Mixed lymphocyte reaction suppression by tumour cell lines from naturally occurring squamous cell carcinomata

Seven epithelial tumour cell lines derived from naturally occurring ovine squamous cell carcinomata (OSCC) were examined for their ability to stimulate allogeneic lymphocytes in vitro. All cell lines failed to stimulate any proliferative response; a failure which was not due to the absence of alloantigens on the tumour cells. It was found, however, that the cell lines tested caused a marked suppression of a third party mixed lymphocyte reaction. This suppression was mediated only by live tumour cells since the addition of heat-killed tumour cells had no effect on the response.