M. tuberculosis infection initiates when fine aerosol particles containing the bacteria coughed up by an individual with active disease are deposited in the lower lungs of a new host. The bacteria recruit macrophages to the surface of the lung, which become infected, and serve to transport the bacteria across the lung epithelium to deeper tissues. A new round of macrophage recruitment to the original infected macrophage is initiated, forming the granuloma, an organized aggregate of differentiated macrophages and other immune cells. The granuloma in its early stages expands infection by allowing bacteria to spread to the newly arriving macrophages. As adaptive immunity develops, the granuloma can restrict bacterial growth. However, under many circumstances, the infected granuloma macrophages can undergo necrosis, forming a necrotic core that supports bacterial growth and transmission to the next host.

Dica da página veio da minha grande mestra em microbiologia, a Dra Angela von Nowakonski.