Biological implications of preformed mast cell mediators

Abstract

Mast cells store an impressive array of preformed compounds (mediators) in their secretory granules. When mast cells degranulate, these are released and have a profound impact on any condition in which mast cell degranulation occurs. The preformed mast cell mediators include well-known substances such as histamine, proteoglycans, proteases, and preformed cytokines, as well as several recently identified compounds. Mast cells have recently been implicated in a large number of novel pathological settings in addition to their well-established contribution to allergic reactions, and there is consequently a large current interest in the molecular mechanisms by which mast cells act in the context of a given condition. In many cases, preformed mast cell mediators have been shown to account for functions ascribed to mast cells, and these compounds are hence emerging as major players in numerous pathologies. In this review we summarize the current knowledge of preformed mast cell mediators.

Fig. 1

Examples of biological functions of secreted, preformed MC mediators

Fig. 2

a, b Transmission electron micrographs showing an intact rat peritoneal MC (a) and a MC undergoing anaphylactic degranulation (b). The block arrows indicate regions where multiple granules have fused; the arrow depicts an exocytosed granule remnant. c, d Scanning electron micrographs showing an intact (c) and degranulated (d) rat peritoneal MC. Note the extensive membrane alterations in d. Arrows in d depict exocytosed granule remnants. Images are courtesy of Prof. Giuliano Zabucchi, Prof. Maria Rosa Soranzo, and Dr. Francesca Vita (Electron Microscopy Section of Centro Coordinamento e Sviluppo Progetti e Apparecchiature (CSPA), University of Trieste)