CD4 and pulmonary fibrosis: Boveda-Ruiz et al. showed that depletion of CD4+CD25+ regulatory T-cells subpopulation at early stages of BLM-induced lung damage is associated with fibrosis reduction, but this depletion later leads to increased lung fibrosis, meaning that Tregs can be harmful at early stages, but protective at later stages of pulmonary fibrosis in mice [180].