Chemo-immunotherapy of mouse tumours using cyclophosphamide and C. parvum.

Treatment of a chemically induced mouse solid fibrosarcoma using either non-specific (C. parvum 350 mu i.v.), or specific active (s.c. C. parvum mixed with 5.10(5) irradiated tumour cells) immunotherapy, 4 days after a single dose of cyclophosphamide (200 mg/kg) was synergistically more effective than either C. parvum or drug treatment alone. A contributory factor may be that cyclophosphamide pretreatment has been shown to potentiate the specific antitumour immunity that arises from C. parvum interaction with tumour antigen. Systemic C. parvum before cyclophosphamide will potentiate the antitumour effects of the drug--previously ineffective low doses becoming effective. No similar potentiation of the effects of another alkylating agent, Melphalan, was evident.