IL17A and autoimmune disease: In addition to the fact that the differentiation of Th17 and Treg cells is closely related (Zhou et al., 2008), both cells display instability and plasticity during immune responses; Foxp3+ Treg cells can be converted into IL-17-producing cells in certain inflammatory environments and may potentially contribute to pathogenesis of autoimmune diseases, whereas Th17 cells transdifferentiate into Treg cells during resolution of inflammation (Gagliani et al., 2015; Obermajer et al., 2014).