HLA-DRB1 and rheumatoid arthritis: Analysis of six GWAS cohorts involving 19 992 individuals, including 5018 cases of anti-citrullinated peptide-positive RA, at the level of SNP, haplotype, and HLA type revealed the strongest association was with rs17878703, corresponding to amino acid position 11 of DRβ1, with further independent signals revealed for variants at amino acids 71 and 74, all located centrally in the peptide-binding groove [43].