Molecular analysis of HLA class II polymorphism in Croatians.

HLA-class II polymorphisms have been studied in a population of 141 unrelated healthy Croatians using PCR amplification, followed by non-radioactive oligonucleotide hybridization. Thirty one DRB1, 8 DQA1, 13 DQB1 and 16 DPB1 alleles were found in the tested population. DRB1*1601, 0701, 1501, 0101 and 1104 are the most frequent alleles at the DRB1 locus. At the DQA1 locus two alleles predominate: DQA1*0501 and 0102, while the most frequent DQB1 allele is *0301. Analysis of HLA-DPB1 polymorphism showed that, as in other Europeans, DPB1*0401 is the most frequent allele. Four different two locus haplotypic associations (DRB1-DRB3, DRB1-DRB5, DRB1-DQB1 and DQA1-DQB1) as well as three locus DRB1-DQA1-DQB1 haplotypic associations were assigned on the basis of known linkage disequilibria. Several unusual two-locus associations have been observed: DRB1*0301-DRB3*0202, DRB1*1501-DRB5*02, DRB1*1601-DRB5*0101, DRB1*1502-DRB5*0101, DQA1*0103-DQB1*0503 and DQA1*0501-DQB1*0302. Among 236 examined DRB1-DQA1-DQB1 haplotypic combinations, the most frequent was DRB1*1601-DQA1*0102-DQB1*0502 that was found with statistically significant higher frequency than in other Europeans. Twenty-eight distinct probable haplotypes were observed just once, suggesting that the main characteristic of Croatian population is great heterogeneity of haplotypes. This study will serve as a reference for further anthropology studies, HLA and disease associations studies and for donor/recipient matching in organ and bone marrow transplantation.