In vitro analysis of the cellular mechanisms involved in immunity to tuberculosis.

Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis. Protection against and pathogenesis of tuberculosis greatly depend on specific T lymphocytes, and it is generally assumed that CD4+ T cells--through lymphokine-mediated macrophage activation--are the major mediators of the host response to tuberculosis. In the present report, results from experimental tuberculosis studies in mice are summarized which indicate that both CD4+ and CD8+ T lymphocytes are generated during tuberculosis. Furthermore, evidence is presented that both T cell populations are involved in protection against and pathogenesis of tuberculosis and that the final outcome of the host response depends on an intricate balance between these two types of T cells.