Figure 8

Figure 8

Origin of Mtb and early events in the development of post-primary TB. (A) An often-cited description for the evolution of post-primary (reactivation) TB is that immune dysfunction results in progressive necrosis and liquefaction of the granuloma, exuberant multiplication of dormant Mtb, disruption of the integrity of the granuloma wall, and spillage Mtb-filled necrotic granulomatous content into the airways. Pneumonia forms due to endobronchial spread of granuloma content. (B) An alternative description of post-primary TB is based on the paradigm chronic stable granulomas are mostly sterile and that the dormant Mtb that “reawaken” originated from lymph nodes. fat cells, and airway epithelial cells causing a bronchogenic lipoid pneumonia. Granulomas may form around pockets of necrotizing pneumonia. As discussed in the text, it is plausible that both reactivation models occur. Mtb, Mycobacterium tuberculosis; TB, tuberculosis.