Proteoglycans, proteases, chemotaxis, and aggregation of inflammatory, cells

A trypsin-like protease activity present in rabbit alveolar macrophages was shown to be activated by hyaluronic acid (HA) at 10(-9) M, but not by other proteoglycans. This activation of proteases by HA was accompanied by aggregation of alveolar macrophages and by the release of chemotactic activity. This chemotactic activity was destroyed by proteases and was less active for polymorphonuclear leukocytes than for alveolar macrophages. These effects of HA appear to be sepcific for alveolar macrophages, because no similar effects of HA on human polymorphonuclear leukocytes or lymphocytes could be observed. These observations suggest that HA, which is secreted into airways, plays a specific role in the macrophage-mediated chronic inflammatory processes in the distal lung.