CD4 and renal fibrosis: Similar anti-fibrogenic effects were observed when CD4+ T cells were depleted in wild-type mice after obstructive injury (Tapmeier et al., 2010), whereas reconstitution with purified CD4+ T cells in RAG1-knockout (B, T cell-deficient) mice led to restored fibrogenic responses following obstructive injury (Tapmeier et al., 2010), suggesting that lymphocytes, especially CD4+ T cells, have a critical role in the pathogenesis of renal fibrosis induced by obstructive injury.