Polymorphism and distribution of HLA-DR2 alleles and haplotypes in a Greek population.

HLA-DR2 serological subtyping has indicated that the DR16 serotype appears at a higher frequency relative to the DR15 serotype in the Greek population, differing from the distribution observed in most other Caucasian groups. In this study, we have analyzed by the PCR-SSP technique a DR2-positive group of unrelated Greek individuals selected from our normal control panel for the different DRB1, DRB5, DQB1 and DQA1 DR2-associated alleles present. Six of the 50 individuals analyzed were homozygous for DR2, contributing a total of 56 haplotypes for DR2. The observed frequencies of the DR2-related DRB1 alleles were as follows: 58.9% for the DRB11601, 7.1% for the DRB11602, 25.0% for the DRB11501 and 7.1 % for the DRB11502 allele. The rare allele DRB11605 was detected in one heterozygous sample and its presence was definitively established by DNA sequencing. The alleles 1503, 1504, 1505, 1603 and 1604 were not detected. Three DRB5 alleles were identified: DRB50202 (67.8%), DRB50101 (25.0%) and DRB50102 (7.1%). Ten different DRB1/DQB1/ DQA1 DR2-associated haplotypes were defined. The most frequently observed haplotype was DRB11601-DQB10502-DQA10102 (relative frequency=57%) followed by DRB11501-DQB10602-DQA10102 (relative frequency=14.3%). In conclusion, the refined analysis of the DR2-associated DRB1 alleles in the Greek population revealed the prevalence of the DRB11601 allele. The rare allele DRB1*1605 was demonstrated once. A considerable variety of different DR2-related DR/DQ haplotypes was detected and the overall haplotypic frequencies in the Greek population are distributed differently compared to those reported for most other Caucasian populations.