HLA-DRB1 and multiple sclerosis: To refine the relation between the MHC and multiple sclerosis, we first screened the region by genotyping 110 SNPs and two class II HLA loci (HLA-DRB1 and HLA-DQB1) in a cohort of 930 trio families (an affected individual and their parents): 480 from the United Kingdom and 450 from the United States.