Interferon-gamma promotes the survival and Fc epsilon RI-mediated histamine release in cultured human mast cells

Degranulation of human mast cells: modulation by P2 receptors' agonists

Since the late 1970s, there has been an alarming increase in the incidence of asthma and its morbidity and mortality. Acute obstruction and inflammation of allergic asthmatic airways are frequently caused by inhalation of exogenous substances such as allergens cross-linking IgE receptors expressed on the surface of the human lung mast cells (HLMC). The degree of constriction of human airways produced by identical amounts of inhaled allergens may vary from day to day and even hour to hour. Endogenous factors in the human mast cell (HMC)'s microenvironment during allergen exposure may markedly modulate the degranulation response. An increase in allergic responsiveness may significantly enhance bronchoconstriction and breathlessness. This review focuses on the role that the ubiquitous endogenous purine nucleotide, extracellular adenosine 5'-triphosphate (ATP), which is a component of the damage-associated molecular patterns, plays in mast cells' physiology. ATP activates P2 purinergic cell-surface receptors (P2R) to trigger signaling cascades resulting in heightened inflammatory responses. ATP is the most potent enhancer of IgE-mediated HLMC degranulation described to date. Current knowledge of ATP as it relates to targeted receptor(s) on HMC along with most recent studies exploring HMC post-receptor activation pathways are discussed. In addition, the reviewed studies may explain why brief, minimal exposures to allergens (e.g., dust, cat, mouse, and grass) can unpredictably lead to intense clinical reactions. Furthermore, potential therapeutic approaches targeting ATP-related enhancement of allergic reactions are presented.

Altered leukocyte subsets and immune proteome indicate pro-inflammatory mechanisms in mastocytosis

BACKGROUND

Indolent systemic mastocytosis (ISM) is characterized by pathological accumulation of mast cells. The mechanism behind its phenotypic heterogeneity is not well understood. Interaction of mast cells with other immune cells might cause systemic inflammation and thereby associated symptoms.

OBJECTIVE

To investigate peripheral leukocyte compartments and serum immune proteome in ISM.

METHODS

Peripheral blood leukocyte phenotyping using flowcytometry in a cohort of 18 adults with ISM and 12 healthy controls. Targeted proteomics was performed to measure 169 proteins associated with inflammation on serum of another 20 ISM patients and 20 healthy controls.

RESULTS

Proportions of plasmacytoid dendritic cells (pDC) and monocytes were significantly decreased while T-helper 2 cells were increased in peripheral blood of ISM patients. Furthermore, a shift from naïve to memory T-cells was observed. Hierarchical clustering of the serum proteome revealed two distinct subgroups within ISM patients. In subgroup A (n=8), 62 proteins were significantly overexpressed, whereas subgroup B (n=12) was comparable to healthy controls. Patients in subgroup A displayed upregulated signaling pathways downstream of Toll-like receptor 4, TNF-α and interferon-γFatigue was more often present in subgroup A compared to B (75% vs. 33% respectively, p 0.06).

CONCLUSIONS

Altered distribution of leukocyte subsets and a pro-inflammatory proteome were observed in subsequent two cohorts of ISM patients. We hypothesize that neoplastic mast cells recruit and activate pDC, monocytes and T-cells leading to a vicious cycle of inflammation.

CLINICAL IMPLICATION

Characterization of inflammatory mechanisms in ISM might uncover additional targets for treatment, in particular for constitutional symptoms such as fatigue.

Genetic Regulation of Tryptase Production and Clinical Impact: Hereditary Alpha Tryptasemia, Mastocytosis and Beyond

Tryptase is a serine protease that is predominantly produced by tissue mast cells (MCs) and stored in secretory granules together with other pre-formed mediators. MC activation, degranulation and mediator release contribute to various immunological processes, but also to several specific diseases, such as IgE-dependent allergies and clonal MC disorders. Biologically active tryptase tetramers primarily derive from the two genes TPSB2 (encoding β-tryptase) and TPSAB1 (encoding either α- or β-tryptase). Based on the most common gene copy numbers, three genotypes, 0α:4β, 1α:3β and 2α:2β, were defined as “canonical”. About 4–6% of the general population carry germline TPSAB1-α copy number gains (2α:3β, 3α:2β or more α-extra-copies), resulting in elevated basal serum tryptase levels. This condition has recently been termed hereditary alpha tryptasemia (HαT). Although many carriers of HαT appear to be asymptomatic, a number of more or less specific symptoms have been associated with HαT. Recent studies have revealed a significantly higher HαT prevalence in patients with systemic mastocytosis (SM) and an association with concomitant severe Hymenoptera venom-induced anaphylaxis. Moreover, HαT seems to be more common in idiopathic anaphylaxis and MC activation syndromes (MCAS). Therefore, TPSAB1 genotyping should be included in the diagnostic algorithm in patients with symptomatic SM, severe anaphylaxis or MCAS.

IL-2-Agonist-Induced IFN-γ Exacerbates Systemic Anaphylaxis in Food Allergen-Sensitized Mice

Food allergies are common, costly and potentially life-threatening disorders. They are driven by Th2, but inhibited by Th1 reactions. There is also evidence indicating that IL-2 agonist treatment inhibits allergic sensitization through expansion of regulatory T cells. Here, we tested the impact of an IL-2 agonist in a novel model for food allergy to hen´s egg in mice sensitized without artificial adjuvants. Prophylactic IL-2 agonist treatment expanded Treg populations and inhibited allergen-specific sensitization. However, IL-2 agonist treatment of already sensitized mice increased mast cell responses and allergic anaphylaxis upon allergen re-challenge. These effects depended on allergen-specific IgE and were mediated through IFN-γ, as shown by IgE transfer and blockade of IFN-γ with monoclonal antibodies. These results suggest that although shifting the allergic reaction toward a Treg/Th1 response inhibits allergic sensitization, the prototypic Th1 cytokine IFN-γ promotes mast cell activation and allergen-induced anaphylaxis in individuals that are already IgE-sensitized. Hence, while a Th1 response can prevent the development of food allergy, IFN-γ has the ability to exacerbate already established food allergy.

Type I Interferon α/β Receptor-Mediated Signaling Negatively Regulates Antiviral Cytokine Responses in Murine Bone-Marrow-Derived Mast Cells and Protects the Cells from Virus-Induced Cell Death

Mast cells (MCs) are critical for initiating inflammatory responses to pathogens including viruses. Type I interferons (IFNs) that exert their antiviral functions by interacting with the type I IFN receptor (IFNAR) play a central role in host cellular responses to viruses. Given that virus-induced excessive toxic inflammatory responses are associated with aberrant IFNAR signaling and considering MCs are an early source of inflammatory cytokines during viral infections, we sought to determine whether IFNAR signaling plays a role in antiviral cytokine responses of MCs. IFNAR-intact, IFNAR-blocked, and IFNAR-knockout (IFNAR^−/−) bone-marrow-derived MCs (BMMCs) were treated in vitro with a recombinant vesicular stomatitis virus (rVSVΔm51) to assess cytokine production by these cells. All groups of MCs produced the cytokines interleukin-6 and tumor necrosis factor-α in response to rVSVΔm51. However, production of the cytokines was lowest in IFNAR-intact cells as compared with IFNAR^−/− or IFNAR-blocked cells at 20 h post-stimulation. Surprisingly, rVSVΔm51 was capable of infecting BMMCs, but functional IFNAR signaling was able to protect these cells from virus-induced death. This study showed that BMMCs produced pro-inflammatory cytokines in response to rVSVΔm51 and that IFNAR signaling was required to down-modulate these responses and protect the cells from dying from viral infection.

The Response of Tissue Mast Cells to TLR3 Ligand Poly(I:C) Treatment

Mast cells (MCs) are found mainly at the anatomical sites exposed to the external environment; thus, they are localized close to blood vessels, lymphatic vessels, and a multitude of immune cells. Moreover, those cells can recognize invading pathogens through a range of surface molecules known as pathogen recognition receptors (PRRs), mainly Toll-like receptors (TLRs). MCs are extensively engaged in the control and clearance of bacterial infections, but much less is known about their contribution to antiviral host response as well as pathomechanisms of virus-induced diseases. In the study, we employed in vivo differentiated mature tissue mast cells freshly isolated from rat peritoneal cavity. Here, we demonstrated that rat peritoneal mast cells (rPMCs) express viral dsRNA-specific TLR3 molecule (intracellularly and on the cell surface) as well as other proteins associated with cellular antiviral response: IRF3, type I and II IFN receptors, and MHC I. We found that exposure of rPMCs to viral dsRNA mimic, i.e., poly(I:C), induced transient upregulation of surface TLR3 (while temporarily decreased TLR3 intracellular expression), type II IFN receptor, and MHC I. TLR3 ligand-stimulated rPMCs did not degranulate but generated and/or released type I IFNs (IFN-α and IFNβ) as well as proinflammatory lipid mediators (cysLTs), cytokines (TNF, IL-1β), and chemokines (CCL3, CXCL8). We documented that rPMC priming with poly(I:C) did not affect FcεRI-dependent degranulation. However, their costimulation with TLR3 agonist and anti-IgE led to a significant increase in cysLT and TNF secretion. Our findings confirm that MCs may serve as active participants in the antiviral immune response. Presented data on modulated FcεRI-mediated MC secretion of mediators upon poly(I:C) treatment suggests that dsRNA-type virus infection could influence the severity of allergic reactions.

Mast Cells as a Double-Edged Sword in Immunity: Their Function in Health and Disease. First of Two Parts

Mast cells (MCs) have recently been re-interpreted in the context of the immune scenario in the sense that their pro-allergic role is no longer exclusive. In fact, MCs even in steady state conditions maintain homeostatic functions, producing mediators and intensively cross-talking with other immune cells. Here, emphasis will be placed on the array of receptors expressed by MCs and the variety of cytokines they produce. Then, the bulk of data discussed will provide readers with a wealth of information on the dual ability of MCs not only to defend but also to offend the host. This double attitude of MCs relies on many variables, such as their subsets, tissues of residency and type of stimuli ranging from microbes to allergens and food antigens. Finally, the relationship between MCs with basophils and eosinophils will be discussed.

Mast cells as sources of cytokines, chemokines, and growth factors

Mast cells are hematopoietic cells that reside in virtually all vascularized tissues and that represent potential sources of a wide variety of biologically active secreted products, including diverse cytokines and growth factors. There is strong evidence for important non-redundant roles of mast cells in many types of innate or adaptive immune responses, including making important contributions to immediate and chronic IgE-associated allergic disorders and enhancing host resistance to certain venoms and parasites. However, mast cells have been proposed to influence many other biological processes, including responses to bacteria and virus, angiogenesis, wound healing, fibrosis, autoimmune and metabolic disorders, and cancer. The potential functions of mast cells in many of these settings is thought to reflect their ability to secrete, upon appropriate activation by a range of immune or non-immune stimuli, a broad spectrum of cytokines (including many chemokines) and growth factors, with potential autocrine, paracrine, local, and systemic effects. In this review, we summarize the evidence indicating which cytokines and growth factors can be produced by various populations of rodent and human mast cells in response to particular immune or non-immune stimuli, and comment on the proven or potential roles of such mast cell products in health and disease.

Interferon α2 and interferon γ induce the degranulation independent production of VEGF-A and IL-1 receptor antagonist and other mediators from human mast cells

Background

Mast cells are resident immune effector cells, often studied in the context of allergic disease. Found in substantial numbers at sites of potential infection they are increased at sites of angiogenesis and can be pivotal for the sensing and clearance of a variety of pathogens. Interferons (IFNs) are cytokines that are critical for host defence against intracellular pathogens. Increased levels of IFNs are observed during viral infection and in autoimmune diseases. IFNs are also widely used therapeutically and have been examined in the therapy of severe asthma.

Objective

To define the selective human mast cell cytokine and chemokine response following activation with type I or type II IFN's.

Methods

The ability of both IFNα2 and IFNγ to induce cytokine production by human cord blood‐derived mast cells was examined in vitro. Cytokine and chemokine production at 6 and 24 h was assessed by multiplex protein analysis. Degranulation was assessed by β‐hexosaminidase release. Mast cells were also treated with reovirus or respiratory syncytial virus and their production of CXCL10, IL‐1 receptor antagonist (IL‐1Ra), and vascular endothelial growth factor (VEGF) examined after 24 h.

Results

In addition to increased expression of classical IFN response genes, such as CXCL10, small but significant increases in CCL5 and IL‐17 production were observed following IFN activation. Notably, human mast cells produced both VEGF and IL‐1Ra in a dose dependent manner. These responses occurred in the absence of mast cell degranulation by a mechanism consistent with classical IFN signaling. Both reovirus and respiratory syncytial virus infection of mast cells, were also associated with IFN‐dependent IL‐1Ra expression.

Conclusion and Clinical Relevance

Our findings demonstrate that IFNs have profound impact on cytokine and chemokine expression by human mast cells, alone or in the context of viral infection. Mast cell VEGF and IL‐1Ra responses to IFNs could impact the regulation of local inflammatory responses and subsequent tissue remodeling.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

Nonmarrow hematopoiesis occurs in a hyaluronic-acid-rich node and duct system in mice

A hyaluronic-acid-rich node and duct system (HAR-NDS) was found on the surface of internal organs of mice, and inside their blood and lymph vessels. The nodes (HAR-Ns) were filled with immune cells of the innate system and were especially enriched with mast cells and histiocytes. They also contained hematopoietic progenitor cells (HPCs), such as granulocyte-macrophage, erythroid, multipotential progenitors, and mast cell progenitors (MCPs). MCPs were the most abundant among the HPCs in HAR-Ns. Their frequency was fivefold higher than that of the MCPs in bone marrow. In addition, the system contained pluripotent stem cells (PSCs) capable of producing CD45(-)Flk1(+) hemangioblast-like cells, which subsequently generated various types of HPCs and differentiated blood cells. Although HAR-Ns did not appear to harbor enough number of cells capable of long-term reconstitution or short-term radioprotection of lethally irradiated recipients, bone marrow cells were able to engraft in the HAR-NDS and reconstitute hematopoietic potentials of the system. PSCs and HPCs were consistently found in intravenous, intralymphatic, and intestinal HAR-ND. We infer that PSCs and HPCs reside in the HAR-ND and that this novel system may serve as an alternative means to traffic immature and mature blood cells throughout the body.

Interferon-γ regulates growth and controls Fcγ receptor expression and activation in human intestinal mast cells

Background

Development and function of tissue resident mast cells (MCs) is tightly controlled by various cytokines, most of which belong to the typical T helper (Th) 2-type cytokines such as IL-3 and IL-4. The effects of the Th1-type cytokine IFN-γ on human MCs is less clear.

Results

Here, we analyzed the effects of IFN-γ on tissue-derived, mature human MCs. We found that INF-γ decreases proliferation, without affecting apoptosis in human intestinal MCs cultured in the presence of optimal concentrations of stem cell factor (SCF) or SCF and IL-4. However, in the absence of growth factors or at suboptimal concentrations of SCF, INF-γ promotes survival through inhibition of MC apoptosis. Interestingly, we found that INF-γ has no effect on FcϵRI expression and FcϵRI-mediated release of histamine and leukotriene (LT)C_4, while it has profound effects on FcγR expression and activation. We show that intestinal MCs express FcγRI, FcγRIIa, and FcγRIIc, whereas FcγRIIb expression was found in only 40% of the isolates and FcγRIII was never detectable. INF-γ strongly increases FcγRI and decreases FcγRIIa expression. INF-γ-naïve MCs produce LTC₄ but fail to degranulate upon crosslinking of surface-bound monomeric IgG. In contrast, INF-γ-treated MCs rapidly release granule-stored histamine in addition to de novo-synthesized LTC₄.

Conclusion

In summary, we identify INF-γ as an important regulator of tissue-resident human MCs. IFN-γ displays a dual function by blocking extensive MC proliferation, while decreasing apoptosis in starving MCs and enhancing FcγRI expression and activation. These results emphasize the involvement of mucosal MCs in Th1-mediated disorders.

Somatostatin inhibits the production of interferon-γ by intestinal epithelial cells during intestinal ischemia-reperfusion in macaques

BACKGROUND

Our previous study found that somatostatin (SST) inhibited the intestinal inflammatory injury in a macaque model of intestinal ischemia-reperfusion (IIR); however, the underlying mechanism was unclear.

AIMS

The present study was aimed to investigate the effects of SST on IFN-γ and the systemic inflammatory response after IIR.

METHODS

Fifteen macaques were randomly divided into controls, IIR and SST+ IIR groups. ELISA was performed to measure IFN-γ in ileum tissues, ileac epithelial cells (IECs) and ileal lymphocytes, as well as the systemic levels of IL-6, IL-1β, TNF-α and IFN-γ in the peripheral circulation and the portal vein. HE staining was performed to evaluate morphological changes in vital organs. Immunohistochemistry was performed to identify the distribution of IFN-γ, CD4, CD8 and CD57 in the ileum.

RESULTS

After IIR, IFN-γ level was significantly increased in the IECs. IL-6, IL-1β and TNF-α were significantly increased in both the portal vein and the peripheral circulation; in contrast, IFN-γ level was increased in the portal vein alone. Prophylactic SST reversed the change in IFN-γ in the IECs and portal vein. SST led to an alleviation of the pathological changes in systemic vital organs. The distribution of CD4(+), CD57(+) and CD8(+) cells was not positively correlated with the secretion of IFN-γ.

CONCLUSION

IECs are the main source of IFN-γ production after IIR. SST may indirectly lead to mast cell deactivation through the inhibition of IFN-γ production by IECs. Pretreatment with SST may be beneficial for preventing a massive systemic inflammatory response in vital organs after IIR.

Identification of an IFN-γ/mast cell axis in a mouse model of chronic asthma

Asthma is considered a Th2 cell–associated disorder. Despite this, both the Th1 cell–associated cytokine IFN-γ and airway neutrophilia have been implicated in severe asthma. To investigate the relative contributions of different immune system components to the pathogenesis of asthma, we previously developed a model that exhibits several features of severe asthma in humans, including airway neutrophilia and increased lung IFN-γ. In the present studies, we tested the hypothesis that IFN-γ regulates mast cell function in our model of chronic asthma. Engraftment of mast cell–deficient KitW(-sh/W-sh) mice, which develop markedly attenuated features of disease, with wild-type mast cells restored disease pathology in this model of chronic asthma. However, disease pathology was not fully restored by engraftment with either IFN-γ receptor 1–null (Ifngr1–/–) or Fcε receptor 1γ–null (Fcer1g–/–) mast cells. Additional analysis, including gene array studies, showed that mast cell expression of IFN-γR contributed to the development of many FcεRIγ-dependent and some FcεRIγ-independent features of disease in our model, including airway hyperresponsiveness, neutrophilic and eosinophilic inflammation, airway remodeling, and lung expression of several cytokines, chemokines, and markers of an alternatively activated macrophage response. These findings identify a previously unsuspected IFN-γ/mast cell axis in the pathology of chronic allergic inflammation of the airways in mice.

Strain-specific immunomodulatory effects of Lactobacillus plantarum strains on birch-pollen-allergic subjects out of season

BACKGROUND

Allergic diseases are increasing world-wide, and according to the hygiene hypothesis may be related to a decreased exposure to environmental bacteria. Probiotic bacteria are recognized for their immunomodulating properties, and may benefit allergy patients. In vitro studies reveal immunomodulatory effects that are strain dependent. Differential immunomodulatory in vitro capacities cannot be extrapolated directly to in vivo efficacy. Thus, in vitro screening should preferably be followed by a comparative analysis of the selected immunomodulatory strains in an in vivo setting.

OBJECTIVE

We selected five Lactobacillus strains on their IL-10-inducing capacity, and evaluated the immunomodulatory properties in birch-pollen-allergic subjects outside the hayfever season, with a reduction of IL-13 as the primary outcome.

METHODS

A double-blind, placebo-controlled parallel study was performed in which 62 subjects with a proven birch-pollen allergy consumed one of five different probiotic yoghurts containing four Lactobacillus plantarum strains and one Lactobacillus casei strain or a placebo yoghurt. Blood samples were collected at the start and after 4 weeks. Several immune parameters were determined in serum and peripheral blood mononuclear cell cultures (PBMC) derived from these subjects. Results A decrease in birch-pollen-specific IgE was found for four probiotic strains. L. casei Shirota reduced the number of CD16(+) /CD56(+) cells in peripheral blood mononuclear cells. For strain L. plantarum CBS125632, the decrease in IgE coincided with significant decreases in IL-5 and IL-13 production by αCD3/αCD28-stimulated PBMC cultures.

CONCLUSION AND CLINICAL RELEVANCE

Subjects with seasonal allergy can be used to determine immunomodulatory responses outside the pollen season within a 4-week study period. L. plantarum CBS125632 decreased several immune markers related to allergy, and may have the potential to alleviate the severity of seasonal allergy symptoms.

Granulocytes: effector cells or immunomodulators in the immune response to helminth infection?

Granulocytes are effector cells in defence against helminth infections. We review the current evidence for the role of granulocytes in protective immunity against different helminth infections and note that for each parasite species the role of granulocytes as effector cells can vary. Emerging evidence also points to granulocytes as immunomodulatory cells able to produce many cytokines, chemokines and modulatory factors which can bias the immune response in a particular direction. Thus, the role of granulocytes in an immunomodulatory context is discussed including the most recent data that points to an important role for basophils under this guise.

Interferon-gamma regulates chemokine expression and release in the human mast cell line HMC1: role of nitric oxide

Mast cells (MCs) are critical immune effector cells that release cytokines and chemokines involved in both homeostasis and disease. Interferon-gamma (IFN-gamma) is a pleiotropic cytokine that regulates multiple cellular activities. IFN-gamma modulates rodent MC responsiveness via production of nitric oxide (NO), although the effects in human MC populations is unknown. We sought to investigate the effects of IFN-gamma on expression of the chemokines interleukin-8 (IL-8) and CCL1 (I-309) in a human mast cell line (HMC1) and to determine the underlying regulatory mechanism. Nitric oxide synthase (NOS), IL-8 and CCL1 expression was determined using real-time polymerase chain reaction (PCR). NOS protein expression was analysed using western blot. NOS activity was determined using the citrulline assay. IL-8 and CCL1 release was measured by specific enzyme-linked immunosorbent assay (ELISA). IFN-gamma inhibited phorbol 12-myristate 13-acetate (PMA)-induced release of IL-8 and CCL1 (by 47 and 38%). Real-time PCR analysis of IFN-gamma-treated HMC1 showed a significant (P < 0.05) time-dependent increase in NOS1 and NOS3 mRNA. NOS3 protein was significantly increased at 18 hr, which correlated with a significant (P < 0.05) increase in constitutive NOS (cNOS) activity. IFN-gamma-induced inhibition of chemokine expression and release was NO dependent, as treatment with the NOS inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) reduced the IFN-gamma inhibitory effect on IL-8 and CCL1 mRNA expression. NO donors mimicked the IFN-gamma effect. IFN-gamma inhibited PMA-induced cAMP response element binding protein (CREB) phosphorylation and DNA-binding activity. Our observations indicate for the first time that IFN-gamma enhances endogenous NO formation through NOS3 activity, and that NO regulates the transcription and release of IL-8 and CCL1 in a human MC line.

Establishment and characterization of continuous hematopoietic progenitors-derived pig normal mast cell lines

Mast cells (MCs) are tissue resident, hematopoietic stem cells-derived elements, distributed throughout the body. They are the pivotal mediating cells of allergic reactions. In addition, in mice, MCs play a critical role in the defense against several pathogens, such as bacteria, parasites and viruses. Whereas the biology of rodent and human MCs has been extensively studied using in vitro derived populations, the role of MCs in pigs has not yet been evaluated, given the very low availability of pure porcine MCs populations. In the present report, we describe an original method to obtain continuous factor-dependent normal pig MCs (PMC) lines from fetal hematopoietic progenitors. These Stem Cell Factor (SCF) and Interleukin-3- (IL-3)-dependent PMC lines retain their capacity to growth after conventional freezing methods and exhibit most of the morphological and biochemical properties of normal, although immature, MCs, including metachromatic granules containing sulfated polysaccharides, the expression of c-kit and high-affinity IgE receptors (FcepsilonRI), and the ability to store histamine that is released upon cross-linking of FcepsilonRI. In vitro derived PMC lines might thus be valuable tools to further investigate the reactivity of these elements towards several parasites frequently encountered in pig, such as, but not limited to, Ascaris suum, Trichinella spiralis or Trichuris suis, or towards antigens derived from these pathogens.

Interleukin-6 enhances whereas tumor necrosis factor alpha and interferons inhibit integrin expression and adhesion of human mast cells to extracellular matrix proteins

Integrins are expressed on mast cells and constitute an essential prerequisite for the accumulation of the cells at sites of inflammation. In order to clarify a potential contribution of inflammatory cytokines to this process, we have studied the modulation of integrin expression and adhesion of immature human mast cells (HMC-1) to extracellular matrix proteins by interleukin-6, tumor necrosis factor alpha, interferon-alpha and interferon-gamma. Corticosteroids were used for comparison. On fluorescence-activated cell sorter analysis, preincubation of cells for 48 h with different concentrations of interleukin-6 induced a significant, up to 40%, increase of alpha v alpha 5, CD49b (alpha 2), CD49e (alpha 5), CD49f (alpha 6), and CD51 (alpha v). In contrast, different concentrations of tumor necrosis factor alpha, interferon-alpha, interferon-gamma, and dexamethasone (10-8-10-10 M) inhibited expression of adhesion receptors by up to 60%, reaching significance for some but not all integrins. On semiquantitative polymerase chain reaction analysis, interleukin-6, the other cytokines, and corticosteroids significantly modulated expression of alpha1, alpha v and alpha 5 integrin chains at mRNA level. Functional significance of these findings was proven in adhesion assays using fibronectin, laminin, and vitronectin, with interleukin-6 causing significant enhancement of adhesion in all cases, tumor necrosis factor alpha and dexamethasone inducing significant reduction of adhesion to fibronectin and laminin, and interferon-gamma significantly inhibiting adhesion to fibronectin only. Specificity of interleukin-6-induced changes was demonstrated using antibodies against alpha1 and alpha 5 integrins in unstimulated and interleukin-6-prestimulated cells. These data show that interleukin-6 stimulates mast cell adhesion to extracellular matrix and thus allows for the accumulation of the cells at tissue sites by enhancing integrin expression, whereas tumor necrosis factor alpha, interferon-alpha, interferon-gamma, and dexamethasone downmodulate this process.

Inhibitory effect of murine kidney extracts on mast cells derived from human umbilical cord blood

We examined the effect of aqueous murine kidney extract (MKE) on the growth of mast cells prepared from the liquid culture of human umbilical cord blood CD34+ cells in the presence of a combination of recombinant human stem cell factor (SCF) and interleukin-6 (IL-6). Cultured cells were mature mast cells that expressed CD117 antigen on their surface, a specific marker for human mast cell, and they contained 6.53 pg histamine per cell. Adding MKE resulted in a 53% inhibition of mast cell growth and a 40% decrease in histamine content in mast cells in a serum-free liquid culture stimulated by SCF and IL-6. The inhibitory molecule for the growth of human mature mast cells was estimated at about 30 kDa of protein from gel-filtration HPLC. This fraction also inhibited the growth of murine peritoneal cells-derived mast cells. These results suggest that MKE contains regulator(s) that suppress the growth of mast cells and histamine synthesis. and that act beyond species specificity.

Reciprocal regulation of cultured human mast cell cytokine production by IL-4 and IFN-gamma

BACKGROUND

T(H)1 and T(H)2 cytokines are thought to regulate allergic inflammation.

OBJECTIVE

Two key regulatory cytokines, IL-4 and IFN-gamma, were examined for their effects on cytokine production by cultured human mast cells (CHMCs).

METHODS

CHMCs were obtained by culturing cord blood-derived CD34(+) cells in the presence of stem cell factor and IL-6 for 14 to 16 weeks. CHMCs were passively sensitized with human myeloma IgE and supplemented with or without IL-4 or IFN-gamma. After the sensitization, CHMCs were stimulated with anti-FcepsilonRIalpha mAb. Concentrations of secreted cytokines were measured by using ELISA, and cytokine messenger RNA was analyzed by using quantitative competitive RT-PCR.

RESULTS

IL-4 profoundly enhanced FcepsilonRI-mediated production of macrophage inflammatory protein (MIP) 1alpha, IL-8, and GM-CSF. For example, the enhancement by IL-4 (10 ng/mL) of the production of MIP-1alpha, IL-8, and GM-CSF was 25-, 7-, and 90-fold, respectively, after 6 hours. IL-4 also enhanced levels of FcepsilonRI-induced cytokine messenger RNA but to a lesser degree. In contrast, IFN-gamma inhibited FcepsilonRI-induced production of MIP-1alpha, IL-8, and GM-CSF. For example, the inhibition by IFN-gamma (10 ng/mL) of FcepsilonRI-mediated production of MIP-1alpha, IL-8, and GM-CSF was 80%, 75%, and 95%, respectively. IFN-gamma also suppressed FcepsilonRI-induced messenger RNA expression of these cytokines. Neither IL-4 nor IFN-gamma affected the kinetics of cytokine production by CHMCs.

CONCLUSION

These data suggest that IL-4 and IFN-gamma may influence allergic reactions by modulating human mast cell cytokine production.

IFN-gamma induces apoptosis in mouse embryonic stem cells, a putative mechanism of its embryotoxicity

It has been reported that interferon (IFN)-gamma should inhibit in vitro mouse embryo growth by direct cell toxicity. However, the mechanism involved has not been clearly established. In the present study, this question was addressed using the embryonic stem (ES) cell model. It was found that IFN-gamma, induces a dose-dependent apoptosis in ES cells, as assessed by trypan-blue staining, by Annexin-V labeling and DNA analysis, Moreover, IFN-gamma treatment cooperates with Fas-mediated apoptosis, a phenomenon that has been recently reported. As Bcl-2 oncoprotein functions as a death repressor molecule in an evolutionarily conserved cell death pathway, its expression was analyzed by flow cytometry. It was demonstrated that Bcl-2 is expressed in ES cells. When compared to untreated ES cells, IFN-gamma-treated, apoptotic cells expressed a lower Bcl-2 level and a normal level of Fas, whereas surviving cells expressed a normal level of Bcl-2 but a lower Fas expression. Altogether, these data suggest that IFN-gamma may influence early mouse embryo development by promoting apoptosis, which may constitute a novel mechanism of IFN-gamma embryotoxicity.

Regulation of mast cell number and function

Mast cells are complex, multifunctional cells that have unique phenotypes and growth requirements. Regulation in vitro of human mast cell growth and function differs from regulation of rodent mast cells. Human cell yields in vitro vary depending on tissue of origin, use of mononuclear or CD34+ progenitor cells, presence of cytokines, and serum-free versus serum-containing mediums. This article presents a summary of recent advances in the understanding of cytokine regulation of mast cell numbers and function in rodents and humans.

IgE reactivity to alpha1 and alpha2 chains of bovine type 1 collagen in children with bovine gelatin allergy

BACKGROUND

Anaphylactic reactions to measles, mumps, and rubella vaccines, including gelatin as a stabilizer, have been reported. It had been found that most of these reactions to live vaccines are caused by the bovine gelatin included in these vaccines. Gelatin mainly includes denatured type I collagen, which consists of alpha1 and alpha2 chains.

OBJECTIVE

The current study was designed to investigate the IgE reactivity to alpha1 and alpha2 chains of bovine type I collagen in gelatin-sensitive children.

METHODS

Serum samples were taken from 10 children who had anaphylaxis to the vaccines and high levels of specific IgE to bovine gelatin. Bovine type I collagen was isolated from bovine skin and then separated to alpha1 and alpha2 chains by column chromatography. IgE reactivity to denatured type I collagen and its alpha1 and alpha2 chains was analyzed by immunoblotting, ELISA, and histamine release from the mast cells passive sensitized with IgE antibodies in pooled serum of the children.

RESULTS

All children had specific IgE to bovine type I collagen. Furthermore, IgE antibodies in their sera reacted with the alpha;2 chain but not with the alpha1 chain. Similarly, the mast cells sensitized with pooled sera in the children showed alpha2 chain-specific histamine release but not alpha1 chain-specific histamine release.

CONCLUSION

In gelatin allergy denatured bovine type I collagen is a major allergen and IgE-binding sites exist in the alpha2 chain of type I collagen.

Interferon-gamma regulates the interaction of RBL-2H3 cells with fibronectin through production of nitric oxide

Interferon-gamma (IFN-gamma) is an important regulatory cytokine in cell proliferation, differentiation, adhesion, mediator release, and gene induction. This diversity of effector roles is achieved by a variety of incompletely understood mechanisms. In the mast cell (MC), IFN-gamma downregulates mediator synthesis and secretion. The present study demonstrates and characterizes for the first time IFN-gamma inhibition of adhesion of the MC analogue RBL-2H3 to the extracellular matrix protein fibronectin (FN). Inhibition requires preincubation of the cells with IFN-gamma for 20 hr, and is statistically significant at 100 U/ml IFN-gamma. Flow cytometry indicates that cell surface expression of very late antigen-4 (VLA-4), VLA-5, and the vitronectin receptor (VNR) remain constant following IFN-gamma treatment, indicating the inhibitory effect of IFN-gamma on adhesion to FN is not achieved through a reduction in integrin receptors for FN. Fluorescent labelling with Texas red phalloidin demonstrated rearrangement of the actin cytoskeleton in response to IFN-gamma was not significant. The tyrosine phosphatase inhibitor vanadate, and the nitric oxide (NO) synthase inhibitor L-NAME, reduced the IFN-gamma effect on adhesion to FN by 62 and 70%, respectively, demonstrating that the IFN-gamma effect is dependent upon the production of NO, potentially though a tyrosine phosphatase dependent mechanism. The NO donors sodium nitroprusside and S-nitrosoglutathione mimicked the effect of IFN-gamma. Thus, following stimulation with IFN-gamma, NO plays an autocrine role in the MC, and is able to modulate integrin function. This adds to the pathways NO is able to inhibit in the mast cell, shows that endogenous NO is able to inhibit these pathways, and suggests NO is impinging upon an element common to many signalling mechanisms in the MC.

Interferon-gamma is involved in photoimmunoprotection by UVA (320-400 nm) radiation in mice

Ultraviolet B radiation not only inflicts tumor-initiating DNA damage, but also impairs T cell-mediated immunity relevant to survival of the initiated cells. We have reported, however, that ultraviolet A radiation, in contrast, is immunologically innocuous in hairless mice and opossums, but renders the animals resistant to the immunosuppression by ultraviolet B, or its mediator cis-urocanic acid. Ultraviolet B irradiation of skin causes abundant release of numerous cytokines (interleukin-1, interleukin-6, interleukin-10, tumor necrosis factor-alpha); notably interleukin-12 and interferon-gamma do not appear to be upregulated. A recent report has indicated that interleukin-12 protects from photoimmunosuppression in mice, but it remains unclear whether interleukin-12 acts directly or via interferon-gamma, which it is known to stimulate. Here we investigate the possible role of interferon-gamma in UVA photoimmunoprotection, using interferon-gamma gene knockout mice in comparison with control C57/BL6 mice, and the systemic contact hypersensitivity reaction (induced by sensitization through a nonirradiated skin site) to measure immunity. interferon-gamma-/- mice raised normal contact hypersensitivity responses, and were unaffected, as were C57BL control mice, by ultraviolet A exposure. In response to ultraviolet B irradiation or topical cis-urocanic acid treatment, control mice became immunosuppressed by 69% and 27%, respectively, and interferon-gamma-/- mice by 79% and 27%. When ultraviolet B exposure or cis-urocanic acid was followed by ultraviolet A irradiation, however, contact hypersensitivity was totally restored in control mice, but remained suppressed by 55% and 25%, respectively, in interferon-gamma-/- mice. Injection of recombinant interferon-gamma in the interferon-gamma-/- mice restored the ultraviolet A protective effect against cis-urocanic acid-induced immunosuppression. These observations suggest that interferon-gamma plays a part in ultraviolet A immunoprotection from the suppressive effect of ultraviolet B radiation and, and that the mechanism appears to be via antagonism by this cytokine of the cis-urocanic acid immunosuppressive action.

Reactivity of the immunoglobulin E in bovine gelatin-sensitive children to gelatins from various animals

It has been reported that most children who showed anaphylaxis to measles, mumps and rubella vaccines containing bovine gelatin as a stabilizer have anti-bovine gelatin IgE. The present study was designed to investigate the reactivity of IgE in bovine gelatin-sensitive children to gelatins from various animals, and the antigenic cross-reactivity between the gelatins. Serum samples taken from 10 children who showed anaphylaxis to vaccines containing bovine gelatin were used in this study. The level of anti-bovine gelatin IgE in these serum samples ranged from 11.0 to 251 Ua/ml. The IgE in most of the children reacted to kangaroo and mouse gelatins, to which they had had little or no exposure as a food or a vaccine stabilizer. The IgE binding to kangaroo and mouse gelatins was completely inhibited by bovine gelatin, whereas reciprocal inhibition was not complete, indicating that antigenic cross-reactivity is present between the mammalian gelatins. Only one child had strong IgE reactivity to fish gelatins, and this reactivity was not inhibited by bovine gelatin, indicating that no antigenic cross-reactivity exists between bovine and fish gelatins. Most of the children who displayed sensitivity to bovine gelatin showed IgE reactivity to other mammalian gelatins. This reactivity may be due primarily to the antigenic cross-reactivity between mammalian gelatins.

Rat mucosal mast cells: the cultured bone marrow-derived mast cell is biochemically and functionally analogous to its counterpart in vivo

Mast cells (MC) are biochemically and functionally heterogeneous and the mixture of MC phenotypes varies according to anatomical location. Intestinal mucosal MC (IMMC) have been used to study the mucosal MC subset in the rat, but they are difficult to isolate in sufficient numbers and with consistent purity and viability. Bone marrow-derived MC (BMMC), with an apparent mucosal MC phenotype, can be cultured in large numbers and with high purity from normal rat bone marrow using supernatants from mesenteric lymph node cells of rats infected with the nematode, Nippostrongylus brasiliensis. We have compared serine proteinase content, tumour necrosis factor-alpha (TNF-alpha) storage and secretion, and TNF-alpha-dependent cytotoxicity of IMMC and BMMC to assess the appropriateness of BMMC as in vitro models of mucosal MC. Two-dimensional gel electrophoretic analysis revealed that the overall protein constituents of BMMC and IMMC were highly homologous. Immunoblotting confirmed that both MC types expressed the MMC-associated enzyme, rat mast cell proteinase-2 (RMCP-2), but not RMCP-1, mast cell proteinase-5 (MCP-5) or carboxypeptidase A (CPA), which characterize the connective tissue MC in the rat and which were detected in a representative of this subset, namely, the periotoneal MC (PMC). BMMC demonstrated levels of TNF-alpha-dependent cytotoxicity that were equivalent to those of IMMC. Like IMMC, BMMC contained little stored TNF-alpha, in comparison with PMC, but both MC types generated substantial amounts of TNF-alpha 6 hr following IgE-mediated activation. Pretreatment of PMC with recombinant rat interferon-gamma (IFN-gamma) for 20 hr inhibited anti-immunoglobulin E (anti-IgE)-mediated release of the granule-associated enzyme, beta-hexosaminidase, whereas identically treated BMMC were unresponsive to this cytokine. Similar results have previously been reported for IMMC. Rat BMMC, unlike their more immature and less phenotypically committed counterparts in the mouse, appear therefore to be more appropriate models for studies on the mucosal MC.