[Effects of a synthetic peptide on the cytotoxic activity of the lymphocytes of animals with tumors].

The influence of Peptichemio on cell immunity was studied by examining the in vitro response of lymphocytes from animals bearing a tumour treated with the drug. Two experimental tumours with different features, i.e. an adenocarcinoma (ADK-1t) and a plasmacytoma (MOPC-460) were used. The former was more sensitive to Peptichemio. The colony inhibition test was used for the ADK-1t and 51Cr release for the MOPC-460 owing to the fact that two different methods of culture in vitro were employed. In the case of ADK-1t 4mg/Kg Peptichemio given on alternate days, five times beginning from the 3rd day after challenge, was followed by 40% reduction in lymphocyte toxicity by comparison with the controls. In the case of MOPC-460, on the other hand, no significant lymphocyte toxicity was observed, even in the controls. It was concluded that, in both cases, Peptichemio at this dose does not interfere with the immunity response of the host to any great extent, and is selectively active against neoplastic cells.