HLA-DRB1 and Autoimmunity: Of the three HLA regions, class II HLA exhibits the greatest polymorphism and gene density [1]. Genes most frequently associated with class II include HLA-DPB, HLA-DQB and HLA-DRB, with HLA-DRB being the most frequent. There has also been a stronger association of HLA class II alleles with several autoimmune conditions compared to other classes of HLA [1].