Mycobacterium tuberculosis (MTB) is an intracellular pathogen that has evolved strategies to enable growth in macrophages. The bacterium is able to inhibit fusion of phagosomes with lysosomes through secretion of some bacterial components and modulation of host intracellular signaling pathways. Furthermore, it has been shown that phagositosed MTB is killed within macrophages after treatment with IFN-γ in vitro. However, virulent MTB is capable of surviving in macrophages in vivo and persists in host even after acquired immunity has developed. These data suggest that MTB has developed a sophisticated immune evasion mechanism. In this issue, the strategies of MTB for intracellular survival and immune evasion, which have been unraveled so far, are shown and the mechanisms are discussed.
