolated T lymphocytes were coincubated with peptide-loaded irradiated T2 cells for 3 hours using 2 different peptide concentrations (0.1 and 10 µmol/L). Total RNA was isolated and qRT-PCR was performed. IFN-γ mRNA expression was normalized to CD8 mRNA levels and expressed as relative expression compared with stimulation with the irrelevant antigen gp100. (A) Peptide concentration of 0.1 µmol/L. (B) Peptide concentration of 10 µmol/L. The dashed lines indicate the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup.

Figure 1

Immune responses against TAAs in 114 HLA-A*02:01+ volunteer blood donors (cross-sectional study group I). CD8+ isolated T lymphocytes were coincubated with peptide-loaded irradiated T2 cells for 3 hours using 2 different peptide concentrations (0.1 and 10 µmol/L). Total RNA was isolated and qRT-PCR was performed. IFN-γ mRNA expression was normalized to CD8 mRNA levels and expressed as relative expression compared with stimulation with the irrelevant antigen gp100. (A) Peptide concentration of 0.1 µmol/L. (B) Peptide concentration of 10 µmol/L. The dashed lines indicate the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup.

Close modal
Figure 2

Immune responses against HER2/neu and WT1 in 76 HLA-A*02:01+ women and 38 HLA-A*02:01+ men (cross-sectional study group I). IFN-γ mRNA expression upon antigen-specific stimulation with the TAAs HER2/neu and WT1 in nulligravidous as well as primi- or multiparous women compared with men. The dashed line indicates the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup. Closed triangles represent women, and open triangles represent men.

Figure 2

Immune responses against HER2/neu and WT1 in 76 HLA-A*02:01+ women and 38 HLA-A*02:01+ men (cross-sectional study group I). IFN-γ mRNA expression upon antigen-specific stimulation with the TAAs HER2/neu and WT1 in nulligravidous as well as primi- or multiparous women compared with men. The dashed line indicates the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup. Closed triangles represent women, and open triangles represent men.

Close modal

Functional analysis of immune responses against TAAs.

A selection of donors showing positive immune responses in the qRT-PCR-based assay were tested again using the ELISPOT technique confirming the previously described results. Two representative experiments are displayed in Figure 3. Furthermore, the ability of WT1-specific CD8+ T lymphocytes to expand in vitro upon peptide stimulation is shown in Figure 4 in 2 representative donors. CD8+ T lymphocytes were technically depicted using WT1-specific multimers for flow cytometry showing that the frequency of WT1-specfic immune responses increased from 0.034% to 0.620% after 21 days in one subject and from 0.069 to 0.741% after 16 days in another subject. These experiments reflect a 10 to 20-fold expansion of WT1-specific CD8+ T lymphocytes. Finally, the ability of donor-derived CD8+ T lymphocytes to kill WT1-positive target cells was shown against WT1-expressing leukemic K562-A2 cells and peptide-loaded T2 cells using a CD107a/b-based degranulation assay. Killing could be detected after using 0.1 and 10 µmol/L peptide concentrations, suggesting that low- and high-avidity CD8+ T lymphocytes carry the ability to lyse HLA-A*02:01–positive target cells (Figure 5).

Figure 3

IFN-γ ELISPOT assay results. IFN-γ ELISPOT assay was performed using a commercially available kit according to the manufacturer’s instructions. PBMCs were resuspended in CTL medium and incubated for 48 hours (“Restore” protocol). Peptide-pulsed and irradiated T2 cells served as stimulator cells. Each error bar represents the standard deviation. (A) Representative subject UPN T64. (B) Representative subject UPN T14.

Figure 3

IFN-γ ELISPOT assay results. IFN-γ ELISPOT assay was performed using a commercially available kit according to the manufacturer’s instructions. PBMCs were resuspended in CTL medium and incubated for 48 hours (“Restore” protocol). Peptide-pulsed and irradiated T2 cells served as stimulator cells. Each error bar represents the standard deviation. (A) Representative subject UPN T64. (B) Representative subject UPN T14.

Close modal
Figure 4

In vitro T-cell expansion. Two batches of PBMCs from each donor were peptide-stimulated (10 µmol/L) over a course of 9 days. The first batch was analyzed on day 16 without further restimulation. The second batch was restimulated with CD3/CD28-coated beads on day 14 and analyzed on day 21. Cells were analyzed using dextramer staining on day 0 (ex vivo), day 16 (first batch), and day 21 (second batch). After gating cells with the forward and side light scatter properties of lymphocytes, dextramer-positive cells were measured as percentage of CD3/CD8-positive cells. Empty dextramer was used as negative control; CMV-pp65 was used as positive control. (A) Fluorescence-activated cell sorter (FACS) dot plots of representative female subject UPN T6. (B) FACS dot plots of representative male subject UPN T14.

Figure 4

In vitro T-cell expansion. Two batches of PBMCs from each donor were peptide-stimulated (10 µmol/L) over a course of 9 days. The first batch was analyzed on day 16 without further restimulation. The second batch was restimulated with CD3/CD28-coated beads on day 14 and analyzed on day 21. Cells were analyzed using dextramer staining on day 0 (ex vivo), day 16 (first batch), and day 21 (second batch). After gating cells with the forward and side light scatter properties of lymphocytes, dextramer-positive cells were measured as percentage of CD3/CD8-positive cells. Empty dextramer was used as negative control; CMV-pp65 was used as positive control. (A) Fluorescence-activated cell sorter (FACS) dot plots of representative female subject UPN T6. (B) FACS dot plots of representative male subject UPN T14.

Close modal
Figure 5

CD107a/b-degranulation assay. PBMCs were peptide-stimulated over a course of 9 days. The first analysis was performed on day 16 without further restimulation; the second analysis was performed on day 21 after 7 days of restimulation with CD3/CD28-coated beads. After gating cells with the forward and side light scatter properties of lymphocytes, the degranulation was measured as percentage of CD107a/b-positive cells of CD3/CD8-positive cells. gp100 was used as negative control; CMV-pp65 was used as positive control. Two different cell lines were used as targets. (A) FACS dot plots of 2 representative subjects (UPN T6 and UPN T46) for T2 cells as targets. (B) FACS dot plots of 2 representative subjects (UPN T14 and UPN T46) for K562-A2 cells as targets.

Figure 5

CD107a/b-degranulation assay. PBMCs were peptide-stimulated over a course of 9 days. The first analysis was performed on day 16 without further restimulation; the second analysis was performed on day 21 after 7 days of restimulation with CD3/CD28-coated beads. After gating cells with the forward and side light scatter properties of lymphocytes, the degranulation was measured as percentage of CD107a/b-positive cells of CD3/CD8-positive cells. gp100 was used as negative control; CMV-pp65 was used as positive control. Two different cell lines were used as targets. (A) FACS dot plots of 2 representative subjects (UPN T6 and UPN T46) for T2 cells as targets. (B) FACS dot plots of 2 representative subjects (UPN T14 and UPN T46) for K562-A2 cells as targets.

Close modal

Longitudinal analysis in first-time pregnant women

Subject characteristics.

Between March 2010 and November 2011, 93 women in their first pregnancy were screened for eligibility in the longitudinal analysis after providing written informed consent. Of these, 50 women (54%) were confirmed to be HLA-A*02:01-positive and PBMCs were collected from 47 women, 3 of whom dropped out due to a violation of inclusion criteria (1 HLA subtype was analyzed incorrectly and 2 women had already a history of a prior pregnancy). Finally, 44 HLA-A*02:01–positive first-time pregnant women participated in this prospectively planned longitudinal study group II. Their characteristics are displayed in Table 3. Acquisition of blood samples was terminated in May 2013.

Table 3

Characteristics of 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II)

First to second trimester (baseline) n = 43*1 to 4 d after delivery n = 34*2 to 3 mo after delivery n = 34*After completion of nursing n = 15
Age, y     
 Median 28 — — — 
 Range 19-39 — — — 
Time point     
 Median 22 gestational weeks 1.5 d postpartum 54.5 d postpartum 478 d postpartum 
 Range 11-34 gestational weeks 0-4 d postpartum 43-92 d postpartum 313-669 d postpartum 
First to second trimester (baseline) n = 43*1 to 4 d after delivery n = 34*2 to 3 mo after delivery n = 34*After completion of nursing n = 15
Age, y     
 Median 28 — — — 
 Range 19-39 — — — 
Time point     
 Median 22 gestational weeks 1.5 d postpartum 54.5 d postpartum 478 d postpartum 
 Range 11-34 gestational weeks 0-4 d postpartum 43-92 d postpartum 313-669 d postpartum 

A total of 44 women participated in this longitudinal study. None of the women received blood transfusions during the course of the study.

*

Blood samples could not be drawn at each time point due to various reasons (loss of follow-up or contact, refusal).

After the ethical amendment, blood could be drawn in 15 women at an additional time point after completion of nursing.

Immune levels and frequencies against TAAs.

The course of CD8-mediated immune levels against the TAAs HER2/neu, MUC1, PRAME, and WT1 as measured by IFN-γ qRT-PCR after peptide stimulation is depicted in Figure 6. Here, it is shown that medians of immune responses against the different TAAs decreased over time. The highest levels were found at the first time point (first to second trimester) declining after delivery and reaching the lowest levels after completion of nursing (Figure 6). Using the 1-way analysis of variance, differences in immune responses against HER2/neu and WT1 were found to be significantly different between the first and the last time points (Figure 6). Looking at frequencies of positive immune responses against TAAs in this longitudinal analysis, this general decline over time could be confirmed for MUC1, PRAME, and WT1, but not for HER2/neu, where positive responses were rare (Table 4). For MUC1, PRAME, and WT1, the highest frequencies were found in the first to second trimester, declining after delivery and disappearing after completion of nursing (Table 4).

Figure 6

Immune responses against TAAs in 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II). (A) Peptide concentration of 0.1 µmol/L. (B) Peptide concentration of 10 µmol/L. The dashed lines indicate the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup.

Figure 6

Immune responses against TAAs in 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II). (A) Peptide concentration of 0.1 µmol/L. (B) Peptide concentration of 10 µmol/L. The dashed lines indicate the threshold for positive immune responses (relative expression level of 2.0). Bars represent the median of a subgroup.

Close modal
Table 4

Frequency of CD8+ T-cell IFN-γ immune responses against TAAs and CMV in 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II)

First to second trimester1 to 4 d after delivery2 to 3 mo after deliveryAfter completion of nursing
n%n%n%n%
HER2/neu         
 0.1 µmol/L 0/39 1/31 0/34 1/13 
 10 µmol/L 0/36 0/24 0/26 0/13 
 0.1 and/or 10 µmol/L 0/43 1/31 0/34 1/14 
MUC1         
 0.1 µmol/L 4/36 11 2/31 1/34 0/11 
 10 µmol/L 2/32 0/20 0/24 0/11 
 0.1 and/or 10 µmol/L 6/43 14 2/31 1/34 0/12 
PRAME         
 0.1 µmol/L 2/37 1/31 2/33 0/12 
 10 µmol/L 1/33 2/20 10 1/25 0/13 
 0.1 and/or 10 µmol/L 3/43 2/31 2/33 0/13 
WT1         
 0.1 µmol/L 11/41 27 3/31 10 1/34 0/14 
 10 µmol/L 7/39 17 1/29 0/32 0/14 
 0.1 and/or 10 µmol/L 13/43 30 3/31 10 1/34 0/14 
CMV         
 10 µmol/L 12/23 52 6/21 29 15/30 50 8/11 73 
First to second trimester1 to 4 d after delivery2 to 3 mo after deliveryAfter completion of nursing
n%n%n%n%
HER2/neu         
 0.1 µmol/L 0/39 1/31 0/34 1/13 
 10 µmol/L 0/36 0/24 0/26 0/13 
 0.1 and/or 10 µmol/L 0/43 1/31 0/34 1/14 
MUC1         
 0.1 µmol/L 4/36 11 2/31 1/34 0/11 
 10 µmol/L 2/32 0/20 0/24 0/11 
 0.1 and/or 10 µmol/L 6/43 14 2/31 1/34 0/12 
PRAME         
 0.1 µmol/L 2/37 1/31 2/33 0/12 
 10 µmol/L 1/33 2/20 10 1/25 0/13 
 0.1 and/or 10 µmol/L 3/43 2/31 2/33 0/13 
WT1         
 0.1 µmol/L 11/41 27 3/31 10 1/34 0/14 
 10 µmol/L 7/39 17 1/29 0/32 0/14 
 0.1 and/or 10 µmol/L 13/43 30 3/31 10 1/34 0/14 
CMV         
 10 µmol/L 12/23 52 6/21 29 15/30 50 8/11 73 

This decline in immune responses against TAAs could not be observed for cytomegalovirus (CMV), which was used as a positive control (Figure 6). As expected, pregnancy-induced leukocytosis was primarily a consequence of an increase in neutrophil granulocytes (Table 5), reaching the maximum shortly after delivery and declining further on while absolute lymphocyte counts remained stable. In Table 6, hormonal levels including β-hCG, estradiol, progesterone, and prolactin are displayed, reflecting the expected course over time and being consistent with an intact pregnancy.

Table 5

Blood parameters of 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II)

First to second trimester (n = 8)1 to 4 d after delivery (n = 16)2 to 3 mo after delivery (n = 27)After completion of nursing (n = 15)
RBC (×106/µL) 3.9 ± 0.4 3.6 ± 0.5 4.5 ± 0.2 5.3 ± 0.7 
Hemoglobin (g/dL) 11.8 ± 0.8 10.3 ± 1.6 12.3 ± 0.9 15.0 ± 2.2 
WBC (×103/µL) 9.3 ± 2.9 12.9 ± 3.0 6.0 ± 1.1 6.1 ± 1.3 
ALC (×103/µL) 1.7 ± 0.5 2.0 ± 0.6 2.1 ± 0.3 2.2 ± 0.6 
ANC (×103/µL) 7.0 ± 2.3 10.1 ± 2.5 3.4 ± 0.9 3.5 ± 1.1 
Platelets (×103/µL) 240 ± 57 232 ± 53 283 ± 60 231 ± 67 
First to second trimester (n = 8)1 to 4 d after delivery (n = 16)2 to 3 mo after delivery (n = 27)After completion of nursing (n = 15)
RBC (×106/µL) 3.9 ± 0.4 3.6 ± 0.5 4.5 ± 0.2 5.3 ± 0.7 
Hemoglobin (g/dL) 11.8 ± 0.8 10.3 ± 1.6 12.3 ± 0.9 15.0 ± 2.2 
WBC (×103/µL) 9.3 ± 2.9 12.9 ± 3.0 6.0 ± 1.1 6.1 ± 1.3 
ALC (×103/µL) 1.7 ± 0.5 2.0 ± 0.6 2.1 ± 0.3 2.2 ± 0.6 
ANC (×103/µL) 7.0 ± 2.3 10.1 ± 2.5 3.4 ± 0.9 3.5 ± 1.1 
Platelets (×103/µL) 240 ± 57 232 ± 53 283 ± 60 231 ± 67 

ALC, absolute lymphocyte count; ANC, absolute neutrophil count; RBC, red blood cell count; WBC, white blood cell count.

Table 6

Hormone levels of 44 HLA-A*02:01+ women in their first pregnancy (longitudinal study group II)

First to second trimester (n = 43)1 to 4 d after delivery (n = 34)2 to 3 mo after delivery (n = 34)After completion of nursing (n = 15)
β-hCG (mU/mL)     
 Median 17 477 2116 0.10 — 
 Range 1202-103 863 78-46 187 0.10-2.8 — 
Estradiol (pg/mL)     
 Median 9343 191 29 29 
 Range 1269-25 770 38-5464 5.0-302 5.0-234 
Progesterone (ng/mL)     
 Median 57 7.8 0.26 0.56 
 Range 12-605 0.90-91 0.09-8.9 0.09-20 
Prolactin (ng/mL)     
 Median 125 255 30 7.8 
 Range 0.50-272 51-470 1.8-167 5.0-23 
First to second trimester (n = 43)1 to 4 d after delivery (n = 34)2 to 3 mo after delivery (n = 34)After completion of nursing (n = 15)
β-hCG (mU/mL)     
 Median 17 477 2116 0.10 — 
 Range 1202-103 863 78-46 187 0.10-2.8 — 
Estradiol (pg/mL)     
 Median 9343 191 29 29 
 Range 1269-25 770 38-5464 5.0-302 5.0-234 
Progesterone (ng/mL)     
 Median 57 7.8 0.26 0.56 
 Range 12-605 0.90-91 0.09-8.9 0.09-20 
Prolactin (ng/mL)     
 Median 125 255 30 7.8 
 Range 0.50-272 51-470 1.8-167 5.0-23 

Association of TAA- and CMV-specific immune responses

There was no correlation of CD8-mediated immune responses against CMV and TAAs during and after pregnancy (Figure 6 and Table 7). However, there was a borderline significant correlation between immune responses against CMV and HER2/neu as well as MUC1 in volunteer blood donors (Table 7), whereas there was no correlation with PRAME or WT1.

Table 7

Correlation analysis between relative CD8+ T-cell IFN-γ immune responses against TAAs and CMV in HLA-A*02:01+ volunteer blood donors and women in their first pregnancy

HER2/neuMUC1PRAMEWT1
nrnrnrnr
Cross-sectional study group I         
 All donors 107 0.203* 107 0.225* 108 0.168 109 0.149 
 Nulligravidous women 36 0.023 36 0.252 36 0.216 37 0.034 
 Primi-/multiparous women 35 0.180 35 0.045 35 0.016 35 0.078 
 Men 36 0.347* 36 0.292 37 0.205 37 0.305 
Longitudinal study group II         
 First to second trimester 18 −0.015 16 −0.124 17 0.033 19 −0.056 
 1 to 4 d after delivery 19 0.059 16 0.225 16 0.034 21 0.056 
 2 to 3 mo after delivery 17 0.296 16 0.353 17 0.048 22 0.211 
 After completion of nursing 11 −0.309 10 −0.273 11 −0.009 11 0.355 
HER2/neuMUC1PRAMEWT1
nrnrnrnr
Cross-sectional study group I         
 All donors 107 0.203* 107 0.225* 108 0.168 109 0.149 
 Nulligravidous women 36 0.023 36 0.252 36 0.216 37 0.034 
 Primi-/multiparous women 35 0.180 35 0.045 35 0.016 35 0.078 
 Men 36 0.347* 36 0.292 37 0.205 37 0.305 
Longitudinal study group II         
 First to second trimester 18 −0.015 16 −0.124 17 0.033 19 −0.056 
 1 to 4 d after delivery 19 0.059 16 0.225 16 0.034 21 0.056 
 2 to 3 mo after delivery 17 0.296 16 0.353 17 0.048 22 0.211 
 After completion of nursing 11 −0.309 10 −0.273 11 −0.009 11 0.355 

Peptide concentration for stimulation was 10 µmol/L for TAAs and CMV.

r, Spearman’s rank correlation coefficient of relative immune responses; n, number of individuals for whom the correlation between CMV and respective TAA was performed (this number varied, as results for both antigens needed to be available for each individual).

*

P < .05.

Harnessing the allograft’s immunity against leukemia offers a unique mechanism to provide cure to an otherwise lethal disease. Although nonrelapse mortality rates in allogeneic hematopoietic stem cell transplantation (HSCT) have declined steadily over time, relapse rates remain consistently high.32,33  Thus, current research in allogeneic HSCT focuses on the enhancement of GVL effects to optimize disease control.32,34  However, the appearance of severe GVHD requiring immediate immunosuppression regularly compromises these beneficial effects of the allograft.35,36  Consequently, several immunotherapeutic approaches nowadays focus on TAAs as target antigens to mount antileukemic immune responses in the absence of GVHD.34,37  Although it is well accepted that TAA-specific immune responses play a central role in overall GVL,10,38-40  little is known about their origin and ability to persist as functionally active immune cells in the host preventing relapse.

Several groups have shown that patients with hematologic malignancies harbor increased frequencies of TAA-specific immune responses.11,36-42  So far, the presence of these immune responses in healthy individuals could be only demonstrated in cohorts of limited size.11,39  The current study represents, to the best of our knowledge, the first comprehensive work to study the exact frequencies of T-lymphocyte responses against clinically relevant TAAs in a large group of healthy individuals. Here, we could show that one-third of volunteer donors do carry significant immune responses against at least 1 of the studied TAAs. In our study, immune responses were measured directly following a single course of antigen presentation without prior expansion, intending to recruit memory rather than naive responses. Frequencies varied for different TAAs. Against WT1, 15% of the volunteer donors had low- and/or high-avidity immune responses, which is consistent with the original observation in a much smaller cohort.12,41  Similar frequencies were found for MUC1, whereas frequencies against HER2/neu and PRAME were lower. Interestingly, Weber et al were able to detect WT1-specific immune responses in 9 out of a total of 10 healthy donors following multiple rounds of stimulation, suggesting that upon professional and repetitive antigen presentation under the condition of optimal cytokine support, WT1-specific immune responses could be generated from virtually everyone, opening opportunities for immunotherapy.42 

For patients with leukemia, it is well known that the high-level expression of TAAs in the malignant tissue facilitates autoimmune reactions mounting in frequencies of 60% and higher as described for patients with WT1-overexpressing acute myeloid leukemias and myelodysplastic syndrome.41,43  Thus, we hypothesized that due to the well-described overexpression of TAAs in placental and fetal tissues, prior pregnancy and the resultant fetomaternal transfer during delivery could have an influence on the generation of long-lasting TAA-specific immune responses in women, as it is known for Y-chromosomal responses in women with male infants.21-24,44  Interestingly, women with prior pregnancy did not have higher frequencies or higher levels of immune responses against 1 of the 4 studied TAAs. These results could be confirmed by the longitudinal analysis performed in the second study group of women with no known history of prior pregnancy. These intraindividual longitudinal courses showed that immune responses were gained in the first 2 trimesters of pregnancy, declined after delivery, and fully lost after completion of nursing. Most likely, the gain of immune responses in early pregnancy is induced by the growth of the fetoplacental unit expressing high levels of TAAs,45  whereas abrogation of the immune response is probably a consequence of the loss of the target antigen after delivery and the continuing immunosuppressive hormonal influence during pregnancy by estrogens.46,47  This steady decline in immune responses against TAAs could not be observed for CMV used as a positive control, suggesting that the observed pattern was specific and independent of the general immune environment. Looking at the blood counts of a representative group of these women in the course of and after pregnancy, the observed trend in TAA-specific immune responses was not accountable to an overall decline in absolute numbers of lymphocytes that stayed stable over time, consistent with physiological conditions of pregnancy.48 

Interestingly, men showed a general tendency toward higher frequencies and higher levels of immune responses to TAAs, particularly to HER2/neu and WT1, where the differences between the genders reached statistical significance. Based on the experience from leukemic patients and women at early pregnancy, the appearance of high frequencies of TAA-specific immune responses is most likely associated with tissues overexpressing antigens such as WT1 and HER2/neu.21,41,44,49,50  Thus, a continuous gonadal presence of cancer-testis-antigen–expressing tissues not compromised by an immunosuppressive hormonal environment remains as the likely driving force behind this immunity against TAAs in men.51-53 

In volunteer blood donors, responses against TAAs were poorly correlated with those against CMV, reaching only borderline significance for HER2/neu and MUC1, whereas there was no association in pregnant women. In light of the multiple correlations performed, this suggests that a potential cross-reactivity between immune responses against CMV and TAAs appears to be rather unlikely but cannot be fully ruled out.

Taken together, memory-type immune responses against HER2/neu, MUC1, PRAME, and/or WT1 are generally present in one-third of healthy individuals. However, providing the optimal immunologic milieu and repetitive antigen stimulation may allow the exertion of TAA-specific autoimmunity in the majority of healthy individuals as shown for WT1.42  These low- and high-avidity immune cells have the capacity to expand and exert killing functions on leukemic cells as shown in vitro and in animal models postvaccination.12,54,55  The exploitation of donor-derived autoimmunity against selected TAAs by improving donor selection and facilitating adoptive immunotransfer of donor-derived T lymphocytes may significantly contribute to the control of the malignant disease in the absence of GVHD after allotransplantation, where an optimal environment offers unique opportunities for homeostatic expansion.11,56  The presence of the target antigen represents an essential condition for the persistence of the TAA-specific immune responses, as suggested by the studies in the course of pregnancy. Thus, vaccination strategies may avoid their abrogation in the allogeneic recipient.57  Additional depletion of regulatory T lymphocytes, application of immunomodulatory agents such as lenalidomide and the reduction of immunosuppression in the context of selective depletion strategies could antagonize a permissive immune environment particularly enhancing the effects of T lymphocytes of lower avidity against TAAs.58-64  Furthermore, these unique effects may be also facilitated after autologous HSCT, providing a strong antimalignant autoimmune effect on top of high-dose chemotherapy.65  Finally, this study provides novel insights in the regulation of TAA-specific immunity in healthy individuals, best exemplified by the results from pregnancy and in men. Whether increased immune responses in healthy donors as they are found in men generally contribute to an improved TAA-specific immune reconstitution and clinical outcome in allogeneic recipients remains open and should be addressed in clinical trials.

Presented in part at the annual meetings of the Association for Cancer Immunotherapy (Mainz, Germany, May 25-27, 2011) and the American Society for Hematology (Atlanta, GA, December 8-11, 2012 and New Orleans, LA, December 7-10, 2013).66-68 

The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked “advertisement” in accordance with 18 USC section 1734.

The authors thank the subjects for their participation in the study; Dr Silvia Hobert, Professor Jael Backe, Dr Helmut Spingler, Renate Vieth-Laßmann, Dr Martin Witteler, and their assistants as well as Marianne Ahmed for the recruitment of pregnant women; Professor Markus Böck, Dr Sabine Kuhn, Dr Evelyn Putz, and the staff of the Institute of Clinical Transfusion Medicine and Hemotherapy for the recruitment of platelet donors; Monika Koospal and Anita Pietschmann for technical assistance; and Dr Uwe Mäder for statistical assistance. The authors also thank Dr Judy Mielke for critical reading of the manuscript.

This work was supported by grants from the Interdisciplinary Center for Clinical Research (IZKF) of the University of Würzburg, Germany (D-150); “Hilfe im Kampf gegen Krebs e.V.,” Würzburg, Germany (M.L.); and “Deutscher Akademischer Austausch Dienst e.V.,” Bonn, Germany (A.W.).

Contribution: M.L., A.W., and M.A. collected samples, performed experiments, analyzed data, and wrote the paper; S.G. and L.B. collected samples and performed experiments; M.S., S.O., H.E., and U.K. provided administrative support; P.H. performed statistical analysis; E.K. provided administrative support; C.O. and S.M. designed the study, analyzed data, and wrote the paper; and all authors critically revised the manuscript for important intellectual content and approved the manuscript to be published.

The current affiliation for A.W. is the Department of Genetic Medicine, Weill Cornell Medical College in Qatar, Doha, Qatar.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Stephan Mielke, Allogeneic Stem Cell Transplantation Program, Department of Internal Medicine II, Hematology and Oncology, Würzburg University Medical Center, Oberdürrbacher Strasse 6, D-97080 Würzburg, Germany; e-mail: mielke_s@ukw.de.

1
Weiden
 
PL
Flournoy
 
N
Thomas
 
ED
et al. 
Antileukemic effect of graft-versus-host disease in human recipients of allogeneic-marrow grafts.
N Engl J Med
1979
, vol. 
300
 
19
(pg. 
1068
-
1073
)
2
Sullivan
 
KM
Storb
 
R
Buckner
 
CD
et al. 
Graft-versus-host disease as adoptive immunotherapy in patients with advanced hematologic neoplasms.
N Engl J Med
1989
, vol. 
320
 
13
(pg. 
828
-
834
)
3
Horowitz
 
MM
Gale
 
RP
Sondel
 
PM
et al. 
Graft-versus-leukemia reactions after bone marrow transplantation.
Blood
1990
, vol. 
75
 
3
(pg. 
555
-
562
)
4
Loren
 
AW
Bunin
 
GR
Boudreau
 
C
et al. 
Impact of donor and recipient sex and parity on outcomes of HLA-identical sibling allogeneic hematopoietic stem cell transplantation.
Biol Blood Marrow Transplant
2006
, vol. 
12
 
7
(pg. 
758
-
769
)
5
Mutis
 
T
Verdijk
 
R
Schrama
 
E
Esendam
 
B
Brand
 
A
Goulmy
 
E
Feasibility of immunotherapy of relapsed leukemia with ex vivo-generated cytotoxic T lymphocytes specific for hematopoietic system-restricted minor histocompatibility antigens.
Blood
1999
, vol. 
93
 
7
(pg. 
2336
-
2341
)
6
Feng
 
X
Hui
 
KM
Younes
 
HM
Brickner
 
AG
Targeting minor histocompatibility antigens in graft versus tumor or graft versus leukemia responses.
Trends Immunol
2008
, vol. 
29
 
12
(pg. 
624
-
632
)
7
Falkenburg
 
JH
Marijt
 
WA
Heemskerk
 
MH
Willemze
 
R
Minor histocompatibility antigens as targets of graft-versus-leukemia reactions.
Curr Opin Hematol
2002
, vol. 
9
 
6
(pg. 
497
-
502
)
8
Falkenburg
 
JH
Willemze
 
R
Minor histocompatibility antigens as targets of cellular immunotherapy in leukaemia.
Best Pract Res Clin Haematol
2004
, vol. 
17
 
3
(pg. 
415
-
425
)
9
Nonn
 
M
Herr
 
W
Khan
 
S
et al. 
Selective depletion of alloreactive T lymphocytes using patient-derived nonhematopoietic stimulator cells in allograft engineering.
Transplantation
2008
, vol. 
86
 
10
(pg. 
1427
-
1435
)
10
Molldrem
 
JJ
Lee
 
PP
Wang
 
C
et al. 
Evidence that specific T lymphocytes may participate in the elimination of chronic myelogenous leukemia.
Nat Med
2000
, vol. 
6
 
9
(pg. 
1018
-
1023
)
11
Rezvani
 
K
Barrett
 
AJ
Characterizing and optimizing immune responses to leukaemia antigens after allogeneic stem cell transplantation.
Best Pract Res Clin Haematol
2008
, vol. 
21
 
3
(pg. 
437
-
453
)
12
Rezvani
 
K
Grube
 
M
Brenchley
 
JM
et al. 
Functional leukemia-associated antigen-specific memory CD8+ T cells exist in healthy individuals and in patients with chronic myelogenous leukemia before and after stem cell transplantation.
Blood
2003
, vol. 
102
 
8
(pg. 
2892
-
2900
)
13
Molldrem
 
JJ
Komanduri
 
K
Wieder
 
E
Overexpressed differentiation antigens as targets of graft-versus-leukemia reactions.
Curr Opin Hematol
2002
, vol. 
9
 
6
(pg. 
503
-
508
)
14
Morris
 
EC
Bendle
 
GM
Stauss
 
HJ
Prospects for immunotherapy of malignant disease.
Clin Exp Immunol
2003
, vol. 
131
 
1
(pg. 
1
-
7
)
15
Natzke
 
AM
Shaw
 
JL
McKeller
 
MR
Emo
 
KL
Mullen
 
CA
Hematopoietic stem cell recipients do not develop post-transplantation immune tolerance to antigens present on minimal residual disease.
Biol Blood Marrow Transplant
2007
, vol. 
13
 
1
(pg. 
34
-
45
)
16
Wrzesinski
 
C
Paulos
 
CM
Gattinoni
 
L
et al. 
Hematopoietic stem cells promote the expansion and function of adoptively transferred antitumor CD8 T cells.
J Clin Invest
2007
, vol. 
117
 
2
(pg. 
492
-
501
)
17
Piper
 
KP
McLarnon
 
A
Arrazi
 
J
et al. 
Functional HY-specific CD8+ T cells are found in a high proportion of women following pregnancy with a male fetus.
Biol Reprod
2007
, vol. 
76
 
1
(pg. 
96
-
101
)
18
Verdijk
 
RM
Kloosterman
 
A
Pool
 
J
et al. 
Pregnancy induces minor histocompatibility antigen-specific cytotoxic T cells: implications for stem cell transplantation and immunotherapy.
Blood
2004
, vol. 
103
 
5
(pg. 
1961
-
1964
)
19
Takami
 
A
Sugimori
 
C
Feng
 
X
et al. 
Expansion and activation of minor histocompatibility antigen HY-specific T cells associated with graft-versus-leukemia response.
Bone Marrow Transplant
2004
, vol. 
34
 
8
(pg. 
703
-
709
)
20
Nakamura
 
R
La Rosa
 
C
Tsai
 
W
et al. 
Ex vivo detection of CD8 T cells specific for H-Y minor histocompatibility antigens in allogeneic hematopoietic stem cell transplant recipients.
Transpl Immunol
2014
, vol. 
30
 
4
(pg. 
128
-
135
)
21
Meden
 
H
Mielke
 
S
Schauer
 
A
Kuhn
 
W
Serum levels of the c-erbB-2 (HER2/neu) encoded oncoprotein fragment p105 in normal pregnancies.
In Vivo
1997
, vol. 
11
 
1
(pg. 
51
-
54
)
22
Jeschke
 
U
Richter
 
DU
Hammer
 
A
Briese
 
V
Friese
 
K
Karsten
 
U
Expression of the Thomsen-Friedenreich antigen and of its putative carrier protein mucin 1 in the human placenta and in trophoblast cells in vitro.
Histochem Cell Biol
2002
, vol. 
117
 
3
(pg. 
219
-
226
)
23
Ikeda
 
H
Lethé
 
B
Lehmann
 
F
et al. 
Characterization of an antigen that is recognized on a melanoma showing partial HLA loss by CTL expressing an NK inhibitory receptor.
Immunity
1997
, vol. 
6
 
2
(pg. 
199
-
208
)
24
Feingold
 
M
Zilberstein
 
M
Srivastava
 
RK
Seibel
 
MM
Bar-Ami
 
S
Hambartsoumian
 
E
Expression of Wilms’ tumor suppressor gene (WT1) in term human trophoblast: regulation by cyclic adenosine 3′,5′-monophosphate.
J Clin Endocrinol Metab
1998
, vol. 
83
 
7
(pg. 
2503
-
2508
)
25
Dietz
 
AB
Bulur
 
PA
Emery
 
RL
et al. 
A novel source of viable peripheral blood mononuclear cells from leukoreduction system chambers.
Transfusion
2006
, vol. 
46
 
12
(pg. 
2083
-
2089
)
26
Fisk
 
B
Blevins
 
TL
Wharton
 
JT
Ioannides
 
CG
Identification of an immunodominant peptide of HER-2/neu protooncogene recognized by ovarian tumor-specific cytotoxic T lymphocyte lines.
J Exp Med
1995
, vol. 
181
 
6
(pg. 
2109
-
2117
)
27
Brossart
 
P
Schneider
 
A
Dill
 
P
et al. 
The epithelial tumor antigen MUC1 is expressed in hematological malignancies and is recognized by MUC1-specific cytotoxic T-lymphocytes.
Cancer Res
2001
, vol. 
61
 
18
(pg. 
6846
-
6850
)
28
Rezvani
 
K
Yong
 
AS
Tawab
 
A
et al. 
Ex vivo characterization of polyclonal memory CD8+ T-cell responses to PRAME-specific peptides in patients with acute lymphoblastic leukemia and acute and chronic myeloid leukemia.
Blood
2009
, vol. 
113
 
10
(pg. 
2245
-
2255
)
29
Salter
 
RD
Howell
 
DN
Cresswell
 
P
Genes regulating HLA class I antigen expression in T-B lymphoblast hybrids.
Immunogenetics
1985
, vol. 
21
 
3
(pg. 
235
-
246
)
30
Britten
 
CM
Meyer
 
RG
Kreer
 
T
Drexler
 
I
Wölfel
 
T
Herr
 
W
The use of HLA-A*0201-transfected K562 as standard antigen-presenting cells for CD8(+) T lymphocytes in IFN-gamma ELISPOT assays.
J Immunol Methods
2002
, vol. 
259
 
1-2
(pg. 
95
-
110
)
31
Römer
 
PS
Berr
 
S
Avota
 
E
et al. 
Preculture of PBMCs at high cell density increases sensitivity of T-cell responses, revealing cytokine release by CD28 superagonist TGN1412.
Blood
2011
, vol. 
118
 
26
(pg. 
6772
-
6782
)
32
Bleakley
 
M
Turtle
 
CJ
Riddell
 
SR
Augmentation of anti-tumor immunity by adoptive T-cell transfer after allogeneic hematopoietic stem cell transplantation.
Expert Rev Hematol
2012
, vol. 
5
 
4
(pg. 
409
-
425
)
33
Gooley
 
TA
Chien
 
JW
Pergam
 
SA
et al. 
Reduced mortality after allogeneic hematopoietic-cell transplantation.
N Engl J Med
2010
, vol. 
363
 
22
(pg. 
2091
-
2101
)
34
Warren
 
EH
Deeg
 
HJ
Dissecting graft-versus-leukemia from graft-versus-host-disease using novel strategies.
Tissue Antigens
2013
, vol. 
81
 
4
(pg. 
183
-
193
)
35
Arora
 
M
Therapy of chronic graft-versus-host disease.
Best Pract Res Clin Haematol
2008
, vol. 
21
 
2
(pg. 
271
-
279
)
36
Inamoto
 
Y
Flowers
 
ME
Lee
 
SJ
et al. 
Influence of immunosuppressive treatment on risk of recurrent malignancy after allogeneic hematopoietic cell transplantation.
Blood
2011
, vol. 
118
 
2
(pg. 
456
-
463
)
37
Kotsiou
 
E
Davies
 
JK
New ways to separate graft-versus-host disease and graft-versus-tumour effects after allogeneic haematopoietic stem cell transplantation.
Br J Haematol
2013
, vol. 
160
 
2
(pg. 
133
-
145
)
38
Rezvani
 
K
Yong
 
AS
Savani
 
BN
et al. 
Graft-versus-leukemia effects associated with detectable Wilms tumor-1 specific T lymphocytes after allogeneic stem-cell transplantation for acute lymphoblastic leukemia.
Blood
2007
, vol. 
110
 
6
(pg. 
1924
-
1932
)
39
Fujiwara
 
H
Adoptive T-cell therapy for hematological malignancies using T cells gene-modified to express tumor antigen-specific receptors.
Int J Hematol
2014
, vol. 
99
 
2
(pg. 
123
-
131
)
40
Kolb
 
HJ
Graft-versus-leukemia effects of transplantation and donor lymphocytes.
Blood
2008
, vol. 
112
 
12
(pg. 
4371
-
4383
)
41
Rezvani
 
K
Brenchley
 
JM
Price
 
DA
et al. 
T-cell responses directed against multiple HLA-A*0201-restricted epitopes derived from Wilms’ tumor 1 protein in patients with leukemia and healthy donors: identification, quantification, and characterization.
Clin Cancer Res
2005
, vol. 
11
 
24 Pt 1
(pg. 
8799
-
8807
)
42
Weber
 
G
Karbach
 
J
Kuçi
 
S
et al. 
WT1 peptide-specific T cells generated from peripheral blood of healthy donors: possible implications for adoptive immunotherapy after allogeneic stem cell transplantation.
Leukemia
2009
, vol. 
23
 
9
(pg. 
1634
-
1642
)
43
Scheibenbogen
 
C
Letsch
 
A
Thiel
 
E
et al. 
CD8 T-cell responses to Wilms tumor gene product WT1 and proteinase 3 in patients with acute myeloid leukemia.
Blood
2002
, vol. 
100
 
6
(pg. 
2132
-
2137
)
44
Agrawal
 
B
Reddish
 
MA
Krantz
 
MJ
Longenecker
 
BM
Does pregnancy immunize against breast cancer?
Cancer Res
1995
, vol. 
55
 
11
(pg. 
2257
-
2261
)
45
Jungbluth
 
AA
Silva
 
WA
Iversen
 
K
et al. 
Expression of cancer-testis (CT) antigens in placenta.
Cancer Immun
2007
, vol. 
7
 pg. 
15
 
46
Lahita
 
RG
The effects of sex hormones on the immune system in pregnancy.
Am J Reprod Immunol
1992
, vol. 
28
 
3-4
(pg. 
136
-
137
)
47
Jansson
 
L
Holmdahl
 
R
Estrogen-mediated immunosuppression in autoimmune diseases.
Inflamm Res
1998
, vol. 
47
 
7
(pg. 
290
-
301
)
48
Valdimarsson
 
H
Mulholland
 
C
Fridriksdottir
 
V
Coleman
 
DV
A longitudinal study of leucocyte blood counts and lymphocyte responses in pregnancy: a marked early increase of monocyte-lymphocyte ratio.
Clin Exp Immunol
1983
, vol. 
53
 
2
(pg. 
437
-
443
)
49
Inoue
 
K
Ogawa
 
H
Sonoda
 
Y
et al. 
Aberrant overexpression of the Wilms tumor gene (WT1) in human leukemia.
Blood
1997
, vol. 
89
 
4
(pg. 
1405
-
1412
)
50
Rezvani
 
K
Yong
 
AS
Mielke
 
S
et al. 
Leukemia-associated antigen-specific T-cell responses following combined PR1 and WT1 peptide vaccination in patients with myeloid malignancies.
Blood
2008
, vol. 
111
 
1
(pg. 
236
-
242
)
51
Boon
 
T
van der Bruggen
 
P
Human tumor antigens recognized by T lymphocytes.
J Exp Med
1996
, vol. 
183
 
3
(pg. 
725
-
729
)
52
Scanlan
 
MJ
Simpson
 
AJ
Old
 
LJ
The cancer/testis genes: review, standardization, and commentary.
Cancer Immun
2004
, vol. 
4
 pg. 
1
 
53
Simpson
 
AJ
Caballero
 
OL
Jungbluth
 
A
Chen
 
YT
Old
 
LJ
Cancer/testis antigens, gametogenesis and cancer.
Nat Rev Cancer
2005
, vol. 
5
 
8
(pg. 
615
-
625
)
54
Kohrt
 
HE
Müller
 
A
Baker
 
J
et al. 
Donor immunization with WT1 peptide augments antileukemic activity after MHC-matched bone marrow transplantation.
Blood
2011
, vol. 
118
 
19
(pg. 
5319
-
5329
)
55
Bos
 
R
Marquardt
 
KL
Cheung
 
J
Sherman
 
LA
Functional differences between low- and high-affinity CD8(+) T cells in the tumor environment.
OncoImmunology
2012
, vol. 
1
 
8
(pg. 
1239
-
1247
)
56
Dummer
 
W
Niethammer
 
AG
Baccala
 
R
et al. 
T cell homeostatic proliferation elicits effective antitumor autoimmunity.
J Clin Invest
2002
, vol. 
110
 
2
(pg. 
185
-
192
)
57
Smyth
 
K
Garcia
 
K
Sun
 
Z
Tuo
 
W
Xiao
 
Z
Repetitive peptide boosting progressively enhances functional memory CTLs.
Biochem Biophys Res Commun
2012
, vol. 
424
 
3
(pg. 
635
-
640
)
58
Mielke
 
S
McIver
 
ZA
Shenoy
 
A
et al. 
Selectively T cell-depleted allografts from HLA-matched sibling donors followed by low-dose posttransplantation immunosuppression to improve transplantation outcome in patients with hematologic malignancies.
Biol Blood Marrow Transplant
2011
, vol. 
17
 
12
(pg. 
1855
-
1861
)
59
Mielke
 
S
Nunes
 
R
Rezvani
 
K
et al. 
A clinical-scale selective allodepletion approach for the treatment of HLA-mismatched and matched donor-recipient pairs using expanded T lymphocytes as antigen-presenting cells and a TH9402-based photodepletion technique.
Blood
2008
, vol. 
111
 
8
(pg. 
4392
-
4402
)
60
Nishikawa
 
H
Sakaguchi
 
S
Regulatory T cells in cancer immunotherapy.
Curr Opin Immunol
2014
, vol. 
27
 (pg. 
1
-
7
)
61
Hobeika
 
AC
Morse
 
MA
Osada
 
T
Peplinski
 
S
Lyerly
 
HK
Clay
 
TM
Depletion of human regulatory T cells.
Methods Mol Biol
2011
, vol. 
707
 (pg. 
219
-
231
)
62
Sugiyama
 
D
Nishikawa
 
H
Maeda
 
Y
et al. 
Anti-CCR4 mAb selectively depletes effector-type FoxP3+CD4+ regulatory T cells, evoking antitumor immune responses in humans.
Proc Natl Acad Sci USA
2013
, vol. 
110
 
44
(pg. 
17945
-
17950
)
63
Mielke
 
S
Solomon
 
SR
Barrett
 
AJ
Selective depletion strategies in allogeneic stem cell transplantation.
Cytotherapy
2005
, vol. 
7
 
2
(pg. 
109
-
115
)
64
Alsina
 
M
Becker
 
PS
Zhong
 
X
et al. 
Resource for Clinical Investigation in Blood and Marrow Transplantation
Lenalidomide maintenance for high-risk multiple myeloma after allogeneic hematopoietic cell transplantation.
Biol Blood Marrow Transplant
2014
, vol. 
20
 
8
(pg. 
1183
-
1189
)
65
Suzuki
 
K
Aida
 
K
Miyakawa
 
R
et al. 
Preimmunization of donor lymphocytes enhances antitumor immunity of autologous hematopoietic stem cell transplantation.
Cancer Med
2013
, vol. 
2
 
5
(pg. 
636
-
645
)
66
Worschech
 
A
Lutz
 
M
Methner
 
L
et al. 
 
Correlation of humoral and cellular Cytomegalovirus-specific immune responses in healthy donors: who is really negative or positive [abstract]? CIMT Annual Meeting Abstracts. 2011:121
67
Lutz
 
M
Worschech
 
A
Gahn
 
S
et al. 
Immune responses against the tumor-associated antigens WT1, MUC-1, PRAME and HER2/neu in 114 prospectively screened healthy donors: Effects of gender and prior pregnancy and implications for immunotherapy [abstract].
Blood
2012
, vol. 
120
 pg. 
4115
 
68
Lutz
 
M
Alb
 
M
Worschech
 
A
et al. 
Boost and loss of immune responses against tumor-associated antigens in the course of pregnancy as a model for immunotherapy [abstract].
Blood
2013
, vol. 
122
 pg. 
4505
 

Author notes

M.L. and A.W. contributed equally to this study.

C.O. and S.M. contributed equally to this study.

Sign in via your Institution