Molecular analysis of HLA genes for the selection of unrelated bone marrow donor.

The selection of fully matched unrelated volunteer donors (UVD) in BMT requires a molecular characterization of MHC polymorphism, since most phenotypically HLA-identical donors can be non-identical when analyzed at a genomic level. The present report describes a molecular typing protocol for HLA genes developed for the selection of UVD, and its application to some donor-recipient pairs. The protocol involves three successive steps. Firstly, PCR with sequence-specific primers for HLA-DRB1 and -DQB1 genes is performed to identify the major alleles of the recipient. PCR-fingerprint matching is then introduced for HLA-A, B, C and DRB, DQB and DPB genes to screen prospective donors. Those showing matched fingerprinting patterns are finally submitted to direct sequencing of the DRB1 gene. DPB compatibility is assessed by oligotyping when there are several potential class I and DRB matched donors. This strategy was applied retrospectively to three BMT recipients and their previously selected donors. Three other patients and their 12 prospective donors were submitted to our protocol before BMT. Clinical evaluation of transplant outcomes indicates the primary importance of complete DRB and class I matching, while DQB and DPB compatibility seems to be less critical.