HLA-DRB1 and rheumatoid arthritis: Further analysis of the DRB1*04 subtype SE alleles (DRB1*0401, DRB1*0404, DRB1*0405, DRB1*0408 and DRB1*0410) in the context of ACPA subgroups revealed a significant association between DRB1*04 SE alleles and ACPA-positive RA in all the three ethnic groups.