Soluble IgG-containing immune complexes are unable to initiate oxidant production in unprimed neutrophils. However, priming of the neutrophils with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or cytochalasin B prior to exposure to these complexes results in activation of a rapid and extensive secretion of reactive oxidants. In this study, we have investigated the ability of soluble immune complexes to: (1) induce oxidant generation; (2) bind to the cell surface; and (3) induce Ca2+ transients in neutrophils primed by incubation with GM-CSF or cytochalasin B. Our findings give new insight into the molecular processes involved in the "priming" phenomenon.