Dan Littman Part 1: Th17 Cells and Innate Lymphoid Cells in Barrier Defense and Inflammatory Diseases

Dan Littman discusses the opposing roles of Th17 cells. They protect mucosal surfaces from infection with bacteria and fungi, but they can also cause autoimmune inflammation. Using a mouse model of autoimmunity called experimental autoimmune encephalomyelitis (EAE), Littman and his lab have shown that there are two types of Th17 cells. Non-pathogenic Th17 cells are induced by the microbiota and protect barrier surfaces, while pathogenic Th17 cells are induced by the presence of IL-23, likely the result of inflammation elsewhere in the body.  Both types Th17 cells secrete the cytokines IL-17A, IL-17F and IL-22, however, pathogenic Th17 cells also secrete interferon gamma (IFNγ) which induces further inflammation and autoimmune disease.  In the last 10 years, several classes of innate lymphoid cells have been found to share similar cytokine profiles to T helper cells and these cells appear to be another important layer in protecting surfaces in the gut and lung from infection.