Figure 2
From: Apoptosis is an innate defense function of macrophages against Mycobacterium tuberculosis
Extrinsic and intrinsic pathways of apoptosis. During Mtb infection, several signals generated by the infected macrophage can trigger apoptosis. For example, TNF production can activate the extrinsic pathway resulting in caspase-8 activation. What triggers the intrinsic pathway is unknown. Cellular stress or caspase-8 activation can result in BID cleavage, leading to BAX activation, and the ensuing events lead to cytochrome c translocation from the mitochondrial intermembrane space into the cytosol where it activates caspase-9. Alternately, caspase-8 activation can directly lead to caspase-3 activation in certain cells (type I). cyt c, cytochrome c; IM, inner mitochondrial membrane; Mtb, Mycobacterium tuberculosis; OM, outer mitochondrial membrane; TNF, tumor necrosis factor; TNFR, TNF receptor..
