Mast Cells as Key Players in Allergy and Inflammation.

Mast cells (MCs) are a key structural and functional component of both the innate and the adaptive immune systems. They are involved in many different processes, but play a major role in the response to infections and in inflammatory reactions. In addition, MCs are the main effector cells in allergy. MC biology is far more complex than initially believed. Thus, MCs may act directly or indirectly against pathogens and show a wide variety of membrane receptors with the ability to activate cells in response to various stimuli. Depending on where MCs complete the final stages of maturation, the composition of their cytoplasmic granules may vary considerably, and the clinical symptoms associated with tissue MC activation and degranulation may be also different. MCs are activated by complex signalling pathways characterized by multimolecular activating and inhibitory interactions. This article provides a comprehensive overview of MC biology, focusing predominantly on mechanisms of MC activation and the role of MCs in the pathogenesis of allergic diseases.