IL-12 attenuates bleomycin-induced pulmonary fibrosis

Interleukin (IL)-12 is a potent inducer of interferon (IFN)-gamma. We postu lated that IL-12 would attenuate bleomycin-induced pulmonary fibrosis. To t est this hypothesis, we administered IL-12 or murine serum albumin to bleom ycin-treated mice by daily intraperitoneal injection until day 12. Mice tre ated with IL-12 demonstrated decreased hydroxyproline levels compared with control treated mice. Furthermore, administration of IL-12 led to a time-de pendent increase in both lung and bronchoalveolar lavage fluid IFN-gamma. T he antifibrotic effect of IL-12 could be attenuated with simultaneous admin istration of neutralizing anti-IFN-gamma antibodies. These findings support the notion that IL-12 attenuates bleomycin-induced pulmonary fibrosis via modulation of IFN-gamma production.