The effects of syngeneic tumor vaccine preparations on resistance against s.c. and pulmonary implants of a spontaneous C3H mouse mammary carcinoma have been compared during progressive primary tumor growth, after surgical cure, and during declining immune resistance following complete tumor removal.

Concomitant antitumor immunity reached a higher level of effectiveness in the lungs than in s.c. tissue. The concomitant immune resistance in the lungs also remained effective longer than did s.c. resistance, which was the first to decline under the increasing antigen burden of a growing tumor implant.

Resistance to challenge recovered quickly after the complete removal of a large tumor burden, but recovery was impeded if killed tumor tissue was reinjected too soon after tumor removal. If injections of killed tumor tissue were given 7 days after tumor removal, the completed recovery was not affected. If injections of killed tumor tissue were given 30 days after tumor removal, immune resistance to challenge, at this time much declined, was stimulated.

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This work was supported by USPHS Grants CA-15960 and CA-16039 and by a Cancer Research Scholar Award from the American Cancer Society, Massachusetts Division, Inc., to Jan Vaage. The work was started at the Massachusetts General Hospital and completed at the Pondville Hospital.

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