Human natural cell-mediated cytotoxicity

Natural cell-mediated cytotoxicity has been shown to be age-dependent in both rats and mice. The present study was undertaken to study age-related levels of natural cytotoxicity in humans. Mononuclear peripheral blood cells from over 200 normal volunteers were co-incubated with 51Cr-labeled K-562 for 4 h and the supernatants assayed for released isotope. No striking age-related variations in natural cytotoxicity were observed. Cord blood was shown to exhibit both high and low levels of natural cell-mediated cytotoxicity. There was no significant difference in the levels of natural cytotoxicity between males and females. Thoracic duct lymphocytes (TDL) from prospective kidney graft recipients were tested for natural cytotoxicity at intervals during drainage. Natural cytotoxic activity was undetectable in samples from initial drainage but increased as the drainage progressed. This increased activity was correlated with decreased in vitro responsiveness to PHA and decreased levels of E-rosettes in these TDL.