Changes in the expression of macrophage antigens associated with activation for tumor cell killing

Cultured murine bone marrow macrophages (BMM phi) can be induced to kill tumor cells in vitro by combined treatment with a priming (IFN-gamma) and a triggering (LPS) agent. We have examined the expression of cellular antigens accompanying this activation by Western blot analysis with rabbit antisera raised against unstimulated and fully activated BMM phi and assayed the effect of these antisera on macrophage-mediated tumor cytotoxicity. Killing of Yac-1 target cells was slightly enhanced by antiserum against unstimulated BMM phi but inhibited 54% by antiserum against activated BMM phi. The following changes in antigen expression are shown to be associated with discrete stages of activation and localized to the cytosolic or membrane fractions. Antigens with apparent molecular weights of 109, 67, and 48 kd are expressed after priming with IFN-gamma whereas LPS induces the enhanced expression of antigens with molecular weights of 46, 30, and 14.4 kd. One antigen with a molecular weight of 54 kd apparently is only expressed by fully activated BMM phi treated with a combination of IFN-gamma and LPS. Antigens with molecular weights of 170 and 21 kd are repressed by LPS and IFN-gamma respectively. IFN-gamma partially counteracts changes induced by treatment with LPS alone when used in combination with LPS. All antigens are localized in the cytosolic fraction except the 54 kd and to some extent the 30 kd, which were detected in the membrane fraction. The 21 kd was only detectable in crude lysates and thus presumably is of nuclear origin.(ABSTRACT TRUNCATED AT 250 WORDS)