IgE-mediated Responses Research Articles

The use of single versus multiple antigens in specific allergen immunotherapy for allergic rhinitis

Allergen-specific immunotherapy (AIT) targets the IgE-mediated response to specific allergen(s). Accordingly, a monosensitized patient would be the ideal candidate for AIT. However, most patients are polysensitized; thus, two main problems emerge: first, whether AIT with a clinically relevant allergen is effective in polysensitized patients, and second, whether the use of a few allergens (European approach) or of mixtures containing all the possibly sensitizing allergens (USA approach) should be used. Of note, only in recent years has the so-called 'component resolved diagnosis' introduced new diagnostic opportunities. In the present article, the available experimental data concerning the controversial aspects of single versus multiallergen AIT are reviewed. Some data are only available from isolated studies, which are often not controlled, and few trials on the argument have been recently conducted. Main findings are that AIT can be effective in both monosensitized and polysensitized patients, as shown by large trials with grass extracts. The evidence for the efficacy of allergen mixes is still weak, but component-resolved diagnosis could represent a valuable help in selecting the allergen. As a matter of fact, comparative trials on multiple versus single allergen immunotherapy would be expensive and time-consuming: this justifies the paucity of data.

IgE-mediated mast cell responses are inhibited by thymol-mediated, activation-induced cell death in skin inflammation

Mast cells play a critical role in inflammatory skin diseases through releasing proinflammatory mediators; however, few therapies directly target these cells. In 1878, the use of topical thymol, a now recognized potent agonist for transient receptor potential channels, was first described to treat eczema and psoriasis. We sought to determine the mechanisms through which thymol can alter skin inflammation. We examined the effect of topical thymol on IgE-dependent responses using a mast cell-dependent passive cutaneous anaphylaxis (PCA) model, as well as in vitro-cultured mast cells. Thymol dose-dependently inhibited PCA when administered topically 24 hours before antigen challenge but provoked an ear-swelling response directly on application. This direct effect was associated with local mast cell degranulation and was absent in histamine-deficient mice. However, unlike with PCA responses, there was no late-phase swelling. In vitro thymol directly triggered calcium flux in mast cells through transient receptor potential channel activation, along with degranulation and cytokine transcription. However, no cytokine protein was produced. Instead, thymol induced a significant increase in apoptotic cell death that was seen both in vitro and in vivo. We propose that the efficacy of thymol in reducing IgE-dependent responses is through promotion of activation-induced apoptotic cell death of mast cells and that this likely explains the clinical benefits observed in early clinical reports.

A tryptophan metabolite, kynurenine, promotes mast cell activation through aryl hydrocarbon receptor

Tryptophan metabolites have been suggested to play a role in immune modulation, wherein those have recently been shown to be endogenous ligands of aryl hydrocarbon receptor (AhR; a unique cellular chemical sensor). However, the involvement of tryptophan metabolites and AhR in modulating mast cell function remains to be fully defined. We therefore investigated that the functional impacts of tryptophan metabolites on human and mouse mast cell responses in vitro and their functional importance in vivo. Three tryptophan metabolites, kynurenine (KYN), kynurenic acid (KA) and quinolinic acid (QA), were examined in terms of their effect on IgE-mediated responses in mouse bone marrow-derived mast cells (BMMCs) and in human peripheral blood-derived cultured mast cells (HCMCs) and on in vivo anaphylactic responses. For evaluation of AhR involvement, we examined the responses of mast cells from AhR-null or AhR-wild-type mice with the use of a known AhR antagonist, CH223191. Kynurenine, but not KA and QA, enhanced IgE-mediated responses, including degranulation, LTC4 release, and IL-13 production in BMMCs through the activation of PLCγ1, Akt, MAPK p38, and the increase of intracellular calcium. KYN also enhanced cutaneous anaphylaxis in vivo. These enhancing effects of KYN were not observed in AhR-deficient BMMCs and could be inhibited by CH223191 in BMMCs. Further, KYN had similar enhancing effects on HCMCs, which were inhibited by CH223191. The AhR-KYN axis is potentially important in modulating mast cell responses and represents an example of AhR's critical involvement in the regulation of allergic responses.

Oral allergy syndrome caused by crown daisy and sesame leaf

Oral allergy syndrome (OAS) is a subtype of food allergy composing of itching sense and edema in the oral cavity, lips, throat, pharynx, and larynx following ingestion of some fresh fruits or vegetables. Although the major pathogenic mechanism of OAS is known to be IgE-mediated response, here we experienced a case of OAS due to crown daisy (CD) and sesame leaf (SL) mediated by a non-IgE antibody mediated mechanism. A 33-year-old female visited our clinic to evaluate numbness of the tongue and gingiva after eating fresh CD and SL for 2 years. The patient had suffered from allergic rhinitis and atopic dermatitis for 20 years and took medications intermittently. There had been a history of food allergy to crab and shrimp. The serum total IgE level was elevated (404 kU/mL). The skin prick test showed strong positive reactions to tree and weed pollens, but not to CD and SL extracts. Enzyme-linked immunosorbant assay for detecting serum specific IgE to crude extracts of CD and SL showed negative results. The basophil activation test performed with crude extracts of CD or SL showed significant up-regulation of CD63-positive basophils by both CD and SL. In conclusion, we report a case of OAS due to CD and SL, not associated with pollen allergy, which is shown to be mediated by a non-IgE mediated mechanism.

A retrospective study for allergic dermatitis in 35 dogs

Allergic disorders are exaggerated immune responses to foreign antigens, regardless of the mechanism, while atopic disorders are exaggerated IgE-mediated immune responses (type I hypersensitivity). Allergic dermatitis is a common pathological condition of skin in humans and dogs. Canine allergic dermatitis presents with clinical signs similar to those reported in humans, and its causes are complex; therefore, diagnostic tests and treatments may need to be adjusted for each patient. Dogs with allergic dermatitis can suffer from secondary infections, which must be considered and confirmed or excluded for successful treatment. In this report, 35 cases of canine allergic dermatitis diagnosed using variable methods, including histological and cytological examination, are described. Patients were treated with oral or topical medications (antimicrobials, anti-inflammatories, immune modulators, topical ointments, and medicated shampoos), and their diets and environmental surroundings were also modified. This report provides an analysis of the breed, gender, age of onset, clinical signs, diagnostic methods, and treatments for canine allergic dermatitis. The information on canine allergic dermatitis presented here could be helpful in the study of human cases because these two species often share living spaces, environments, and lifestyles more closely than other animals. However, previous reports have suggested that human and canine allergies differ in some features, such as involvement of histamine in induction of pruritus, and in histopathological characteristics such as cutaneous structures.

Myeloid-derived suppressor cells enhance IgE-mediated mast cell responses

Mast cells and MDSCs are increased by parasitic infection and tumor growth. We previously demonstrated that enhanced MDSC development in ADAM10 transgenic mice yielded resistance to Nb infection and that coculturing MDSCs and mast cells enhanced cytokine production. In the current work, we show that MDSC-mast cell coculture selectively enhances IgE-mediated cytokine secretion among mast cells, without increasing MDSC cytokine production. This effect was independent of cell contact and elicited by Ly6C(+) and Ly6C/G+ MDSC subsets. These interactions were functionally important. MDSC depletion with the FDA-approved drug gemcitabine exacerbated Nb or Trichinella spiralis infection and reduced mast cell-dependent AHR and lung inflammation. Adoptive transfer of MDSC worsened AHR in WT but not mast cell-deficient Wsh/Wsh mice. These data support the hypothesis that MDSCs enhance mast cell inflammatory responses and demonstrate that this interaction can be altered by an existing chemotherapeutic.

Circadian regulation of allergic reactions by the mast cell clock in mice

It remains elusive how allergic symptoms exhibit prominent 24-hour variations. In mammals the circadian clocks present in nearly all cells, including mast cells, drive the daily rhythms of physiology. Recently, we have shown that the circadian clocks drive the daily rhythms in IgE/mast cell-mediated allergic reactions. However, the precise mechanisms, particularly the specific roles of the mast cell-intrinsic clockwork in temporal regulation, remain unclear. We determined whether the mast cell clockwork contributes to the temporal regulation of IgE/mast cell-mediated allergic reaction. The kinetics of a time of day-dependent variation in passive cutaneous anaphylactic reactions were compared between mast cell-deficient mice reconstituted with bone marrow-derived cultured mast cells generated from mice with a wild-type allele and a dominant negative type mutation of the key clock gene Clock. We also examined the temporal responses of wild-type and Clock-mutated bone marrow-derived cultured mast cells to IgE stimulation in vitro. Furthermore, factors influencing the mast cell clockwork were determined by using in vivo imaging. The Clock mutation in mast cells resulted in the absence of temporal variations in IgE-mediated degranulation in mast cells both in vivo and in vitro associated with the loss of temporal regulation of FcεRI expression and signaling. Additionally, adrenalectomy abolished the mast cell clockwork in vivo. The mast cell-intrinsic clockwork, entrained by humoral factors from the adrenal gland, primarily contributes to the temporal regulation of IgE/mast cell-mediated allergic reactions. Our results reveal a novel regulatory mechanism for IgE-mediated mast cell responses that might underlie the circadian pathophysiology in patients with allergic diseases.

Effects of magnolialide isolated from the leaves of Laurus nobilis L. (Lauraceae) on immunoglobulin E-mediated type I hypersensitivity in vitro

Ethnopharmacological relevanceLaurus nobilis L. (Lauraceae) has been used for folk medicines in the Mediterranean area and Europe to treat various disorders including skin inflammation (dermatitis) and asthma. Aim of the studyOur aim was to investigate the scientific evaluation of the compounds from Laurus nobilis L. on immuniglobulin E (IgE)-mediated type I hypersensitivity responses in vitro such as atopic dermatitis and asthma. Methods and materialsSeven compounds were isolated and examined for the mast cell stabilizing effect on IgE-sensitized RBL-2H3 mast cells by measuring the β-hexosaminidase activity. In addition, the effects on interleukin (IL)-4 production and IL-5-dependent Y16 early B cell proliferation were investigated as well as their cytotoxic effects on RBL-2H3 cells. ResultsAmong the seven isolated compounds, magnolialide attenuated the release of β-hexosaminidase from RBL-2H3 cells with an IC50 value of 20.2μM, while the other compounds revealed no significant effects at concentrations tested. Furthermore, magnolialide significantly inhibited the IL-4 release with an IC50 value of 18.1μM and IL-4 mRNA expression with an IC50 value of 15.7μM in IgE-sensitized RBL-2H3 cells. In addition, the inhibition of IL-5-dependent proliferation of early B cells (Y16 cells) by magnolialide was demonstrated with an IC50 value of 18.4μM. ConclusionThese results suggest that the magnolialide might be a candidate for the treatment of IgE-mediated hypersensitivity responses such as atopic dermatitis and asthma by inhibiting mast cell degranulation, the IL-4 production, and IL-5-dependent early B cell proliferation, key factors in the development and amplification of type I hypersensitivity reactions.

Existence of Antigen-Specific Immunoglobulin E Is Not Sufficient for Allergic Nasal Eosinophil Infiltration in Mice

Background: Immunoglobulin E (IgE) is important for the development of allergic rhinitis (AR), though the contribution of IgE to the infiltration of eosinophils in the nasal mucosa has not been fully elucidated. In this study, antigen-induced sneezing and nasal eosinophil accumulation were comparatively investigated in anti-ovalbumin (OVA)-IgE transgenic (Tg) and wild-type (WT) mice. Methods: Tg and OVA-immunized WT mice were intranasally challenged with OVA. Antigen-specific serum IgE level, sneezing and infiltration of eosinophil into the nasal cavity were then examined. Results: The level of serum OVA-specific IgE in Tg mice was significantly higher than that in antigen-immunized WT mice. Compared to saline challenge, intranasal challenge with OVA significantly induced sneezing in both Tg and immunized WT mice. However, antigen-induced nasal eosinophil infiltration was observed in immunized WT mice but not in Tg mice. Conclusions: IgE-mediated responses might not play a crucial role in antigen-induced eosinophil infiltration in AR.

IgE-Mediated Immune Responses and Airway Detection of Aspergillus and Candida in Adult Cystic Fibrosis

The recovery of Aspergillus and Candida from the respiratory secretions of patients with cystic fibrosis (CF) is common. Their relationship to the development of allergic sensitization and effect on lung function has not been established. Improved techniques to detect these organisms are needed to increase knowledge of these effects. A 2-year prospective observational cohort study was performed. Fifty-five adult patients with CF had sputum monitored for Aspergillus by culture and real-time polymerase chain reaction and Candida by CHROMagar and carbon assimilation profile (API/ID 32C). Skin prick tests and ImmunoCAP IgEs to a panel of common and fungal allergens were performed. Lung function and pulmonary exacerbation rates were monitored over 2 years. Sixty-nine percent of patient sputum samples showed chronic colonization with Candida and 60% showed colonization with Aspergillus. There was no association between the recovery of either organism and the presence of specific IgE responses. There was no difference in lung function decline for patients with Aspergillus or Candida colonization compared with those without (FEV₁ percent predicted, P = .41 and P = .90, respectively; FVC % predicted, P = .87 and P = .37, respectively). However, there was a significantly greater decline in FEV1 and increase in IV antibiotic days for those sensitized to Aspergillus (FEV₁ decline, P = .03; IV antibiotics days, P = .03). Allergic sensitization is not associated with recovery of Candida or Aspergillus from the sputum of patients with CF. Aspergillus but not Candida sensitization is associated with greater lung function decline and pulmonary exacerbations.

Frequent ingestion of the curry spice curcumin inhibits mastocytosis and suppresses intestinal anaphylaxis in a murine model of food allergy (P6034)

Abstract IgE antibodies and mast cells play critical roles in the establishment of allergic responses to food antigens. Curcumin, the active ingredient of the curry spice turmeric, has anti-allergic properties, and thus may have the capacity to modulate mucosal mast cell activation and function during allergic responses. Here we show that frequent ingestion of curcumin inhibits mast cell expansion and suppresses intestinal anaphylaxis in a murine model of ovalbumin (OVA)-induced food allergy. Intragastric exposure to OVA in i.p. sensitized BALB/c mice induced a robust IgE-mediated response accompanied by enhanced OVA-IgE levels, intestinal mastocytosis, elevated serum mMCP-1 and acute diarrhea. In contrast, mice exposed to oral curcumin throughout the experimental regimen appeared to be normal and did not exhibit intense allergic diarrhea or a significant enhancement of OVA-IgE and intestinal mast cell expansion and activation. Furthermore, allergic diarrhea, and mast cell activation and expansion were also suppressed in mice exposed to curcumin during the challenge phase alone, despite the presence of normal levels of OVA-IgE. This suggested that curcumin may have a direct suppressive effect on intestinal mast cell homeostasis and function during food allergy. In summary, our data demonstrate a protective role for curcumin during allergic responses to food antigens, suggesting that frequent ingestion of this spice may modulate the outcome of disease in susceptible individuals.

Abstract 2848: IgE-mediated immune activation targeting the prostate specific antigen: a potential prostate cancer therapy.

Abstract Prostate cancer (PCa) is the second leading cause of cancer deaths among men in the United States. The prostate-specific antigen (PSA), often found at high levels in the serum of PCa patients, has been used as a marker for PCa detection and as a target of immunotherapy. The murine IgG1 monoclonal antibody AR47.47, specific for human PSA, has been shown to enhance antigen presentation by human dendritic cells and induce both CD4 and CD8 T-cell activation when complexed with PSA. In this study, we explored the properties of a novel mouse/human chimeric anti-PSA IgE containing the variable regions of AR47.47 as a potential therapy for PCa. Our goal is to take advantage of the unique properties of the IgE molecule in order to trigger immune activation against PCa. The properly assembled and secreted anti-PSA IgE binds the antigen and the Fc epsilon RI (FcεRI) as demonstrated by ELISA and flow cytometry, respectively. This novel IgE antibody is capable of triggering effector cell degranulation in vitro as determined by the release of β-hexosaminidase from rat basophil leukemic effector cells that express human FcεRI (RBL SX-38). Furthermore, the IgE triggered degranulation in vivo in human FcεRIα transgenic mice using the passive cutaneous anaphylaxis assay. Degranulation was only observed when the IgE was artificially cross-linked, but not in the presence of the natural soluble antigen, suggesting that such an interaction will not trigger systemic anaphylaxis in patients. Importantly, when incubated in vitro with human dendritic cells the anti-PSA IgE complexed with the antigen (PSA) triggered autologous CD4 and CD8 T-cell activation, suggesting enhancement of antigen presentation. Immune activation was also observed in vivo where a prophylactic vaccination with the anti-PSA IgE complexed to PSA significantly prolonged the survival of human FcεRIα transgenic mice challenged with PSA-expressing tumors, under conditions in which its chimeric mouse/human anti-PSA IgG1 counterpart failed to confer protection. Our results provide initial proof-of principle that the anti-PSA IgE can stimulate immune activation against tumor cells expressing PSA, and further studies on the anti-tumor activity of this antibody are warranted. These studies belong to the new field of AllergoOncology that aims to reveal the function of IgE-mediated immune responses against cancer and develop novel IgE-based cancer therapies. Citation Format: Tracy R. Daniels-Wells, Gustavo Helguera, Richard K. Leuchter, Rafaela Quintero, Maggie Kozman, Jose A. Rodríguez, Elizabeth Ortiz-Sánchez, Otoniel Martínez-Maza, Birgit C. Schultes, Christopher F. Nicodemus, Manuel L. Penichet. IgE-mediated immune activation targeting the prostate specific antigen: a potential prostate cancer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2848. doi:10.1158/1538-7445.AM2013-2848

Role of parental atopy in cow's milk allergy: a population-based study

BackgroundA family history of atopy has been considered an independent risk factor for atopic diseases in children. ObjectiveTo relate the risk of an infant developing IgE-mediated cow's milk allergy (IgE-CMA) to the atopic status of parents. MethodsAssessment of the parental atopic status of children with IgE-CMA (n = 66) previously identified in a large-scale prospective study was compared with the parental atopic status of a control group of healthy infants (n = 156). The atopic status was identified both by self-reporting and skin prick tests (SPTs). ResultsAnalysis for the risk for infants to develop IgE-CMA depended on the assessment method used. No significant differences were noted in self-reported parental atopic status between the IgE-CMA patients and the control group. However, among the subgroup of infants with persistent IgE-CMA (n = 25), maternal but not paternal self-reporting for atopy was more likely compared with parents of the control group (P = .04). In contrast, when analyzed by SPT, in both this persistent subgroup and the total allergic cohort, no significant differences were noted whether analyzed by single parent or both parents and whether the parent tested singly or multiply positive on the SPT. ConclusionIn families with children with persistent IgE-CMA, self-reporting of atopy by parents may be biased. Furthermore, the demonstration of IgE-mediated responses to allergens in parents is insufficient by itself, in a general population cohort, to predict which infants are at greatest risk of developing IgE-CMA.

Comparative Analysis of IgE Binding Proteins in GM and Non-GM Rice Varieties Using Atopic Patients Sera

Food allergy is recognized as IgE-mediated immune response. Safety issues regarding foods derived from genetically modified (GM) plants are central to their acceptance into the food supply and its commercial production.

End‐Organ Testing for Allergic Rhinitis with Fungi Is Poorly Correlated with Fungal Sensitivity

To evaluate optical rhinometry (ORM) using nasal provocation testing (NPT) as an objective tool to diagnose fungal allergic rhinitis (AR). Prospective. Tertiary academic center. We prospectively enrolled healthy controls (HCs) and subjects with a clinical history of AR and positive skin prick test to Alternaria or Aspergillus antigens. Baseline measurements with an optical and acoustic rhinometer (AcR) were taken, and all subjects underwent NPT with increasing concentrations of Alternaria and then Aspergillus in each nasal cavity. Optical density (OD), nasal mean cross-sectional area (MCA), visual analog scale (VAS), and nasal allergen provocation scale (NAP) were measured after each provocation. A NAP score ≥ 3 was considered positive. Receiver operating characteristic (ROC) curve analysis was performed on measured parameters. Eleven HCs and 11 AR subjects were enrolled. Of the 8 AR patients with an Alternaria-positive skin test, 50% had a positive NAP score (4/8) vs 0% in HCs (0/11, P = .01). Although VAS could differentiate Alternaria-sensitive patients from controls, change in OD and MCA could not. Of the 7 skin test-positive Aspergillus patients, 43% had a positive NAP score (3/7) vs 0% in HCs (0/11, P = .02). The VAS and change in OD and MCA did not differentiate Aspergillus-sensitive patients from controls. In this study, fungal antigens caused irritation but did not elicit early phase changes in nasal patency or blood flow in fungal-sensitive AR patients. The poor correlation of skin testing and objective nasal response to fungi argues against a pure IgE-mediated immune response in the nasal cavity.

The Development of Allergic Rhinitis in Children Previously Diagnosed as Nonallergic Rhinitis

Nonallergic rhinitis (NAR) is characterized by nasal symptoms similar to allergic rhinitis (AR) without an IgE-mediated immune response. Limited data are available on the natural history of NAR in its progression toward AR, particularly in children. This study evaluates the development of AR in children who were previously diagnosed with NAR. Children with the diagnosis of NAR during the period of 2005-2007 were reevaluated in 2010. Nasal symptoms, disease severity, comorbidities, rescue medication scores (RMSs), and skin-prick test to aeroallergens were assessed. We recruited 175 children with an early diagnosis of NAR. The median age was 5.7 years, 62.9% were boys and 45.7% had family history of atopy. At reevaluation, 41% of children with previously diagnosed NAR developed sensitization to aeroallergens and were reclassified as having AR. The most frequent aeroallergen sensitization was Dermatophagoides pteronyssinus (59.7%), followed by Dermatophagoides farinae (54.2%) and American cockroach (38.9%). Children who developed AR had more nasal/eye symptoms, higher severity, and RMSs than children who did not develop AR. The predictors of developing AR were persistent nasal symptoms (adjusted odds ratio [OR], 8.9; 95% CI, 3.2-24.6), nasal itching (adjusted OR, 3.4; 95% CI, 1.2-9.5), triggered by house dust (adjusted OR, 4.3; 95% CI, 1.6-11.9) and animal danders (adjusted OR, 15.8; 95% CI, 3.3-76.1), and family history of atopy (adjusted OR, 6.0; 95% CI, 2.3-15.9). Children with NAR who had family history of atopy, persistent nasal symptoms, and symptoms triggered by aeroallergens should be reevaluated periodically for the development of AR. This study was part of the clinical trial NCT01068808 registered in www.clinicaltrials.gov.

Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation

ENWEndNote BIBJabRef, Mendeley RISPapers, Reference Manager, RefWorks, Zotero AMA Witczak P, Pietrzak A, Słodka A, Brzezińska-Błaszczyk E. Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation. Central European Journal of Immunology. 2013;38(3):343-348. doi:10.5114/ceji.2013.37755. APA Witczak, P., Pietrzak, A., Słodka, A., & Brzezińska-Błaszczyk, E. (2013). Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation. Central European Journal of Immunology, 38(3), 343-348. https://doi.org/10.5114/ceji.2013.37755 Chicago Witczak, Piotr, Anna Pietrzak, Aleksandra Słodka, and Ewa Brzezińska-Błaszczyk. 2013. "Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation". Central European Journal of Immunology 38 (3): 343-348. doi:10.5114/ceji.2013.37755. Harvard Witczak, P., Pietrzak, A., Słodka, A., and Brzezińska-Błaszczyk, E. (2013). Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation. Central European Journal of Immunology, 38(3), pp.343-348. https://doi.org/10.5114/ceji.2013.37755 MLA Witczak, Piotr et al. "Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation." Central European Journal of Immunology, vol. 38, no. 3, 2013, pp. 343-348. doi:10.5114/ceji.2013.37755. Vancouver Witczak P, Pietrzak A, Słodka A, Brzezińska-Błaszczyk E. Toll-like receptors 3 ligation directly and indirectly affects mast cell cysteinyl leukotriene generation. Central European Journal of Immunology. 2013;38(3):343-348. doi:10.5114/ceji.2013.37755.

The effect of lipoprotein-associated phospholipase A2 deficiency on pulmonary allergic responses in aspergillus fumigatus sensitized mice

BackgroundLipoprotein-associated phospholipase A2 (Lp-PLA2)/platelet-activating factor acetylhydrolase (PAF-AH) has been implicated in the pathogenesis of cardiovascular disease. A therapeutic targeting of this enzyme was challenged by the concern that increased circulating platelet activating factor (PAF) may predispose to or increase the severity of the allergic airway response. The aim of this study was to investigate whether Lp-PLA2 gene deficiency increases the risk of PAF and IgE-mediated inflammatory responses in vitro and in vivo using mouse models.MethodsLp-PLA2-/- mice were generated and back crossed to the C57BL/6 background. PAF-AH activity was measured using a hydrolysis assay in serum and bronchoalveolar lavage (BAL) samples obtained from mice. Aspergillus fumigatus (Af)-specific serum was prepared for passive allergic sensitization of mice in vivo and mast cells in vitro. β- hexosaminidase release was studied in bone marrow derived mast cells sensitized with Af-specific serum or DNP-IgE and challenged with Af or DNP, respectively. Mice were treated with lipopolysaccharide (LPS) and PAF intratracheally and studied 24 hours later. Mice were sensitized either passively or actively against Af and were studied 48 hours after a single intranasal Af challenge. Airway responsiveness to methacholine, inflammatory cell influx in the lung tissue and BAL, immunoglobulin (ELISA) and cytokine (Luminex) profiles were compared between the wild type (WT) and Lp-PLA2-/- mice.ResultsPAF-AH activity was reduced but not completely abolished in Lp-PLA2-/- serum or by in vitro treatment of serum samples with a high saturating concentration of the selective Lp-PLA2 inhibitor, SB-435495. PAF inhalation significantly enhanced airway inflammation of LPS treated WT and Lp-PLA2-/- mice to a similar extent. Sensitized WT and Lp-PLA2-/- bone-marrow derived mast cells released β-hexosaminidase following stimulation by allergen or IgE crosslinking to equivalent levels. Wild type and Lp-PLA2-/- mice responded to passive or active allergic sensitization by significant IgE production, airway inflammation and hyperresponsiveness after Af challenge. BAL cell influx was not different between these strains while IL-4, IL-5, IL-6 and eotaxin release was attenuated in Lp-PLA2-/- mice. There were no differences in the amount of total IgE levels in the Af sensitized WT and Lp-PLA2-/- mice.ConclusionsWe conclude that Lp-PLA2 deficiency in C57BL/6 mice did not result in a heightened airway inflammation or hyperresponsiveness after PAF/LPS treatment or passive or active allergic sensitization and challenge.

Molecular mechanisms of spontaneous and directed mast cell motility.

Migration is a fundamental function of immune cells, and a role for Ca(2+) in immune cell migration has been an interest of scientific investigations for many decades. Mast cells are the major effector cells in IgE-mediated immune responses, and cross-linking of IgE-FcεRI complexes at the mast cell surface by antigen activates a signaling cascade that causes mast cell activation, resulting in Ca(2+) mobilization and granule exocytosis. These cells are known to accumulate at sites of inflammation in response to parasite and bacterial infections. Using real-time imaging, we monitored chemotactic migration of RBL and rat BMMCs in response to a gradient of soluble multivalent antigen. Here, we show that Ca(2+) influx via Orai1 plays an important role in regulating spontaneous motility and directional migration of mast cells toward antigen via IgER complexes. Inhibition of Ca(2+) influx or knockdown of the Ca(2+) entry channel protein Orai1 by shRNA causes inhibition of both of these processes. In addition, a mutant Syk- shows impaired spontaneous motility and chemotaxis toward antigen that is rescued by expression of Syk. Our findings identify a novel Ca(2+) influx-mediated, Orai1-dependent mechanism for mast cell migration.

Trib3 is regulated by IL-3 and affects bone marrow-derived mast cell survival and function

Mast cells are the principal effectors of IgE-mediated immune responses, including allergic reactions. Tribbles homolog 3 (Trib3) encodes a pseudokinase implicated in the cellular stress response and has been linked to inflammation in certain situations. Here we report the role of Trib3 in mouse bone marrow-derived mast cells (BMMCs). Our results show that Trib3 mRNA expression in BMMCs is positively regulated by the growth factor interleukin (IL)-3. BMMCs originating from Trib3 knockout mice demonstrate unaltered differentiation kinetics and cell surface expression of mast cell markers. When challenged with transient IL-3 deprivation, Trib3-deficient BMMCs display delayed recovery, and during prolonged IL-3 starvation, cell death is accelerated in Trib3-null cultures. IgE-dependent and pharmacologically induced degranulation is impaired in Trib3-deficient BMMCs, as is activation-induced cytokine mRNA expression. Thus, Trib3 contributes to the survival and activity of primary cultured mast cells, which suggests a role for Trib3 in the modulation of the immune response.