Natural cytotoxicity of isolated rat liver cells.

Unfractionated liver cells and parenchymal liver cells from untreated male Lewis rats were tested for natural cytotoxicity in a 4-hr 51chromium-release assay against YAC-1. Minimal cytotoxicity was observed. Nonparenchymal liver cells obtained by either differential centrifugation or metrizamide gradient centrifugation exerted strong cytotoxicity against YAC-1 and P815. Resident peritoneal exudate cells and spleen cells displayed cytotoxicity only against YAC-1. Furthermore, the cytotoxicity of these nonparenchymal liver cells was diminished by carbonyl iron treatment. Therefore, on the basis of these and other characteristics, the majority of the effector cells in the liver resemble tumoricidal macrophages. Finally, parenchymal liver cells or their cellfree supernatants were able to inhibit the cytotoxicity of these tumoricidal nonparenchymal liver cells, suggesting that the tumoricidal capacity of the liver was under some regulatory control.