scholarly journals Mast Cell Activation in Sickle Mice Stimulates Endothelial Dysfunction

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 453-453
Author(s):  
Kathryn Luk ◽  
Julia Nguyen ◽  
Jinny Paul ◽  
Barbara Benson ◽  
Yann Y Lamarre ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Endothelial Dysfunction ◽  
Er Stress ◽  
Cell Activation ◽  
Nerve Fibers ◽  
Molecular Probes ◽  
Mast Cell Activation ◽  
Stress Markers ◽  
Cell Supernatant

Abstract We showed that mast cell activation/degranulation contributes to pain and neurogenic inflammation characterized by increased vascular permeability in sickle mice (Vincent et al., Blood 2013). Mast cells are tissue resident inflammatory cells, which are located in the vicinity of vasculature and nerve fibers. Neurogenic inflammation is mediated by activation of peripheral nerve fibers via the release of vasoactive and neurinflammatory peptide, substance P. However, the products of mast cell activation may have direct effects on the vasculature. Sickle pathobiology is characterized by endothelial dysfunction, inflammation and oxidative stress. We hypothesized that the neuropeptides, proteases, and cytokines released from activated mast cells lead to endothelial dysfunction by stimulating endoplasmic reticulum (ER) stress, and mitochondrial dysfunction, leading to oxidative stress. We examined the direct effect of mast cell activation on endothelium. Since morphine is used to treat pain in sickle cell disease (SCD) and also influences endothelial signaling (Gupta et al., Cancer Res 2002), we investigated if morphine contributes to endothelial dysfunction. Methods. We isolated mast cells from the skin of HbSS-BERK sickle mice, which demonstrate severe mast cell activation and hyperalgesia (pain) and HbAA-BERK control mice. Mast cells from sickle mouse skin continue to degranulate in culture, but the mast cells from control mice do not. We collected the supernatant from mast cell cultures and used it to treat primary mouse brain microvascular endothelial cells (MBMEC) in vitro. ER stress was assayed using ER-Tracker Green (Glibenclamide BODIPY FL) dye (Molecular Probes) on live cells followed by laser scanning confocal microscopy (LSCM). ER stress markers, E74-like factor 2a (ELF2a), X-box binding protein 1 (XBP1), and glucose regulated protein 78 (GRP78), were analyzed with Western Immunoblotting. Mitochondrial function was analyzed by estimating mitochondrial membrane potential with MitoProbe JC-1 (Molecular Probes), which exhibits potential-dependent accumulation in mitochondria, causing a fluorescence emission shift from green (~529 nm) to red (~590 nm). Mitochondrial depolarization (dysfunction) was analyzed by a decrease in red/green ratio using LSCM. ROS was assayed using 2’7’-dichlorofluorescein diacetate and quantifying the fluorescence at the max excitation and emission spectra of 495 nm and 529 nm, respectively. Results. Supernatant from sickle mast cells led to significant ER stress in MBMEC, as compared to the supernatant from control mast cells (p<0.05). Western blotting demonstrated an increase in ER stress markers, phosphor-elF2a, sXBP1 and GRP78, in MBMEC incubated with sickle mast cell supernatant as compared to control mast cell supernatant. Complementary to the sickle mast cell-induced ER stress, mitochondria potential decreased in MBMEC treated with sickle mast cell supernatant as compared to control mast cell supernatant (p < 0.05). We observed that supernatant from activated cutaneous mast cells stimulated a 10-fold increase in reactive oxygen species (ROS) in MBMEC (p < 0.05). This effect was further exacerbated in MBMEC treated with both sickle mast cell supernatant and morphine (p < 0.01). Morphine alone increased ROS production 4-fold in MBMEC. ER stress inhibitor, Salubrinal, inhibited ROS production in MBMEC induced by sickle mast cells. Together, these data suggest that mast cell activation stimulates ER stress in MBMEC, which may lead to mitochondrial dysfunction and generation of ROS. Thus, mast cell degranulation alone/and in addition to morphine, may contribute to endothelial dysfunction in SCD. Disclosures No relevant conflicts of interest to declare.

scholarly journals Mast Cells Contribute to Brain Microvascular Permeability in Sickle Cell Disease

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 269-269 ◽  
Author(s):  
Aditya M Mittal ◽  
Huy Tran ◽  
Varun Sagi ◽  
Aithanh Nguyen ◽  
Kathryn Luk ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Er Stress ◽  
Sickle Cell ◽  
Cell Activation ◽  
Cell Activity ◽  
Mast Cell Activation ◽  
Bbb Permeability ◽  
The Brain

Abstract Mast cells are in close proximity to the vasculature and cause endothelial activation, plasma extravasation, and vascular dysfunction (Gupta & Harvima, Immunol Rev 2018). Vascular dysfunction in sickle cell disease (SCD) is accompanied by increased expression of P-selectin. Treatment with Crizanlizumab, an antibody against P-selectin, led to significantly less sickle cell-related pain crises (Ataga et al., NEJM 2017) highlighting the role of endothelial P-selectin in vasoocclusive crises (VOC). Earlier studies demonstrated that mast cell activation with morphine or ischemia/reperfusion stimulates endothelial E- and/or P-selectin expression. However, it is unknown how mast cells stimulate endothelial selectin expression in SCD. Endothelial dysfunction contributes significantly to the pathobiology of SCD including VOC and may play a critical role in increased blood-brain barrier (BBB) permeability, which may contribute to stroke, another major comorbidity of SCD. One of the known triggers of endothelial dysfunction, inflammation and oxidative stress is endoplasmic reticulum (ER) stress. We hypothesize that in a sickle microenvironment, mediators derived from activated mast cells stimulate endothelial P-selectin expression via ER stress leading to increased BBB permeability. We examined the ability of mast cells to stimulate P-selectin expression and BBB permeability via ER stress in a sickle microenvironment. We isolated MCs from HbAA-BERK and HbSS-BERK, control and sickle mice, respectively; incubated them in vitro and collected mast cell conditioned media (MCCM) from HbAA MCs and HbSS MCs. Normal mouse brain microvascular endothelial cells (mBMECs) were treated with unconditioned MCCM, HbAA MCCM, or HbSS MCCM to examine the effect of mast cell activation on endothelium. We observed increased mast cell activity in HbSS mice evinced by significantlyhigher plasma and skin histamine levels, compared to HbAA mice (p< 0.02 for both). Mast cells from HbSS mouse skin showed significantly increased expression of histamine compared to HbAA skin mast cells (p< 0.04). mBMECs incubated with HbAA and HBSS MCCM exhibited about 3- and 6-fold fold increases in P-selectin expression, compared to unconditioned culture medium, respectively (p< 0.0001 for both). Therefore, mast cells in culture release substances that stimulate P-selectin expression which is further increased by mast cells from sickle (HbSS) microenvironment. Preincubation of mBMEC with 5 microM salubrinal, an inhibitor of dephosphorylation of elongation initiation factor-a, which reduces ER stress, significantly inhibited HbSS MCCM-induced P-selectin expression on mBMEC (p< 0.0001) to the level induced by HbAA-MCCM. In contrast, salubrinal did not inhibit HbAA-MCCM-induced P-selectin expression on mBMEC, suggesting that in a sickle microenvironment mast cells contribute to P-selectin expression via ER stress. We next examined mast cell activity on endothelial permeability in vitro on mBMEC monolayers and in vivo in the brain of HbSS mice. mBMECs incubated with HbSS MCCM showed a significant increase in Evans blue leakage compared to unconditioned or HbAA MCCM (p<0.0001 for both), which was inhibited by preincubation of mBMEC with 5 microM salubrinal prior to incubation with HbSS MCCM (p< 0.0001). In vivo female HbSS mice showed a significantly increased leakage in the brain of FITC-dextran injected through tail vein compared to HbAA mice (p< 0.01). HbSS mice treated with 1 mg/kg salubrinal demonstrated inhibition of FITC-dextran leakage in the brain compared to vehicle (p< 0.05). Thus, ER stress contributes to increased BBB permeability in HbSS mice. We observed activated degranulating mast cells in the brain parenchyma of HbSS mice. In HbAA mice, quiescent mast cells were confined to the meninges of the brain but not seen in the parenchyma. Together, these data suggest that mast cell activation contributes to BBB permeability in a sickle microenvironment via ER stress-mediated P-selectin expression. In turn, this mast cell-initiated activity in the brain may underlie the pathobiology of stroke in SCD. Inhibitors of mast cells and P-selectin have been tested clinically leading to reduced VOC in SCD without known adverse events. Therefore, mast cell activation-induced P-selectin via ER stress may serve as a treatable target for reducing the risk of stroke in SCD. Disclosures Gupta: Novartis: Honoraria; Tau tona: Consultancy.

scholarly journals Brain mast cells link the immune system to anxiety-like behavior

2008 ◽  
Vol 105 (46) ◽  
pp. 18053-18057 ◽  
Author(s):  
Katherine M. Nautiyal ◽  
Ana C. Ribeiro ◽  
Donald W. Pfaff ◽  
Rae Silver
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Cell Activation ◽  
Mast Cell Activation ◽  
Neural Systems ◽  
Loss Of Function ◽  
Littermate Control ◽  
Cytokines And Chemokines ◽  
Function Models ◽  
The Brain

Mast cells are resident in the brain and contain numerous mediators, including neurotransmitters, cytokines, and chemokines, that are released in response to a variety of natural and pharmacological triggers. The number of mast cells in the brain fluctuates with stress and various behavioral and endocrine states. These properties suggest that mast cells are poised to influence neural systems underlying behavior. Using genetic and pharmacological loss-of-function models we performed a behavioral screen for arousal responses including emotionality, locomotor, and sensory components. We found that mast cell deficient KitW−sh/W−sh (sash−/−) mice had a greater anxiety-like phenotype than WT and heterozygote littermate control animals in the open field arena and elevated plus maze. Second, we show that blockade of brain, but not peripheral, mast cell activation increased anxiety-like behavior. Taken together, the data implicate brain mast cells in the modulation of anxiety-like behavior and provide evidence for the behavioral importance of neuroimmune links.

Association of Mast Cell Burden and TIM-3 Expression with Recalcitrant Chronic Rhinosinusitis with Nasal Polyps

2021 ◽  
pp. 000348942199503
Author(s):  
Michael A. Belsky ◽  
Erica Corredera ◽  
Hridesh Banerjee ◽  
John Moore ◽  
Li Wang ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Chronic Rhinosinusitis ◽  
Nasal Polyps ◽  
Cell Activation ◽  
Enzymatic Digestion ◽  
Sinus Surgery ◽  
Mast Cell Activation ◽  
Need For Treatment ◽  
Inflammatory State

Objectives: Previous work showed that higher polyp mast cell load correlated with worse postoperative endoscopic appearance in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). Polyp epithelial mast cells showed increased expression of T-cell/transmembrane immunoglobulin and mucin domain protein 3 (TIM-3), a receptor that promotes mast cell activation and cytokine production. In this study, CRSwNP patients were followed post-operatively to investigate whether mast cell burden or TIM-3 expression among mast cells can predict recalcitrant disease. Methods: Nasal polyp specimens were obtained via functional endoscopic sinus surgery (FESS) and separated into epithelial and stromal layers via enzymatic digestion. Mast cells and TIM-3-expressing mast cells were identified via flow cytometry. Mann-Whitney U tests and Cox proportional hazard models assessed whether mast cell burden and TIM-3 expression were associated with clinical outcomes, including earlier recurrence of polypoid edema and need for treatment with steroids. Results: Twenty-three patients with CRSwNP were studied and followed for 6 months after undergoing FESS. Higher mast cell levels were associated with earlier recurrence of polypoid edema: epithelial HR = 1.283 ( P = .02), stromal HR = 1.103 ( P = .02). Percent of mast cells expressing TIM-3 in epithelial or stromal layers was not significantly associated with earlier recurrence of polypoid edema. Mast cell burden and TIM-3+ expression were not significantly associated with need for future treatment with steroids post-FESS. Conclusions: Mast cell load in polyp epithelium and stroma may predict a more refractory postoperative course for CRSwNP patients. The role of TIM-3 in the chronic inflammatory state seen in CRSwNP remains unclear.

Abstract 1193: Mast Cell Activation Promotes Leukocyte Recruitment And Adhesion To The Atherosclerotic Plaque

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Ilze Bot ◽  
Saskia C de Jager ◽  
Alma Zernecke ◽  
Christian Weber ◽  
Theo J van Berkel ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Carotid Artery ◽  
Atherosclerotic Plaque ◽  
Cell Activation ◽  
Ex Vivo ◽  
Leukocyte Adhesion ◽  
Leukocyte Recruitment ◽  
Mast Cell Activation ◽  
Labeled Leukocytes

Activated mast cells have been identified in the perivascular tissue of human coronary artery plaques. As mast cells have been described to release a whole array of chemokines including interleukin 8 (IL-8) and MIP1 α, we propose that activated mast cells play a pivotal role in leukocyte recruitment at advanced stages of atherosclerotic plaque development. Peritoneal mast cells of either C57Bl/6 or mast cell deficient Kit(W −sh /W −sh ) mice were activated by injection of compound 48/80 (1.2 mg/kg). Interestingly, mast cell activation led to a massive neutrophil influx into the peritoneal cavity at 3 hours after activation (controls: 1 ± 0.7*10 4 Gr1 + -neutrophils/ml up to 8 ± 0.2*10 4 Gr1 + neutrophils/ml at 3 hours after activation, *P<0.05), while neutrophil numbers in Kit(W −sh /W −sh ) mice were not affected by compound 48/80 administration. Moreover, increased levels of CXCR2 + Gr1 + neutrophils (t=0: 0.55 ± 0.07% versus t=3 hours: 1.00 ± 0.12%, *P<0.05) were observed after mast cell activation. Next, we investigated whether mast cell activation also translated in induced leukocyte adhesion to advanced atherosclerotic plaques. Adventitial mast cells of advanced collar aided carotid artery plaques were activated by local application of a dinitrophenyl-BSA (DNP) challenge in ApoE −/− mice. Three days later, the carotid artery segments carrying the plaques were isolated and perfused ex vivo with rhodamine labeled leukocytes, showing a dramatically increased number of adherent leukocytes after mast cell activation (49 ± 6 versus 19 ± 4 leukocytes/microscopic field for DNP versus control plaques, respectively, **P<0.001). Strikingly, antibody blockade of either the CXCR2 or VCAM-1 receptor VLA-4 on labeled leukocytes completely inhibited leukocyte adhesion to the atherosclerotic plaque (*P<0.05), while blockade of CCR1, -3 and -5 with Met-RANTES had no effect. In conclusion, our data suggest that chemokines such as IL-8 released from activated perivascular mast cells induce leukocyte recruitment and adhesion to the atherosclerotic plaque, aggravating the ongoing inflammatory response and thus effecting plaque destabilization. We propose that mast cell stabilization could be a new therapeutic approach in the prevention of acute coronary syndromes.

scholarly journals Mast cell activation is not required for induction of airway hyperresponsiveness by ozone in mice

1999 ◽  
Vol 86 (1) ◽  
pp. 202-210 ◽  
Author(s):  
N. Noviski ◽  
J. P. Brewer ◽  
W. A. Skornik ◽  
S. J. Galli ◽  
J. M. Drazen ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Airway Hyperresponsiveness ◽  
Essential Role ◽  
Cell Activation ◽  
Mast Cell Degranulation ◽  
Mast Cell Activation ◽  
Polymorphonuclear Cell ◽  
Pulmonary Parenchyma

Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1- kitW/ kitW-v( kitW/ kitW-v) mice and the congenic normal WBB6F1(+/+) mice to air or to 1 or 3 parts/million O3for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/ kitW-vand +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice.

scholarly journals Granzyme D Is a Novel Murine Mast Cell Protease That Is Highly Induced by Multiple Pathways of Mast Cell Activation

2013 ◽  
Vol 81 (6) ◽  
pp. 2085-2094 ◽  
Author(s):  
Elin Rönnberg ◽  
Gabriela Calounova ◽  
Bengt Guss ◽  
Anders Lundequist ◽  
Gunnar Pejler
Keyword(s):  
T Cells ◽  
Mast Cell ◽  
Mast Cells ◽  
Serine Proteases ◽  
Cell Activation ◽  
Calcium Ionophore ◽  
Mast Cell Activation ◽  
Activated T Cells ◽  
Mast Cell Protease ◽  
Murine Mast Cell

ABSTRACTGranzymes are serine proteases known mostly for their role in the induction of apoptosis. Granzymes A and B have been extensively studied, but relatively little is known about granzymes C to G and K to M. T cells, lymphohematopoietic stromal cells, and granulated metrial gland cells express granzyme D, but the function of granzyme D is unknown. Here we show that granzyme D is expressed by murine mast cells and that its level of expression correlates positively with the extent of mast cell maturation. Coculture of mast cells with live, Gram-positive bacteria caused a profound, Toll-like receptor 2 (TLR2)-dependent induction of granzyme D expression. Granzyme D expression was also induced by isolated bacterial cell wall components, including lipopolysaccharide (LPS) and peptidoglycan, and by stem cell factor, IgE receptor cross-linking, and calcium ionophore stimulation. Granzyme D was released into the medium in response to mast cell activation. Granzyme D induction was dependent on protein kinase C and nuclear factor of activated T cells (NFAT). Together, these findings identify granzyme D as a novel murine mast cell protease and implicate granzyme D in settings where mast cells are activated, such as bacterial infection and allergy.

scholarly journals Mast cell function in prostate inflammation, fibrosis, and smooth muscle cell dysfunction

2021 ◽  
Author(s):  
Goutham Pattabiraman ◽  
Ashlee J Bell-Cohn ◽  
Stephen F. Murphy ◽  
Daniel J Mazur ◽  
Anthony J Schaeffer ◽  
...  
Keyword(s):  
Mast Cell ◽  
Smooth Muscle ◽  
Mast Cells ◽  
Cell Activation ◽  
Cell Function ◽  
Critical Role ◽  
Smooth Muscle Contraction ◽  
Urinary Dysfunction ◽  
Mast Cell Activation ◽  
Prostate Inflammation

Intraurethral inoculation of mice with uropathogenic E. coli (CP1) results in prostate inflammation, fibrosis, and urinary dysfunction, recapitulating some but not all of the pathognomonic clinical features associated with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). In both patients with LUTS and in CP1-infected mice, we observed increased numbers and activation of mast cells and elevated levels of prostate fibrosis. Therapeutic inhibition of mast cells using a combination of mast cell stabilizer (MCS), cromolyn sodium, and the histamine 1 receptor antagonist (H1RA), cetirizine di-hydrochloride, in the mouse model resulted in reduced mast cell activation in the prostate and significant alleviation of urinary dysfunction. Treated mice showed reduced prostate fibrosis, less infiltration of immune cells, and decreased inflammation. In addition, as opposed to symptomatic CP1-infected mice, treated mice showed reduced myosin light chain (MLC)-2 phosphorylation, a marker of prostate smooth muscle contraction. These results show that mast cells play a critical role in the pathophysiology of urinary dysfunction and may be an important therapeutic target for men with BPH/LUTS.

scholarly journals A Practical Guide for Treatment of Pain in Patients with Systemic Mast Cell Activation Disease

2017 ◽  
Vol 6 (20;6) ◽  
pp. E849-E861
Author(s):  
Gerhard J. Molderings
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Cell Activation ◽  
Mast Cell Activation ◽  
German Population ◽  
Common Symptom ◽  
Mast Cell Mediator ◽  
Practical Guide ◽  
Mast Cell Activation Disease ◽  
High Prevalence

Systemic mast cell activation disease (MCAD, a subclass of mastocytosis), which has a prevalence of around 17% (at least in the German population), is characterized by accumulation of genetically altered dysfunctional mast cells with abnormal release of these cells’ mediators. Since mast cells affect functions in potentially every organ system, often without causing abnormalities in routine laboratory or radiologic testing, this disease has to be considered routinely in the differential diagnosis of patients with chronic multisystem polymorbidity of a generally inflammatory and allergic theme. Pain in its different manifestations is a common symptom in MCAD found in more than three-quarters of the MCAD patients. Because of the specific mast cell-related causes of pain in MCAD it should be treated specifically, if possible, deduced from their putative mast cell mediator-related causes. As yet, there is no official guideline for treatment of MCAD at all. The present review focuses on mast cell mediator-induced acute and chronic pain and the current state of analgesic drug therapy options in MCAD. Due to the high prevalence of MCAD, many physicians are often faced with the issue of pain management in MCAD patients. Hence, our practical guide should contribute to the improvement of patient care.

scholarly journals The rat c-kit ligand, stem cell factor, induces c-kit receptor-dependent mouse mast cell activation in vivo. Evidence that signaling through the c-kit receptor can induce expression of cellular function.

1992 ◽  
Vol 175 (1) ◽  
pp. 245-255 ◽  
Author(s):  
B K Wershil ◽  
M Tsai ◽  
E N Geissler ◽  
K M Zsebo ◽  
S J Galli
Keyword(s):  
Mast Cell ◽  
Stem Cell ◽  
Mast Cells ◽  
Stem Cell Factor ◽  
Cell Activation ◽  
Mast Cell Activation ◽  
Tyrosine Kinase Receptor ◽  
Kit Ligand ◽  
Kit Receptor

Interactions between products of the mouse W locus, which encodes the c-kit tyrosine kinase receptor, and the Sl locus, which encodes a ligand for c-kit receptor, which we have designated stem cell factor (SCF), have a critical role in the development of mast cells. Mice homozygous for mutations at either locus exhibit several phenotypic abnormalities including a virtual absence of mast cells. Moreover, the c-kit ligand SCF can induce the proliferation and maturation of normal mast cells in vitro or in vivo, and also can result in repair of the mast cell deficiency of Sl/Sld mice in vivo. We now report that administration of SCF intradermally in vivo results in dermal mast cell activation and a mast cell-dependent acute inflammatory response. This effect is c-kit receptor dependent, in that it is not observed when SCF is administered to mice containing dermal mast cells expressing functionally inactive c-kit receptors, is observed with both glycosylated and nonglycosylated forms of SCF, and occurs at doses of SCF at least 10-fold lower on a molar basis than the minimally effective dose of the classical dermal mast cell-activating agent substance P. These findings represent the first demonstration in vivo that a c-kit ligand can result in the functional activation of any cellular lineage expressing the c-kit receptor, and suggest that interactions between the c-kit receptor and its ligand may influence mast cell biology through complex effects on proliferation, maturation, and function.

scholarly journals Beyond IgE: Alternative Mast Cell Activation Across Different Disease States

2020 ◽  
Vol 21 (4) ◽  
pp. 1498 ◽  
Author(s):  
David O. Lyons ◽  
Nicholas A. Pullen
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Cell Activation ◽  
Autoimmune Disorders ◽  
Receptor Expression ◽  
Mast Cell Activation ◽  
Food Allergies ◽  
Type I ◽  
Disease States ◽  
Ige Mediated

Mast cells are often regarded through the lens of IgE-dependent reactions as a cell specialized only for anti-parasitic and type I hypersensitive responses. However, recently many researchers have begun to appreciate the expansive repertoire of stimuli that mast cells can respond to. After the characterization of the interleukin (IL)-33/suppression of tumorigenicity 2 (ST2) axis of mast cell activation—a pathway that is independent of the adaptive immune system—researchers are revisiting other stimuli to induce mast cell activation and/or subsequent degranulation independent of IgE. This discovery also underscores that mast cells act as important mediators in maintaining body wide homeostasis, especially through barrier defense, and can thus be the source of disease as well. Particularly in the gut, inflammatory bowel diseases (Crohn’s disease, ulcerative colitis, etc.) are characterized with enhanced mast cell activity in the context of autoimmune disease. Mast cells show phenotypic differences based on tissue residency, which could manifest as different receptor expression profiles, allowing for unique mast cell responses (both IgE and non-IgE mediated) across varying tissues as well. This variety in receptor expression suggests mast cells respond differently, such as in the gut where immunosuppressive IL-10 stimulates the development of food allergy or in the lungs where transforming growth factor-β1 (TGF-β1) can enhance mast cell IL-6 production. Such differences in receptor expression illustrate the truly diverse effector capabilities of mast cells, and careful consideration must be given toward the phenotype of mast cells observed in vitro. Given mast cells’ ubiquitous tissue presence and their capability to respond to a broad spectrum of non-IgE stimuli, it is expected that mast cells may also contribute to the progression of autoimmune disorders and other disease states such as metastatic cancer through promoting chronic inflammation in the local tissue microenvironment and ultimately polarizing toward a unique Th17 immune response. Furthermore, these interconnected, atypical activation pathways may crosstalk with IgE-mediated signaling differently across disorders such as parasitism, food allergies, and autoimmune disorders of the gut. In this review, we summarize recent research into familiar and novel pathways of mast cells activation and draw connections to clinical human disease.

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