Neutrophil Fc gamma RI expression as a determinant of oxidative responses in human blood

Neutrophils express Fc receptors on their surface to trap immune complexes. While the roles of Fc{gamma}RIIa and Fc{gamma}RIIIb have extensively been studied in that context, that of Fc{gamma}RI remains elusive. Recently, aggregated IgGs have been shown to induce rapid Fc{gamma}RI up-regulation and reactive oxygen species (ROS) generation, but the biological relevance of this process is still unclear. In this study, incubation of blood samples from healthy volunteers with heat-aggregated IgGs, used as a model of immune complexes, rapidly up-regulated the surface expression of Fc{gamma}RI, predominantly on neutrophils, as measured by flow cytometry. Stimulation of isolated neutrophils with aggregated IgGs resulted in the production of ROS in an Fc{gamma}RI-dependent fashion, as monitored with a luminol-based chemiluminescence assay. Cytochalasin B potentiated Fc{gamma}RI expression and ROS production. In resting blood, positive correlations between neutrophil Fc{gamma}RI and ROS production were observed, both in healthy volunteers and patients with lupus. This study unveils a potentially central regulatory role for neutrophil Fc{gamma}RI in ROS production, both in healthy individuals and patients with lupus, and identifies neutrophil Fc{gamma}RI as a promising target to modulate oxidative response.