| Abstract: | HLA-B44 is one of the most common HLA class I alleles in Caucasians. Exon 3 oligotyping and sequence analysis have define five B44 subtypes: B*4402, B*4403, B*4404, B*4405 and B*4406, with variations in exons 2 and 3. We have developed a conventional DNA typing system by using a single B12-group specific amplification including exon2-intron2-exon3 in combination with 6 oligoprobes to define all B44 subtypes. 140 HLA-B44 positive unrelated Spanish Caucasians were typed. Family studies established 30 B44-bearing haplotypes. The distribution of B44 subtypes in our population was: B*4402 32.5%, B*4403 66.5%, B*4404 0.5%, B*4405 0.5%, B*4406 not found. B*4402 and B*4403 represented the 99% of the B44 alleles, as described in Caucasians. However, these two major subtypes showed an inverted frequency when compared with other Caucasian populations, B*4403 twice as frequently as B*4402 in Spaniards. HLA-B44-associated chromosomes showed 20 different haplotypes (including HLA-A,-C,-DR,-DQ), although demonstrating clear separated haplotype composition between B*4402 and B*4403: B*4402 associated to class I alleles A2 (
) and Cw5 (
), and B*4403 associated to the class II allele DRB1*0701 (
). These findings, in addition to the validation of a complete B44 oligotyping system, revealed further evidence of antigen frequency differences among populations of the same ethnic origin. |
