Macrophages mediate the first line of defense in the host against various intracellular pathogens. They are armed with several immune-effector mechanisms to detect and combat pathogens. However, intracellular pathogens have developed strategies to overcome the macrophage protective immune responses and colonize inside the macrophages. Tuberculosis (TB), both pulmonary and extrapulmonary, is an infectious disease of global concern caused by Mycobacterium tuberculosis. M. tuberculosis is a highly successful pathogen and has acquired various strategies to downregulate critical innate-effector immune responses of macrophages such as phagosome-lysosome fusion, antigen presentation, autophagy, and inhibition of reactive oxygen (ROI) and reactive nitrogen (RNI) species to ensure its longer survival inside the macrophages. In addition to these, the bacilli also modulate T cell immune response which can help the bacilli to survive inside the host for a long time. In this chapter, we focus to describe important macrophage innate defense mechanisms and the signaling that can influence T cell adaptive response and the strategies adopted by the bacilli to exploit these signaling cascades to favor its replication and persistence inside the macrophages for establishing a productive infection.
Part of the book: Mycobacterium