Dietary docosahexaenoic acid in combination with arachidonic acid ameliorates allergen-induced dermatitis in mice.

OBJECTIVE: In this study, we investigated the impact of dietary docosahexaenoic (DHA) and arachidonic acid (AA) on development and severity of allergen-induced dermatitis. STUDY DESIGN: In sensitized mice, skin inflammation was induced by ovalbumin. Mice received either a diet containing 0.015% DHA, 0.029% AA or the combination of both. The severity of dermatitis was evaluated by using a clinical skin score (CSS), followed by immunohistologic and cytokine analysis. To unravel potential mechanisms, interleukin (IL)-4 or tumor necrosis factor α-stimulated keratinocytes from the cell line Kera-308 was cultured with different DHA/AA compositions and analyzed regarding proliferation and cytokine production. RESULTS: Dietary DHA/AA significantly improved the severity of allergen-induced dermatitis as the CSS was reduced by 36 ± 23% (p=0.005). Furthermore, reduced epidermal KI67 expression, increased number of forkhead box P3(+) cells, and elevated IL-10 expression were determined in skin lesions of dietary-treated mice. Correspondingly, in vitro DHA/AA-treated keratinocytes exhibited increased IL-10 expression and produced less thymic stromal lymphopoietin. CONCLUSION: Dietary DHA/AA supplementation leads to a significant amelioration of allergen-induced dermatitis. This was accompanied with the presence of increased regulatory T cells and IL-10 expression in lesional skin. Moreover, we identify keratinocytes, which play a crucial role in the regulation of skin inflammation, as important targets of DHA/AA supplementation. Future studies are needed to clarify whether DHA/AA acts directly or whether its biologic active metabolites are responsible for these findings. This may unravel novel therapeutical compounds for allergen-induced dermatitis.

Cloning, expression, and mapping of allergenic determinants of alphaS1-casein, a major cow's milk allergen.

Milk is one of the first components introduced into human diet. It also represents one of the first allergen sources, which induces IgE-mediated allergies in childhood ranging from gastrointestinal, skin, and respiratory manifestations to severe life-threatening manifestations, such as anaphylaxis. Here we isolated a cDNA coding for a major cow's milk allergen, alphaS1-casein, from a bovine mammary gland cDNA library with allergic patients' IgE Abs. Recombinant alphaS1-casein was expressed in Escherichia coli, purified, and characterized by circular dichroism as a folded protein. IgE epitopes of alphaS1-casein were determined with recombinant fragments and synthetic peptides spanning the alphaS1-casein sequence using microarrayed components and sera from 66 cow's milk-sensitized patients. The allergenic activity of ralphaS1-casein and the alphaS1-casein-derived peptides was determined using rat basophil leukemia cells transfected with human FcepsilonRI, which had been loaded with the patients' serum IgE. Our results demonstrate that ralphaS1-casein as well as alphaS1-casein-derived peptides exhibit IgE reactivity, but mainly the intact ralphaS1-casein induced strong basophil degranulation. These results suggest that primarily intact alphaS1-casein or larger IgE-reactive portions thereof are responsible for IgE-mediated symptoms of food allergy. Recombinant alphaS1-casein as well as alphaS1-casein-derived peptides may be used in clinical studies to further explore pathomechanisms of food allergy as well as for the development of new diagnostic and therapeutic strategies for milk allergy.

Induction of autoallergy with an environmental allergen mimicking a self protein in a murine model of experimental allergic asthma.

BACKGROUND: Allergy and autoimmunity are traditionally considered as 2 exclusive entities related to the development of either TH2-dominated or TH1-dominated immune responses. OBJECTIVE: This study investigated whether allergic sensitization to a foreign antigen mimicking a self protein can induce allergy accompanied by an autoimmune response. METHODS: BALB/c mice were sensitized to human alpha-NAC, an evolutionary conserved component of the nascent polypeptide-associated complex, recently identified as an IgE-reactive autoantigen in patients with severe forms of atopy. By using nitrocellulose-blotted murine lung and skin extracts, purified recombinant human as well as murine alpha-NAC and murine alpha-NAC-derived synthetic peptides, the IgE, IgG1, and IgG2a antibody responses were measured, and their epitope specificity was mapped. RESULTS: Cross-reactivity of IgE and IgG antibodies with murine alpha-NAC was found in mice sensitized with human alpha-NAC. The biological relevance of the antibody response was demonstrated by the induction of immediate skin reactions in sensitized mice and by the fact that skin sensitivity could be passively transferred with serum to naive mice. Antigen challenge of sensitized mice resulted in airway inflammation accompanied by eosinophil and neutrophil accumulation, airway hyperresponsiveness to methacholine and perivasculitis of lung veins. CONCLUSION: Our data demonstrate that sensitization with a foreign antigen mimicking self can induce an allergic immune response of a mixed TH2 and TH1 profile that is associated with autoreactivity. Cross-sensitization to self may represent an important pathomechanism involved in the maintenance of severe and chronic forms of allergy.

Inhibition of IgE-production by peroxisome proliferator-activated receptor ligands.

In this study we analyzed the effect of peroxisome proliferator-activated receptor-alpha and -gamma ligands on immunoglobulin synthesis and cytokine production in non-allergic and atopic dermatitis donors in vitro, but also in vivo ovalbumin-sensitized mice. A significant inhibition in CD40+ interleukin-4-mediated, but also basal IgE synthesis from peripheral blood mononuclear cells of atopic dermatitis donors was observed in the presence of the peroxisome proliferator-activated receptor-alpha ligand (up to 47+/-12%) and peroxisome proliferator-activated receptor-gamma ligand (69+/-5%). By contrast, the production of other isotypes such as IgA, IgG, and IgM was only modest inhibited. Analysis of cytokine production from the peripheral blood mononuclear cells shows inhibition of several cytokines by both peroxisome proliferator-activated receptor ligands. The most inhibitory effect on cytokine production was observed by the peroxisome proliferator-activated receptor-gamma ligand in peripheral blood mononuclear cells from atopic dermatitis donors with high IgE baseline production. Coculture experiments show that the decrease of IgE production by ciglitazone was monocyte dependent (up to 63+/-7%). Finally, in vivo experiments from ovalbumin-sensitized mice confirmed the in vitro findings showing that the interleukin-4-mediated immune response was inhibited in ciglitazone-treated mice.

Critical role of preconceptional immunization for protective and nonpathological specific immunity in murine neonates.

Expression of Th2 immunity against environmental Ags is the hallmark of the allergic phenotype and contrasts with the Th1-like pattern, which is stably expressed in healthy adults throughout life. Epidemiological studies indicate that the prenatal environment plays an important and decisive role in the development of allergy later in life. Since the underlying mechanisms were unclear, an animal model was developed to study the impact of maternal allergy on the development of an allergic immune response in early life. An allergic Th2 response was induced in pregnant mice by sensitization and aerosol allergen exposure. Both, IgG1 and IgG2a, but not IgE, Abs cross the placental barrier. Free allergen also crosses the placental area and was detected in serum and amniotic fluids of neonatal F(1) mice. These F(1) mice demonstrated a suppressed Th1 response, as reflected by lowered frequencies and reduced levels of IFN-gamma production. Development of an IgE response against the same allergen was completely prevented early in life. This effect was mediated by diaplacental transfer of allergen-specific IgG1 Abs. In contrast, allergic sensitization against a different allergen early in life was accelerated in these mice. This effect was mediated by maternal CD4 and OVA-specific Th2 cells induced by allergic sensitization during pregnancy. These data indicate a critical role for maternal T and B cell response in shaping pre- and postnatal maturation of specific immunity to allergens.

Retinoid- and carotenoid-enriched diets influence the ontogenesis of the immune system in mice.

Vitamin A (VA) has been identified as an important factor for the development of the immune system, especially during ontogenesis. It has been shown that antibody secretion and proliferation of lymphocyte populations depend on retinoids. In the present study we investigated the influence of a base VA diet and diets enriched with VA, beta-carotene and lycopene, on the ontogenesis of the immune system in mice. We examined the absolute and relative concentrations of splenic B lymphocytes (CD45R/B220), T lymphocytes (CD3+) and their subpopulations (CD4+ and CD8+), and measured serum immunoglobulin G (IgG) concentrations in the offspring of supplemented dams at different ages (1, 3, 5, 7, 14, 21 and 65 days). The experimental diets resulted in higher numbers of T and B lymphocytes after VA and carotenoid enrichment, when compared, at various time-points, with the base diet. Higher values of total serum IgG were found in the beta-carotene-enriched diet group on day 7. On days 7 and 14, the enriched diets induced significant alterations in the percentages and total numbers of splenic lymphocytes in comparison to the base diet. Our results confirm that supplementation with VA and carotenoids affect the immune-cell function during ontogenesis and suggest a possible role of these nutritional factors on the development of the immune system.

Inhibition of the IL-4/IL-13 receptor system prevents allergic sensitization without affecting established allergy in a mouse model for allergic asthma.

BACKGROUND: IL-4 and IL-13 are considered as key regulators for the development of atopic disease. OBJECTIVE: This study addresses the therapeutic potential of an IL-4/IL-13 inhibitor on the basis of a mutated IL-4 variant (Q116D, Y119D) during allergic sensitization and in established disease in a murine asthma model with persistent airway pathologic condition. METHODS: BALB/c mice were sensitized with ovalbumin intranasally. Mice were treated with the IL-4/IL-13 inhibitor during the sensitization phase or alternatively after ovalbumin allergy was established. Specific antibodies were measured, and histologic lung sections were examined for goblet cell metaplasia. In addition, bronchoalveolar lavages were performed and checked for airway eosinophilia, IL-5 levels, and the number of IL-4 secreting CD4(+) T cells. Furthermore, airway responsiveness to inhaled methacholine was assessed. RESULTS: The inhibition of the IL-4/IL-13 system during allergic sensitization resulted in a dose-dependent reduction of ovalbumin-specific IgEs and inhibition of airway eosinophilia together with decreased IL-5 levels and decreased numbers of IL-4 secreting CD4(+) T cells. Moreover, goblet cell metaplasia and airway responsiveness to methacholine could be reduced significantly by the IL-4/IL-13 inhibitor. However, the inhibition of the IL-4/IL-13 system at various time points after allergy was established showed only little effect on all measured allergic parameters. CONCLUSION: Although the inhibition of the IL-4/IL-13 system can efficiently prevent the development of the allergic phenotype, these cytokines seem to play a minor role in established allergy. This is relevant for estimating the therapeutic effects of IL-4/IL-13 inhibitors in patients with allergic asthma.

Influenza A virus infection inhibits the efficient recruitment of Th2 cells into the airways and the development of airway eosinophilia.

Most infections with respiratory viruses induce Th1 responses characterized by the generation of Th1 and CD8(+) T cells secreting IFN-gamma, which in turn have been shown to inhibit the development of Th2 cells. Therefore, it could be expected that respiratory viral infections mediate protection against asthma. However, the opposite seems to be true, because viral infections are often associated with the exacerbation of asthma. For this reason, we investigated what effect an influenza A (flu) virus infection has on the development of asthma. We found that flu infection 1, 3, 6, or 9 wk before allergen airway challenge resulted in a strong suppression of allergen-induced airway eosinophilia. This effect was associated with strongly reduced numbers of Th2 cells in the airways and was not observed in IFN-gamma- or IL-12 p35-deficient mice. Mice infected with flu virus and immunized with OVA showed decreased IL-5 and increased IFN-gamma, eotaxin/CC chemokine ligand (CCL)11, RANTES/CCL5, and monocyte chemoattractant protein-1/CCL2 levels in the bronchoalveolar lavage fluid, and increased airway hyperreactivity compared with OVA-immunized mice. These results suggest that the flu virus infection reduced airway eosinophilia by inducing Th1 responses, which lead to the inefficient recruitment of Th2 cells into the airways. However, OVA-specific IgE and IgG1 serum levels, blood eosinophilia, and goblet cell metaplasia in the lung were not reduced by the flu infection. Flu virus infection also directly induced AHR and goblet cell metaplasia. Taken together, our results show that flu virus infections can induce, exacerbate, and suppress features of asthmatic disease in mice.

Levels of antibodies specific to tetanus toxoid, Haemophilus influenzae type b, and pneumococcal capsular polysaccharide in healthy children and adults.

Antibody levels specific for capsular polysaccharides of Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) and for tetanus toxoid were measured in serum samples of 386 age-stratified subjects. The study group consists of healthy adult blood donors and hospitalized children undergoing elective surgery, excluding individuals with a history of infection. In children, anti-tetanus toxoid antibody levels displayed two peaks of 1.20 IU/ml (20.4 mg/liter) and 1.65 IU/ml (28.1 mg/liter) related to the schedule of routine childhood immunization in the first year and at 8 years of age. Eighty percent of the antibodies are of the immunoglobulin G1 (IgG1) isotype. For pneumococcal capsular polysaccharide (PCP), the specific antibody levels represent the acquisition of natural immunity. The initial concentration of 9.2 mg/liter was low in infancy (0.5 to 1 years of age) and remained low until 3 to 4 years of age (14.6 mg/liter). During this period PCP antibodies were almost 100% of the IgG2 subclass. Thereafter, IgG anti-PCP antibody titers increased steadily to adult levels (59.5 mg/liter). The data are intended to provide reference ranges to aid in the interpretation of specific antibody determinations in the clinical setting.

Environmental exposure to endotoxin and its relation to asthma in school-age children.

BACKGROUND: In early life, the innate immune system can recognize both viable and nonviable parts of microorganisms. Immune activation may direct the immune response, thus conferring tolerance to allergens such as animal dander or tree and grass pollen. METHODS: Parents of children who were 6 to 13 years of age and were living in rural areas of Germany, Austria, or Switzerland where there were both farming and nonfarming households completed a standardized questionnaire on asthma and hay fever. Blood samples were obtained from the children and tested for atopic sensitization; peripheral-blood leukocytes were also harvested from the samples for testing. The levels of endotoxin in the bedding used by these children were examined in relation to clinical findings and to the cytokine-production profiles of peripheral-blood leukocytes that had been stimulated with lipopolysaccharide and staphylococcal enterotoxin B. Complete data were available for 812 children. RESULTS: Endotoxin levels in samples of dust from the child's mattress were inversely related to the occurrence of hay fever, atopic asthma, and atopic sensitization. Nonatopic wheeze was not significantly associated with the endotoxin level. Cytokine production by leukocytes (production of tumor necrosis factor alpha, interferon-gamma, interleukin-10, and interleukin-12) was inversely related to the endotoxin level in the bedding, indicating a marked down-regulation of immune responses in exposed children. CONCLUSIONS: A subject's environmental exposure to endotoxin may have a crucial role in the development of tolerance to ubiquitous allergens found in natural environments.