Immunologic basis of tuberculosis: Disease and the treatment paradox

Tuberculosis is a disease of varied presentations. In endemic countries, the diagnosis is usually made by exclusion. It is caused by an intracellular bacterium, which stimulates and represses the immune system simultaneously by means of different cytokines. A delicate balance between the pro-inflammatory and the anti-inflammatory stimuli is required for effective containment of infection with minimal host cell damage. Antitubercular therapy may offset this balance by killing the pathogen and releasing new antigens in the locally infected tissue. Heightened immunological response seen after initiation of therapy caused exacerbation or appearance of new symptoms. Two cases of immunocompetent young adults have been presented to highlight the paradoxical response to antitubercular therapy and immunological basis of such reactions. Paradoxical response to therapy should be recognized and managed effectively and unnecessary or invasive investigations should be avoided.