1) alveolar macrophages recognize, engulf & attempt to destroy bacilli 2)bac grow on log scale within macrophages, unable to stop bac growth 3)infected areas transform into granuloma(wall of lymphocytes) -->chest pain. Granuloma forms solid caseous center where bac can survive for years, most don't exhibit disease progression (latent state) 4)caseous center liquifies and fills lungs with free-floating bac=pulmonary TB. Bac can go to organs via lymphatic system or bloodstream=extrapulmonary TB