Complement activation on immunoglobulin G-coated hydrophobic surfaces enhances the release of oxygen radicals from neutrophils through an actin-dependent mechanism.

Neutrophil granulocytes are among the first cells to encounter a plasma protein-coated implant and may through frustrated phagocytosis release toxic oxidative species. We used two model surfaces, hydrophobic and hydrophilic glass, to investigate the effects of plasma immunoglobulin G (IgG)-complement interactions for neutrophil adhesion and respiratory burst. The respiratory burst was measured with luminol-amplified chemiluminescence and cell adhesion was determined by labeling neutrophils with 2', 7'-bis-(carboxy-ethyl)-5(6)-carboxyfluorescein. We demonstrate that the IgG-triggered neutrophil adhesion and oxygen radical production is augmented in the presence of normal human serum, in particular on hydrophobic surfaces, indicating that complement factors enhance the neutrophil activation. We propose that the complement factors C3, C5a, and C1q are especially important for this amplification, but factor B is probably not. Disturbance of the actin filament dynamics with cytochalasin B or jasplakinolide blocked the neutrophil radical generation on all surfaces. However, these drugs did not affect the number of adherent neutrophils. We suggest that there is a synergistic interaction between adsorbed IgG, and the complement system, which amplifies the neutrophil acute inflammatory responses through a dynamic actin cytoskeleton on synthetic surfaces.