CD4 and renal fibrosis: Reconstitution of lymphopenic immune-deficient recombination activating gene (RAG) knockout mice with purified CD4+ T cells prior to ureteric obstruction significantly increased the interstitial expansion and collagen deposition [6] We previously found that depletion of CD8+ T cells increases renal fibrosis following ureteric obstruction, and interferon-γ (IFN-γ)-expressing CD8+ T cells contribute to this process [8].