Host response to Mycobacterium tuberculosis.

Critical to the complete expression of the virulence of M. tuberculosis and thereby its pathogenesis in human infection, is the ability of this pathogen to interact with the host in a specific manner. To date, cytokine circuits during tuberculosis and M. tuberculosis infection have been studied most intensely. With this regard, both the whole M. tuberculosis and its protein and non-protein moieties appear to be influential on the in situ cytokine profile, and consequently, to the final outcome of infection. The interplay and final balance of macrophage activating and immuno-enhancing cytokines versus macrophage deactivating and immunosuppressive cytokines most likely determines the final expression of M. tuberculosis infection. Further, cytokine circuits also underlie the immunopathology of tuberculosis. Modulation of the in vivo cytokine milieu may allow the development of more effective vaccines to prevent M. tuberculosis infection, and adjunctive immunotherapy to improve treatment of tuberculosis.