CD4 and renal fibrosis: Furthermore, depletion of CD4+ T cells was proved to retard UUO-induced renal fibrosis (Liu et al., 2012), and reconstitution of lymphopenic recombination activating gene (RAG)−/− mice with CD4+ T cells but not CD8+ T cells prior to unilateral ureteric obstruction (UUO) led to more severe renal fibrosis manifesting a significant increase in interstitial expansion and collagen deposition, which revealed the pivotal role of CD4+ T cells in renal fibrosis (Tapmeier et al., 2010).