Comparative Study of French Unrelated Registered Stem Cell Donors and Cryopreserved Cord Blood Units.

The question of the HLA complementarity between unrelated Donors Registries and Cord Blood banks is often raised. On december 31th 2006, three methods were used to qualify and quantify the genetic diversity and complementarity between French marrow unrelated donors (FMUD) and French cryopreserved cord blood units (FCBU). The first one is based on HLA haplotype frequencies performed according to the EM algorithm method, the second on the contribution in new phenotypes (CinNP), the third on the presence of no, one or two frequent haplotypes within MUD/CBU phenotypes. Preliminary operations on HLA typings were necessary to homogenize data: split level, exclusion of only typed at class I level donors. HLA haplotype frequencies comparison does not lead to a global significant difference between FMUD and FCBU. The 5 most frequent haplotypes are identical in both populations: 01-08-17, 29-44-07, 03-07-15, 02-44-04, 02-07-15. Then some haplotypes, characteristic of either Nord or South of Europe, were more frequent among the FMUD than among the FCBU: 02-44-07, 02-51-13, 11-35-01, 02-60-13. On the contrary, some haplotypes of Middle East and Eastern Europe were more frequent among the FCBU than among the FMUD: 30-18-17, 24-35-11, 02-13-07, 33-65-01. In 2006 CinNP does not differ significantly between FMUD and FCBU. 49% of new MUD/CBU bring new HLA-ABDR low resolution split level phenotypes to the FMUD and FCBU populations present the year before, with differences between regions: Martinique and Reunion islands have the largest CinNP, Britanny the smallest. Effectiveness in term of CinNP have been studied for France during the past 6 years, by 2 year sections: 2001–2002, 2003–2004, 2005–2006. As expected, in order to reach an equivalent rate of CinNP, a growing number of donors must be registered every year. The 25 most frequent haplotypes among the FMUD and FCBU were calculated, and called “frequent haplotypes” (FH) among the French population. We could then categorize individuals according to the number of FH they had: none, one or two. 85% of harvested FMUD for a national patient between 2000 and 2006 had one or two FH versus 54% of infused FCBU. 50% of harvested FMUD/ infused FCBU for an international patient had no FH, versus 26% for a national patient. FMUD registry and FCBU banks are complementary: they answer to various HLA haplotypes needs for national and international patients. Incontestably, international patients benefit from French MUD/CBU, which present HLA characteristics not or under-represented in their Registry of origin.