Host immunity to growing sarcomas: Tumor-specific serum inhibition of tumor-specific cellular immunity

Host immunity to growing antigenic sarcomas was studied in a methylcholanthrene-induced guinea pig tumor system (MCA-25/Strain 2 GP) and in patients with skeletal and soft tissue sarcomas. Tumor-specific cellular immunity was assayed by cell-mediated cytotoxicity. Sera from animals and patients with growing sarcomas were evaluated for specific inhibition of this cellular immunity. The degree of tumor-specific cellular immunity in MCA-25 bearing and tumor-free animals was similar. Sera from animals with palpable MCA-25 tumors inhibited MCA-25 specific cellular cytotoxicity, but sera 2 weeks after tumor removal were non-inhibitory. Data suggest this inhibition is mediated by peripheral enhancing antibody. Human sarcoma-specific cellular cytotoxicity was present in most sarcoma-bearing patients. Sera from 14/16 sarcoma-bearing patients inhibited sarcoma-specific cellular immunity, but not cellular immunity against carcinoma. Serum inhibition correlated with the clinical stage of the disease. Data demonstrate an immunologic phenomenon which may explain progressive sarcoma growth in the presence of tumor-specific cellular immunity.