NOVEL HLA-B ALLELES, B-ASTERISK-8201, B-ASTERISK-3515 AND B-ASTERISK-5106, ADD TO THE COMPLEXITY OF SEROLOGIC IDENTIFICATION OF HLA TYPES

Three class I alleles, B8201, B*3515 and B*5106, have been described using DNA and cDNA sequencing. The B8201 allele is most structurally related to B5602, differing from it by 14 nucleotide substitutions re sulting in 5 amino acid differences. The other two alleles, B3515 and B5106, differ from their most closely related HLA-B alleles by 2-3 n ucleotide substitutions resulting in 1-2 amino acid substitutions, res pectively. The majority of nucleotide substitutions marking these new alleles are observed in other HLA-B alleles suggesting that gene conve rsion and/or reciprocal recombination have created this diversity. All of the amino acid substitutions are predicted to alter the antigen bi nding site of the HLA-B molecule. The newly defined HLA-B allelic prod ucts were originally defined by their unusual serologic reactivity pat terns. The B8201 allelic product is serologically typed as a B ''blan k'' or as a variant of B22 or B45. These patterns and the serologic re activity of the other newly described allelic products are consistent with the protein sequence homology among specific HLA-B molecules. Whi le serology remains a powerful tool for detecting HLA diversity, allel es generated by events resulting in the sharing of HLA sequence polymo rphisms among alleles at a locus will continue to create complexity in the interpretation of typing results.