Figure 5.

Sequestration of secreted mycobacterial antigens. Secreted mycobacterial antigens are asymptomatically produced and sequestered in foamy alveolar macrophages of the early lesion of PPTB for months before the onset of caseous pneumonia and clinical disease. Simultaneously, the tissue develops extreme hypersensitivity related to T cells in the alveolar walls. Evidence suggests that this is the essential developmental lesion of PPTB. Release of this antigen causes inflammation and necrosis. (Immunostain for mycobacterium tuberculosis (MTB) antigens 400×, Insert 1000×).