CD4 and myeloid sarcoma: When I was reviewing grant applications for the National MS Society from 1998 to 2005, many applications began their background section with the statement: “MS is a T-cell mediated autoimmune disease.” The literature is also full of such confident assertions, e.g., “(MS) is characterized histologically by the infiltration of encephalitogenic TH1/TH17-polarized CD4(+) T cells” (27).