title: Clostridium difficile toxins A and B inhibit human immune response in vitro.
abstract: Two Clostridium difficile toxins isolated from strain VPI 10463 were tested for their effect on different human T-cell proliferation systems. In mitogen- and antigen-driven T-cell proliferation systems, toxins inhibited the proliferative response in a dose-dependent fashion. In interleukin-2-driven culture systems, no effect of toxins could be found on preactivated T cells. We suspected that monocytes were the influenced cells, since in antigen- and mitogen-driven systems monocytes were necessary for the proliferative response, whereas the interleukin-2-driven system was independent of monocytes. To prove this concept, purified monocytes were treated with toxins. The treatment was found to markedly reduce the capacity of monocytes to stimulate T-cell proliferation. No inhibition of the proliferative response was measured when, instead of monocytes, resting or preactivated T cells were treated with toxins. These experiments clearly show that C. difficile toxins interact with monocytes and not with T cells. The effect of toxins on cells of the immune system might be one factor in the development of pseudomembranous colitis.
mesh_terms: D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology*; D004768:Enterotoxins; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D008934:Mitogens / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; D007376:Interleukin-2; D008934:Mitogens; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile