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A Role for the Macrophage in in Vivo and in Vitro Resistance to Murine Bladder Tumor Cell Growth¹

Department of Surgery, Division of Urology [M. J. D.]; and Department of Medicine, Division of Infectious Diseases [J. S. R.], Stanford University School of Medicine, Stanford, California 94305; and Palo Alto Medical Research Foundation, Division of Allergy, Immunology, and Infectious Diseases, Palo Alto, California 94301 [M. J. D., J. S. R.]

Studies were performed to determine the role of macrophages in inhibition of growth of the same tumor cell type both in vitro and in vivo. Bladder transitional epithelium tumor cells were injected s.c. into Toxoplasma-infected mice, previously shown to contain activated macrophages, and into uninfected controls. The subsequent growth of solid tumor was significantly less in the Toxoplasma-infected animals. Bladder tumor cells from the same cell line were grown in vitro either alone or in the presence of peritoneal lymphocytes and/or macrophages from Toxoplasma-infected and control, uninfected mice. [³H]Thymidine incorporation by the tumor cells was inhibited only in the presence of macrophages from the Toxoplasma-infected animals. Lymphocytes alone did not appear to be cytotoxic under the conditions used. Moreover, lymphocytes from Toxoplasma-infected mice did not convey cytotoxicity to macrophages from control animals under the experimental conditions used.

¹ This work was supported by USPHS Training Grant 5T01 AM05513, by NIH Grant AI-04717, by a grant from the John A. Hartford Foundation, Inc., and by USPHS Research Contract N01-CB-43873 from the National Cancer Institute.

² To whom requests for reprints should be addressed, at Palo Alto Medical Research Foundation, 860 Bryant Street, Palo Alto, Calif. 94301.

Received 7/ 3/74. Accepted 9/ 4/74.