IL17A and Hepatic fibrosis: The protective role of CD4+CD25+ cells and the progressive role of CD4+ IL-17+ cells during liver fibrosis were then demonstrated by mRNA levels of the pro-fibrotic genes (α-SMA, TGF-β1, PDGF-BB, collagen I/III) in liver tissues, for the depletion of CD25+ cells up-regulated, whereas the depletion of IL-17+ cells down-regulated these genes.