Assay of cell-mediated cytotoxicity by tritiated thymidine labeled tumor cells

A microtechnique for quantitating cell-mediated cytotoxicity using tritiated thymidine labeled target cells is presented. Target cell incorporation of tritiated thymidine is augmented by using methotrexate to arrest endogenous thymidine synthesis. Complete solubilization of labeled cells is accomplished by oxidizing samples to tritiated water and carbon dioxide prior to quantitation in a scintillation counter. This versatile technique, using various combinations of lymphocytes, sera and target cells, permits the simultaneous comparison of 500 or more individual samples.