For instance, TH1 and TH17 cells, characterized by their secretion of interferon gamma (IFNγ) and interleukin (IL)-17 (IL-17A/F), respectively, have deleterious activities in tissue-specific autoimmune diseases, including inflammatory bowel disease and MS, as demonstrated in mouse models and suggested in human pathology12,13. The gene discussed is IL17A; the disease is myeloid sarcoma.