Polymorphonuclear leukocyte secretory and metabolic responses to immunoglobulin aggregates

Biologic activities of soluble immunoglobulin G (IgG) aggregates, insoluble IgG aggregates and precipitates resulting from addition of serum containing rheumatoid factor (RF) to soluble or insoluble IgG aggregates were examined in terms of lysosomal enzyme release and/or stimulation of the hexose monophosphate pathway (HMP) in human polymorphonuclear leukocytes (PMN). Granular enzyme release and HMP stimulation were consistently greater for insoluble aggregates and complexes than for soluble aggregates and controls. One role of IgM rheumatoid factor may be its ability to convert relatively inactive soluble IgG aggregates into insoluble IgG-RF complexes capable of stimulating selective release of PMN lysosomal enzymes.