Immunotherapy with a combination of Corynebacterium parvum and specific heteroantiserum is significantly more effective than treatment with either single agent in prolonging the survival of mice that have received an i.p. injection of syngeneic murine ovarian carcinoma (MOT) cells. In vitro, a combination of C. parvum-activated peritoneal cells and specific heteroantiserum has proven significantly more effective than either single component in destroying 51Cr-labeled MOT cells in the absence of complement. Activation of peritoneal cells to produce lysis of tumor in the presence of specific antiserum peaked 3 to 7 days after a single injection of C. parvum and declined to baseline over 3 to 4 weeks. With repeated i.p. injections of C. parvum at appropriate intervals, activation of peritoneal cells could be prolonged and augmented. Among the routes tested, only i.p. administration of C. parvum was effective, although activation of peritoneal cells for cooperation with heteroantiserum was observed over a broad range of i.p. dosage (0.45 to 4.20 mg). These data suggest that the administration of C. parvum by appropriate doses, routes, and schedules can attract and activate a population of peritoneal effectors that mediate antibody-dependent cytotoxicity more effectively than resident peritoneal cells.

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This work was supported by Contract N01-CB-74194 from the National Cancer Institute, by a Center Grant 2P01 CA12662-06 awarded to the Joint Center for Radiation Therapy, Harvard Medical School, and by funds from the National Cancer Cytology Center.

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