MMP9 and infection: This event will trigger a pro-inflammatory reaction and secretion of MMP9 by epithelial cells and M. tuberculosis-infected macrophages, leading to the recruitment of uninfected macrophages and other immune cells to contain the infection in a granuloma (48, 49), although the arrival of uninfected cells may be exploited by pathogenic mycobacteria to further disseminate the infection (50–52).