Induction of TNF-alpha, IL-12, IL-10, MCP-1 and IL-8 in Human Peripheral Blood Monocytes in Response to the Cell Wall-Associated Triton X-100 Soluble Protein (TSP) Antigens of Mycobacterium tuberculosis

ABSTRACT

Mycobacterium tuberculosis is a potent inducer of cytokine production by mononuclear phagocytes, which are an important cellular component in the first line immune defence. In this study, the cell wall-associated Triton X-100 soluble protein (TSP) antigens, TSP-H37Rv, TSP-H37Ra, TSP-K, and TSP-BCG, were isolated from M. tuberculosis H37Rv, M. tuberculosis H37Ra, M. tuberculosis K-strain, and M. bovis BCG, respectively. The monocytes were isolated from the peripheral blood mononuclear cells of healthy individuals and were co-cultured with each TSP antigens and the secretory proteins of M. tuberculosis (PPD and 30-kDa antigen) to measure the production of cytokines; tumor necrosis factor (TNF)-a, interleukin (IL)-12, IL-8 and monocyte chemotactic protein-1 (MCP-1). The TSP-H37Rv antigen- stimulated monocytes showed higher level of TNF-a and IL-12 production compared to those of other TSP antigens and PPD. Especially, IL-12 production in response to the TSP-H37Rv antigen was significantly elevated in comparison with that of PPD-stimulated monocytes (TSP-H37Rv, 255.5+/-256.9 pg/ml; PPD, 55.7+/-55.4 pg/ml). However, the 30-kDa antigen did not induce TNF-alpha expression and also showed the lowest level of cytokine and chemokine production by monocytes. MCP-1 and IL-8 production were similarly increased in response to all TSP antigens and the PPD antigen. The production of IL-12 by the TSP-H37Rv antigen stimulation was significantly increased in PPD reactors than that in the non-reactor group, while the levels of other cytokines stimulated with each TSP antigens, 30-kDa and PPD antigen were not significantly different between the tuberculin reactor and the non-reactor groups. These results suggest that the cell wall-associated TSP antigen isolated from M. tuberculosis H37Rv acts as a more potent IL-12 inducer than the PPD antigen in innate immune response and thus it could further activate the Th1-mediated immune responses effectively against M. tuberculosis infection.