The immunological life cycle of tuberculosis.

Immune responses to Mycobacterium tuberculosis are only partially effective; they drive the bacteria into a latent state, but rarely eliminate them. Unfortunately, the latent state of M. tuberculosis is reversible, and reactivation tuberculosis is the source of most transmission. Studies in animal models and in humans have not yet yielded a comprehensive picture of the mechanisms or correlates of immunity to M. tuberculosis infection, or of why immunity fails to eradicate the pathogen. This Review proposes that there are distinct stages in the immune response to M. tuberculosis that form an 'immunological life cycle'. It is hoped that this thesis will provide a framework for investigation to understand immunity to M. tuberculosis and to guide tuberculosis vaccine discovery and development.