T- and B-cell-independent activation of syngeneic macrophages by murine sarcoma cells

Mouse peritoneal macrophages were achieved by cocultivation with syngeneic sarcoma cells. The tumor cells died progressively during the cocultivation, leaving highly activated marcophages. Because of great changes in macrophage morphology during the activation, special efforts were made to identify the activated cells as macrophages by their ability to phagocytose latex and to bind opsonized sheep red cells to C3 and Fc receptors and by indirect immunofluorescence with an antimacrophage antiserum. Activation was evaluated by morphology and incorporation of [14C]glucosamine. The activation was found to be independent of the presence of T-cells, B-cells, and immunoglobulin bound to tumor cell surfaces. This was shown by removal of T-cells from the system by treatment with anti-theta and complement and by use of nude mice as the macrophage source and for tumor maintenance. Similarly, B-cells were removed by treatment with anti-immunoglobulin and complement as well as adherence to anti-immunoglobulin-coated plastic dishes. Immunoglobulin bound to tumor cells was removed by trypsinization and by elution at low pH. Culture supernatants from tumor cells and cell-free tumor ascites fluid also induced some activation of the macrophages. This activation differed from the coculture activation in both the extent and kinetics of morphological changes and gave only a small increase in [14C]glucosamine incorporation.