Inhibition of Mycobacterium bovis BCG-Induced Tumor Necrosis Factor Alpha Secretion in Human Cells by Transforming Growth Factor β

The effect of exogenous transforming growth factor β (TGF-β) on Mycobacterium bovis BCG-induced tumor necrosis factor alpha (TNF-α) production by human mononuclear cells was studied. It was found that TNF-α production by human cells stimulated with BCG was significantly inhibited by TGF-β. The specificity of the observed inhibition was demonstrated, since the addition of an anti-TGF-β neutralizing monoclonal antibody completely reversed the inhibitory effect. Furthermore, the suppressive effect of TGF-β on TNF-α secretion in this system was not due to a direct cytotoxic effect, since cell viability was comparable in the presence or absence of TGF-β. Interestingly, our results demonstrated comparative suppressive effects of TGF-β and interleukin-10 on BCG-induced TNF-α secretion. Together, the data demonstrate, for the first time, that TGF-β inhibits BCG-induced TNF-α secretion by human cells.