Activated macrophages release a factor which lyses malignant cells but not normal cells.

Abstract

When rat macrophages are activated by exposure to bacterial endotoxin they acquire the capacity to lyse sarcoma cells in tissue culture. Although showing no immunological specificity this lytic effect was only detectable on malignant cells; normal cells were unaffected. This tumor-selective lytic effect is mediated by a labile supernatant product.