Even though a pathogenic role of CD4+ T cells in MS would be supported by the genetic association of MS with MHC class II haplotypes and associated molecules [23], the inflammatory cells from the adaptive immune system within MS lesions mainly consist of MHC class I restricted CD8+ T cells [24] while MHC class II restricted CD4+ T cells are rare and restricted to locations deep within CNS lesions and the cerebrospinal fluid (CSF) [25, 26]. The gene discussed is CD8A; the disease is myeloid sarcoma.