GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR PRETREATMENT INDUCESAN INCREASE OF RAT KUPFFER CELLS WITH ENHANCED CYTOTOXICITY IN-VITRO AND PREVENTION OF TUMOR OUTGROWTH IN-VIVO

Male Wag rats were pretreated for 7 days with 1000 U/ml recombinant mu rine granulocyte macrophage colony stimulating factor (rmGM-CSF). Rat Kupffer cells (KC) were isolated by a enzymatic method. We injected de creasing numbers of CC531 tumor cells in the portal system. Mean KC yi eld increased from 1.5 +/- 0.2 to 2.2 +/- 0.2 (p < 0.05). Mean percent age of KC-mediated cytotoxicity against CC531 increased from 20.0 +/- 0.5 to 42 +/- 1.0 after rmGM-CSF (p < 0.05). At 1 x 10(5) CC531 tumor cells we demonstrated prevention of formation of small foci of CC52(+) tumor cells. We demonstrate increased isolated KC with enhanced cytot oxic capacity after rmGM-CSF. rmGM-CSF induced prevention of minimal r esidual disease in the rat liver.