HEAT-KILLED BACILLUS-SUBTILIS INHIBITS T-CELL PROLIFERATIVE RESPONSE TO MITOGENS AND RECALL ANTIGENS

Heat-killed vegetative forms of Bacillus subtilis were found to impair considerably the capacity of human T-lymphocytes to secrete interleuk in-2 (IL-2) and to proliferate (in terms of [H-3]thymidine incorporati on) after phytohaemagglutinin (PHA) stimulation. B. subtilis was also found to interfere with T-cell proliferation induced by concanavalin A (Con A) and the recall antigen tetanus toroid (TT). The suppressive a ctivity was dependent on bacterial concentration, and was not ascribed to mitogen, medium-nutrient absorption or cell killing. Moreover, B. subtilis did not interfere with mitogen-induced IL-2 receptor expressi on on the T-cell surface. On the other hand, B. subtilis did not inter fere with T-cell proliferation induced by phorbol myristate acetate (P MA) and ionomycin stimulation. All data obtained suggest the binding o f B. subtilis subcomponents to - or very close to - the T-cell recepto r (TCR). Identification and purification of the basic structure(s) or component(s) of B. subtilis with TCR antagonist activity in vitro will help to exploit different aspects of T-cell activity and development, and possibly, will provide a means of specific control or modificatio n of the immune response. (C) 1997 International Society for Immunopha rmacology.