Multimodal immunotherapy of primary gastrointestinal tumors in rats. 1. Histologic correlation.

The effect of multimodal immunotherapy was studied in rats bearing primary gastrointestinal tumors induced by 1,2-dimethylhydrazine dihydrochloride. Multimodal immune manipulation consisted of combinations of splenectomy, C. parvum, unblocking serum, unblocked lymphoid cells, and levamisole. Such immunologic intervention resulted in significant inhibition of tumor growth, and their metastasis. Ten of 10 untreated rats, 8 of 8 rats treated with splenectomy alone and 10 of 10 rats treated with normal rabbit serum died of progressive tumor growth. None of the rats treated with combinations of splenectomy, unblocking serum, unblocked lymphoid cells, C. parvum and levamisole succumbed to progressive tumor growth during the observation period. The histologic evidence of tumor destruction was obtained in 18 of 22 tumors in rats of groups receiving multimodal immunotherapy.