FIG 1.

Progression of tuberculosis. Here we consider symptomatic disease the beginning of the disease. During infection, MTBC bacteria (red dots) actively colonize different areas of the lungs. During this phase, most cells are actively growing. Thus, they are potentially susceptible to treatment and the immune response. Macrophages (blue cells) phagocytose MTBC cells, but dormant cells are better able to survive inside macrophages. T cells (light green), B cells (dark green), and giant foam cells (orange) contain the infection in a structure called a granuloma. Thus, there are three possible outcomes after treatment starts: interruption or failure of treatment that leads to a relapse where MTBC bacteria break the barrier of the granuloma, reactivating infection (A); partially effective treatment that leads to a stable quiescent structure with contained viable cells, which persist after treatment stops (B); or eradication of the disease (MTBC cells are entirely removed from the healing granuloma) (C).