Cytotoxic potential of different lymphoid cell populations against chromium-51 labelled tumour cells.

Release of chromium-51 (Cr) from pre-labelled target cells was used as an assay of cytotoxicity. Different immune and non-immune lymphoid cell populations were tested for cytotoxicity against pre-labelled tissue culture target cells (Ha 3) which originated from a tumour induced by murine sarcoma virus (MSV) in a CBA mouse. Anti-Ha 3 peritoneal exudate and spleen cells showed significant specific cytotoxicity against these target cells. This was true for cells taken from animals immunized against either strong (H-2 plus non-H-2) or weak (non-H-2) antigenic determinants on the Ha 3 cells. Exogenous complement was not required for this cytotoxic activity. Tissue culture cells derived from a methylcholanthrene-induced tumour (MBE) of CBA origin were not damaged by peritoneal exudate cells from mice immunized against non-H-2 antigens on the Ha 3 cells. Anti-Ha 3 lymph node cells were relatively ineffective in these experiments although some cytotoxic activity was detected with lymph node cells sensitized against strong antigens. Direct morphological observation confirmed the cytotoxicity of anti-Ha 3 peritoneal exudate cells measured by Cr release.