Human neutrophil swelling induced by immune complexes and aggregated IgG

Using a Coulter counter method, the effects of various types of IgG-dependent phagocytic stimuli on human neutrophil (PMN) swelling were determined. Human heat aggregated IgG, ovalbumin-antiovalbumin (OV-anti-OV) immune complexes, and opsonized latex particles all induced PMN swelling. The OV-anti-OV immune complexes were effective, whether prepared at antigen-antibody equivalence (insoluble) or at 4 or 9 times antigen excess (soluble). Swelling of PMN occurred at 37 degrees C, but not at 4 degrees C. Complement was not present in any of the experiments. In contrast to the above results, native IgG, OV-anti-OV F(ab')2 immune complexes and unopsonized latex particles did not induce PMN swelling. These results suggest that the PMN swelling observed in this study is due to Fc-dependent, complement-independent membrane stimulation and/or phagocytosis.