Striking diversity of DR15 haplotypes in Croatians.

Analysis of HLA class II polymorphism revealed DR2 as the most frequent antigen in Croatians (20, 9%). The observed DR2 subtypes and their frequencies were as follows: DRB11601-9.9%; 1501-8.5%; 1602-1.8%, 1502-1.4% and 1503-0.7%. Furthermore, analysis of probable DRB1-DQA1-DQB1 haplotype associations in unrelated individuals revealed a high diversity of DR15 haplotype associations. Now, to confirm this observation from unrelated individuals, family studies have been performed. Sixty-eight families, with at least one parent and one offspring DR2 positive, have been studied. DRB11601-DQA10102-DQB10502 seems to be conserved haplotype in Croatians while DRB115 haplotypes showed extremely high diversity. Seven rare DR15 haplotypes are observed; six of these appear twice and one only once. Two haplotypes appear to be unique to Croatians: DRB11501-DQA10102-DQB10501 and DRB11501-DQA10102-DQB1*0604. This confirmation of extremely high diversity of DR15 haplotypes in Croatians is a valuable tool for unrelated bone marrow transplantation and DR2 disease association studies.