IL17A and Autoimmunity: In mouse models, microbiota species that skew T helper differentiation toward Th17 have shown to worsen autoimmunity, and in turn, IL17A-deficient mice are protected from experimental autoimmune encephalomyelitis due to changes in gut microflora [65,68] In terms of cancer, IL-17 has been shown to have both pro- and anti- tumorigenic effects based on the cancer type.