Abstract
Mast cells (MCs) play important roles in normal immune responses and pathological states. The location of MCs on the boundaries between tissues and the external environment, including gut mucosal surfaces, lungs, skin, and around blood vessels, suggests a multitude of immunological functions. Thus, MCs are pivotal for host defense against different antigens, including allergens and microbial pathogens. MCs can produce and respond to physiological mediators and chemokines to modulate inflammation. As long-lived, tissue-resident cells, MCs indeed mediate acute inflammatory responses such as those evident in allergic reactions. Furthermore, MCs participate in innate and adaptive immune responses to bacteria, viruses, fungi, and parasites. The control of MC activation or stabilization is a powerful tool in regulating tissue homeostasis and pathogen clearance. Moreover, MCs contribute to maintaining the homeostatic equilibrium between host and resident microbiota, and they engage in crosstalk between the resident and recruited hematopoietic cells. In this review, we provide a comprehensive overview of the functions of MCs in health and disease. Further, we discuss how mouse models of MC deficiency have become useful tools for establishing MCs as a potential cellular target for treating inflammatory disorders.
Highlights
Mast cells (MCs) constitute a major component of innate immunity due to their distribution in the superficial dermis proximal to blood and lymphatic vessels, nerve fibers, and in muscle tissues [1]
We provide a comprehensive overview of the functions of MCs in health and disease
The MC adhesion to endothelial cells and extracellular matrix (ECM) ligands is upregulated by interaction with the T cells, which is accompanied by the mitogen-activated protein (MAP) kinase activation, and further enhanced by the FcεRI-mediated degranulation of MCs
Summary
Mast cells (MCs) constitute a major component of innate immunity due to their distribution in the superficial dermis proximal to blood and lymphatic vessels, nerve fibers, and in muscle tissues [1]. MCs are important for the recognition and clearance of microbial pathogens and the initiation of adaptive immune responses during microbial infection, as well as for the activation of the cell–cell crosstalk [3,4]. We comprehensively discuss the research into roles of MCs in immune homeostasis as well as their multiple roles in the host defense against pathogens, whereby MCs act as sensors and effectors of responses, as controllers of infection and modulators of local inflammation. We discuss the significance of MCs in complex interactions with other components of the mucus layers, tissue-resident microbiota, and epithelial cells, and their role in the recruitment of other innate and adaptive immune cells. We discuss the functions of MCs in maintaining the equilibria and homeostasis between host and microbiota, including the crosstalk between resident hematopoietic cells. We focus on the induction of MC degranulation, which is often associated with microbial invasion and IgE-receptor aggregation, and we review their role during allergic and autoimmune inflammation
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