The human gut harbors a wide range of microorganisms that play a fundamental role in the well-being of their host. A dysregulation of the microbial composition can lead to the development or exacerbation of gastrointestinal (GI) disorders. Emerging evidence supports the hypothesis that mast cells (MCs) play a role in host-microbiota communication, modulating the mutual influence between the host and its microbiota through changes in their activation state. The ability of some bacteria to specifically affect MC functions and activation has been extensively studied, with different and sometimes conflicting results, while only little is known about MC-fungi interactions. In this review, the most recent advances in the field of MC-bacteria and MC-fungi interactions will be discussed, with a particular focus on the role of these interactions in the onset of GI disorders such as inflammatory bowel diseases (IBD). Moreover, the connection between some MC-targeting drugs and IBD was discussed, suggesting probiotics as reasonable and promising therapy in the management of IBD patients.
Keywords: Inflammatory bowel disease (IBD) r Intestine r Mast cells r Microbiota r Neurons Additional supporting information may be found online in the Supporting Information section at the end of the article. of the high affinity receptor for IgE on the surface of the cell and of the proteases-containing granules in the cytosol, under the influence of tissue-specific molecules (including SCF, IL-3, and IL-9) and bacterial-derived molecules (LPS and peptidoglycan) present in the local microenvironment [1]. Intestinal homing of MCs progenitors is mainly mediated by the interaction of α4β7 integrin expressed by MCs with ICAM-1, V-CAM, or MAdCAM-1 expressed by endothelial cells and it is influenced by CXCR2 ligation [2, 3].MCs possess a great number of costimulatory molecules, including members of the B7 family (ICOSL, PD-L1, and PD-L2,) and of the TNF/TNFR families (OX40L, CD153, Fas, 4-1BB, and glucocorticoid-induced TNFR), which allow them to interact with different partners both from immune and nonimmune cells populations as well as with bacteria and fungi through the expression of different pattern-recognition receptors (PRRs) [4]. Moreover, MCs harbor a high number of cytoplasmic granules that contain preformed immunomodulatory compounds such as proteases, histamine, heparin, and TNF-α. Given the wide pattern Eur.