Enhancement of tumour growth in two syngeneic C3H murine systems by immunization via the intracaecal route.

Over the past 70 years many experiments have been designed to promote tumour growth. These studies were all carried out in allogeneic tumour systems or by artificially influencing the immunization process. In the present study, the growth of syngeneic mammary tumour cells was enhanced by prior immunization via the intracaecal route. Such induced enhancement could be transferred to untreated animals by serum or by spleen cells. Tumour growth was also enhanced in another syngeneic system by immunization via the intestinal route with frozen-thawed ascites tumour cells. The result is in direct contrast to that obtained by similar immunization with live cells, which affords protection against a later challenge.