| Abstract: | The in vitro cytotoxic action of patients' lymphocytes against colon carcinoma cells was evaluated following incubation of the lymphocytes with papain-solubilized tumour-membrane preparations. Soluble extracts of pooled colon carcinomas inhibited cytotoxicity by sensitized lymphocytes, but similar extracts of normal colon or melanoma had no inhibitory effect. The results suggest that soluble tumour antigen may play a role in abolishing lymphocyte reactivity, and this is interpreted as supporting the concept that cellular immunity against tumours in vivo may be inhibited by circulating antigen. |
