Mast cells as effector cells: a co-stimulating question

Mast Cells in Autism Spectrum Disorder-The Enigma to Be Solved?

Autism Spectrum Disorder (ASD) is a disturbance of neurodevelopment with a complicated pathogenesis and unidentified etiology. Many children with ASD have a history of "allergic symptoms", often in the absence of mast cell (MC)-positive tests. Activation of MCs by various stimuli may release molecules related to inflammation and neurotoxicity, contributing to the development of ASD. The aim of the present paper is to enrich the current knowledge on the relationship between MCs and ASD by discussing key molecules and immune pathways associated with MCs in the pathogenesis of autism. Cytokines, essential marker molecules for MC degranulation and therapeutic targets, are also highlighted. Understanding the relationship between ASD and the activation of MCs, as well as the involved molecules and interactions, are the main points contributing to solving the enigma. Key molecules, associated with MCs, may provide new insights to the discovery of drug targets for modeling inflammation in ASD.

Atherosclerosis: The Involvement of Immunity, Cytokines and Cells in Pathogenesis, and Potential Novel Therapeutics

As a leading contributor to coronary artery disease (CAD) and stroke, atherosclerosis has become one of the major cardiovascular diseases (CVD) negatively impacting patients worldwide. The endothelial injury is considered to be the initial step of the development of atherosclerosis, resulting in immune cell migration and activation as well as inflammatory factor secretion, which further leads to acute and chronic inflammation. In addition, the inflammation and lipid accumulation at the lesions stimulate specific responses from different types of cells, contributing to the pathological progression of atherosclerosis. As a result, recent studies have focused on using molecular biological approaches such as gene editing and nanotechnology to mediate cellular response during atherosclerotic development for therapeutic purposes. In this review, we systematically discuss inflammatory pathogenesis during the development of atherosclerosis from a cellular level with a focus on the blood cells, including all types of immune cells, together with crucial cells within the blood vessel, such as smooth muscle cells and endothelial cells. In addition, the latest progression of molecular-cellular based therapy for atherosclerosis is also discussed. We hope this review article could be beneficial for the clinical management of atherosclerosis.

Activation Markers on B and T Cells and Immune Checkpoints in Autoimmune Rheumatic Diseases

In addition to identifying the major B- and T-cell subpopulations involved in autoimmune rheumatic diseases (ARDs), in recent years special attention has been paid to studying the expression of their activation markers and immune checkpoints (ICPs). The activation markers on B and T cells are a consequence of the immune response, and these molecules are considered as sensitive specific markers of ARD activity and as promising targets for immunotherapy. ICPs regulate the activation of the immune response by preventing the initiation of autoimmune processes, and they modulate it by reducing immune cell-induced organ and tissue damage. The article considers the possible correlation of ICPs with the activity of ARDs, the efficacy of specific ARD treatments, and the prospects for the use of activation molecules and activation/blocking ICPs for the treatment of ARDs.

The Multifaceted Roles of Mast Cells in Immune Homeostasis, Infections and Cancers

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.

Serum CD203c+ Extracellular Vesicle Serves as a Novel Diagnostic and Prognostic Biomarker for Succinylated Gelatin Induced Perioperative Hypersensitive Reaction

Background

Perioperative hypersensitivity reaction (HR) is an IgE-FcϵRI-mediated hypersensitivity reaction with degranulation and activation of mast cells and basophils. Several studies have focused on assessing the degranulation and activation of mast cells and basophils to diagnose and predict the prognosis of drug induced HR. However, it is challenging to isolate sufficiently pure mast cells and basophils from human sources to investigate. Effective biomarkers to assess mast cells and basophils activation in vivo could potentially have high diagnostic and prognostic values. In the present study, we investigated EVs pelleted from serum in patients with succinylated gelatin induced HR.

Methods

Extracellular vesicles (EVs) were isolated using a total exosome isolation kit and ultracentrifugation, characterized by Western blot, transmission electron microscopy, and nanoparticle tracking analysis. Basophils were isolated from fresh peripheral blood by negative selection using Basophil Isolation Kit II. Human mast cell line was stimulated with IL4. The expression levels of proteins related to the hypersensitive response were evaluated by Western blotting and flow Cytometer. Histamine and tryptase levels were tested using a commercial ELISA kit, and gene expression of inflammatory mediators was evaluated by qRT-PCR. The receiver operating characteristic (ROC) curve was used to evaluate the specificity and sensitivity of biomarker in predicting HR.

Results

The concentration of EVs and protein expression level of CD63, FcϵRI, CD203c and tryptase were significantly (p< 0.05) increased in HR samples. The expression level of mast cell/basophil specific CD203c were significantly increased in EVs derived from serum and basophils of HR patients, and the CD203c⁺-EVs production in mast cells is dramatically increased in the presence of IL4, which positively correlated with histamine, tryptase and inflammatory mediators. Moreover, the ROC curve of EVs concentration and CD203c expression indicated that CD203c⁺-EVs had a strong diagnostic ability for HR.

Conclusion

Serum CD203c+-EVs serves as a novel diagnostic and prognostic biomarker for HR.

Perfluorooctane sulfonate and bisphenol A induce a similar level of mast cell activation via a common signaling pathway, Fyn-Lyn-Syk activation

Perfluoroalkyl compounds (PFCs) as food contaminants are widely distributed persistent organic pollutants (POPs) and have been suggested to induce immune dysfunction. However, their effects on immune function are not conclusive. Mast cells play a central role in allergic and non-allergic inflammatory responses. Therefore, we have examined the effects of PFCs (PFHxS, PFOA, PFOS) on mast cell-mediated inflammatory responses using in vitro mouse bone marrow-derived mast cells (BMMCs) and human mast cells (HMC-1) and in vivo mice model. The effects of PFCs were compared with those of bisphenol A (BPA), a well-studied environmental pollutant. Among PFCs tested, PFOS had the highest effects. Both PFOS and BPA increased degranulation and production of inflammatory eicosanoids in mast cells at a similar level, which subsequently led to increased skin edema and serum LTC₄ and PGD₂ in mice. Both PFOS and BPA increased not only downstream signaling (PLCγ1, AKT, ERK), but also upstream signaling (Fyn, Lyn, Syk/LAT) in mast cells. Taken together, PFOS and BPA induce mast cell-mediated inflammatory responses via a common signaling pathways. Our results may help establish the scientific basis for understanding the etiology of mast cell-mediated inflammatory responses and improve the immune dysfunction risk assessment for emerging POPs such as PFCs.

A possible way to prevent the progression of bone lesions in multiple myeloma via Src-homology-region-2-domain-containing-phosphatase-1 activation

On the basis of our recent findings, in which multiple receptor-mediated mast cell functions are regulated via a common signaling cascade, we posit that the formation and functioning of osteoclasts are also controlled by a similar common mechanism. These cells are derived from the same granulocyte/monocyte progenitors and share multiple receptors except those that are cell-specific. In both types of cells, all known receptors reside in lipid rafts, form multiprotein complexes with recruited signaling molecules, and are internalized upon receptor engagement. Signal transduction proceeds in a chain of protein phosphorylations, where adaptor protein LAT (linker-for-activation-of-T-cells) plays a central role. The key kinase that associates LAT phosphorylation and lipid raft internalization is Syk (spleen-tyrosine-kinase) and/or an Src-family-kinase, most probably Lck (lymphocyte-specific-protein-tyrosine-kinase). Dephosphorylation of phosphorylated Syk and Lck by activated SHP-1 (Src-homology-region-2-domain-containing-phosphatase-1) terminates the signal transduction and endocytosis of receptors, resulting in inhibition of osteoclast differentiation and other functions. In malignant plasma cells (MM cells) too, SHP-1 plays a similar indispensable role in controlling signal transduction required for survival and proliferation, though BLNK (B-cell-linker-protein), a functional equivalent of LAT and SLP-76 (SH2-domain-containing-leukocyte-protein-of-76-kDa) in B cells, is used instead of LAT. In both osteoclasts and MM cells, therefore, activated SHP-1 acts negatively in receptor-mediated cellular functions. In osteoblasts, however, activated SHP-1 promotes differentiation, osteocalcin generation, and mineralization by preventing both downregulation of transcription factors, such as Ostrix and Runx2, and degradation of β-catenin required for activation of the transcription factors. SHP-1 is activated by tyrosine phosphorylation and micromolar doses (M-dose) of CCRI-ligand-induced SHP-1 activation. Small molecular compounds, such as A770041, Sorafenib, Nitedanib, and Dovitinib, relieve the autoinhibitory conformation. Activation of SHP-1 by M-dose CCRI ligands or the compounds described may prevent the progression of bone lesions in MM.

Lymph node fibroblastic reticular cells deposit fibrosis-associated collagen following organ transplantation

Although the immune response within draining lymph nodes (DLNs) has been studied for decades, how their stromal compartment contributes to this process remains to be fully explored. Here, we show that donor mast cells were prominent activators of collagen I deposition by fibroblastic reticular cells (FRCs) in DLNs shortly following transplantation. Serial analysis of the DLN indicated that the LN stroma did not return to its baseline microarchitecture following organ rejection and that the DLN contained significant fibrosis following repetitive organ transplants. Using several FRC conditional-knockout mice, we show that induction of senescence in the FRCs of the DLN resulted in massive production of collagen I and a proinflammatory milieu within the DLN. Stimulation of herpes virus entry mediator (HVEM) on FRCs by its ligand LIGHT contributed chiefly to the induction of senescence in FRCs and overproduction of collagen I. Systemic administration of ex vivo-expanded FRCs to mice decreased DLN fibrosis and strengthened the effect of anti-CD40L in prolonging heart allograft survival. These data demonstrate that the transformation of FRCs into proinflammatory myofibroblasts is critically important for the maintenance of a proinflammatory milieu within a fibrotic DLN.

Regulatory Role of Immune Cell-Derived Extracellular Vesicles in Cancer: The Message Is in the Envelope

Extracellular vesicles (EVs) are a heterogenous group of membrane-surrounded structures. Besides serving as a harbor for the unwanted material exocytosed by cells, EVs play a critical role in conveying intact protein, genetic, and lipid contents that are important for intercellular communication. EVs, broadly comprised of microvesicles and exosomes, are released to the extracellular environment from nearly all cells either via shedding from the plasma membrane or by originating from the endosomal system. Exosomes are 40–150 nm, endosome-derived small EVs (sEVs) that are released by cells into the extracellular environment. This review focuses on the biological properties of immune cell-derived sEVs, including composition and cellular targeting and mechanisms by which these immune cell-derived sEVs influence tumor immunity either by suppressing or promoting tumor growth, are discussed. The final section of this review discusses how the biological properties of immune cell-derived sEVs can be manipulated to improve their immunogenicity.

A common signaling pathway leading to degranulation in mast cells and its regulation by CCR1-ligand

BACKGROUND

Signal transduction pathways mediated by various receptors expressed on mast cells are thought to be complex, and inhibitory signals that turn off activating signals are not known.

METHODS

Upstream signaling cascades mediated by several known receptors in bone marrow-derived mast cells that lead to degranulation and mediator release were studied by immunoblotting and immunoprecipitation. Small interfering RNAs and knockout mice were used to confirm findings.

RESULTS

All ligands tested including IgE/Ag, SCF, HSP70, CCL3, and its valiant eMIP induced phosphorylation of linker for activation of T cells (LAT), which triggered their receptor-mediated downstream signaling cascades that controlled degranulation and mediator release. Phosphorylation of lymphocyte-specific protein kinase (Lck) was induced by each ligand, which commonly played an indispensable role in LAT phosphorylation. In contrast, phosphorylation of spleen tyrosine kinase was additionally induced in cells stimulated only with IgE/Ag and SCF, which is also associated with LAT phosphorylation in part. Degranulation and mediator release induced by IgE/Ag, SCF, or HSP70 were enhanced by nanomolar doses of CCR1 ligands CCL3 and eMIP via enhanced LAT phosphorylation. On the other hand, micromolar doses of CCR1 ligand inhibited degranulation and mediator release from mast cells stimulated with IgE/Ag, SCF, or HSP70 by de-phosphorylation of phosphorylated Lck with Src homology region 2 domain-containing phosphatase-1.

CONCLUSIONS

Linker for activation of T cells plays a central role in signal transduction pathways in mast cells stimulated with any ligand tested. Dose-dependent alternate costimulation and inhibition of CCR1 ligands in IgE/Ag-, SCF-, or HSP70-stimulated mast cells occur at the level of Lck-LAT phosphorylation.

Mast cell degranulation impairs pneumococcus clearance in mice via IL-6 dependent and TNF-α independent mechanisms

Background

Mast cells participate in immune responses by releasing potent immune system modifiers via degranulation. Due to currently reported controversial roles of mast cells in Streptococcus pneumoniae infections, this study aimed to determine the role and mechanism of mast cells in clearing S. pneumoniae in mice.

Methods

In vivo mouse model of mast cell degranulation established by administration of C48/80 was evaluated for the influences of mast cell degranulation on bacterial colonization and inflammation. In vitro model was established to observe the influences of mast cell degranulation on phagocytic and bactericidal functions of neutrophils and macrophages. IL-6 null and TNF-α null mice on the C57BL/6 background were used to investigate the effects of inflammatory factors released by mast cell degranulation on bacterial clearance.

Results

Mast cell degranulation increased IL-6 and TNF-α levels and immune cell numbers in nasal lavage fluid, and inhibited the bactericidal function of macrophages and neutrophils in vitro. It decreased the number of neutrophils and macrophages recruited to respiratory tract after S. pneumoniae challenge and inhibited the clearance of S. pneumoniae in mice. After pretreatment with C48/80, S. pneumoniae loads were significantly lower in IL-6 null mice than in wild type mice, while no differences were observed between TNF-α null and wild type mice.

Conclusions

Mast cell degranulation can cause inflammation and impair immune cell recruitment to respiratory tract after S. pneumoniae challenge. Products of mast cell degranulation including IL-6 decreased the bactericidal function of neutrophils and macrophages. Through these mechanisms, mast cell degranulation inhibited clearance of S. pneumoniae in mice.

Current progress in the inflammatory background of angiogenesis in gynecological cancers

A tumor growth depends on the potency of the tumor to support itself with nutrients and oxygen. The development of a vascular network within the tumor is key to its survival. The permanent contest between the tumor and its host involves tumor cells on one side and an immunological system and tissue stroma on the other. The angiogenesis is not only a specialty of the tumor, but it also depends on this complex multidirectional interaction. The most common gynecological cancers, cervical, endometrial and ovarian carcinoma are good examples for studying this problem. In this review, we aim to show that an inflammatory response against a tumor can be reverted into an undesirable process leading to the development of a vascular network within the tumor and, subsequently, further growth of the tumor and progression of a disease. Therefore, a key for tumor management should be searched within the immunological system, rather than focused on cell cycle and anti-angiogenic treatment only.

Group A Streptococcus Prevents Mast Cell Degranulation to Promote Extracellular Trap Formation

The resurgence of Group A Streptococcus (GAS) infections in the past two decades has been a rising major public health concern. Due to a large number of GAS infections occurring in the skin, mast cells (MCs), innate immune cells known to localize to the dermis, could play an important role in controlling infection. MCs can exert their antimicrobial activities either early during infection, by degranulation and release of antimicrobial proteases and the cathelicidin-derived antimicrobial peptide LL-37, or by forming antibacterial MC extracellular traps (MCETs) in later stages of infection. We demonstrate that MCs do not directly degranulate in response to GAS, reducing their ability to control bacterial growth in early stages of infection. However, MC granule components are highly cytotoxic to GAS due to the pore-forming activity of LL-37, while MC granule proteases do not significantly affect GAS viability. We therefore confirmed the importance of MCETs by demonstrating their capacity to reduce GAS survival. The data therefore suggests that LL-37 from MC granules become embedded in MCETs, and are the primary effector molecule by which MCs control GAS infection. Our work underscores the importance of a non-traditional immune effector cell, utilizing a non-conventional mechanism, in the defense against an important human pathogen.

Microparticles in nasal lavage fluids in chronic rhinosinusitis: Potential biomarkers for diagnosis of aspirin-exacerbated respiratory disease

BACKGROUND

Microparticles (MPs) are submicron-sized shed membrane vesicles released from activated or injured cells and are detectable by flow cytometry. MP levels have been used as biomarkers to evaluate cell injury or activation in patients with pathological conditions.

OBJECTIVE

We sought to compare MP types and levels in nasal lavage fluids (NLFs) from controls and patients with chronic rhinosinusitis without nasal polyps (CRSsNP), chronic rhinosinusitis with nasal polyps (CRSwNP), and aspirin-exacerbated respiratory disease (AERD).

METHODS

We collected NLFs from patients with CRSsNP (n = 33), CRSwNP (n = 45), and AERD (n = 31) and control (n = 24) subjects. Standardized flow cytometry methods were used to characterize the following MP types: endothelial MPs, epithelial MPs (epithelial cell adhesion molecule [EpCAM](+)MPs, E-cadherin(+)MPs), platelet MPs (CD31(+)CD41(+)MPs), eosinophil MPs (EGF-like module-containing mucin-like hormone receptor-like 1[EMR1](+)MPs), mast cell MPs (high-affinity IgE receptor [FcεRI](+)c-kit(+)MPs), and basophil MPs (CD203c(+)c-kit(-)MPs). Basophil activation was evaluated by the mean fluorescence intensity of CD203c on basophil MPs.

RESULTS

Activated mast cell MPs (CD137(+) FcεRI(+)c-kit(+)MPs) were significantly increased in NLFs of controls compared with NLFs of patients with CRSsNP (2.3-fold; P < .02), CRSwNP (2.3-fold; P < .03), and AERD (7.4-fold; P < .0001). Platelet MPs (3.5-fold; P < .01) and basophil MPs (2.5-fold; P < .05) were increased only in patients with AERD. Mean fluorescence intensity of CD203c on MPs was increased in patients with CRSwNP (P < .002) and AERD (P < .0001), but not in patients with CRSsNP. EpCAM(+)MPs in patients with CRSwNP were no different from control (P = .91) and lower than those in patients with CRSsNP (P < .02) and AERD (P < .002).

CONCLUSIONS

Based on released MPs, mast cells, platelets, and basophils were more highly activated in patients with AERD than in patients with CRS. Epithelial injury was lower in patients with CRSwNP than in patients with CRSsNP and AERD. MP analysis may help identify phenotypes of CRS, and in distinguishing AERD from CRSwNP.

Modulation of mammary tumor vascularization by mast cells: Ultrasonographic and histopathological approaches

AIMS

The inhibition of mast cells' degranulation may be an approach to prevent the formation of new vessels during the mammary carcinogenesis.

MATERIALS AND METHODS

Female Sprague-Dawley rats were randomly divided into five experimental groups. Mammary tumors were induced by intraperitoneal injection of N-methyl-N-nitrosourea (MNU). Animals from group II were treated with ketotifen for 18weeks immediately after the MNU administration, while animals from group III only received the ketotifen after the development of the first mammary tumor. Mammary tumors vascularization was assessed by ultrasonography (Doppler, B Flow and contrast-enhanced ultrasound) and immunohistochemistry (vascular endothelial growth factor-A).

KEY FINDINGS AND SIGNIFICANCE

Similar to what occurs in women with breast cancer, the majority of MNU-induced mammary tumors exhibited a centripetal enhancement order of the contrast agent, clear margin and heterogeneous enhancement. Ultrasonographic and immunohistochemical data suggest that the inhibition of mast cells' degranulation did not change the mammary tumors vascularization.

Recombinant ArtinM activates mast cells

Background

Mast cells are hematopoietically derived cells that play a role in inflammatory processes such as allergy, as well as in the immune response against pathogens by the selective and rapid release of preformed and lipid mediators, and the delayed release of cytokines. The native homotetrameric lectin ArtinM, a D-mannose binding lectin purified from Artocarpus heterophyllus seeds, is one of several lectins that are able to activate mast cells. Besides activating mast cells, ArtinM has been shown to affect several biological responses, including immunomodulation and acceleration of wound healing. Because of the potential pharmacological application of ArtinM, a recombinant ArtinM (rArtinM) was produced in Escherichia coli. The current study evaluated the ability of rArtinM to induce mast cell degranulation and activation.

Results

The glycan binding specificity of rArtinM was similar to that of jArtinM. rArtinM, via its CRD, was able to degranulate, releasing β-hexosaminidase and TNF-α, and to promote morphological changes on the mast cell surface. Moreover, rArtinM induced the release of the newly-synthesized mediator, IL-4. rArtinM does not have a co-stimulatory effect on the FcεRI degranulation via. The IgE-dependent mast cell activation triggered by rArtinM seems to be dependent on NFkB activation.

Conclusions

The lectin rArtinM has the ability to activate and degranulate mast cells via their CRDs. The present study indicates that rArtinM is a suitable substitute for the native form, jArtinM, and that rArtinM may serve as an important and reliable pharmacological agent.

The phylogenetic profile of mast cells

Mast cells (MCs) are tissue-based immune cells that participate to both innate and adaptive immunities as well as to tissue-remodelling processes. Their evolutionary history appears as a fascinating process, whose outline we can only partly reconstruct according to current remnant evidence. MCs have been identified in all vertebrate classes, and a cell population with the overall characteristics of higher vertebrate MCs is identifiable even in the most evolutionarily advanced fish species. In invertebrates, cells related to vertebrate MCs have been recognized in ascidians, a class of urochordates which appeared approximately 500 million years ago. These comprise the granular hemocyte with intermediate characteristics of basophils and MCs and the "test cell" (see below). Both types of cells contain histamine and heparin, and provide defensive functions. The test cell releases tryptase after stimulation with compound 48/80. A leukocyte ancestor operating in the context of a primitive local innate immunity probably represents the MC phylogenetic progenitor. This cell was likely involved in phagocytic and killing activity against pathogens and operated as a general inducer of inflammation. This early type of defensive cell possibly expressed concomitant tissue-reparative functions. With the advent of recombinase activating gene (RAG)-mediated adaptive immunity in the Cambrian era, some 550 million years ago, and the emergence of early vertebrates, MC progenitors differentiated towards a more complex cellular entity. Early MCs probably appeared in the last common ancestor we shared with hagfish, lamprey, and sharks about 450-500 million years ago.

Isoflavones inhibit poly(I:C)-induced serum, brain, and skin inflammatory mediators - relevance to chronic fatigue syndrome

Background

Chronic Fatigue Syndrome (CFS) is a neuroimmunoendocrine disease affecting about 1% of the US population, mostly women. It is characterized by debilitating fatigue for six or more months in the absence of cancer or other systemic diseases. Many CFS patients also have fibromyalgia and skin hypersensitivity that worsen with stress. Corticotropin-releasing hormone (CRH) and neurotensin (NT), secreted under stress, activate mast cells (MC) necessary for allergic reactions to release inflammatory mediators that could contribute to CFS symptoms.

Objective

To investigate the effect of isoflavones on the action of polyinosinic:polycytidylic acid (poly(I:C)), with or without swim stress, on mouse locomotor activity and inflammatory mediator expression, as well as on human MC activation.

Methods

Female C57BL/6 mice were randomly divided into four groups: (a) control/no-swim, (b) control/swim, (c) polyinosinic:polycytidylic acid (poly(I:C))/no swim, and (d) polyinosinic:polycytidylic acid (poly(I:C))/swim. Mice were provided with chow low or high in isoflavones for 2 weeks prior to ip injection with 20 mg/kg poly(I:C) followed or not by swim stress for 15 minutes. Locomotor activity was monitored overnight and animals were sacrificed the following day. Brain and skin gene expression, as well as serum levels, of inflammatory mediators were measured. Data were analyzed using the non-parametric Mann-Whitney U-test.

Results

Poly(I:C)-treated mice had decreased locomotor activity over 24 hours, and increased serum levels of TNF-α, IL-6, KC (IL-8/CXCL8 murine homolog), CCL2,3,4,5, CXCL10, as well as brain and skin gene expression of TNF, IL-6, KC (Cxcl1, IL8 murine homolog), CCL2, CCL4, CCL5 and CXCL10. Histidine decarboxylase (HDC) and NT expression were also increased, but only in the skin, over the same period. High isoflavone diet reversed these effects.

Conclusion

Poly(I:C) treatment decreased mouse locomotor activity and increased serum levels and brain and skin gene expression of inflammatory mediators. These effects were inhibited by isoflavones that may prove useful in CFS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0168-5) contains supplementary material, which is available to authorized users.

Mast cells and vascular diseases

Mast cells are increasingly being recognized as effector cells in many cardiovascular conditions. Many mast-cell-derived products such as tryptase and chymase can, through their enzymic action, have detrimental effects on blood vessel structure while mast cell-derived mediators such as cytokines and chemokines can perpetuate vascular inflammation. Mice lacking mast cells have been developed and these are providing an insight into how mast cells are involved in cardiovascular diseases and, as knowledge increase, mast cells may become a viable therapeutic target to slow progression of cardiovascular disease.

Mast cell: an emerging partner in immune interaction

Mast cells (MCs) are currently recognized as effector cells in many settings of the immune response, including host defense, immune regulation, allergy, chronic inflammation, and autoimmune diseases. MC pleiotropic functions reflect their ability to secrete a wide spectrum of preformed or newly synthesized biologically active products with pro-inflammatory, anti-inflammatory and/or immunosuppressive properties, in response to multiple signals. Moreover, the modulation of MC effector phenotypes relies on the interaction of a wide variety of membrane molecules involved in cell–cell or cell-extracellular-matrix interaction. The delivery of co-stimulatory signals allows MC to specifically communicate with immune cells belonging to both innate and acquired immunity, as well as with non-immune tissue-specific cell types. This article reviews and discusses the evidence that MC membrane-expressed molecules play a central role in regulating MC priming and activation and in the modulation of innate and adaptive immune response not only against host injury, but also in peripheral tolerance and tumor-surveillance or -escape. The complex expression of MC surface molecules may be regarded as a measure of connectivity, with altered patterns of cell–cell interaction representing functionally distinct MC states. We will focalize our attention on roles and functions of recently discovered molecules involved in the cross-talk of MCs with other immune partners.

Interferon α-stimulated natural killer cells from patients with acute hepatitis C virus (HCV) infection recognize HCV-infected and uninfected hepatoma cells via DNAX accessory molecule-1

BACKGROUND

Natural killer (NK) cells are an important component of the innate immune defense against viruses, including hepatitis C virus (HCV). The cell culture system using HCV-permissive Huh-7.5 cells make studies on interaction of NK cells and HCV-infected target cells possible. We used this system to characterize interactions of HCV-infected Huh-7.5 cells and NK cells from healthy controls and patients with acute HCV infection.

METHODS

IFNα- and IL-2 stimulated NK cells were cultured with HCV-infected hepatoma cells and subsequently analyzed (for degranulation and cytokine production) via multicolour flow cytometry. Luciferase assyas have been used to study inhibition of HCV replication. Further, PBMC from patients with acute hepatitis C as well as HCV-infected Huh7.5 cells have been analyzed via flow cytometry for expression of NK cell receptors and ligands, respectively.

RESULTS

After interferon (IFN) α stimulation, NK cells from healthy controls and patients with acute hepatitis C efficiently recognized both HCV-infected and uninfected hepatoma cells. Subsequent dissection of receptor-ligand interaction revealed a dominant role for DNAM-1 and a complementary contribution of NKG2D for NK cell activation in this setting. Furthermore, IFN-α-stimulated NK cells effectively inhibited HCV replication in a DNAM-1-dependent manner.

CONCLUSIONS

Human NK cells recognize HCV-infected hepatoma cells after IFN-α stimulation in a DNAM-1-dependent manner. Furthermore, interaction of IFN-α-stimulated NK cells with HCV-infected hepatoma cells efficiently reduced HCV replication. This study opens up future studies of NK cell interaction with HCV-infected hepatocytes to gain further insight into the pathogenesis of human HCV infection and the therapeutic effects of IFN-α.

Mast cell synapses and exosomes: membrane contacts for information exchange

In addition to their central role in allergy, mast cells are involved in a wide variety of cellular interactions during homeostasis and disease. In this review, we discuss the ability of mast cells to extend their mechanisms for intercellular communication beyond the release of soluble mediators. These include formation of mast cell synapses on antigen presenting surfaces, as well as cell–cell contacts with dendritic cells and T cells. Release of membrane bound exosomes also provide for the transfer of antigen, mast cell proteins, and RNA to other leukocytes. With the recognition of the extended role mast cells have during immune modulation, further investigation of the processes in which mast cells are involved is necessary. This reopens mast cell research to exciting possibilities, demonstrating it to be an immunological frontier.

Coupling inflammation with evo-devo

Inflammation integrates diverse mechanisms that are associated not only with pathological conditions, such as cardiovascular diseases, type 2 diabetes, obesity, neurodegenerative diseases and cancer, but also with physiological processes like reproduction i.e. oogenesis and embryogenesis as well as aging. In the current review we firstly propose that the inflammatory response could recapitulate the phylogenia. In this way, highly conserved inflammatory mechanisms that play a main role in the evolutive development of different animal species, both invertebrates as well as vertebrates, are identified. Therefore, we also hypothesize that inflammation could represent a key tool used by nature to modulate organisms according to the environmental conditions in which these develop. Thus, inflammation could be the pathway by which the environmental factors could be related to the evolutionary development. If so, the diverse human chronic inflammatory diseases that nowadays the Western society suffer would represent the way for adapting to the abrupt changes in their lifestyle. Nonetheless, the distribution of the different pathological conditions varies in terms of intensity and magnitude among Western country populations depending on their genetic polymorphism. In this case, it should be considered that this set of diseases, distributed between all the individuals that constitute the Westernized society, would represent a true Social Inflammatory Syndrome whose final result is its remodeling. In this context, the use of inflammation by the Western society could represent the camouflaged expression of efficient mechanisms of evolution and development. In addition, if the different types of the inflammatory response involved in these diverse chronic pathological conditions could trace the biochemical origins of life, perhaps inflammation could represent an archaeological tool of unsuspected usefulness for understanding our own origin.

Emerging role of mast cells and macrophages in cardiovascular and metabolic diseases

Mast cells are essential in allergic immune responses. Recent discoveries have revealed their direct participation in cardiovascular diseases and metabolic disorders. Although more sophisticated mechanisms are still unknown, data from animal studies suggest that mast cells act similarly to macrophages and other inflammatory cells and contribute to human diseases through cell-cell interactions and the release of proinflammatory cytokines, chemokines, and proteases to induce inflammatory cell recruitment, cell apoptosis, angiogenesis, and matrix protein remodeling. Reduced cardiovascular complications and improved metabolic symptoms in animals receiving over-the-counter antiallergy medications that stabilize mast cells open another era of mast cell biology and bring new hope to human patients suffering from these conditions.

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.

Mast cell interleukin-2 production contributes to suppression of chronic allergic dermatitis

The incidence of chronic allergic dermatitis is rapidly increasing. Regulatory control of this disease has not been adequately explored. Here we report that mast cell-derived interleukin-2 (IL-2) contributes to the suppression of chronic allergic dermatitis. Mice deficient in IL-2 production, or deficient in mast cells (Kit(W-sh/W-sh)), showed exacerbated dermatitis upon repeated oxazolone challenge when compared to their wild-type counterparts. Adoptive transfer of wild-type, but not Il2(-/-), mast cells into Kit(W-sh/W-sh) mice dampened the inflammatory response. During the course of disease, mast cell expansion occurred at the site of inflammation and also in the spleen, where production of IL-2 by mast cells was markedly enhanced. In the absence of mast cell IL-2 production, the ratio of activated to regulatory T cells at the site of inflammation was increased. Thus, MC-derived IL-2 contributes to the maintenance of suppression in chronic allergic skin inflammation.

Single-cell dynamics of mast cell-CD4+ CD25+ regulatory T cell interactions

The biological behavior of immune cells is determined by their intrinsic properties and interactions with other cell populations within their microenvironment. Several studies have confirmed the existence of tight spatial interactions between mast cells (MCs) and Tregs in different settings. For instance, we have recently identified the functional cross-talk between MCs and Tregs, through the OX40L-OX40 axis, as a new mechanism of reciprocal influence. However, there is scant information regarding the single-cell dynamics of this process. In this study, time-lapse video microscopy revealed direct interactions between Tregs and MCs in both murine and human cell co-cultures, resulting in the inhibition of the MC degranulation response. MCs incubated with WT, but not OX40-deficient, Tregs mediated numerous and long-lasting interactions and displayed different morphological features lacking the classical signs of exocytosis. MC degranulation and Ca2+ mobilization upon activation were inhibited by Tregs on a single-cell basis, without affecting overall cytokine secretion. Transmission electron microscopy showed ultrastructural evidence of vesicle-mediated secretion reconcilable with the morphological pattern of piecemeal degranulation. Our results suggest that MC morphological and functional changes following MC-Treg interactions can be ascribed to cell-cell contact and represent a transversal, non-species-specific mechanism of immune response regulation. Further research, looking at the molecular composition of this interaction will broaden our understanding of its contribution to immunity.

Musashi-1 expression in atherosclerotic arteries and its relevance to the origin of arterial smooth muscle cells: histopathological findings and speculations

The origin of smooth muscle cells in developing atherosclerotic lesions is a controversial topic with accumulating evidence indicating that at least some arterial smooth muscle cells might originate from bone marrow-derived smooth muscle cell precursors circulating in the blood. The stem cell markers currently used for the identification of stem cells in the arterial intima can be expressed by a number of different cell types residing in the arterial wall, such as mast cells, endothelial cells and dendritic cells, which can make interpretation of the data obtained somewhat ambiguous. In the present study we examined whether the putative intestinal stem cell marker Musashi-1 is expressed in the arterial wall. Using a multiplexed tandem polymerase chain reaction method (MT-PCR) and immunohistochemistry, Musashi-1 expression was revealed in human coronary arterial wall tissue segments, and this finding was followed by the demonstration of significantly higher expression levels of Musashi-1 in atherosclerotic plaques compared with those in undiseased intimal sites. Double immunohistochemistry demonstrated that in the arterial wall Musashi-1 positive cells either did not display any specific markers of cells that are known to reside in the arterial intima or Musashi-1 was co-expressed by smooth muscle α-actin positive cells. Some Musashi-1 positive cells were found along the luminal surface of arteries as well as within microvessels formed in atherosclerotic plaques by neovascularization, which supports the possibility that Musashi-1 positive cells might intrude into the arterial wall from the blood and might even represent circulating smooth muscle cell precursors.

Mast cells, angiogenesis, and tumour growth

Accumulation of mast cells (MCs) in tumours was described by Ehrlich in his doctoral thesis. Since this early account, ample evidence has been provided highlighting participation of MCs to the inflammatory reaction that occurs in many clinical and experimental tumour settings. MCs are bone marrow-derived tissue-homing leukocytes that are endowed with a panoply of releasable mediators and surface receptors. These cells actively take part to innate and acquired immune reactions as well as to a series of fundamental functions such as angiogenesis, tissue repair, and tissue remodelling. The involvement of MCs in tumour development is debated. Although some evidence suggests that MCs can promote tumourigenesis and tumour progression, there are some clinical sets as well as experimental tumour models in which MCs seem to have functions that favour the host. One of the major issues linking MCs to cancer is the ability of these cells to release potent pro-angiogenic factors. This review will focus on the most recent acquisitions about this intriguing field of research. This article is part of a Special Issue entitled: Mast cells in inflammation.

Cell secretion mediated by granule-associated vesicle transport: a glimpse at evolution

Regulated secretion allows extrusion of cell products stored in specialized membrane-bound organelles called secretory granules or secretory vesicles. Regulated secretion provides basic functions in living organisms, and in a phylogenetic perspective, it is recognizable in the most primitive eukaryotic forms. This article is an attempt to trace the evolutionary history of a special type of secretory pattern, which has been referred to as vesicle-mediated degranulation or piecemeal degranulation (PMD). First described in the early 70s of the last century in inflammatory cells, such as the basophils, mast cells, and eosinophils, this regulated secretory route has subsequently been recognized in endocrine cells, in particular in the chromaffin cells of the adrenal medulla. This vesicle-mediated degranulation is held to mobilize small and specific aliquots of granule-associated material for selective paracrine or endocrine transport to the cell exterior. PMD has been identified in many vertebrate classes. By contrast, no data are available for invertebrates. We speculate that this pattern of cell secretion emerged early in phylogenesis, when the first metazoans appeared. In this review article, we will first revise the concept of vesicle-mediated degranulation in the light of the most recent experimental discoveries and theoretical implications. Then, the distribution of this secretory mode among vertebrates and its molecular basis will be highlighted. Finally, the potential occurrence of PMD in invertebrates, its biological significance from an evolutionary perspective and the future direction of investigations will be briefly sketched.

Interaction between activated chemokine receptor 1 and FcepsilonRI at membrane rafts promotes communication and F-actin-rich cytoneme extensions between mast cells

Chemokines play important regulatory roles in immunity, but their contributions to mast cell function remain poorly understood. We examined the effects of FcepsilonRI-chemokine receptor (CCR) 1 co-stimulation on receptor localization and cellular morphology of bone marrow-derived mast cells. Whereas FcepsilonRI and CCR1 co-localized at the plasma membrane in unsensitized cells, sensitization with IgE promoted internalization of CCR1 molecules. Co-stimulation of FcepsilonRI and CCR1 with antigen and macrophage inflammatory protein-1alpha was more effective than FcepsilonRI stimulation alone in causing leading edge formation, flattened morphology, membrane ruffles and ganglioside (GM1(+)) lipid mediator release. Co-stimulation resulted in phalloidin-positive cytoneme-like cellular extensions, also known as tunneling nanotubes, which originated at points of calcium accumulation. This is the first report of cytoneme formation by mast cells. To determine the importance of lipid rafts for mast cell function, the cells were cholesterol depleted. Cholesterol depletion enhanced degranulation in resting, sensitized and co-stimulated cells, but not in FcepsilonRI-cross-linked cells, and inhibited formation of filamentous actin(+) cytonemes but not GM1(+) cytonemes. Treatment with latrunculin A to sequester globular-actin abolished cytoneme formation. The cytonemes may participate in intercellular communication during allergic and inflammatory responses, and their presence in the co-stimulated mast cells suggests new roles for CCRs in immunopathology.

The mast cell: an evolutionary perspective

This review article is an attempt to trace the evolution of mast cells (MCs). These immune cells have been identified in all vertebrate classes as single-lobed cells containing variable amounts of membrane-bound secretory granules which store a large series of mediators, namely histamine, proteases, cytokines and growth factors. Other MC features, at least in mammals, are the c-kit receptor for the stem cell factor and the high-affinity receptor, FcepsilonRI, for immunoglobulin E (IgE). The c-kit receptor also has been identified in fish MCs. The FcepsilonRI receptor seems to be a more recent acquisition in MC phylogenesis given that IgE originated in mammalian species. Tryptase and histamine have also been recognized in MCs of teleost fish. Thus, a cell population with the overall characteristics of higher vertebrate MCs is identifiable in the most evolutionarily advanced fish species. Two potential MC progenitors have been identified in ascidians (urochordates which appeared approximately 500 million years ago): the basophil/MC-like granular haemocyte and the test cell. Both contain histamine and heparin, and provide defensive functions. Some granular haemocytes in Arthropoda also closely approximate the ultrastructure of modern MCs. The origin of MCs is probably to be found in a leukocyte ancestor operating in the context of a primitive local innate immunity and involved in phagocytic and killing activity against pathogens. From this type of defensive cell, the MC phylogenetic progenitor evolved into a tissue regulatory and remodelling cell, which was incorporated into the networks of recombinase activating genes (RAG)-mediated adaptive immunity in the Cambrian era, some 550 million years ago. Early MCs probably appeared in the last common ancestor we shared with hagfish, lamprey and sharks about 450-500 million years ago.

Autism: an emerging 'neuroimmune disorder' in search of therapy

BACKGROUND

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by difficulties in communication and by repetitive and stereotypic behaviors, as well as by social impairment, attention, cognitive, and learning defects. ASDs present in early childhood and their prevalence has increased significantly to 1/150 children. Despite a number of theories, the actual reasons for this increase are still not clear. There is no reliable screening test, and no definite pathogenesis or curative therapy. Consequently, there is a major gap hampering development of effective treatments.

OBJECTIVE

To review recent publications on ASDs pathogenesis and treatment with emphasis on neuroimmune processes and new therapeutic approaches.

METHODS

Mostly original papers (450) on epidemiology, possible pathogenesis or treatment of ASDs in Medline from 1990 to May 2009 were reviewed. All authors contributed to this review.

RESULTS/CONCLUSION

Increased oxidative stress and immune dysregulation are present in ASDs. Mast-cell activation may contribute to gut-blood-brain barrier disruption and brain inflammation. No effective treatments have emerged. Well-designed clinical trials with nonpsychotropic drugs were few and ASD characteristics varied considerably, making conclusions difficult. Psychotropic drugs are often used for stereotypic and aggressive behaviors. Unique combinations with antioxidant and anti-inflammatory flavonoids hold promise. New potential translational research areas and possible treatments are suggested.

Autism Spectrum Disorders and Mastocytosis

Autism Spectrum Disorders (ASD) are diagnosed in early childhood and include Autism, Asperger's disorder and Pervasive neurodevelopmental disorder - not otherwise specified (PDD-NOS, or atypical autism). ASD are associated with varying degrees of dysfunctional communication and social skills, repetitive and stereotypic behaviors, as well as attention and learning disabilities. Most ASD patients also have food intolerance and other allergic symptomatology indicative of mast cell activation. The number of ASD cases have increased over the last decade to 1/100, but there is no definite pathogenesis or curative therapy. We report that the apparent prevalence of ASD in patients with mastocytosis, a rare disease occuring in 1/4,000 children and characterized by an increased number of hypersensitive mast cells in many organs, is about 1/10 or 10 times higher than the general population. A child with skin mastocytosis [urticaria pigmentosa, (UP)] and regressive autism is presented to illustrate the point. Allergic, infectious, neuroimmune and environmental triggers may activate mast cells to release vasoactive, inflammatory and neurotoxic molecules. These could disrupt the gut-blood-brain-barriers (BBB), and/or activate susceptibility genes, thus contributing to brain inflammation and ASD.

The hydroxyflavone, fisetin, suppresses mast cell activation induced by interaction with activated T cell membranes

BACKGROUND AND PURPOSE

Cell-to-cell interactions between mast cells and activated T cells are increasingly recognized as a possible mechanism in the aetiology of allergic or non-allergic inflammatory disorders. To determine the anti-allergic effect of fisetin, we examined the ability of fisetin to suppress activation of the human mast cell line, HMC-1, induced by activated Jurkat T cell membranes.

EXPERIMENTAL APPROACH

HMC-1 cells were incubated with or without fisetin for 15 min and then co-cultured with Jurkat T cell membranes activated by phorbol-12-myristate 13-acetate for 16 h. We determined gene expression in activated HMC-1 cells by DNA microarray and quantitative reverse transcription (RT)-PCR analysis. We also examined activation of the transcription factor NF-kappaB and MAP kinases (MAPKs) in activated HMC-1 cells.

KEY RESULTS

Fisetin suppresses cell spreading and gene expression in HMC-1 cells stimulated by activated T cell membranes. Additionally, we show that these stimulated HMC-1 cells expressed granzyme B. The stimulatory interaction also induced activation of NF-kappaB and MAPKs; these activations were suppressed by fisetin. Fisetin also reduced the amount of cell surface antigen CD40 and intercellular adhesion molecule-1 (ICAM-1) on activated HMC-1 cells.

CONCLUSIONS AND IMPLICATIONS

Fisetin suppressed activation of HMC-1 cells by activated T cell membranes by interfering with cell-to-cell interaction and inhibiting the activity of NF-kappaB and MAPKs and thereby suppressing gene expression. Fisetin may protect against the progression of inflammatory diseases by limiting interactions between mast cells and activated T cells.

CCR1 expression and signal transduction by murine BMMC results in secretion of TNF-alpha, TGFbeta-1 and IL-6

Chemokine receptors (CCRs) are important co-stimulatory molecules found on many blood cells and associated with various diseases. The expression and function of CCRs on mast cells has been quite controversial. In this study, we report for the first time that murine bone marrow-derived mast cells (BMMC) express messenger RNA and protein for CCR1. BMMC cultured in the presence of murine recombinant stem cell factor and murine IL-3 expressed CCR1 after 5-6 weeks. We also report for the first time that mBMMC(CCR1+) cells endogenously express neurokinin receptor-1 and intercellular adhesion molecule-1. To examine the activity of CCR1 on these BMMC, we simultaneously stimulated two receptors: CCR1 by its ligand macrophage inflammatory protein-1alpha and the IgE receptor FcepsilonRI by antigen cross-linking. We found that co-stimulation enhanced BMMC degranulation compared with FcepsilonRI stimulation alone, as assessed by beta-hexosaminidase activity (85 versus 54%, P < 0.0001) and Ca(2+) influx (223 versus 183 nM, P < 0.05). We also observed significant increases in mast cell secretion of key growth factors, cytokines and chemokine mediators upon CCR1-FcepsilonRI co-stimulation. These factors include transforming growth factor beta-1, tumor necrosis factor-alpha and the cytokine IL-6. Taken together, our data indicate that CCR1 plays a key role in BMMC function. These findings contribute to our understanding of mechanisms for immune cell trafficking during inflammation.

Inducible MHC class II expression by mast cells supports effector and regulatory T cell activation

In addition to their well-established role as regulators of allergic response, recent evidence supports a role for mast cells in influencing the outcome of physiologic and pathologic T cell responses. One mechanism by which mast cells (MCs) influence T cell function is indirectly through secretion of various cytokines. It remains unclear, however, whether MCs can directly activate T cells through Ag presentation, as the expression of MHC class II by MCs has been controversial. In this report, we demonstrate that in vitro stimulation of mouse MCs with LPS and IFN-gamma induces the expression of MHC class II and costimulatory molecules. Although freshly isolated peritoneal MCs do not express MHC class II, an in vivo inflammatory stimulus increases the number of MHC class II-positive MCs in situ. Expression of MHC class II granted MCs the ability to process and present Ags directly to T cells with preferential expansion of Ag-specific regulatory T cells over naive T cells. These data support the notion that, in the appropriate setting, MCs may regulate T cell responses through the direct presentation of Ag.

Novel therapeutic targets for autism

Autism spectrum disorders (ASDs) are pervasive neurodevelopmental disorders, diagnosed in early childhood when acquired skills are lost or the acquisition of new skills becomes delayed. ASDs are associated with varying degrees of dysfunctional communication and social skills, in addition to repetitive and stereotypic behaviors. The diagnosis has increased considerably to approximately one in 180 people, but it is not clear whether this is because of a higher prevalence of the disorder, improved awareness by clinicians or a combination of both. There are no defined mechanisms of pathogenesis or curative therapy presently available. Oxidative stress, overactivation of the hypothalamic-pituitary-adrenal axis and increased gut-blood-brain-barrier permeability might be involved. The scope of this article is to integrate these findings and present the opinion that non-allergic activation of gastrointestinal and brain mast cells could contribute to many of the pathologic findings and provide unique targets for ASD therapy. We make suggestions for new research directives and possible novel therapies from readily available molecules.

The master switch: the role of mast cells in autoimmunity and tolerance

There are many parallels between allergic and autoimmune responses. Both are considered hypersensitivity responses: pathologies that are elicited by an exuberant reaction to antigens that do not pose any inherent danger to the organism. Although mast cells have long been recognized as central players in allergy, only recently has their role in autoimmunity become apparent. Because of the commonalities of these responses, much of what we have learned about the underlying mast cell-dependent mechanisms of inflammatory damage in allergy and asthma can be used to understand autoimmunity. Here we review mast cell biology in the context of autoimmune disease. We discuss the huge diversity in mast cell responses that can exert either proinflammatory or antiinflammatory activity. We also consider the myriad factors that cause one response to predominate over another in a particular immune setting.

[Functional histology of dermis]

The skin is composed of epidermis, dermis and subcutaneous tissue that interconnect anatomically. The dermis is an integrated system of fibrous and amorphous connective tissue that accommodates nerve and vascular networks, epidermally derived appendages, fibroblasts, macrophages and mast cells. Elastic and collagen tissue are the main types of fibrous connective tissue. The elastic connective tissue is assembled in a continuous network including mature elastic fibers, immature elaunin fibers and oxytalan fibers. Mature elastic fibers and elaunin have microfibrillar and amorphous matrix components while oxytalan fibers only contain microfibrils. Several molecules have been identified as constituents of the elastic fibers. Among the most characterized of these molecules is elastin in amorphous matrix, fibrillins 1 and 2 and LTBP-2 (ligand of latent TGFbeta) in microfibrils and fibulins which interconnect elastin and fibrillins. Elastic fibers provides elasticity to the skin. Under electron microscope, collagen fibers appears as of bundles of periodically banded fibrils which are composed of collagens types I, III and V; type V collagen is believed to assist in regulating fibril diameter. They are associated with FACITs (fibril-associated collagen with interrupted triple helixes) collagens types XIV et XVI. Collagen fibers provide tensile strength to the skin. Non fibrous connective tissue molecules include finely filamentous glycoproteins, glycosaminoglycans and proteoglycans of "the ground substance" (hyaluronic acid and chondroitin sulphate, dermatan sulphate, versican, decorin). Fibroblasts, macrophages and mast cells are regular residents of the dermis. The main function of these cells are well known. Fibroblasts are responsible for the synthesis and the degradation of fibrous and non fibrous connective tissue matrix proteins. Macrophages are phagocytic; they process and present antigen to immunocompetent lymphoid cells. Mast cells are responsible for IgE mediated acute, subacute and chronic inflammation. All these cells have a long list of other functions, in particular they are involved in coagulation, wound healing and tissue remodeling.

Discovery of aryl aminoquinazoline pyridones as potent, selective, and orally efficacious inhibitors of receptor tyrosine kinase c-Kit

Inhibition of c-Kit has the potential to treat mast cell associated fibrotic diseases. We report the discovery of several aminoquinazoline pyridones that are potent inhibitors of c-Kit with greater than 200-fold selectivity against KDR, p38, Lck, and Src. In vivo efficacy of pyridone 16 by dose-dependent inhibition of histamine release was demonstrated in a rodent pharmacodynamic model of mast cell activation.