Cytokine regulation of disease progression in leprosy and tuberculosis.

Studies in our laboratory have focussed on the role of cytokines in the regulation of the cellular immune response and disease progression in two important mycobacterial infection of man, namely leprosy and tuberculosis. Our studies in leprosy have involved the use of key regulatory cytokines such as IFN-gamma in the modulation of the cellular response of infected patients. We have investigated the effect of intradermal administration of low dose IFN-gamma on the lesions of anergic lepromatous patients and have reported an accelerated bacillary clearance from the skin. This was associated with the local accumulation of mononuclear cells and killing of infected macrophages. However, IFN-gamma administration also resulted in the induction of erythema nodosum leprosum, a toxic syndrome associated with excess TNF-alpha production. Both the toxic symptoms and the high levels of TNF-alpha production could be inhibited by thalidomide treatment, a drug we have shown reduces the half life of TNF-alpha mRNA. In preliminary clinical trials in tuberculosis patients we have attempted to use thalidomide to reduce TNF-alpha production and toxicities. These results are discussed.