We studied the role of inflammatory neutrophils in the antitumor effects that follow i.p. injection of Corynebacterium parvum (1400 µg)into C3HeB/FeJ mice challenged with the murine ovarian teratocarcinoma. Peritoneal neutrophils, obtained from mice 6 hr after injection of C. parvum, exerted significant antitumor effects when injected admixed with murine ovarian teratocarcinoma cells into the peritoneal cavities of normal mice. Treatment of recipient mice with whole-body irradiation or repeated injections of silica prevented the antitumor effects, indicating that neutrophils were activating a second effector mechanism in recipient mice. Peritoneal cells obtained at 24 or 72 hr or at 7 or 11 days following C. parvum injection were considerably less effective in activation of this effector mechanism. Heat-killed C. parvum (6 hr)-induced neutrophils activated antitumor responses, but thioglycolate-induced cells were without effect. Antitumor responses in mice receiving peritoneal neutrophils were not due to simple transfer of C. parvum organisms in the inocula. These results indicate that inflammatory neutrophils, elicited into the peritoneal cavity by injection of C. parvum, play an important role in the activation of subsequent antitumor effects.

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This investigation was supported by Grant CA 12800 awarded by the National Cancer Institute, Bethesda, MD, Research Funds of the Veterans Administration, and grants from the California Institute for Cancer Research, The Cancer Research Coordinating Committee of California, and the Concern Foundation.

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