Corynebacterium parvum-induced peritoneal exudate cells with rapid cytolytic activity against tumour cells are non-phagocytic cells with characteristics of natural killer cells.

Peritoneal exudate cells taken from mice 3 days after intraperitoneal treatment with Corynebacterium parvum (Cp) have been shown to kill specifically certain tumour targets in vitro. We have analysed in detail such Cp-induced cytotoxic cells as to their cellular characteristics, considering the fact that size and charge characteristics of cellular subgroups are useful markers in describing their representative characteristics. We could thus show that the cytolytic cell could not be classified as a macrophage. They behaved, in every manner analysed, exactly as the previously defined natural killer cells found in the lymphoid organs of normal mice.