Impaired oxidative burst does not affect human monocyte tumoricidal activity

Human peripheral blood monocytes have been shown to lyse neoplastic cells selectively. It has been suggested that the oxidative burst may mediate monocyte tumoricidal activity. Two patients with chronic granulomatous disease were studied. The first patient had no detectable secretion of hydrogen peroxide and superoxide anion after stimulation with 100 ng/ml PMA. Nevertheless, his tumoricidal activity measured against K562 targets in 4-hr 51Cr-release assays by using highly purified monocytes was reproducibly above the 95th percentile of the normal population. His monocytes lysed WEHI-164 targets pretreated with 1 microgram/ml Actinomycin D with similar efficiency. Another patient whose oxidative burst was 15% of normal nevertheless killed Daudi targets efficiently. In addition, oxygen-deprived monocytes of normal donors manifested normal tumoricidal activity, despite failure to produce any detectable oxidative burst after PMA stimulation. We conclude that reactive oxygen metabolites are not the primary mediators of tumor cytolysis by human peripheral blood monocytes.