HLA-A, -B, and -DRB1 allele-group and haplotype profiles of the Azerbaijani population.

The Human Leukocyte Antigen (HLA) system is critical for immune recognition and transplantation compatibility. Despite its strategic location at the crossroads of the Caucasus, Anatolia, and the Middle East, comprehensive immunogenetic data for the Azerbaijani population remain limited. This study aimed to characterize HLA-A, -B, and -DRB1 allele-group and haplotype frequencies and establish a framework for optimized donor matching. We analyzed HLA-A, -B, and -DRB1 allele-group frequencies in 2301 healthy donors from Azerbaijan. Data were analyzed using the expectation-maximization algorithm for haplotype estimation, Hardy-Weinberg equilibrium (HWE) testing, and linkage disequilibrium (LD) analysis. An in-house donor matching system was developed to facilitate institutional registry searches. A total of 19 HLA-A, 31 HLAB, and 13 HLA-DRB1 allele groups were identified. The most frequent alleles were A*02 (21.3%), B*35 (17.4%), and DRB1*11 (19.3%). The predominant three-locus haplotype was A02 ∼ B51 ∼ DRB104 (1.02%). Statistical analyses revealed modest deviations from HWE and significant LD between loci. Principal Coordinate Analysis (PCoA) demonstrated that the Azerbaijani population occupies an intermediate immunogenetic position, showing strong affinity with Iranian, South Caucasian, and Anatolian Turkish populations. This study provides the first comprehensive immunogenetic reference for Azerbaijan, deposited in the Allele Frequencies Net Database (AFND: 3853). Our findings highlight a distinct yet regionally connected immunogenetic profile, emphasizing the importance of local donor registries. The integration of these data into an in-house donor matching algorithm offers a vital translational strategy to enhance transplantation success and clinical outcomes in the region.