STAT1 and pulmonary fibrosis: This study indicated that STAT-1-/- mice are more susceptible than wild-type mice to bleomycin-induced lung fibrosis owing to (1) enhanced fibroblast proliferation in response to growth factors (EGF and PDGF), (2) stimulation of fibroblast growth by a STAT-1-independent IFN-γ signaling pathway, and (3) increased activation of STAT-3.