HLA-DRB1 and rheumatoid arthritis: The risk of subsequent RA onset was found to be increased in women who had a child with an allele encoded with the share epitope (human leukocyte antigen-DRB1 [HLA-DRB1] alleles encoding QKRAA, QRRAA or RRRAA amino acid sequence at positions 70–74 of the HLA-DRβ1 chain [26]).