The effect of endotoxin on the production of IgE, IgG1 and IgG2a antibodies against the cat allergen Fel d 1 in mice

Effects of Glycosylation Combined with Phosphate Treatment on the Allergenicity and Structure of Tropomyosin in Litopenaeus vannamei

Tropomyosin (TM) is the main allergen in shrimp (Litopenaeus vannamei). In this study, the effects of allergenicity and structure of TM by glycosylation (GOS-TM), phosphate treatment (SP-TM), and glycosylation combined with phosphate treatment (GOS-SP-TM) were investigated. Compared to GOS-TM and SP-TM, the IgG/IgE binding capacity of GOS-SP-TM was significantly decreased with 63.9 ± 2.0 and 49.7 ± 2.7%, respectively. Meanwhile, the α-helix content reduced, surface hydrophobicity increased, and 10 specific amino acids (K30, K38, S39, K48, K66, K74, K128, K161, S210, and K251) were modified by glycosylation on six IgE linear epitopes of GOS-SP-TM. In the BALB/c mice allergy model, GOS-SP-TM could significantly reduce the levels of specific IgE, IgG1, and CD4+IL-4+, while the levels of IgG2a, CD4+CD25+Foxp3+, and CD4+IFN-γ+ were increased, which equilibrated Th1 and Th2 cells, thus alleviating allergic symptoms. These results indicated that glycosylation combined with phosphate treatment can provide a new insight into developing hypoallergenic shrimp food.

The immune modulatory role of marjoram extract on imidacloprid induced toxic effects in thymus and spleen of adult rats

Imidacloprid (IMID), one of environmental persistent neonicotinoid insecticides, has been used a long time ago and categorized from insecticide induced moderate toxicity by World Health Organization (WHO). Marjoram, is one of the most worldwide used herbs in Egypt due to its antioxidant, anti-inflammatory, anti-genotoxic, anti-mutagenic, anticoagulant, and beneficial effects. This study aimed to evaluate the protective role of marjoram extract on the immunotoxic response and oxidative stress induced by IMID in the immune lymphoid organs (thymus and spleen) of rats. Fifty adult male albino rats were divided randomly into five groups; negative and positive (distilled water) control, marjoram extract (200 mg/kg/day), IMID (22.5 mg/kg/day), marjoram extract + IMID (200 mg/kg +22.5 mg/kg) orally for 8 weeks. Marjoram pretreatment reversed reduced animals body, thymus and spleen weights attributed to IMID. It amended the significantly elevated total leukocytes, neutrophils percentage, increased immunoglobulin G and the significantly reduction of lymphocytes percentage, phagocytic activity, phagocytic index and lysozyme activity induced by IMID. Moreover, marjoram administration significantly reduced thymic and splenic gene expression of interleukin-1β, interleukin-6, tumor necrosis factor-α and increased interleukin-10, in addition, it decreased thymic and splenic contents of malondialdehyde and restored the reduced antioxidant enzymes' activities following IMID exposure. Marjoram ameliorated IMID induced histopathological alterations in thymus and spleen and adjusted IMID immunomodulatory effects by increased the downregulation of CD4 and CD8 immune reactive cell expression. Conclusion, Marjoram has a protective role to reverse IMID immune toxic effects in thymus and spleen tissues of rats by its antioxidant, anti-inflammatory and immunomodulatory defense mechanisms.

Microbiological and toxicological hazard assessment in a waste sorting plant and proper respiratory protection

Even though biological hazards in the work environments related to waste management were the subject of many scientific works, the knowledge of the topic is not extensive. This study aimed to conduct a comprehensive assessment of microbiological and toxicological hazards at the workstations in a waste sorting plant and develop guidelines for selecting filtering respiratory protective devices that would consider specific workplace conditions. The research included the assessment of quantity (culture method), diversity (high-throughput sequencing), and metabolites (endotoxin - gas chromatography-mass spectrometry; secondary metabolites - liquid chromatography tandem-mass spectrometry) of microorganisms occurring in the air and settled dust. Moreover, cytotoxicity of settled dust against a human epithelial lung cell line was determined with an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The research was performed in a waste sorting plant (Poland; 240,000 tons waste/year) at six workstations: two feeders, two pre-sorting cabins, secondary raw material press and organic fraction waste feeder for composting. The total dust concentration at tested workstations varied from 0.128 mg m^-3 to 5.443 mg m^-3. The number of microorganisms was between 9.23 × 10⁴ CFU m^-3 and 1.38 × 10⁵ CFU m^-3 for bacteria and between 1.43 × 10⁵ CFU m^-3 and 1.65 × 10⁵ CFU m^-3 for fungi, which suggests high microbial contamination of the sorting facility. The numbers of microorganisms in the air correlated very strongly (R² from 0.70 to 0.94) with those observed in settled dust. Microorganisms representing Group 2 biological agents (acc. to Directive, 2000/54/EC), including Corynebacterium spp., Pseudomonas aeruginosa, Staphylococcus aureus, and others potentially hazardous to human health, were identified. The endotoxins concentration in settled dust ranged from 0.013 nmol LPS mg^-1 to 0.048 nmol LPS mg^-1. Seventeen (air) and 91 (settled dust) secondary metabolites characteristic, e.g., for moulds, bacteria, lichens, and plants were identified. All dust samples were cytotoxic (IC₅₀ values of 8.66 and 56.15 mg ml^-1 after 72 h). A flowchart of respiratory protective devices selection for biological hazards at the workstations in the waste sorting plant was proposed based on the completed tests to help determine the right type and use duration of the equipment.

Immunogenicity of recombinant human bocavirus-1,2 VP2 gene virus-like particles in mice

Human bocavirus (HBoV), a recently identified pathogen with a worldwide distribution is closely related to paediatric acute respiratory infection and gastroenteritis. The present study was performed to evaluate the immunogenicity of HBoV1 and HBoV2 virus-like particles (VLPs) as vaccine candidates in mice. Both HBoV1 and HBoV2 VLPs were expressed in the bacmid virus–SF9 cell system. Mice were inoculated three times at 3-week intervals with HBoV VLPs at one dose intramuscular (i.m.) or intradermal (i.d.) with or without the addition of the alum adjuvant. ELISA was used to detected antibody, and ELISPOT was used to test cellular immune responses. HBoV-specific IgG antibodies were induced and alum adjuvant improved the antibody titres and avidity, while the inoculation pathway had no influence. T helper type 1/ type 2 immune responses were balanced induced by HBoV1 VLPs but not HBoV2 VLPs. Serum IgG antibody cross-reactivity rates of the two subtypes were similar, but cross-reactions of HBoV1 immunization groups were higher. The single i.m. group had more interferon-γ-secreting splenocytes. These data indicate that HBoV VP2 VLPs have good immunogenicity with induction of strong humoral and cellular immune responses, and they may be potential candidate vaccines for HBoV infection.

Characterization of the allergenic potential of proteins: an assessment of the kiwifruit allergen actinidin

Assessment of the potential allergenicity (IgE-inducing properties) of novel proteins is an important challenge in the overall safety assessment of foods. Resistance to digestion with pepsin is commonly measured to characterize allergenicity, although the association is not absolute. We have previously shown that specific IgE antibody production induced by systemic [intraperitoneal (i.p.)] exposure of BALB/c strain mice to a range of proteins correlates with allergenic potential for known allergens. The purpose of the present study was to explore further the utility of these approaches using the food allergen, actinidin. Recently, kiwifruit has become an important allergenic foodstuff, coincident with its increased consumption, particularly as a weaning food. The ability of the kiwifruit allergen actinidin to stimulate antibody responses has been compared with the reference allergen ovalbumin, and with the non-allergen bovine haemoglobin. Haemoglobin was rapidly digested by pepsin whereas actinidin was resistant unless subjected to prior chemical reduction (reflecting intracellular digestion conditions). Haemoglobin stimulated detectable IgG antibody production at relatively high doses (10%), but failed to provoke detectable IgE. In contrast, actinidin was both immunogenic and allergenic at relatively low doses (0.25% to 1%). Vigorous IgG and IgG1 antibody and high titre IgE antibody responses were recorded, similar to those provoked by ovalbumin. Thus, actinidin displays a marked ability to provoke IgE, consistent with allergenic potential. These data provide further encouragement that in tandem with analysis of pepsin stability, the induction of IgE after systemic exposure of BALB/c strain mice provides a useful approach for the prospective identification of protein allergens.

Recognition of the major cat allergen Fel d 1 through the cysteine-rich domain of the mannose receptor determines its allergenicity

Dendritic cells are professional antigen-presenting cells that are specialized in antigen uptake and presentation. Allergy to cat has increased substantially in recent years and has been shown to be positively associated with asthma. We have recently shown that the mannose receptor (MR), a C-type lectin expressed by dendritic cells, recognizes various glycoallergens from diverse sources and is involved in promoting allergic responses to a major house dust mite allergen in vitro. Here we investigated the potential role of MR in allergic responses to Fel d 1, a major cat allergen. Fel d 1 binding to MR was confirmed by ELISA. Using blocking, gene silencing (siRNA) experiments, and MR knock-out (MR(-/-)) cells, we have demonstrated that MR plays a major role in internalization of Fel d 1 by human and mouse antigen-presenting cells. Intriguingly, unlike other glycoallergens, recognition of Fel d 1 by MR is mediated by the cysteine-rich domain, which correlates with the presence of sulfated carbohydrates in natural Fel d 1. WT and MR(-/-) mice were used to study the role of MR in allergic sensitization to Fel d 1 in vivo. MR(-/-) mice sensitized with cat dander extract and Fel d 1 produced significantly lower levels of total IgE, Fel d 1-specific-IgE and IgG1, the hallmarks of allergic response, compared with WT mice. Our data show for the first time that Fel d 1 is a novel ligand of the cysteine-rich domain of MR and that MR is likely to play a pivotal role in allergic sensitization to airborne allergens in vivo.

Allergotoxicology: Research of Pollutant Influence on the Development of Allergic Reactions

Alergotoksikologija je znanstvenoistraživačko područje koje se bavi ispitivanjem utjecaja polutanata (onečišćivača zraka) na nastanak alergijskih reakcija i bolesti. Ispitivanja su prvobitno bila usmjerena na polutante vanjskih prostora, a u novije vrijeme sve više na polutante unutarnjih prostora u kojima ljudi provode većinu vremena. Polutanti po svojoj prirodi mogu biti krute, tekuće ili plinovite čestice, koje se razlikuju s obzirom na veličinu, sastav i izvor iz kojeg nastaju. S obzirom na izvor mogu biti biološkog i nebiološkog podrijetla. Polutanti koji su predmet suvremenih istraživanja s gledišta nastanka alergijskih bolesti su respirabilne krute čestice, ozon, dušični oksidi i bioaerosoli. Mehanizam djelovanja polutanata ovisi o veličini čestica, njihovoj topljivosti i mjestu ulaska u organizam. Dosadašnja ispitivanja su pokazala da različite čestice uvjetuju različite imunosne i neimunosne odgovore u organizmu. Interakcija polutanata i alergena može se zbivati izvan eksponirane osobe, tj. sa samim alergenom ili u eksponiranoj osobi na sluznicama i koži. Polutanti mogu biti nosioci alergena i mogu interferirati na različitim nivoima u nastanku alergijske reakcije. U ovom prikazu razmatraju se dosadašnja saznanja o mehanizmima djelovanja polutanata na alergene, na imunosni sustav izloženih osoba na osnovi epidemioloških populacijskih istraživanja, kliničkih studija ekspozcije u kontroliranim uvjetima i eksperimentalnih testnih sistema in vivo i in vitro.

A draining lymph node assay (DLNA) for assessing the sensitizing potential of proteins

There is a need for a simple and predictive model to identify the respiratory sensitization potential of (novel) proteins. The present study examined the use of a mouse draining lymph node assay (DLNA) approach, employing several routes of exposure, as a possible starting point for assessing protein sensitization potential. Consistent with the experimental procedure for the standard local lymph node assay (LLNA), female BALB/c mice were dosed dermally (topical), intranasally (IN) or by oropharyngeal aspiration (OP) on days 1, 2 and 3, and proliferation in the relevant draining lymph nodes was measured on day 6. For each route, the auricular, superficial cervical and tracheobronchial lymph nodes (TBLN) were evaluated following treatment with Subtilisin Carlsberg (SUB; a potent sensitizer/allergen), ovalbumin (OVA; a potent food allergen), beta-lactoglobulin (BLG; a moderate food allergen), and keyhole limpet hemocyanin (KLH; a strong immunogen with no reports of respiratory sensitization). Initial studies with OVA indicated that dermal administration did not stimulate lymph node proliferation. Responses in the tracheobronchial lymph node were most dramatic (stimulation indices up to 100) and reproducible for both the IN and OP routes. In a comparative experiment, all proteins induced lymph node proliferation with a rank order potency of SUB>KLH>OVA>BLG. The influence of the endotoxin content on lymph node proliferation was determined to be minimal, and did not impact the rank order potency. Molecular characterization of the TBLN at an equipotent proliferative dose was conducted for select gene transcripts based on research examining chemical sensitizers. Expression profiles differed among the four proteins, but the relevance of these responses was not clear and they did not further discriminate their allergic potential. These data illustrate both the opportunities and challenges associated with the examination of the draining lymph node proliferative response to assess the allergenic potential of proteins.

TLR4-mediated signaling induces MMP9-dependent cleavage of B cell surface CD23

IgE production is inversely regulated by circulating and B cell surface levels of the low affinity IgE receptor, CD23. To begin to understand physiologic determinants of CD23 expression, we analyzed effects of BCR and TLR stimulation on CD23 levels. BCR and TLR 2, 3, 4, 6, and 9 agonists induced CD23 down-modulation from the cell surface. However, among the ligands only TLR4 agonists induced transcriptional activation of CD23 and generation of significant soluble CD23. These responses were induced by LPS both in vitro and in vivo, and were seen in both murine and human B cells. LPS also induced expression of matrix metalloprotease 9 (MMP9) and failed to induce CD23 cleaving activity in MMP9(-/-) cells, thus implicating MMP9 in the LPS-induced release of CD23 from the cell surface. Finally, type 1 transitional B cells uniquely produce MMP9 in response to LPS, suggesting a mechanism wherein endotoxin induces T1 cell expression of MMP9, which mediates cleavage of CD23 on distinct, mature B cells.

Early-life co-administration of cockroach allergen and endotoxin augments pulmonary and systemic responses

BACKGROUND

Environmental exposures to cockroach allergen and endotoxin are recognized epidemiological risk factors for the early development of allergies and asthma in children. Because of this, it is important to examine the role of early-life concurrent inhalation exposures to cockroach allergen and endotoxin in the pathogenesis of allergic airways disease.

OBJECTIVE

We examined the effects of repeated concomitant endotoxin and cockroach allergen inhalation on the pulmonary and systemic immune responses of newborn and juvenile mice.

METHODS

C3H/HeBFeJ mice were exposed to inhaled endotoxin and cockroach allergen via intranasal instillation from day 2 to 21 after birth, and systemic and pulmonary responses were examined in serum, bronchoalveolar lavage fluid, and lung tissue.

RESULTS

Cockroach allergen exposures induced pulmonary eosinophilic inflammation, total and allergen-specific IgE, IgG(1), and IgG(2a) production, and alveolar remodelling. Co-exposures with endotoxin and cockroach allergen significantly increased serum IgE and IgG(1), lung inflammation, and alveolar wall thickness, and decreased airspace volume density. Importantly, compared with exposures with individual substances, the responses to co-exposures were more than additive.

CONCLUSIONS

Repeated inhalation exposures of neonatal and juvenile mice to endotoxin and cockroach allergen increased the pulmonary inflammatory and systemic immune responses in a synergistic manner and enhanced alveolar remodelling in the developing lung. These data underscore the importance of evaluating the effect of multiple, concurrent environmental exposures, and of using an experimental model that incorporates clinically relevant timing and route of exposures.

ADAM10-mediated E-cadherin release is regulated by proinflammatory cytokines and modulates keratinocyte cohesion in eczematous dermatitis

Acute eczema is an inflammatory skin disease characterized by the formation of small intraepidermal blisters, reduction of the adhesion molecule E-cadherin from the keratinocyte surface, and impaired keratinocyte cohesion. Here, we reveal that the disintegrin and metalloprotease ADAM10 is critically involved in regulating E-cadherin cell-surface expression in cultured primary human keratinocytes and in diseased human skin. Proinflammatory cytokines, transforming growth factor-beta, and lipopolysaccharide led to increased release of soluble E-cadherin by activating mitogen-activated protein kinase signaling in cultured keratinocytes. Moreover, these stimuli decreased the amount of pro-ADAM10 and increased the level of the active protease, leading to loss of E-cadherin from the cell surface and decreased keratinocyte cohesion. In situ examination and immunoblot analyses of E-cadherin and ADAM10 expression in lesional skin of eczema revealed that the reduction of E-cadherin expression in areas of blister formation closely correlated with increased level of ADAM10 expression and elevated E-cadherin shedding. Our data suggest that ADAM10-mediated E-cadherin proteolysis leads to the impaired cohesion of keratinocytes observed in eczematous dermatitis and provide previously unreported insights into the understanding of the molecular mechanisms involved in inflammatory diseases with loss in epithelial integrity.

Allergy adjuvant effect of particles from wood smoke and road traffic

There is growing evidence that in addition to augmenting the severity of asthma and allergic diseases, particulate air pollution also increases the incidence of allergy and asthma. We studied the adjuvant effect of particles from wood smoke and road traffic on the immune response to the allergen ovalbumin (OVA). OVA with and without particles was injected into one hind footpad of Balb/cA mice. All particles together with OVA significantly increased the level of OVA-specific immunoglobulin E (IgE) in serum, compared to groups given OVA or particles alone. Reference diesel exhaust particles (DEP) with OVA induced the highest levels of IgE, whereas no clear difference was observed between particles from road traffic and wood smoke. Road traffic particles collected in the autumn induced higher IgE values with OVA than corresponding particles collected during the winter season when studded tires are used, suggesting that studded tire-generated road pavement particles have less allergy adjuvant activity than exhaust particles. Compared to OVA or particles alone, all particles with OVA increased popliteal lymph node cell numbers, cell proliferation, ex vivo secretion of IL-4 and IL-10 after ConA stimulation, and the expression of several cell surface molecules (CD19, MHC class II, CD86 and CD23). Wood smoke particles with OVA induced somewhat higher cellular responses than road traffic particles, but less than DEP with OVA which seemed to be the most potent particle in inducing cellular as well as antibody responses. Thus, wood smoke particles had about the same capacity to enhance allergic sensitization as road traffic particles, but less than diesel exhaust particles.

Gut microbiota and development of atopic eczema in 3 European birth cohorts

BACKGROUND

Stimulation of the immune system by gut microbes might prevent allergy development.

OBJECTIVE

The present study examined the hypothesis that sensitization to food allergens and atopic eczema are influenced by the infantile intestinal colonization pattern.

METHODS

Infants were recruited perinatally in Göteborg (n = 116), London (n = 108), and Rome (n = 100). Commensal bacteria were identified to the genus or species level in rectal (3 days) and quantitative stool cultures (7, 14, and 28 days and 2, 6, and 12 months of age). At 18 months of age, atopic eczema and total and food-specific IgE levels were assessed. These outcomes were modeled in relation to time to colonization with 11 bacterial groups and to ratios of strict anaerobic to facultative anaerobic bacteria and gram-positive to gram-negative bacteria at certain time points. Study center, mode of delivery, parity, and infant diet were included as covariates.

RESULTS

Neither atopic eczema nor food-specific IgE by 18 months of age were associated with time of acquisition of any particular bacterial group. Cesarean section delayed colonization by Escherichia coli and Bacteroides and Bifidobacterium species, giving way to, for example, Clostridium species. Lack of older siblings was associated with earlier colonization by Clostridium species and lower strict anaerobic/facultative anaerobic ratio at 12 months.

CONCLUSIONS

This study does not support the hypothesis that sensitization to foods or atopic eczema in European infants in early life is associated with lack of any particular culturable intestinal commensal bacteria.

CLINICAL IMPLICATIONS

The nature of the microbial stimulus required for protection from allergy remains to be identified.

Oral bacterial lipopolysaccharide acts in mice to promote sensitisation to ovalbumin and to augment anaphylaxis via platelets

Microbial infection is thought to modulate allergic disorders, and we previously demonstrated that not only mast cells (which release histamine), but also platelets are involved in the anaphylaxis induced in mice sensitised to ovalbumin (OVA). Here, we examined the effects of a lipopolysaccharide (LPS) from the oral bacterium Prevotella intermedia (Pi) on OVA-induced anaphylaxis. Upon intraperitoneal co-injection of Pi-LPS plus OVA into BALB/c mice, the Pi-LPS displayed a potent adjuvant effect comparable to that of alum (a standard adjuvant) in terms of its abilities to induce both anaphylactic shock and histamine-release following an antigen (OVA)-challenge. Moreover, an injection of Pi-LPS given to OVA+alum-sensitised mice shortly before an OVA-challenge augmented the shock-response. This LPS-pretreatment did not affect histamine-release, but did augment pulmonary platelet accumulation. Histamine was not by itself causal for shock-induction in sensitised mice. These results suggest that oral bacteria and/or their constituents (such as LPS) may help to sensitise the host to an antigen or exacerbate the host's allergic reactions ("aggravation effect"), probably by enhancing the platelet response to the antigen OVA.

Popliteal lymph node (PLN) assay to study adjuvant effects on respiratory allergy

Different variants of the popliteal lymph node (PLN) assay have been published. Here we describe the adjuvant popliteal lymph node assay, an immune response assay to study the adjuvant activity of soluble substances as well as particulate matter. The substance to be studied for adjuvant activity is injected into the hind footpad of mice or rats together with an antigen. Adjuvant activity is determined as the increase in PLN weight and cell numbers in animals receiving antigen together with the substance under study, compared with PLN weight and cell numbers in animals given the antigen without the substance in question, and animals given the putative adjuvant alone. Because lymph node weight and cell numbers are immunologically non-specific parameters, specific immune response assays like serum antibody responses or antibody-forming cell numbers should additionally be performed. Different antigens and immune response assays may be used, depending on the research question asked. In relation to respiratory (or food) allergy, the assays should as a minimum include determination of specific IgE in serum, and preferably also IgG1 (mouse). Serum specific IgG2a antibody determination may be added to get an indication of the Th1-Th2-balance of the response. The adjuvant PLN assay, with cellular response assays performed in the draining popliteal lymph node and antibody determinations in serum, requires small amounts of test material. The assay offers a practical, sensitive and reproducible method to determine the adjuvant activity of soluble substances as well as particulate material, with the possibility to also perform mechanistic studies.

The fungal biopesticide Metarhizium anisopliae has an adjuvant effect on the allergic response to ovalbumin in mice

The parasitic fungus, Metarhizium anisopliae, is non-pathogenic to humans and licensed for indoor control of cockroach infestation. An important reason for the elimination of this vermin is that sensitisation to cockroaches is associated with asthma. Previously M. anisopliae has been shown to cause allergic- and asthma-like responses in mice and in the present study we have examined the adjuvant activity of M. anisopliae on the allergic response to the model allergen ovalbumin (OVA) in a mouse model. Levels of OVA-specific IgE, IgG1 and IgG2a in serum were measured and the weight and cell number of the excised popliteal lymph node were determined. Mice primed with mycelium+OVA and boosted with OVA had increased anti-OVA IgE and IgG1 levels compared with mice primed with OVA alone or mycelium. Priming with M. anisopliae (as mycelium or MACA) increased weight or cell number of the excised PLNs. These results suggest that M. anisopliae has the ability to increase an allergic response to an allergen and consequently, may worsen allergy in susceptible individuals.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

Molecular and cellular targets of anti-IgE antibodies

Immunoglobulin E (IgE) was the last of the immunoglobulins discovered. It is present in very low amounts (nano- to micro-gram per ml range) in the serum of normal healthy individuals and normal laboratory mouse strains and has a very short half-life. This contrasts with the other immunoglobulin classes, which are present in much higher concentrations (micro- to milligram per ml range) and form a substantial component of serum proteins. Immunoglobulins play a role in homeostatic mechanisms and they represent the humoral arm of defence against pathogenic organisms. Since IgE antibodies play a key role in allergic disorders, a number of approaches to inhibit IgE antibody production are currently being explored. In the recent past the use of nonanaphylactic, humanized anti-IgE antibodies became a new therapeutic strategy for allergic diseases. The therapeutic rational beyond the idea derives from the ability of the anti-IgE antibodies to bind to the same domains on the IgE molecule that interact with the high-affinity IgE receptor, thereby interfering with the binding of IgE to this receptor without cross-linking the IgE on the receptor (nonanaphylactic anti-IgE antibodies). Treatment with anti-IgE antibodies leads primarily to a decrease in serum IgE levels. As a consequence thereof, the number of high-affinity IgE receptors on mast cells and basophils decreases, leading to a lower excitability of the effector cells reducing the release of inflammatory mediator such as histamine, prostaglandins and leukotrienes. Experimental studies in mice indicate that injection of some monoclonal anti-IgE antibodies also inhibited IgE production in vivo. The biological mechanism behind this reduction remains speculative. A possible explanation may be that these antibodies can also interact with membrane bound IgE on B cells, which could interfere the IgE production.

Hygiene hypothesis and endotoxin: what is the evidence?

PURPOSE OF REVIEW

The hygiene hypothesis has gained strong support over the past few years. Exposure to microbial products in early life could be an underlying factor in this hypothesis, but the mechanisms that lead from a less clean and more crowded environment to a lower prevalence of asthma and allergies are not known. Among the variety of potential microbial molecules that may confer protection against the development of asthma and allergies, endotoxin, a component of Gram-negative bacteria, has incited lively as well as controversial discussions. This review focuses on recent studies on endotoxin and its role in the context of the hygiene hypothesis.

RECENT FINDINGS

Results from cross-sectional surveys, prospective cohorts, and experimental studies in vitro and in rodents suggest that exposure to house dust endotoxin in early life protects from atopic sensitization and IgE-mediated diseases, but is a risk factor for wheezing in infancy.

SUMMARY

Numerous studies have supported the hygiene hypothesis, but whether endotoxin by itself confers the protection or whether it acts as a marker for another environmental exposure is still unclear. The challenge for the future will be to identify those factors that confer the protection proposed by the hygiene hypothesis, and to find strategies to modify the environment without causing harm to susceptible individuals.

Respiratory allergy adjuvant and inflammatory effects of urban ambient particles

PM(10) and PM(2.5) fractions were collected by high-volume cascade impactors during 4-week periods in spring, summer and winter seasons in Amsterdam, Lodz, Oslo and Rome and at a Dutch seaside site. The samples were screened for respiratory allergy potential with the mouse popliteal lymph node (PLN) and the ELISA-based IgE antibody assays. For inflammatory screening, release of the cytokine macrophage inflammatory protein-2 (MIP-2) from primary rat type 2 cells was determined. Most fractions gave an increase in the lymph node response with the model allergen ovalbumin indicating adjuvant activity. Some of the coarse fractions gave a lymph node response even in the absence of ovalbumin, caused probably by non-specific inflammation. With the exception of a few of the coarse fractions, all ambient fractions increased the production of specific IgE. Fine particles had stronger adjuvant effect than coarse particles. A significant increase in the allergen specific IgG2a response was observed for the fine and some of the coarse fractions, indicating a non-allergic Th1 response. No consistent differences in adjuvant effects between the locations were observed. Particle samples collected in the different European cities differed in their potency to induce MIP-2 in type 2 cells. Coarse fractions of the urban particles samples, as well as the coarse fraction collected at the seaside, were more potent than the fine fractions to induce MIP-2. With respect to seasonal variations, the coarse fractions collected in summer seemed to be the most potent.

Enhanced inflammatory responses in alpha-tocopherol transfer protein null mice

The liver preferentially secretes alpha-tocopherol into plasma under the control of the hepatic alpha-tocopherol transfer protein (alpha-TTP). alpha-TTP-null mice (Ttpa(-/-) mice) are vitamin E deficient, therefore were used for investigations of in vivo responses to sub-normal tissue alpha-tocopherol concentrations during inflammation. Increased basal oxidative stress in Ttpa(-/-) mice was documented by increased plasma lipid peroxidation, and superoxide production by bone marrow-derived neutrophils stimulated in vitro with phorbol 12-myristate 13-acetate. Lipopolysaccharide (LPS) injected intraperitoneally induced increases in lung and liver HO-1 and iNOS, as well as plasma NO(x) in Ttpa(+/+) mice. LPS induced more modest increases in these markers in Ttpa(-/-) mice, while more marked increases in plasma IL-10 and lung lavage TNF alpha were observed. Taken together, these results demonstrate that alpha-tocopherol is important for proper modulation of inflammatory responses and that sub-optimal alpha-tocopherol concentrations may derange inflammatory-immune responses.