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. DRB11601, 0701, 1501, 0101 and 1104 are the most frequent alleles at the DRB1 locus. At the DQA1 locus two alleles predominate: DQA10501 and 0102, while the most frequent DQB1 allele is 0301. Analysis of HLA-DPB1 polymorphism showed that, as in other Europeans, DPB10401 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: DRB10301-DRB30202, DRB11501-DRB502, DRB11601-DRB50101, DRB11502-DRB50101, DQA10103-DQB10503 and DQA10501-DQB10302. Among 236 examined DRB1-DQA1-DQB1 haplotypic combinations, the most frequent was DRB11601-DQA10102-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.