Culture supernatants of lymphokine-activated killer (LAK) cells contain a high-molecular-weight cytotoxic lymphokine

Abstract Supernatants of human lymphokine-activated killer (LAK) cells grown in vitro were tested for cytotoxic activity against several mouse and human neoplastic cell lines. All LAK preparations tested (14/14) exhibited cytotoxic activity (40–90% killing of the target cells). Sephacryl S-300 Gel filtration experiments indicated that the biological activity of the LAK supernatant is associated with molecular moities ranging from 800 kDa or more, to less than 10 kDa. The finding of strong cytotoxic activity in LAK supernatants against several tumor lines points to the possibility of employing soluble products of these cells, rather than the living cells themselves, for therapeutic purposes.