RESUMEN
BACKGROUND: The soluble isoform of FcÉRI, the high-affinity IgE receptor (sFcεRI), is a protein of the IgE network with poorly defined functions. OBJECTIVE: To define cellular sources and signals that result in the production of human sFcεRI and study its in vivo functions. METHODS: FcεRI-transfected human cell lines (MelJuso), human monocyte-derived dendritic cells (moDCs), and murine bone marrow-derived mast cells (MC) were stimulated by FcεRI cross-linking and release of sFcεRI was analyzed (ELISA, Western Blot). Lysosomal-associated membrane protein 1 degranulation assays and human basophil activation tests (BATs) were used to study IgE-dependent activation. Recombinant sFcεRI (rsFcεRI) was used to assess its role in murine models of anaphylaxis with WT (wild-type) and IgE-/- (IgE-deficient) mice. RESULTS: Antigen-specific cross-linking of IgE-loaded FcÉRI on MelJuso cells that express the trimeric or tetrameric receptor isoform induced the production of sFcεRI. Using MCs and moDCs, we confirmed that IgE/FcÉRI activation induces sFcÉRI release. We demonstrated that generation of sFcÉRI requires Src phosphorylation and endo/lysosomal acidification. In experimental mouse models, sFcÉRI diminishes the severity of IgE-mediated anaphylaxis. BATs confirmed that, comparable to the anti-IgE monoclonal antibody omalizumab, sFcÉRI is an inhibitor of the human innate IgE effector axis, implying that sFcÉRI and omalizumab potentially inhibit each other in vivo. CONCLUSION: sFcÉRI is produced after antigen-specific IgE/FcÉRI-mediated activation signals and functions as an endogenous inhibitor of IgE loading to FcÉRI and IgE-mediated activation. Our results imply, therefore, that sFcÉRI contributes to a negative regulatory feedback loop that aims at preventing overshooting responses after IgE-mediated immune activation.
Asunto(s)
Inmunoglobulina E/inmunología , Inmunoglobulina E/metabolismo , Mastocitos/inmunología , Mastocitos/metabolismo , Receptores de IgE/metabolismo , Animales , Basófilos/inmunología , Basófilos/metabolismo , Biomarcadores , Degranulación de la Célula/inmunología , Línea Celular Tumoral , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Endosomas/metabolismo , Humanos , Inmunoglobulina E/química , Lisosomas/metabolismo , Ratones , Ratones Noqueados , Unión Proteica , Isoformas de Proteínas , Multimerización de Proteína , Receptores de IgE/químicaRESUMEN
IgE-mediated reactions to food allergens are the most common cause of anaphylaxis in childhood. Although allergies to cow's milk, egg, or soy proteins, in contrast to peanut and tree nut allergens, resolve within the first 6 years of life in up to 60% due to natural tolerance development, this process is not well understood. At present, there is no cure or treatment for food allergy that would result in an induction of tolerance to the symptom-eliciting food. Avoidance, providing an emergency plan and education, is the standard of treatment. Oral immunotherapeutic approaches have been proven reasonable efficacy; however, they are associated with high rates of side-effects and low numbers of patients achieving tolerance. Nevertheless, mechanisms that take place during oral immunotherapy may help to understand tolerance development. On the basis of these therapeutic interventions, events like loss of basophil activation and induction of regulatory lymphocyte subsets and of blocking antibodies have been described. Their functional importance at a clinical level, however, remains to be investigated in detail. Consequently, there is eminent need to understand the process of tolerance development to food allergens and define biomarkers to develop and monitor new treatment strategies for food allergy.
Asunto(s)
Alérgenos/inmunología , Hipersensibilidad a los Alimentos/inmunología , Alimentos/efectos adversos , Tolerancia Inmunológica , Animales , Biomarcadores , Desensibilización Inmunológica , Modelos Animales de Enfermedad , Femenino , Hipersensibilidad a los Alimentos/diagnóstico , Hipersensibilidad a los Alimentos/terapia , Humanos , Inmunidad Mucosa , Inmunización , Inmunoglobulina E/inmunología , Exposición Materna , Ratones , Embarazo , Efectos Tardíos de la Exposición Prenatal/inmunologíaAsunto(s)
Ciclopentolato/efectos adversos , Hipersensibilidad a las Drogas/etiología , Midriáticos/efectos adversos , Preescolar , Ciclopentolato/administración & dosificación , Erupciones por Medicamentos/diagnóstico , Erupciones por Medicamentos/etiología , Hipersensibilidad a las Drogas/diagnóstico , Humanos , Obstrucción del Conducto Lagrimal/diagnóstico , Masculino , Midriáticos/administración & dosificación , Soluciones OftálmicasAsunto(s)
Trastornos de la Conciencia/etiología , Hipersensibilidad al Huevo/diagnóstico , Pruebas Intradérmicas/efectos adversos , Especificidad de Anticuerpos/inmunología , Preescolar , Trastornos de la Conciencia/inmunología , Dermatitis Atópica/diagnóstico , Dermatitis Atópica/inmunología , Relación Dosis-Respuesta a Droga , Hipersensibilidad al Huevo/inmunología , Proteínas Dietéticas del Huevo/efectos adversos , Proteínas Dietéticas del Huevo/inmunología , Femenino , Humanos , Inmunoglobulina E/sangre , Hipersensibilidad a la Leche/diagnóstico , Hipersensibilidad a la Leche/inmunologíaRESUMEN
Bacterial and viral infections cause high rates of morbidity and mortality in premature newborns. In the setting of viral infection, pDCs play a key role as strong producers of IFN-α upon TLR9 activation. We analyzed pDC frequency, phenotype, morphology, and function in CB of preterm and term newborns in comparison with adults. Whereas all age groups show similar pDC numbers, BDCA-2, CD123, and TLR9 levels, the expression of BDCA-4 and capacity to produce IFN-α upon TLR9 challenge were decreased significantly in preterm neonates. Furthermore, we show by means of electron microscopy that pDCs from preterm newborns exhibit a distinct, "immature" morphology. Taken together, these findings suggest decreased functionality of pDCs in the premature newborn. The reduced capacity to produce IFN-α is likely to render such infants more susceptible to viral infections.
Asunto(s)
Células Dendríticas/fisiología , Recien Nacido Prematuro/inmunología , Adulto , Factores de Edad , Antígenos de Superficie/análisis , Recuento de Células , Células Cultivadas , Células Dendríticas/ultraestructura , Humanos , Recién Nacido , Interferón-alfa/biosíntesis , Subunidad alfa del Receptor de Interleucina-3/análisis , Trombomodulina , Receptor Toll-Like 9/fisiologíaRESUMEN
BACKGROUND: With respect to the cellular players, mast cells and basophils have been well studied in experimental murine systemic anaphylaxis models, but the role of neutrophils and platelets is not fully understood today. OBJECTIVE: We tested the hypothesis that neutrophils and platelets might participate in an antigen-induced anaphylaxis model. METHODS: BALB/c mice were sensitized intraperitoneally with alum-adsorbed casein. A period of 2 weeks later, mice were challenged with 100 µg casein intravenously and immediate hypersensitivity reactions were assessed by rectal temperature measurements and monitoring the physical activity. Subsequently, leucocytes were counted in the peripheral blood as well as quantified in situ in typical shock organs like lung, liver and spleen, heart and kidney. RESULTS: Mice sensitized with casein showed casein-specific IgG1, IgE, and IgG2a. When sensitized mice were specifically challenged with casein they developed immediate hypersensitivity reactions including drop of temperature and reduced activity. Furthermore, pronounced peripheral neutropenia and reduced platelet counts correlated with the severity of the hypersensitivity reactions. In the histological analyses of collected tissues we observed lung interstitial neutrophilia using Gr-1 staining. These events occurred specifically in mice sensitized and challenged with casein, in contrast to control groups. CONCLUSIONS: On the basis of our data we suggest that in addition to mast cells and basophils, neutrophils and platelets participate in the anaphylactic response in this BALB/c mouse model. Platelet and neutrophils expressing relevant immunoglobulin receptors may therefore have a synergistic effect with allergen specific IgE as well as IgG antibodies in food-induced anaphylaxis. We suggest that management of these cells could be of clinical importance to handle anaphylaxis.
Asunto(s)
Anafilaxia/sangre , Anafilaxia/inducido químicamente , Plaquetas/metabolismo , Caseínas/toxicidad , Neutrófilos/metabolismo , Animales , Modelos Animales de Enfermedad , Inmunoglobulina E/sangre , Inmunoglobulina G/sangre , Recuento de Leucocitos , Ratones , Ratones Endogámicos BALB C , Recuento de PlaquetasRESUMEN
BACKGROUND: Elevation of the gastric pH increases the risk for sensitization against food allergens by hindering protein breakdown. This can be caused by acid-suppressing medication like sucralphate, H2-receptor blockers and proton pump inhibitors, as shown in recent murine experimental and human observational studies. OBJECTIVE: The aim of the present study was to assess the sensitization capacity of the dietary supplement base powder and of over-the-counter antacids. METHODS: Changes of the pH as well as of protein digestion due to base powder or antacids were measured in vitro. To examine the in vivo influence, BALB/c mice were fed codfish extract with one of the acid-suppressing substances. Read-out of antibody levels in the sera, of cytokine levels of stimulated splenocytes and of intradermal skin tests was performed. RESULTS: The pH of hydrochloric acid was substantially increased in vitro by base powder as well as antacids in a time- and dose-dependent manner. This elevation hindered the digestion of codfish proteins in vitro. A significant increase in codfish-specific IgE antibodies was found in the groups fed codfish combined with Rennie Antacidum or with base powder; the latter also showed significantly elevated IgG1 and IgG2a levels. The induction of an anaphylactic immune response was proven by positive results in intradermal skin tests. CONCLUSIONS: Antacids and dietary supplements influencing the gastric pH increase the risk for sensitization against allergenic food proteins. As these substances are commonly used in the general population without consulting a physician, our data may have a major practical and clinical impact.
Asunto(s)
Antiácidos/efectos adversos , Suplementos Dietéticos/efectos adversos , Hipersensibilidad a los Alimentos/complicaciones , Hipersensibilidad a los Alimentos/inmunología , Alérgenos/inmunología , Animales , Relación Dosis-Respuesta a Droga , Ensayo de Inmunoadsorción Enzimática , Femenino , Proteínas de Peces/inmunología , Humanos , Concentración de Iones de Hidrógeno , Ratones , Medicamentos sin Prescripción/efectos adversos , Úlcera Gástrica/complicacionesRESUMEN
BACKGROUND: Animal models are essential for analyzing the allergenic potential of food proteins and for investigating mechanisms underlying food allergy. Based on previous studies revealing acid-suppression medication as risk factor for food allergy induction, we aimed to establish a mouse model mimicking the natural route of sensitization in patients. METHODS: The effect of acid-suppressing medication on murine gastric pH was assessed by intragastric pH measurements after two injections of a proton pump inhibitor (PPI). To investigate dose-dependency, mice were fed different concentrations of ovalbumin (OVA; 0.2, 0.5, 1.0, 2.5 or 5.0mg) either with or without anti-ulcer medication. Additionally, different routes of exposure (i.p. vs. oral) were compared in a second immunization experiment. Sera were screened for OVA-specific antibody titers (IgG1, IgG2a and IgE) in ELISA and RBL assay. Clinical reactivity was evaluated by measuring rectal temperature after oral challenge and by type I skin tests. RESULTS: Two intravenous injections of PPI significantly elevated the gastric pH from 2.97 to 5.3. Only oral immunization with 0.2mg OVA under anti-acid medication rendered elevated IgG1, IgG2a and IgE titers compared to all other concentrations. Protein feeding alone altered antibody titers only marginally. Even though also i.p. immunizations induced high levels of specific IgE, only oral immunizations under anti-acids induced anaphylactic reactions evidenced by a significant decrease of body temperature. CONCLUSION: Only low-dosage ovalbumin feedings under anti-acid medication resulted in IgE mediated food allergy. Based on this knowledge we have established a suitable food allergy model for further investigations of food adverse reactions.