HLA-DRB1 and multiple sclerosis: The fourth most cited study, “Mapping Multiple Sclerosis Susceptibility to the HLA-DR Locus in African Americans” (Hollenbach and Oksenberg, 2015), was one of the first to examine MS genetics outside European populations, demonstrating that HLA-DRB1 (not DQB1) is the primary risk gene in African Americans.