INCREASED DIVERSITY WITHIN THE HLA-A-ASTERISK-66 GROUP - IMPLICATIONSFOR MATCHING IN UNRELATED BONE-MARROW TRANSPLANTATION

We have identified a new A66 allele (A*6603) in three related individ uals, an Arabic patient suffering from acute myeloid leukemia and two of her relatives. The A66 alleles differ in three amino acid residues at positions 70, 90 and 163. The closer relationship between A6602 a nd A6603, which only differ at amino acid 70, replacing GLN with HIS, suggests that the alloreactive potential in this mismatch combination is lower than in all other mismatched A66 donor-recipient combinatio ns, which exhibit two (A6601 versus A*6602) and three (A*6601 versus A6603) differences at the pivotal positions, respectively This emphas izes the potential role of the A66 subtypes in bone marrow transplant ation with alternative donors. For that reason, allelic subtyping shou ld be considered in donor-recipient matching to identify the kind of d isparity.