Host immunity to a growing transplanted methylcholanthrene-induced guinea pig sarcoma.

Host immunity to a growing antigenic solid tumor was studied with a transplanted methylcholanthrene-induced sarcoma (MCA-25) in inbred female strain 2 guinea pigs. Tumor-specific cellular immunity was evaluated in vivo by delayed cutaneous hypersensitivity reactions to a transplanta tion antigen extract of the tumor and in vitro by splenic lymphocyte-mediated cytoxicity. Animals receiving 100,000 MCA-25 cells i.m. demonstrated tumor-specific cellular cytotoxicity from 7 days to the conclusion of the study 28 days after tumor transplant. Tumors were 10% body weight at this time. MCA-25-bearing animals had a degree of tumor-specific cellular cytotoxicity similar to those of guinea pigs "hyperimmunized" to the