Abstract
Incubation in vitro of lymphnode cells (LNC) from rats bearing a transplanted syngeneic methylcholanthrene-induced sarcoma (Mc7) resulted in the generation of a potent cytotoxic activity. Four to seven days' culture was required for development of cytotoxic activity, which was shown to be mediated by a heat-stable soluble factor. The cytotoxicity was not detectable in a 3 h or 15 h 51Cr-release assay, but was demonstrated in a 48 h microcytotoxicity assay, where post-labeling with isotopically labelled cell precursors was used to quantitate cell survival. The cytotoxicity of the cultured tumour-bearer LNC and their supernatant factor was shown to be cross-reactive for tumour cell lines other than sarcoma Mc7, and was also expressed against adult or embryonic fibroblasts.