HLA-DRB1 and type 1 diabetes mellitus: For example, the major genetic contribution to rheumatoid arthritis (RA) involves DRB1 alleles such as DRB1*04:01 and *04:04 [17], whereas HLA-DQ alleles, especially DQB1:02:01 and DQB1:03:02, provide the major genetic contribution to type 1 diabetes (T1D) [16].