Restoration of IL-6 signaling in IL-6−/− mice rescues CCl4-induced injury and restores MMP-2 expression to wild-type levels. Hematoxylin and eosin stained liver sections from IL-6−/− mice pretreated with either vehicle (A) or recombinant IL-6 (B) prior to CCl4 (original magnification 10×). Area outlined shown at higher magnification (100×; C, D). Those receiving recombinant IL-6 (B, D) had decreased injury at 24 h compared to control group (A, C). (E) Western blot of MMP-2 protein expression performed on extracts from IL-6−/− mice receiving vehicle (lane 2) compared with those receiving recombinant IL-6 (lanes 3 and 4). At 24 h, there is a significant increase in active MMP-2 expression in IL-6−/− animals, which is decreased in animals receiving recombinant IL-6. The blot probed for β-actin to confirm equal protein loading. Experiments were performed in triplicate.