The main established association between HLA class II molecules and RA has been correlated to the polymorphic region of the β-chain comprising amino acid residues 70–74 (12) that line the MHC-II pocket close to peptide anchor residue p4 and that is shared between HLA-DRB1*04:01, *04:04, and *01 alleles (Figure S1A in Supplementary Material). The gene discussed is HLA-DRB1; the disease is rheumatoid arthritis.