Figure 1.

Transmission and pathogenesis of TB after Mtb infection. (A) Macrophages use PRRs to take up Mtb by recognizing various PAMPs on the surface of the bacteria. Recognition of Mtb is more precisely facilitated by TLR2, which triggers phagocytosis, innate immune responses and various cellular processes such as antigen presentation, inflammasome activation, autophagy, and apoptosis resulting in the eradication of intracellular Mtb. (B) However, failure to eradicate intracellular Mtb after infection, results in either the latent or active form of TB. In the latent phase, the Mtb can remain dormant within the granuloma for years. However, when the immune system becomes weakened, Mtb can become reactivated, subsequently inducing the death of the infected macrophages through necrosis.