Immunomodulatory effect of Listeria monocytogenes infection. II. Natural cell cytotoxicity in infected mice.

The natural cell cytotoxicity of blood leukocytes, splenocytes and peritoneal cells derived from Balb/c mice being on day 1, 3, 5, 7, 9 of listeriosis to allogeneic fibroblast L 929 was examined. The intensity of cytotoxic reaction was assessed by the per cent of specific 51Cr release from target cells. To check if this reaction correlates with the level of monocyte-macrophage lineage cells present in the effector cells of if it depends on the development of delayed type hypersensitivity to Listeria antigen, Balb/c mice were infected with Listeria monocytogenes and simultaneously treated with ATS. It was found that Listeria monocytogenes infection in mice enhanced the natural cell cytotoxicity of tested effectors cells, particularly of peritoneal cells in animals being on the 5th-7th day of listeriosis. The treatment of mice with ATS which is known to inhibit the development of delayed type hypersensitivity to Listeria antigen, completely suppressed the stimulatory effect of this infection on the natural cell cytotoxicity to allogeneic fibroblasts. This finding suggests that the enhancement of natural cytotoxic activity of tested effector cells results from the action of activated macrophages cooperating with Listeria sensitized T lymphocytes.