Cytokines in tuberculosis

Abstract

Tuberculosis continues to be a model to study the immunological aspects of intracellular infections. A better understanding of the mycobacteria.host interaction would allow a more rational approach to the clinical problems of this disease. Cytokines playa key role in the development of protective immunity as well as in the tissue injury that occurs during the disease. In vitro stimulation with specific antigens of Iymphocytes from tuberculin positive healthy subjects induces a type I cytokine pattern (1'IL.2, 1'IFN.y, -VIL.4, -VIL.5) whereas Iymphocytes from tuberculous patients do not exhibit it. Type I cytokines activate macrophages able to inhibit mycobacteria intracellular growth. In mice, nitric oxide produced by activated macrophages is responsible for such effect; however, the productJon of nitric oxide by human macrophages has not been conclusively demonstrated. Recent reports have shown that infection with M. tuberculosis induces apoptosis in infected macrophages. Apoptosis in such conditions is Tumor Necrosis Factor.a and nitric oxide dependent. Paradoxically, mannosylated liparabinomann (ManLAM), a structural component of the rñycobacterial cell wall, inhibits apoptosis of infected macrophages. These results demonstrate a new aspect of the mycobacteria.macrophage relatJonship that must be finely regulated by both the microorganism and the host.