Studies on the activation of mouse bone marrow-derived macrophages by the macrophage cytotoxicity factor (MCF)

The capacity of bone marrow-derived macrophages to be rendered cytotoxic by macrophage cytotoxicity factor (MCF) at different stages of maturation was tested. Under in vitro conditions not only mature macrophages but also nonadherent precursor cells were successfully activated. Mature adherent bone marrow macrophages can be rendered cytotoxic for up to three weeks in tissue culture. Cytotoxic effects are demonstrable even at a killer target ratio of 0.5:1. Granulocytes do not respond to activation with MCF. Bone marrow-derived macrophages can be collected at early stages of maturation, when they grow in suspension or have developed only loose adherence. Macrophages which have differentiated in vitro from bone marrow never show any signs of nonspecific activation as measured by our cytotoxic assay system.