Antibody-dependent cell-mediated cytotoxicity against mouse MM2 tumor cell line by macrophages activated with OK-432.

The action mechanism of antibody-dependent macrophage-mediated cytotoxicity (ADMC) induced by OK-432 against MM2 carcinoma cells was examined. Adherent peritoneal exudate cells (adherent PEC) harvested from mice 4 days after intraperitoneal injection of OK-432 exhibited potent cytotoxic activity against MM2 cells in the presence of anti-serum obtained from tumor-free mice which had survived over 60 days following treatment with OK-432 and resisted rechallenge with MM2 cells. The cytotoxic activity of the adherent PEC was not abolished by treatment with anti-Thy-1.2 and complement, and there were no differences in ADMC between adherent PEC from BALB/c mice and those from athymic BALB/c (nu/nu) mice. Further, ADMC activity was shown not only against MM2 cells, but also against other allogeneic tumor cells, such as MOPC-11 plasmacytoma cells. On the other hand, the effective factor(s) in anti-serum to MM2 cells was eliminated by passage through a protein A-Sepharose CL-4B affinity column. The action mechanism of ADMC caused by the adherent PEC and anti-serum to MM2 cells is discussed.