Fig. 8. Differential effects of a KCl extract and a ß-OG extract of DC membranes on the NADPH oxidase activity of neutrophil membranes elicited in a cell-free system. Bovine neutrophil membranes (6.2 µg protein) were mixed with various amounts of KCl or ß-OG extracts from DC membranes, and their NADPH oxidase was activated in the cell-free system consisting of bovine neutrophil cytosol, GTPS, ATP, MgSO₄, KCN and increasing amounts of arachidonic acid (AA). The elicited oxidase activity was determined by the production of O₂^– (see Materials and Methods) and expressed in terms of heme b turnover. Curve a, control (absence of DC membrane extract). Curves b, c and d correspond to 1.15 µg, 2.3 µg and 4.6 µg protein in the ß-OG extract of DC membranes, respectively. (Inset) Dose-response of the elicited oxidase activity of neutrophil membranes treated with a ß-OG extract of DC membranes (), with a ß-OG extract of neutrophil membranes (), and with a KCl extract (0.5 M KCl) of DC membranes ().