Natural cytotoxicity against chemically induced neurogenic rat tumors

The 51Cr cytotoxicity assay was modified for ethylnitrosourea (ENU) and methylnitrosourea (MNU) induced rat neurogenic tumor cell lines. Investigations on "immune" lymphoid cytotoxicity showed little cytotoxicity above normal. Alteration in the level of lymphocytotoxicity was seen immediately after injection of a highly immunogenic tumor (EA-528). Natural cytotoxicity (NC) was present against all neurogenic tumor cell lines tested and xenogenic cell lines. The level of NC activity was dependent on age, specific tumor cell line and could be increased by isolating the nylon wool non-adherent "T" cell population. Allogenic WFu rat lymphocytes were tested for NC activity in vitro against CDF tumor cells. NC activity has potential use against these tumors in vivo.