Decline of natural nonselective cell-mediated cytotoxicity in patients with tumor progression.

Lymphocytes isolated from the blood of patients and healthy donors include a population of cells that destroy target cells in the direct cell-mediated cytotoxic assay with little indication of specificity. This natural reaction is the dominant feature of most cell-mediated cytotoxic tests and, although it appears to be mostly nonselective, it possesses some selective activity. The observed cytotoxicity from these reactions depends mostly on the reactivity of the effector cell; when several effector cells are tested on different target cells, the relative order of activity is usually maintained on the different target cells. When this natural cytotoxicity was analyzed without regard to the type of cancer of the patient or of the target cells, a weak decline in the average reactivity was observed with increasing tumor involvement.