Enhanced Phagocytic Capacity THE BIOLOGIC BASIS FOR THE ELEVATED HISTOCHEMICAL NITROBLUE TETRAZOLIUM REACTION

Abstract

The biologic basis for the elevated histochemical reduction of nitroblue tetrazolium dye (NBT) in neutrophils from patients with acute bacterial infection or polycythemia vera was studied. A precipitin reaction followed mixing NBT with heparin. NBT was reduced after phagocytosis of this complex (H-NBT) by polymorphonuclear leukocytes (PMNs). Ingestion required divalent cations and was facilitated by the presence of complement. H-NBT incubated with normal but not with C2-deficient human serum converted native C3 to its inactive form. Phagocytic indices were determined in patients and controls by measuring O₂ utilization and hexose monophosphate shunt activity and by visually counting cell-associated latex particles. Significant elevations above controls were observed in phagocytes isolated from all patients with elevated histochemical NBT scores when H-NBT complex, latex, or zymosan was employed as the phagocytic particle. Increased indices were observed in the presence of fresh AB serum, heat-inactivated AB serum, or without serum. Serum from patients with elevated NBT scores did not alter phagocytosis in control phagocytes. With NADH and NADPH as substrates, total NBT diaphorase activity of sonicated leukocytes was normal in all patients. These results suggest that increased phagocytic capacity of PMNs is the primary cause of increased histochemical NBT reduction. The PMNs of patients with acute bacterial infection or polycythemia vera may have alterations in their cell membranes which lead to an enhanced rate of phagocytosis.