Matrix metalloproteinases (MMPs) have shown to play a crucial role in extracellular matrix remodeling in various pathophysiological tissue states. While the role of MMPs in cancer, arthritis, and neurodegenerative diseases has been explored extensively (1,2), the participation of MMPs as central proteases in infectious disease progression is relatively unknown. A recent study from our lab showed significant elevation in the expression of a tissue collagenase, membrane type 1 matrix metalloproteinase (MT1-MMP/MMP14), by macrophages during influenza infection (3). Inhibition of MT1-MMP by highly selective inhibitor suggested a novel host-oriented antipathogenic mechanism. Specifically, our results strongly suggest that MT1-MMP contributes to the progression of pathogen infection mechanisms by shedding cell surface ligands. Here, we investigate the molecular mechanisms by which MT1-MMP effects the course of infection. To achieve this, we established two in vitro infection models: infection of macrophages with salmonella and infection of lung epithelial cells with influenza. We used anti-MT1-MMP inhibitory antibody in order to specifically inhibit MT1-MMP proteolytic activity. Our results show a reduction in bacterial and viral entry after MT1-MMP inhibition. Overall, our results suggest that MT1-MMP proteolytic activity regulates host-pathogen interactions during early stages of both bacterial and viral infections.