HLA-DRB1 and rheumatoid arthritis: In a subset of RA patients (n = 60), positive for HLA-DRB1 SE alleles, the most frequent HLA-ABC allele groups were HLA-A*02 (0–33.3%), HLA-B*39.1 (0–16.7%), and HLA-C*07 (22.2–60.0%), whereas HLA-B*39.2 and HLA-B*52 were the least frequent ones.