Superoxide anion generation by human neutrophils exposed to monosodium urate. effect of protein adsorption and complement activation

We studied the capacities of naked and proteincoated monosodium urate (MSU) crystals to stimulate superoxide anion (O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document}) release by human polymorphonuclear leukocytes (PMN). Uncoated MSU stimulated significant O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document} production by cytochalasin B-treated PMN. Precoating MSU with IgG caused an increase in mean O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document} production, whereas precoating heated MSU with serum or plasma inhibited O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document} release. Unheated MSU crystals, which activate complement to a greater extent than heated crystals, also provoked O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document} generation, an effect again abrogated by precoating with serum but not with plasma. Coincubation of unheated MSU and plasma resulted in an enhancement of O₂documentclass{article}pagestyle{empty}begin{document}$ [bar .] $end{document} generation. The results of these experiments support the hypothesis that adsorbed proteins modulate the phlogistic potential of MSU and that the surface activation of humoral mediators contributes to the local inflammatory response.