CD4 and myeloid sarcoma: Until 2007, only one inherited risk factor had been validated across multiple populations, the major histocompatibility complex (MHC) class II DRB1p1501 allele, which confers a 3- to 4-fold relative risk, and implicates Antigen presentation to CD4 T-cells in MS pathogenesis.5 The advent of whole-genome screening tools has now enabled the discovery of new MS risk genes, including interleukin 7 receptor (IL7R) and interleukin 2 receptor A gene (IL-2RA), CD58, and CLEC16A.6 In 2007, the first genome-wide association study (GWAS) for MS susceptibility was reported.