ANALYSIS OF MONONUCLEAR-CELLS INFILTRATING TUMOR IN SOLITARY HEPATOMAMODEL

Ten million syngeneic hepatocellular carcinoma (FAA-HTC1) cells inject ed into liver are sufficient to kill Fischer rats within 2 months, Fis cher rats became resistant to FAA-HTC1 cells by repeated sensitization with MMC-treated FAA-HTC1 cells. Histopathological studies revealed m assive accumulation of mononuclear cells in tumor tissues of sensitize d rats that were rejecting syngeneic FAA-HTC1 cells, whereas very few mononuclear cells were found in tumor tissues of control rats. Cell po pulations infiltrating the tumor tissues were identified by immunohist ochemical techniques and flow cytometric analysis. Mononuclear cells f ound within the regressing tumors of the sensitized rats were mostly i dentified as being T cells, and two-thirds of these T cells were CD8 p ositive. Compared to control rats, killer activity of mononuclear cell s infiltrating tumor tissues was significantly increased in the sensit ized rats. Depletion of CD8(+) T cells significantly reduced the cytot oxic ability of mononuclear cells infiltrating tumors obtained from se nsitized rats. In contrast, depletion of CD16(+) cells significantly r educed the cytotoxic ability of mononuclear cells infiltrating tumors obtained from control rats.