MOLECULAR AND SEROLOGICAL CHARACTERIZATION OF HLA-B71 IN ASSOCIATION WITH DIFFERENT CLASS-I HAPLOTYPES OR IN DIFFERENT ETHNIC-GROUPS

The HLA-B70 antigen is among the most common antigens present in Afric an Americans; however, monospecific serologic reagents defining B70 an d its subtypes, B71 and B72, are rare. We have recently reported the m olecular characterization of a B71 allele (B1510) from an African Ame rican individual carrying the haplotype HLA-A30, Cw3, B71(w6). In orde r to better define the degree of polymorphism of molecules carrying th e B71 serological specificity in the human population, we have used se rology, cDNA sequencing, and PCR/SSOP typing to characterize B71 allel es from additional individuals from different ethnic populations and c arrying different class I haplotypes. All carried either B1510 or B*1 518 alleles. Other HLA-B alleles isolated from these individuals (B50 01, B4901, B*3501, B*3701) were identical to previously reported sequ ences except for a novel B41 allele (B4102) identified in one Hispani c individual. This allele has concurrently been identified by Rufer an d colleagues in Caucasian individuals. The B4102 allele differs from B4101 at codons 95 (Leu/Trp) and 97 (Ser/Arg). In addition, the B*410 2 allele differs from B4101 by two silent substitutions at codons 94 (ACC/ACT) and 99 (TAC/TAT). Since the polymorphic sequence present in B4102 is also present in other HLA-B alleles (e.g.., B*2707, B*4002. B0703), it may represent a gene conversion cassette. The allelic dive rsity at the class I loci and the scarcity of monospecific alloantiser a support the importance of the application of molecular based methods to identify HLA class I alleles in matching unrelated donor/recipient pairs for bone marrow transplantation.