Regulation of the pleiotropic effects of tissue resident mast cells.

Mast cells, best known for their detrimental role in allergic diseases, act in a diverse array of physiological and pathological functions, made possible by the plurality of mast cell types. Their various developmental avenues and their distinct sensitivity to (micro-) environmental conditions convey extensive heterogeneity, resulting in diverse functions. We briefly summarize this heterogeneity, elaborate on molecular determinants that allow mast cells to communicate with their environment to fulfill their tasks, discuss their protease repertoire stored in secretory lysosomes, and consider different aspects of mast cell signaling. Further, we describe key mast cell governance mechanisms, i.e. the high-affinity receptor for IgE (FcεRI), the stem cell factor receptor KIT, the IL-4 system, and Ca-dependent as well as phosphatase-dependent mechanisms. Finally, we focus on distinct physiological functions such as chemotaxis, phagocytosis, host defense, and the regulation of mast cell functions at the mucosal barriers of the lung, the gastrointestinal tract, and the skin. A deeper knowledge of the pleiotropic functions of mast cell mediators as well as the molecular processes of mast cell regulation and communication should enable us to promote beneficial mast cell traits in physiology and suppress detrimental mast cell functions in disease.