Inhibition of neutrophil phagocytosis and enzyme release by hyaluronic acid.

Hyaluronic acid at a concentration found in normal joints (4 mg/ml) inhibited the uptake of aggregated IgG by human peripheral blood polymorphonuclear leukocytes, but concentrations of hyaluronic acid found in inflammatory joints (1 mg/ml) did not. Similarly, hyaluronic acid at 4 mg/ml, but not 1 mg/ml, inhibited the release of lysozyme from aggregated IgG stimulated polymorphonuclear leukocytes. beta-Glucuronidase release was inhibited by both concentrations of hyaluronic acid. Physiological concentrations of hyaluronic acid inhibit this model system for the fluid phase of rheumatoid arthritis and hyaluronic acid may be an important immunomodulating substance in the rheumatoid joint.