The nature of introns 4-6 suggests reduced lineage specificity in HLA-B alleles.

For most HLA-B alleles, coding sequences of the 3' part of the genes still need to be determined, and sequences of the 3' noncoding regions have yet to be studied systematically. In this study, we have determined the sequences of introns 4-6 in all HLA-B allelic groups, and computed nucleotide substitution rates and phylogenetic relationships. These sequences demonstrated an inconsistent pattern of intralineage specificity, intralineage diversity, and interlineage diversity that is best characterized by a patchwork pattern. Apart from phylogenetic studies about HLA diversity and diversification, the sequence data obtained in our study may prove valuable for haplotype-specific sequencing of the 3' part of HLA-B and for the explanation of recombination events in newly described HLA-B alleles.