Frequency distribution of HLA class I and II alleles in Greek population and their significance in orchestrating the National Donor Registry Program.

Human leukocyte antigens (HLA) represent one of the most polymorphic systems in humans, responsible for the identification of foreign antigens and the presentation of immune responses. Therefore, HLA is considered to play a major role in human disorders, donor-recipient matching and transplantation outcomes. This study aimed to determine the HLA class I and II alleles and haplotypes in the Greek population. Moreover, a comparative analysis of HLA alleles and haplotype frequencies found in Greek and pooled European populations was also performed to acquire a better knowledge about the HLA alleles distribution. A total number of 1896 healthy individuals were typed for their HLA alleles in the National Tissue Typing Center of Greece. High-resolution HLA typing for the HLA-A, -B, -C and -DR, -DQ, -DP with the use of the next-generation sequencing analysis was performed, followed by data analysis for establishing the HLA allele and haplotype differences. The results of this study showed that the most frequent alleles for the HLA-A were the A02:01:01 (27.1%), 24:02:01 (14.4%), 01:01:01 (9.3%), for the HLA-B were the B51:01:01 (15.3%), 18:01:01 (9.7%), 35:01:01 (6.8%) and for the HLA-C were the C04:01:01 (15.4%), 07:01:01 (13.1%), 12:03:01 (9.6%). For the HLA class II, the most frequent alleles for the HLA-DRB1 were the DRB111:04:01 (16.4%), 16:01:01 (11.3%), 11:01:01 (9.5%), for the HLA-DQB1 were the DQB103:01:01 (30.5%), 05:02:01 (15.1%), 05:01:01 (10.6%) and for the HLA-DPB1 were the DPB104:01:01 (34.8%), 02:01:01 (11.6%), 04:02:01 (7.3%). Additionally, the most frequent haplotypes were the A02:01:01∼C07:01:01-B18:01:01∼DRB111:04:01 (2.3%), followed by the A01:01:01∼C07:01:01∼B08:01:01∼DRB103:01:01 (2.2%), A24:02:01∼C04:01:01∼B35:02:01∼DRB111:04:01 (1.4%) and A02:01:01∼C04:01:01∼B35:01:01-DRB114:01:01 (1.2%). The results herein were comparable to those obtained from the pooled European populations. Moreover, these results can be used for the improvement of the donor-recipient matching procedure and to understand better the disease association in Greece.