Inhibition of respiratory burst in macrophages by complement receptor blockade.

Respiratory burst activity was induced in rat peritoneal macrophages by opsonized zymosan. Inhibitors were tested by administering them before or after the inducing agent: OX-42, an anti-rat macrophage complement receptor type 3 antibody, was active at an estimated concentration of 2.1 nM, and was more than 100-fold more potent when administered before, rather than after, opsonized zymosan. Indomethacin and dapsone, two agents with antiinflammatory activity, were also more effective before opsonized zymosan, but only in the 10(-3) to 10(-4) molar range. Inhibitors of eicosanoid synthesis, as well as the antiinflammatory prostaglandin E2, also reduced the respiratory burst.