REGULATION OF GRANULOMA IN TUBERCULOSIS

This proposal is designed to characterize the granulomatous response of tuberculosis. Although generally viewed as a critical element in host defense against M. tuberculosis, little is known about the tuberculous granuloma at the cellular, molecular, and biochemical level. The unusually high incidence of disseminated tuberculosis and the markedly deficient granulomatous response seen in AIDS patients suggest a significant role for T-cells in the regulation of granuloma formation. We have recently developed a murine experimental tuberculosis model of protein calorie malnutrition (PCM) in which mice receiving a protein- deficient diet experienced fulminant and rapidly fatal infection associated with markedly increased bacterial burden and poorly formed granuloma. In contrast, control animals fed a regular diet develop a vigorous granulomatous response and remain clinically well for months. Thus, our PCM model provides a system which allows comparative studies on the granulomatous reaction during the course of tuberculous infection. The goals of this proposal are: i) to characterize the cellular components that participate in the granulomatous reaction by immunocytochemical and electron microscopic studies; ii) to evaluate the role of T-lymphocyte subsets in the regulation of the granulomatous reaction by T-cell cloning, examination of the differentiation of this immune cell in the granuloma, adoptive transfer studies, and analysis of T-cell receptor usage; iii) to study the expression of cytokines in the tuberculous granuloma by immunohistochemical, in situ hybridization, and competitive RT-PCR techniques; and iv) to examine the interaction between granulomatous macrophages and T-cells. It is hoped that these studies would allow identification of immunological elements whose roles in the granulomatous reaction can be tested in vivo. We believe that results generated from these studies would help gain insight into the host defense mechanisms against the tubercle bacillus, and ultimately, to enable appropriate manipulation of the granulomatous response in various disease states that translate into therapeutic augmentation of resistance against pathogens, or abatement of immunopathologic processes triggered by this reaction.