Contribution of CD8+ T cells to innate immunity: IFN-gamma secretion induced by IL-12 and IL-18.
The role of CD8+ T cells in adaptive immunity is well documented and involves numerous effector mechanisms including direct cytolysis of targets and secretion of cytokines. The role of CD8+ T cells in innate immunity has not been previously appreciated. Using J774 macrophages infected in vitro with the intracellular bacterium, Listeria monocytogenes (LM), we show that CD8+ T cells isolated from naïve C57BL/6 (B6) mice respond rapidly by secreting IFN-gamma. CD8+ T cells secreting IFN-gamma can also be found in naïve B6 mice 16 h after infection with LM. This rapid IFN-gamma response is TCR-independent and mediated through the actions of IL-12 and IL-18. Cell surface staining and cell sorting experiments indicate that these novel CD8+ T cells express memory markers. In vitro CFSE-labeling experiments show that IFN-gamma-secreting CD8+ T cells proliferate rapidly after 2 days in culture and after 4 days constitute the majority of the CD8+ T cell population. Together, these data suggest an important role for IFN-gamma-secreting CD8+ T cells in the innate response to bacterial pathogens.
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D007113:Immunity, Innate; D016130:Immunophenotyping; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000502:physiology*; D020382:Interleukin-18 / Q000502:physiology*; D008089:Listeria monocytogenes / Q000276:immunology; D051379:Mice
D020382:Interleukin-18; D018664:Interleukin-12; D007371:Interferon-gamma