Detection of anti-interferon-gamma autoantibodies in subjects infected by Mycobacterium tuberculosis

Among the cytokines involved in defensive mechanisms against Mycobacterium tuberculosis infection, special attention has been given to interferon-gamma (IFN-gamma); a local synthesis of this cytokine as well as IL-2 (type 1 cytokines) at the site of disease in patients with tuberculous pleuritis has been demonstrated. Moreover, high levels of IgG autoantibodies against IFN-gamma have been shown in several clinical situations. It has been suggested that these antibodies could serve to limit the intensity or duration of the immune response or be able to interfere with the pathophysiological effects of IFN-gamma.

To investigate the potential role of anti-IFN-gamma antibodies in the course of M. tuberculosis infection.

Investigation of the presence of these antibodies in sera from healthy and ill subjects infected with M. tuberculosis in relation to the extent of the disease and the presence of IFN-gamma in sera by enzyme-linked-immunosorbent assay (ELISA). In order to investigate the presence of these antibodies at the site of infection we included 12 pleural fluids from tuberculosis patients and 9 pleural fluids from other origins.

In the course of M. tuberculosis infection the production of anti-IFN-gamma IgG antibodies is induced, being particularly higher in healthy skin test converters. Among tuberculosis patients, the presence of anti-IFN-gamma autoantibodies is significantly associated with detectable levels of the cytokine in sera. Levels of anti-IFN-gamma antibodies in moderately advanced and far advanced tuberculosis patients are significantly greater than in healthy individuals. These antibodies increase at the site of infection.

Anti-IFN-gamma antibodies must be considered as a new element in the immune response to M. tuberculosis. It would be of great interest to investigate this point especially at the site of infection.