Assay based on quantitation of cell death caused by sensitized lymphocytes or splenocytes cultured with a fixed number of tumor or other target cells that have been prelabeled with \(\ce{^{51}Cr}\). The \(\ce{^{51}Cr}\) is taken up and reversibly binds to cytosolic proteins. When these target cells are incubated with sensitized lymphocytes, the target cells are killed and the \(\ce{^{51}Cr}\) is released.