Purification of a cytotoxic protein produced by the murine macrophage-like cell line J774.1 in response to Sarcophaga lectin.

A tumor specific cytotoxic protein produced by the murine macrophage-like cell line J774.1 in response to stimulation with Sarcophaga lectin was purified to homogeneity in three steps from the culture medium. This cytotoxin, named tumor killing factor (TKF), was a protein with a molecular weight of 15,000, and aggregated forming an oligomer with a molecular weight of 48,000. Its amino acid composition was similar to that of human TNF. Purified TKF had a significant effect on transplanted murine ascites tumor sarcoma 180. The biological significance of TKF in terms of ontogeny is discussed from the view point of developmental biology.