Comparative Study of Cytotoxicity, Tumor Necrosis Factor, and Prostaglandin Release After Stimulation of Rat Kupffer Cells, Murine Kupffer Cells, and Murine Inflammatory Liver Macrophages

Abstract Macrophages (MØ) and MØ-depleted (nonadherent) nonparenchymal cells (NPC) of the liver were examined for their cytotoxic potential against tumor cells, production of tumor necrosis factor (TNF), and release of prostaglandins (PG) following stimulation by lipopolysaccharide (LPS), interferon-γ (IFNγ), and zymosan. Resident murine liver macrophages had no natural cytotoxicity for the TNF-resistant target cell line P815. Activation of these cells was only obtained by a combination of IFNγ and LPS. Inflammatory murine macrophages were in a primed stage and could be activated by LPS alone in the absence of IFNγ. Rat resident macrophages resembled functionally the inflammatory macrophages of the mouse liver rather than the resident macrophages. They displayed natural cytotoxicity against all targets tested and were further activated by LPS in the absence of IFNγ. Similar results were obtained with respect to macrophage-depleted nonadherent NPC: Mouse NPC had a low level of NK activity against Yac-1 cells. Treatment with pyran copolymer resulted in a strong increase of cytotoxicity against Yac-1; furthermore, a TNF-dependent killing of Wehi 164 and TNF-independent cytotoxicity against P815 cells were now acquired. In the rat NPC prepared from unstimulated animals expressed high levels of natural cytotoxicity against all targets. No major differences could be observed between inflammatory MØ and Kupffer cells of rat and mouse liver with regard to TNF production and TNF-dependent killing of Wehi 164 tumor cells. The same was true for the spectrum of secreted prostanoids. Upon activation of all cell populations a marked shift toward the production of PGE2 occurred. Experiments involving the cyclooxygenase inhibitor indomethacin showed enhanced TNF-dependent tumor cell killing by nonactivated MØ in the absence of prostanoid production.