The human leukocyte antigen (HLA) genes are the most forceful predisposing gene variants for developing RA, within the HLA class II histocompatibility antigen-DRB1-beta chain (HLA-DRB1) gene, a conserved amino acid sequence that is shared through multiple RA-associated risk alleles. Here, HLA-DRB1 is linked to rheumatoid arthritis.