Activation of the Oxidative Metabolism in Human Polymorphonuclear Neutrophilic Granulocytes: The Role of Immuno-Modulating Cytokines

Abstract

Activated polymorphonuclear neutrophilic granulocytes (PMN) play an important role in propagation of inflammatory reactions and are capable of mediating tissue damage particularly by release of reactive oxygen species and lysosomal contents. Cytokines produced by monocytes as well as epidermal cells were recently shown to modulate PMN function. Therefore, the effect of immunomodulating cytokines on the oxidative metabolism of isolated human PMN was tested by functional as well as ultrastructural criteria. The following recombinant human cytokines were tested: tumor necrosis factor (TNF alpha), lymphotoxin (TNF beta), granulocyte-macrophage colony-stimulating factor (GM-CSF), M-CSF, G-CSF, PDGF, TGF-beta, interleukin-1 (IL-1) alpha and beta, IL-2, IL-3, IL-4, IL-5, IL-6, MONAP/MOC/NAF (IL-8), interferon-alpha and -gamma. Only TNF alpha, TNF beta and GM-CSF were found to be direct stimuli of the oxidative burst in human PMN whereas IL-3, IL-5, and IL-8 were active only at extremely high concentrations. None of the other cytokines tested induced any significant effect on isolated human PMN at physiological concentrations. The results clearly demonstrate that only selected cytokines are capable of inducing a long lasting activation of PMN oxidative metabolism. Release of these mediators represents a specific signal for PMN activation in inflammatory disease states.