Non-SE alleles, such as HLA-DRB1*09:01 in Asian populations [32,33], have also been reported to be associated with RA [35] or ACPA levels, and the associations of HLA-DRB1 with ACPA levels are mainly explained by the 74th AA, alanine [32,33]. Here, HLA-DRB1 is linked to rheumatoid arthritis.