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Title: Immunomodulatory effects of mycobacteria
Authors: ZHANG LIN
Keywords: environmental mycobacteria immunomodulatory sensitisation cytotoxic activity cross-protection cell-dependent
Issue Date: 9-May-2006
Citation: ZHANG LIN (2006-05-09). Immunomodulatory effects of mycobacteria. ScholarBank@NUS Repository.
Abstract: Prior studies suggest that exposure to environmental mycobacteria (Env) confers protection against subsequent Mycobacterium tuberculosis infection, but the immunological mechanisms remain unclear. To investigate this, cytotoxic activity of T cells responding to Env, against autologous M. bovis bacille Calmette-Gu??rin (BCG)-infected macrophages, was evaluated in peripheral blood cells of healthy adults and splenocytes of Env-immunised mice. T cell subsets and cytokines involved were also examined. The human study showed that Env-specific cytotoxic activity was CD4+ T cell-dependent but IFN-i?? independent. M. chelonae murine immunisation conferred cross-protection against BCG challenge, with reduced BCG counts and inflammatory cells in the lung, but increased splenic lymphocyte proliferation against BCG antigens. Cross-protective cytotoxic responses upon restimulation with other mycobacteria were most significant in M. chelonae-sensitised mice, and weakest in BCG-immunised mice. Overall, the data provide evidence for Env-mediated protection against pathogenic mycobacteria, and suggest mechanisms for reduced efficacy of BCG vaccination following significant Env exposure.
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