Immunologic functions and in vitro activation of cultured macrophage tumor lines

Five murine monocyte of macrophage tumor lines adapted to culture were characterized for differentiated properties. They ingested zymosan and latex beads, bore receptors for immunoglobulin and complement, synthesized lysozyme (most of which was secreted), and produced granulocyte colony-stimulating activity, either spontaneously or inducibly. Some of the lines also mediated phagocytosis and exocytosis of red blood cells (RBC) and lysis of tumor targets, dependent on the presence of specific antitarget sera. All the lines were growth inhibited by zymosan and Mycobacterium bovis BCG, but not by latex beads. Other macrophage-activating agents, dextran sulfate and lipopolysaccharide (LPS), as well as tuberculin purified protein derivative (PPD), inhibited most of the lines. Except for Fc and C receptors, most of the above properties were not found with other types of hematopoietic tumors in culture. In attempts to activate the macrophage lines in vitro to the "angry" state, we found that preincubation with concentrations of LPS and PPD cytostatic to the cells stimulated antibody-dependent RBC lysis, but not antibody-independent or tumor cytolysis. A classification of monocyte-related tumors and normal cells is proposed based on functional activities and differential sensitivity to immunostimulating agents.