Enhancement and metastasis after immunotherapy of ovine squamous-cell carcinoma.

Extracts of ovine squamous-cell carcinoma (OSCC) prepared by different procedures, were injected at varying concentrations into 184 tumour-bearing sheep. At a total protein of 0.5 mg and greater, there was significant enhancement and metastasis in all 120 sheep examined. Extracts of OSCC containing less than 0.5 mg protein, or of human squamous-cell carcinoma and normal sheep skin containing high levels of protein, had no effect on subsequent tumour development. Extracts of foetal sheep skin at the 3mg-protein level produced significant enhancement and metastasis. The degree of enhancement was inversely proportional to the developmental stage of the tumour at the time of treatment.