Tumor associated macrophage mediated lysis of autologous tumor cells

Lysis of autologous tumor cells (ATC) mediated by the tumor associated macrophages (TAM) was studied by 4 h 51Cr-release assay at different days of growth of a transplantable ascites tumor, S-180, inoculated in adult male Swiss mice. The ATC were coated with serum of tumor bearing mice. On day 3 after tumor inoculation the TAM mediated a remarkable lysis of the tumor serum coated ATC. With advancement of tumor growth the cytolysis by TAM decreased gradually to the basal level at day 10 and totally abrogated at day 12. Also the binding of the tumor serum coated ATC by TAM varied at different days of tumor growth. At early phases of tumor growth high lytic activity of the TAM was correlated with augmented target binding. The observed lysis may be considered as antibody dependent cell mediated cytotoxicity (ADCC) extended by the TAM, since presence of specific tumor antibodies were demonstrated in the tumor serum used for coating ATC. No significant lysis was recorded when the ATC was coated with normal serum or used as such for direct lysis by the TAM. In vitro treatment of the TAM with suitable doses of Levamisole and Polyionosinic-polycyticyclic acid further augmented the TAM mediated high level of ADCC at day 3 with no change in its binding of ATC. The immunopotentiators enhanced both ADCC and target binding ability of the functionally depressed TAM at day 10.