Effects of zinc on the reactive oxygen species generating capacity of human neutrophils and on the serum opsonic activity in vitro

To investigate the effects of zinc on non-specific immune functions, we use d the chemiluminescence method to examine the capacity of human neutrophils to produce reactive oxygen species and accompanying serum opsonic activity . When neutrophils were stimulated with both opsonized zymosan and phorbol myristate acetate in the presence of 1-10(-3) mmol/L zinc lucigenin-depende nt CL responses were stable or declined, whereas luminol-dependent CL respo nses were significantly enhanced. The results suggest that zinc activates p rotein kinase C and promotes MPO degranulation and ROS metabolism, especial ly in hypochlorous acid production, which have the direct action of causing microbial death. Further, the lucigen-dependent CL response stimulated wit h OZ was strongly enhanced by anti-MPO antibodies, whereas the enhancement was less in the presence of zinc, suggesting that zinc may suppress the rec eptor-mediated signal transduction process. Both responses were inhibited a t 10 mmol/L. Serum opsonic activity was enhanced by zinc at 10(-4) and 10(- 3) mmol/L but reduced at 10 mmol/L. These data indicate that addition of zi nc around and above normal physiological concentrations facilitates neutrop hil functional activity and serum opsonic activity, whereas these are inhib ited by a lack of zinc or an excessive amount, suggesting that zinc is esse ntial for optimal functioning of nonspecific immunity. Copyright (C) 2000 J ohn Wiley & Sons, Ltd.