DQB1-ASTERISK-0202 AND THE NEW DQB1-ASTERISK-0203 ALLELE - A 4TH PAIROF DQB1 ALLELES DIFFERING ONLY AT CODON-57

Amino acid 57 of DQ beta chains is of functional importance as it infl uences peptide binding, is part of B and T cell epitopes, and is assoc iated with susceptibility and resistance to insulin-dependent diabetes mellitus and humoral immunodeficiencies. Polymorphism of codon 57 is conserved in primates and in HLA class II B genes implying that balanc ing selection operates on this residue. Previously, three DQB1 allele pairs have been described, that only differ at residue 57. In an Afric an-American Black individual with the HLA phenotype A23,30;B58,63;Cw6; DR18, 12;DR52;DQ5,2, we found a fourth example of this dimorphism; the new DQB10203 allele, that was identical to DQB1*0202 except for codo n 57, which encodes aspartic acid and alanine respectively in the two alleles. The class II haplotype carrying the new allele was deduced to be DRB10302,DRB3*0101,DQA1*05011,DQB1*0203.