Events following entry of bacilli: Phagocytosis of by alveolar macrophages is the firstevent in the host-pathogen relationship that decidesoutcome of infection. Within 2 to 6 wk of infection,cell-mediated immunity (CMI) develops, and thereis an influx of lymphocytes and activatedmacrophages into the lesion resulting in granulomaformation. The exponential growth of the bacilli ischecked and dead macrophages form a caseum. Thebacilli are contained in the caseous centers of thegranuloma. The bacilli may remain forever withinthe granuloma, get re-activated later or may getdischarged into the airways after enormous increasein number, necrosis of bronchi and represents the last-ditch defense mechanismof the host,.
