B.C.A.M. van Esch

Effect of dexamethasone and endogenous corticosterone on airway hyperresponsiveness and eosinophilia in the mouse

1 Mice were sensitized by 7 intraperitoneal injections of ovalbumin without adjuvant (10 μg in 0.5 ml of sterile saline) on alternate days and after 3 weeks exposed to either ovalbumin (2 mg ml−1 in sterile saline) or saline aerosol for 5 min on 8 consecutive days. One day before the first challenge, animals were injected intraperitoneally on a daily basis with vehicle (0.25 ml sterile saline), dexamethasone (0.5 mg kg−1) or metyrapone (30 mg kg−1). 2 In vehicle‐treated ovalbumin‐sensitized animals ovalbumin challenge induced a significant increase of airway responsiveness to metacholine both in vitro (27%, P < 0.05) and in vivo (40%, P < 0.05) compared to saline‐challenged mice. Virtually no eosinophils could be detected after saline challenge, whereas the numbers of eosinophils were significantly increased (P < 0.01) at both 3 and 24 h after the last ovalbumin challenge (5.48 ± 3.8 × 103 and 9.13 ± 1.7 × 103 cells, respectively). Furthermore, a significant increase in ovalbumin‐specific immunoglobulin E level (583 ± 103 units ml−1, P < 0.05) was observed after ovalbumin challenge compared to saline challenge (201 ± 38 units ml−1). 3 Plasma corticosterone level was significantly reduced (−92%, P < 0.001) after treatment with metyrapone. Treatment with metyrapone significantly increased eosinophil infiltration (17.4 ± 9.93 × 103 and 18.7 ± 2.57 × 103 cells, P < 0.05 at 3 h and 24 h, respectively) and potentiated airway hyperresponsiveness to methacholine compared to vehicle‐treated ovalbumin‐challenged animals. Dexamethasone inhibited both in vitro and in vivo hyperresponsiveness as well as antigen‐induced infiltration of eosinophils (0, P < 0.05 and 0.7 ± 0.33 × 103 cells, P < 0.05 at 3 h and 24 h, respectively). Metyrapone as well as dexamethasone did not affect the increase in ovalbumin‐specific immunoglobulin E levels after ovalbumin challenge (565 ± 70 units/ml−1; P < 0.05; 552 ± 48 units ml−1, P < 0.05 respectively). 4 From these data it can be concluded that exogenously applied corticosteroids can inhibit eosinophil infiltration as well as airway hyperresponsiveness. Vise versa, endogenously produced corticosteroids play a down‐regulating role on the induction of both eosinophil infiltration and airway hyperresponsiveness.

Dietary long chain n‐3 polyunsaturated fatty acids prevent allergic sensitization to cow's milk protein in mice

Cows milk allergy is one of the most common food allergies in children and no treatment is available. Dietary lipid composition may affect the susceptibility to develop allergic disease.

CD28/CTLA4 double deficient mice demonstrate crucial role for B7 co-stimulation in the induction of allergic lower airways disease

Background The existence of a third B7‐1/B7‐2 receptor was postulated in a recent study using a novel mouse strain lacking both CD28 and CTLA4 (CD28/CTLA4−/−).

CD25+ regulatory T cells transfer n-3 long chain polyunsaturated fatty acids-induced tolerance in mice allergic to cow's milk protein

Recently, we have shown that dietary long‐chain n‐3 polyunsaturated fatty acids (n‐3 LCPUFA) largely prevent allergic sensitization in a murine model for cows milk allergy. The aim of this study was to assess the contribution of regulatory T cells (Treg) in the prevention of food allergy by n‐3 LCPUFA.

β-agonists can depress oxidative metabolism of alveolar macrophages

Alveolar macrophages (AM) are the primary defenders in the lung against inhaled particles and microorganisms. These cells exhibit a variety of biological activities, like phagocytosis and killing of microorganisms and secretion of enzymes, reactive oxygen metabolites, arachidonic acid metabolites (prostaglandins, leukotrienes) and other mediators of inflammation. The process of phagocytosis of microorganisms by phagocytic cells can be separated into distinct but interrelated phases: adherence, chemotaxis, opsonization, attachment, ingestion, degranulation and killing. Phagocytosis is accompanied by an increase in oxygen metabolism in which hydrogen peroxide (H202) and activated oxygen species are generated [1]. The function of phagocytic cells are under the influence of a great number of physiological and environmental factors [1]. There are some indications that macrophages possess fl-adrenergic receptors on their cell surface [2] and that the activity of phagocytic cells can be regulated by cyclic AMP levels in the cell [3, 4]. Since fl-adrenergic receptor stimulation in different systems results in increased intracellular levels of cyclic AMP, we investigated the effects of a number of ill-, f12and non-specific fl-adrenoceptor stimulants (dobutamine, salbuta0aol and isoprenaline, respectively) on phagocytic and metabolic activity of guinea pig AM. Methods

Depletion of CD4+CD25+ T cells switches the whey-allergic response from immunoglobulin E- to immunoglobulin free light chain-dependent

Background Symptoms of allergy are largely attributed to an IgE‐mediated hypersensitivity response. However, a considerable number of patients also exhibit clinical features of allergy without detectable systemic IgE. Previous work showed that Ig‐free light chains (IgLC) may act as an alternate mechanism to induce allergic responses. CD4+CD25+ T cells are crucial in the initiation and regulation of allergic responses and compromised function might affect the response to allergens.

Production of arachidonic and linoleic acid metabolites by guinea pig tracheal epithelial cells

Pulmonary epithelial cells may be responsible for regulating airway smooth muscle function, in part by release of fatty acid-derived mediators. Incubation of isolated guinea pig tracheal epithelial cells with radiolabeled arachidonic acid (AA) leads to the production of 5- and 15-hydroxyeicosatetraenoic acid (5- and 15-HETE) and smaller amounts of leukotriene (LT) B4 and C4 and 12-hydroxyheptadecatrienoic acid (HHT). Epithelial cells also are able to release linoleic acid (LA) metabolites. Incubation with radiolabeled linoleic acid leads to the formation of 9- and 13-hydroxyoctadecadienoic acid (9- and 13-HODE). The biological significance of these mediators produced by epithelial cells is discussed.

Interlaboratory evaluation of a cow's milk allergy mouse model to assess the allergenicity of hydrolysed cow's milk based infant formulas.

This study describes two phases of a multi-phase project aiming to validate a mouse model for cows milk allergy to assess the potential allergenicity of hydrolysed cows milk based infant formulas (claim support EC-directive 2006/141/E). The transferability and the discriminatory power of this model was evaluated in 4 research centers. Mice were sensitized by oral gavage with whey or extensively hydrolysed whey (eWH) using cholera toxin as an adjuvant. Whey-specific antibodies, mMCP-1 levels, anaphylactic shock symptoms, body temperature and the acute allergic skin response were determined upon whey challenge. In phases I and II, all 4 centers detected elevated levels of whey-specific IgE/IgG1 in whey sensitized animals. Elevated levels of mMCP-1, anaphylactic symptoms, body temperature drop and acute allergic skin response were scored upon whey challenge in 3 out of 4 research centers. In contrast, none of the evaluated parameters were elevated in eWH orally exposed groups. The cows milk allergy mouse model is capable to distinguish the sensitizing capacity of complete or hydrolysed cows milk protein. The model uses straightforward parameters relevant to food allergic responses and can be effectively transferred between different laboratories. We propose this mouse model as a new strategy for the screening of new hypoallergenic cows milk formulas.

Macrophages induce an allergen-specific and long-term suppression in a mouse asthma model

Increasing evidence suggests that macrophages (Mφ) play a crucial downregulatory role in the initiation and progression of allergic asthma. Recently, the current authors demonstrated that ovalbumin (OVA)-loaded Mφ (OVA-Mφ) suppress subsequent OVA-induced airway manifestations of asthma and that this effect could be potentiated upon selective activation. In the present study, the authors further delineated the underlying pathway by which Mφ exert this immunosuppressive effect. To examine the migration of OVA-Mφ, cells were labelled with 5′chloromethylfluorescein diacetate (CMFDA) and were administered (i.v.) into OVA-sensitised BALB/c mice. After 20 h, the relevant organs were dissected and analysed using fluorescent microscopy. Allergen-specificity was investigated by treating OVA-sensitised mice with keyhole limpet haemocyanin (KLH)-Mφ activated with immunostimulatory sequence oligodeoxynucleotide (ISS-ODN). By lengthening the period between treatment and challenge to 4 weeks it was examined whether OVA-Mφ exerted an immunosuppressive memory response. Strikingly, CMFDA-labelled Mφ were not trapped in the lungs, but migrated to the spleen. ISS-ODN-stimulated KLH-Mφ failed to suppress OVA-induced airway manifestations of asthma. Moreover, treatment with ISS-ODN-stimulated OVA-Mφ was still effective after lengthening the period between treatment and challenge. These data demonstrate that allergen-loaded macrophages can induce an indirect immunosuppressive response that is allergen-specific and long lasting, which are both hallmarks of a memory lymphocyte response.

Perinatal programming of murine immune responses by polyunsaturated fatty acids

Linoleic acid and α-linolenic acid are essential fatty acids (eFAs) and have to be acquired from the diet. eFAs are the precursors for long-chain polyunsaturated fatty acids (lcPUFAs), which are important immune-modulating compounds. lcPUFAs can be converted into eicosanoids and other mediators. They affect membrane structure and fluidity and can alter gene expression. There has been a marked change in dietary fatty acid intake over the last several decades. Since eFAs are acquired from the diet and immune development occurs mainly perinatally, the maternal diet may influence fetal and neonatal eFA levels, and thereby lcPUFA status, and thus immune development and function. To study whether early exposure to eFAs can program immune function, mice were fed diets varying in the ratio of ω-3 to ω-6-eFAs during pregnancy and/or lactation. After weaning, pups received a Western-style diet. At 11 weeks of age, the effects of maternal diet on the offsprings allergic and vaccination responses were examined using the T-helper 2 driven ovalbumin-induced allergy model and the T-helper 1 driven influenza-vaccination model, respectively. Offspring of dams fed a high α-linolenic acid diet during lactation showed an enhanced vaccination response. As diets with either low or high ω-3/ω-6-eFA ratio attenuated the T-helper 2 allergic response, the high α-linolenic acid diet fed during lactation had the most pronounced effect. These results indicate that there is a programming effect of maternal diet on the offsprings immune response and that in mice the window of greatest susceptibility to maternal dietary intervention is the lactation/suckling period.