IL21 and myeloid sarcoma: Th17 cells produce a range of inflammatory cytokines, including interleukin 17 A/F (IL-17A/F), interleukin 21 (IL-21) and interleukin 22 (IL-22), which are involved in the development of inflammatory foci in the CNS, and neutralization of the key cytokine IL-17 ameliorated symptoms in an animal model of MS: experimental autoimmune encephalomyelitis (EAE).