The role of macrophage secretory products in chronic inflammatory processes

Mononuclear phagocytes participate in various stages of chronic inflammatory responses and associated diseases. Such participation is mediated by (a) direct interaction with pericellular interstitial tissue components as well as with other cell types present at sites of inflammation and (b) by secretion of soluble mediators. Several of these mediators are synthesized and secreted in increased amounts after macrophages interact with inflammatory stimuli. In this paper we pay particular attention to neutral proteinases and prostaglandins. It is shown that these 2 classes of mediators are released in significant amounts under different conditions. Prostaglandins are synthesized most readily by resident populations of mouse peritoneal macrophages responding to various model inflammatory stimuli. Mouse peritoneal macrophage populations elicited in vivo by inflammatory stimuli are less responsive in this respect. In contrast neutral proteinase secretion does not occur in resident cell populations but is observed on a continuous basis in elicited populations. Such secretion can be increased further by addition of phagocytic stimuli and initiated in resident populations by model inflammatory stimuli such as phorbol myritate acetate. Other secretory products of macrophages with possible relevance to inflammation are discussed briefly. Finally some of the effects of antiinflammatory glucocorticoids, cyclooxygenase inhibitors and dapsone on the secretory activity of macrophages are briefly summarized.