T cell-mediated cytotoxicity induced by Listeria monocytogenes. I. Activation of Listeria antigen-responsive T cells.

Soon after rats are infected with Listeria monocytogenes (LM), Listeria antigen- (LMA) responsive lymphocytes are delivered to the animal's thoracic duct. These LM-responsive lymphocytes can be restimulated in vitro by LMA to generate cells that have a potent cytolytic capability. The activation of LMA responsive lymphocytes is immunologically specific and dependent upon the activity of histocompatible accessory cells. Neither cell-free LMA nor LMA-pulsed allogeneic accessory cells can promote a significant cytotoxic response by negatively selected responder lymphocytes. LM-dependent cytolytic lymphocytes differ from natural killer (NK) cells inasmuch as their activation is not facilitated by interferon (IF). Likewise, supernatants from cultures containing specifically sensitized thymus-derived (T) lymphocytes and histocompatible LMA-pulsed accessory cells fail to augment (day 2 and day 3 supernatants actually inhibit) the activation process. The results imply that the successful activation of LM dependent cytolytic lymphocytes requires the cooperative interplay of responder T cells and specific-antigen-pulsed accessory cells.