Evidence for a superantigen in human tuberculosis.

T cells are not only required for resistance to tuberculosis, but they likely contribute to the tissue damage characteristic of the disease. To define better the T cell populations that contribute to the immunopathogenesis of human tuberculosis, we investigated the T cell receptor (TCR) beta chain repertoire expressed in patients with tuberculous pleuritis. Analysis by polymerase chain reaction and flow cytometry indicated an expansion of V beta 8+ T cells at the site of disease in some donors, suggesting the possibility that Mycobacterium tuberculosis contains a superantigen. M. tuberculosis induced strong T cell proliferative responses in tuberculin-negative healthy donors in vitro, with preferential expansion of V beta 8+ T cells, independent of the CDR3 region. T cell stimulation was MHC class II-dependent and did not require antigen processing by the antigen-presenting cells. These findings are consistent with the presence of a superantigen in M. tuberculosis, aspects of which may contribute to the immunopathology of tuberculosis and to the adjuvant properties of M. tuberculosis.