REGULATORY CAPACITIES OF MONONUCLEAR PHAGOCYTES WITH PARTICULAR REFERENCE TO NATURAL IMMUNITY AGAINST TUMORS11This work was supported by the Swiss National Science Foundation (grant 3.173.77) and the Canton of Zurich. Abbreviations: ADCC: antibody-dependent cellular cytotoxicity. AM: activated macrophages. CSA: colony stimulating activity. DMBA: dimethylbenz(a)anthracene. LPS: bacterial lipopolysaccharide. MAF: macrophage activating factor. PMA: phorbol myristate acetate. PMN: polymorphonuclear leukocyte.