Low-affinity interaction of fibrinogen carboxy-gamma terminus with human monocytes induces an oxidative burst and modulates effector functions

The interaction of highly purified, monomeric fibrinogen (Fg) with human monocytes (MO) was investigated. In contrast to commercial Fg, no high-affinity binding of monomeric Fg to MO or mononuclear cells could be demonstrated. MO preincubated with Fg in the presence or absence of Ca ++ elicited an oxidative burst when triggered with anti-Fg antibodies. Divalency of the antibody and specificity were required, but an intact Fc portion was not. Surface-adsorbed monomeric Fg also promoted an oxidative burst. Evidence is presented that Fg-MO interaction is mediated by the casboxy-γterminus of Fg. MO treated with monomeric Fg or exposed to Fg-coated surfaces show a reduced oxidative burst upon triggering with unrelated stimuli. Thus, MO function may be modulated upon interaction with surface-adsorbed Fg or with fibrin.