The Journal of immunology : official journal of the American Association of Immunologists
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We recently reported that systemic administration of IL-12 into mice activates NK1.1+ alpha beta T cells with intermediate TCR (NK1+TCRint) and induces strong MHC-unrestricted cytotoxicity in C57BL/6 mice. In the present report, we examined the effect of LPS on Kupffer cells and NK1+TCRint, cells in C57BL/6 mice. Administration of LPS, as well as synthetic lipid A analogue (ONO-4007), but not detoxified LPS, induces the increase of NK1 expression of NK1+TCRint cells (NKlhighTCRint) and the acquisition of strong MHC-unrestricted cytotoxicity of these cells against NK-sensitive and NK-resistant targets as does IL-12 administration. ⋯ This antimetastatic effect of LPS in the liver was also observed in different strains of mice and tumors, In contrast to IL-12, however, LPS was not so effective when administered after tumor inoculation. These results revealed that LPS (lipid A) stimulates NK1+TCRint cells through IL-12 production from Kupffer cells and suggest that bacterial components, probably including those from intestine, are activators of Kupffer cells and NK1+TCRint, cells in the liver. It is also suggested that the host condition as well as LPS-induced cytokines other than IL-12 may affect antitumor effect induced by LPS in the liver.