Effect of Macrophages and Antibodies on in Vivo Growth of Moloney Sarcoma in the Rat

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Abstract
Brown Norway and Lewis rats were challenged with a Brown Norway Moloney sarcoma tumor, MST-1, admixed with nonimmune peritoneal exudate macrophages syngeneic to the host; or admixed with nonimmune peritoneal exudate macrophages and hyperimmune anti-MST-1 antibodies. In vivo growth of MST-1 in BN and Lewis rats was inhibited by admixing Brown Norway or Lewis macrophages, respectively, with BN anti-MST-1 antibodies. The inhibiting BN antibodies were of the IgG2 class, lacking IgG2a antibodies. Brown Norway anti-MST-1 of IgG2 class without macrophages did not affect growth of MST-1. Brown Norway and Lewis anti-MST-1 antibodies of IgG2a class enhanced tumor growth, whether admixed with macrophages or not. Anti-MST-1 antibodies of IgM and IgG1 classes did not influence tumor growth. Peritoneal exudate macrophages removed from Lewis donors 8 to 10 days after inoculation of MST-1 inhibited completely growth of the challenge tumor; macrophages of Brown Norway origin were inhibitory only when harvested from hyperimmune donors, that is, 40 or more days after inoculation of MST-1. Macrophages from hyperimmune donors were specifically cytotoxic to MST-1 and did not inhibit an unrelated syngeneic BN tumor of chemical origin.