Distribution of HLA-ABC allele groups in a cohort of Chilean rheumatoid arthritis patients and healthy individuals

BACKGROUND: Rheumatoid Arthritis (RA) is an autoimmune disease in which HLA-DRB1 alleles encoding the "Shared Epitope" (SE), located in the β-chain of class II HLA-DR molecules, constitute the main genetic risk factor. However, there is scarce information about the role of HLA class I genes (HLA-ABC) in RA susceptibility. The present work aimed to evaluate the distribution of HLA-ABC allele groups in a cohort of Chilean RA patients and healthy subjects (HS), and to explore the influence of HLA-DRB1 SE alleles on this distribution. RESULTS: 135 RA patients and 122 HS were genotyped for HLA-ABC. The most frequent allele groups were HLA-A*02 (24.0%), HLA-B*39.1 (14.2%), and HLA-C*07 (24.7%) for RA patients, and HLA-A*02 (31.5%), HLA-A*24 (12.8%) and HLA-C*07 (17.7%) for HS. RA patients presented a significantly higher frequency of HLA-C*07 (p = 0.0015) and HLA-B*39.1 (p = 0.037) allele groups compared to HS. After applying the Bonferroni correction, the significant difference remained only for the HLA-C*07 allele group (p = 0.015). In a subset of RA patients (n = 60), positive for HLA-DRB1 SE alleles, the most frequent HLA-ABC allele groups were HLA-A*02 (0-33.3%), HLA-B*39.1 (0-16.7%), and HLA-C*07 (22.2-60.0%), whereas HLA-B*39.2 and HLA-B*52 were the least frequent ones. Overall, HLA-C*07 was the most frequent allele group across RA patients carrying HLA-DRB1 SE alleles. CONCLUSIONS: The HLA-C*07 allele group shows a significantly higher presence in RA patients compared to HS. In contrast, the distribution of most other HLA-ABC allele groups in this cohort displays a similar frequency between RA patients and HS, consistent with data from different populations.