Research has highlighted the close association between the major histocompatibility complex (MHC) and the genetic predisposition to RA, particularly the polymorphism of human leukocyte antigen (HLA) gene loci, where HLA-DRB1 alleles and their encoded amino acid sequence patterns (shared epitope, SE) play a pivotal role in RA susceptibility (9, 10). Here, HLA-DRB1 is linked to rheumatoid arthritis.