Phenological changes in olive (Ola europaea L.) reproductive cycle in southern Spain due to climate change

INTRODUCTION

Modifications of crop species phenology due to a changing environment are of interest because of their impact on fruit set and final harvest. Pre-flowering and flowering phenophases in olive groves at different sites of southern Spain were examined, in order to chart potential trends and determine major correlations with weather-related parameters, especially temperature and water availability. The high prevalence of olive pollen allergy in the Mediterranean population makes this study highly relevant.

MATERIALS AND METHODS

Ten sites in Cordoba province (Spain) during a 17-year period (1996-2012). BBCH phenology scale. Meteorological data from 1960 were analyzed; data from 1996 included on modeling analysis. Linear Mixed Models (LMMs) were developed, combining phenological and meteorological data.

RESULTS

Since 1960, local spring temperatures have increased 1.5ºC, the number of spring rainfall days has fallen 11 days, total rainfall has declined 150 mm. Despite phenological differences between sites, attributable to altitude, phenological development during the season followed a similar pattern. Flowering dates advanced 2 days, while inflorescence emergence was delayed 24 days. Trend slopes revealed differences, an earlier period (1996-2002) with a sharp flowering advance of 15 days, and a later period (2003-2012) characterized by a gradual advance and a high bud emergence delay of 22 days.

CONCLUSIONS

LMMs was revealed as an appropriate technique for phenology behaviour analysis displaying both fixed and random interactions. Cultivars grown in the study province are adapted to climate with a synchronized response, although climate change is affecting theolive reproductive cycle in southern Spain; therefore, the timing of pollen release, with subsequent consequences on allergic population as phenological changes, could have impacts on flowering period and pollen production. Further investigation is required of the implications for crop production in Mediterranean ecosystems.

[Clustering Sugi-pollen dispersal patterns for the past 26 years]

BACKGROUND

Pollinosis caused by the pollen of Sugi (Cryptopmeria japonica) trees is the most significant allergic disease occurring in the spring in Japan. For pollinosis patients and medical staff, it is important to know when the pollen dispersion would reach maximum or when the pollen count would decrease as well as knowing what would the total density of pollen grains be. These sorts of information could be useful for the purpose of disease prevention and deciding on the therapeutic regimen. In this study, we presented the sugi-dispersal patterns and cited several examples of the dispersal pattern.

METHODS

Airborne pollen grains were collected using a Durham sampler. Total annual pollen counts/cm2 were examined. The sugi-dispersal patterns were classified into several groups by cluster analysis using variables of ten days pollen counts distribution from February to April for the past 26 years. (1987-2012).

RESULT

The annual pollen count revealed an alternate rhythm consisting of an "on" year (high pollen count) and an "off" year (low pollen count). The results of the cluster analysis showed eleven off-years classified as one group (group 1), and fifteen on-years classified into three groups (groups 2A, 2B, and 2C). The dispersal pattern in group 1 was almost symmetrical with the pollen count rapidly decreasing until late-March. On the other hand, the patterns in group 2 were asymmetrical. In group 2A and 2B a high rate of dispersion was indicated after maximum dispersion, whereas in group 2C the high rate of dispersion was indicated before maximum dispersion. In group 2A, a major dispersion of almost 3000 grains was noted in late-March, and immediately proceeded to the cypress (Chamaecyparis) pollen season without any decrease seen in pollen dispersion. The periods of dispersion of over 10 pollen grains/cm2 per day were 38, 47, 47 and 51 days in groups 1, 2A, 2B and 2C, respectively. That in group 2 was significantly longer than that in group 1, but there was no significant differences between groups 2A, 2B and 2C.

CONCLUSION

In conclusion, in the dispersal pattern whereby a major dispersion was seen in late-March and proceeded to the cypress pollen season such as in group 2A, patients' symptoms might be prolonged or be more serious. This new concept of dispersal pattern could very well be useful for clinical management of pollinosis.

Wind-pollination and the roles of pollen allergenic proteins

Over the past few decades, there has been an explosion of understanding of the molecular nature of major allergens contained within pollens from the most important allergenic plant species. Most major allergens belong to only a few protein families. Protein characteristics, cross-reactivity, structures, and IgE binding epitopes have been determined for several allergens. These efforts have led to significant improvements in specific immunotherapy, yet there has been little discussion about the physiological functions of these proteins. Even with large amounts of available information about allergenic proteins from pollens, the incidence of pollen allergy continuously increases worldwide. The reason for this increase is unclear and is most likely due to a combination of factors. One important culprit might be a change in the pollen itself. Knowledge about pollen biology and how pollen is changing as a result of more extreme environmental conditions might improve our understanding of the disease. This review focuses on the characteristics of plants producing allergenic pollens that are relevant to pollen allergy, including the phylogenetic relationships, pollen dispersal distances, amounts of pollen produced, amounts of protein in each type of pollen, and how allergenic proteins are released from pollens. In addition, the physiological roles of major allergenic protein families will be discussed to help us understand why some of these proteins become allergens and why GMO plants with hypoallergenic pollens may not be successful.

Ragweed pollen observed in Turkey: detection of sources using back trajectory models

This paper discusses the pollen season and the source apportionment of ragweed (Ambrosia) grains detected in the atmosphere of Istanbul, Turkey. The dynamic migration of this invasive taxon is a serious environmental issue. Ragweed pollen is highly allergenic and causes sensitization in patients at low concentrations. At present, there is no floristic evidence of this taxon in the region. Aerobiological records presented here, though, indicate a local source. Moreover, we argue that ragweed pollen comes from distant sources through air mass movements. The analysis concerns the ragweed season 2007. Pollens were sampled with a Burkard trap and identified at a magnification of 400 ×. Grains were counted on 12 transverse traverses to estimate bi-hourly changes in concentrations. The peak day was on August 28 with 20 grainsm(-3). Ragweed was observed on 22 days during August and September 2007. On all days, except one, the daily average concentration was below 10 grainsm(-3). Diurnal bi-hourly ragweed concentrations reached a maximum at 11:00 EET. Relatively high concentrations were observed between 21:00 and 01:00 EET. This allowed for the assumption of a local and a remote ragweed pollen source. We used HYSPLIT backward trajectory ensembles to identify possible sources on peak day. A frequency analysis of back trajectories covering the entire ragweed season followed. Firstly, possible local sources were the Istanbul Province and Turkish Thrace; secondly, a likely over-regional source was Bulgaria; and lastly, remote sources of ragweed pollen were the Ukraine, the Russian coastal region of the Black Sea and Moldova. This study provides evidence that pollens detected on our receptor site stem from combined local and remote origins.

In vitro exposure of Acer negundo pollen to atmospheric levels of SO₂ and NO₂: effects on allergenicity and germination

In the last years, a rising trend of pollen allergies in urban areas has been attributed to atmospheric pollution. In this work, we investigated the effects of SO(2) and NO(2) on the protein content, allergenicity, and germination rate of Acer negundo pollen. A novel environmental chamber was assembled to exposure pollen samples with SO(2) or NO(2) at two different levels: just below and two times the atmospheric hour-limit value acceptable for human health protection in Europe. Results showed that protein content was lower in SO(2)-exposed pollen samples and slightly higher in NO(2)-exposed pollen compared to the control sample. No different polypeptide profiles were revealed by SDS-PAGE between exposed and nonexposed pollen, but the immunodetection assays indicated higher IgE recognition by all sera of sensitized patients to Acer negundo pollen extracts in all exposed samples in comparison to the nonexposed samples. A decrease in the germination rate of exposed in contrast to nonexposed pollen was verified, which was more pronounced for NO(2)-exposed samples. Our results indicated that in urban areas, concentrations of SO(2) and NO(2) below the limits established for human protection can indirectly aggravate pollen allergy on predisposed individuals and affect plant reproduction.

Strain differences influence N-methyl-D-aspartate receptor subunit gene expression in the olfactory bulb of an allergic mouse model following toluene exposure

OBJECTIVE

Genetic variation is a causative factor in differing sensitivities to environmental chemicals. The present study explored whether differences in mouse strains influence N-methyl-D-aspartate (NMDA) receptor expression in the olfactory bulb after low-level toluene exposure.

METHODS

Ten-week-old male C3H/HeN (H-2(k)), BALB/c (H-2(d)) and C57BL/10 (H-2(b)) mice were exposed to 0, 5, 50 or 500 ppm of toluene for 6 h per day, 5 days per week for 6 weeks. Because individuals with allergic disease are more susceptible to volatile organic compound exposure, the animals of each strain were divided into 2 main groups, a non-allergy (NAG) group and an allergy (AG) group. The AG groups were stimulated with ovalbumin before toluene exposure. The mRNA levels of NMDA receptor subunits (NR1, NR2A and NR2B) in the olfactory bulbs of the NAG and AG groups were examined using real-time RT-PCR.

RESULTS

In C3H/HeN mice, the expression levels of NR1 and NR2B mRNA decreased significantly in the AG group exposed to 500 ppm of toluene; in the NAG group, however, the NR2A mRNA level increased significantly in mice exposed to 50 ppm while the NR2A and NR2B mRNA levels decreased significantly in mice exposed to 500 ppm of toluene. No significant changes were observed in the NAG groups of BALB/c or C57BL/10 mice. However, in the BALB/c mice, the mRNA levels of NR1, NR2A and NR2B decreased significantly in the AG group exposed to 500 ppm of toluene.

CONCLUSION

Mammalian strain differences in NMDA receptor expression after allergic stimulation can be observed in the mouse olfactory bulb after toluene exposure.

RNA interference-mediated knock-down of Bla g 1 in the German cockroach, Blattella germanica L., implicates this allergen-encoding gene in digestion and nutrient absorption

We used RNA interference (RNAi) to silence the expression of a gene encoding Bla g 1, a human allergen produced by the German cockroach, Blattella germanica L., to study its function in cockroach physiology. Females injected with 1 microg of double-stranded RNA contained 64% less Bla g 1 protein and Bla g 1 mRNA abundance was reduced by 91.4% compared to sham-injected females. Bla g 1 knockdown slowed the pace of weight gain, midgut growth, and colleterial gland and basal oocyte maturation, resulting in delayed egg case formation and lower fecundity. Exogenous juvenile hormone treatments rescued reproduction in RNAi-treated females, suggesting that Bla g 1 silencing lowered endogenous juvenile hormone, probably by reducing food intake and nutrient absorption.

The RNA hydrolysis and the cytokinin binding activities of PR-10 proteins are differently performed by two isoforms of the Pru p 1 peach major allergen and are possibly functionally related

PR-10 proteins are a family of pathogenesis-related (PR) allergenic proteins playing multifunctional roles. The peach (Prunus persica) major allergen, Pru p 1.01, and its isoform, Pru p 1.06D, were found highly expressed in the fruit skin at the pit hardening stage, when fruits transiently lose their susceptibility to the fungal pathogen Monilinia spp. To investigate the possible role of the two Pru p 1 isoforms in plant defense, the recombinant proteins were expressed in Escherichia coli and purified. Light scattering experiments and circular dichroism spectroscopy showed that both proteins are monomers in solution with secondary structures typical of PR-10 proteins. Even though the proteins do not display direct antimicrobial activity, they both act as RNases, a function possibly related to defense. The RNase activity is different for the two proteins, and only that of Pru p 1.01 is affected in the presence of the cytokinin zeatin, suggesting a physiological correlation between Pru p 1.01 ligand binding and enzymatic activity. The binding of zeatin to Pru p 1.01 was evaluated using isothermal titration calorimetry, which provided information on the stoichiometry and on the thermodynamic parameters of the interaction. The structural architecture of Pru p 1.01 and Pru p 1.06D was obtained by homology modeling, and the differences in the binding pockets, possibly accounting for the observed difference in binding activity, were evaluated.

Allergens are distributed into few protein families and possess a restricted number of biochemical functions

BACKGROUND

Existing allergen databases classify their entries by source and route of exposure, thus lacking an evolutionary, structural, and functional classification of allergens.

OBJECTIVE

We sought to build AllFam, a database of allergen families, and use it to extract common structural and functional properties of allergens.

METHODS

Allergen data from the Allergome database and protein family definitions from the Pfam database were merged into AllFam, a database that is freely accessible on the Internet at http://www.meduniwien.ac.at/allergens/allfam/. A structural classification of allergens was established by matching Pfam families with families from the Structural Classification of Proteins database. Biochemical functions of allergens were extracted from the Gene Ontology Annotation database.

RESULTS

Seven hundred seven allergens were classified by sequence into 134 AllFam families containing 184 Pfam domains (2% of 9318 Pfam families). A random set of 707 sequences with the same taxonomic distribution contained a significantly higher number of different Pfam domains (479 +/- 17). Classifying allergens by structure revealed that 5% of 3012 Structural Classification of Proteins families contained allergens. The biochemical functions of allergens most frequently found were limited to hydrolysis of proteins, polysaccharides, and lipids; binding of metal ions and lipids; storage; and cytoskeleton association.

CONCLUSION

The small number of protein families that contain allergens and the narrow functional distribution of most allergens confirm the existence of yet unknown factors that render proteins allergenic.

Elevated allergen-induced IL-13 secretion predicts IgE elevation in children ages 2-5 years

It is unclear if early immune responses to allergens, specifically Th1 and Th2 cytokine production, predict later immune responses, including increased IgE levels. In a group of children (n = 151) with a parental history of allergy or asthma followed from ages 2 through 5 years, we examined IL-13, IL-4, and IFN-gamma secretion by peripheral blood mononuclear cells in response to phytohemagglutinin (PHA), and to dust mite (Der f 1), cockroach (Bla g 2), and cat (Fel d 1) allergens in relation to elevated IgE. Elevated IgE was defined either as a positive IgE-specific response to at least one allergen (dust mite, cockroach, cat, and ovalbumin) or as an elevated total IgE level above a specified cut-off value. In multivariate logistic regression models including 181 observations made between the age of 2 through 5 years and accounting for repeated measures, we found an association between increased IL-13 secretion in response to Der f 1 and elevated IgE (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.09-1.34). Age did not modify this relationship. No association was found between allergen-induced IFN-gamma secretion and IgE production. Among the group of children with measurements made at age 4-5 (n = 70), IL-13 in response to Der f 1 (p = 0.046), and IL-4 in response to PHA (p = 0.04) were increased among children with elevated IgE. In a smaller subset of children with measurements made at both age 2-3 and age 4-5 (n = 36), IL-13 levels at age 2-3 were also significantly increased in response to Der f 1 (p = 0.01) and Fel d 1 (p = 0.002) among those with elevated IgE at age 4-5. In a group of children ages 2-5 years, there is an association between IL-13 and elevated IgE.

Protein Fv: an endogenous immunoglobulin superantigen and superallergen

Protein Fv was isolated and purified by Jean Pierre Bouvet and collaborators in 1990 from stool extracts of patients affected by viral hepatitis B or C. This protein was also identified and purified in biological samples in experimental viral hepatitis. Under normal conditions, protein Fv is synthesized in low concentrations by the human liver, and is increased in biological fluids of patients with viral hepatitis. This protein binds with high affinity to the variable domain of the heavy chains of all human immunoglobulins. Thus, it is an endogenous immunoglobulin superantigen because it binds to human immunoglobulin of the VH3 family. This protein also acts as a superallergen because it activates human basophils and mast cells through the high-affinity interaction with IgE VH3+. The mechanism of activation of immune cells by protein Fv represents a new pathogenetic cascade consisting of viral infection, endogenous immunoglobulin superantigen/superallergen production and tissue injury.

Hypoallergenic fragment of Par j 2 increases functional expression of Toll-like receptors in atopic children

BACKGROUND

Parietaria judaica (Par j) is one of the main causes of allergy in the Mediterranean countries. The activation of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) inhibits nasal inflammation of atopic children.

OBJECTIVE

To examine, in vivo and in vitro, the effect of recombinant Par j 2 (rPar j 2) and of its fragments (1-55 and 52-102) on atopic children.

METHODS

We used skin prick test for in vivo evaluations. We assessed, in vitro, in peripheral blood mononuclear cells (PBMC), the effect of rPar j 2 and of the two fragments on neutrophil chemotaxis, on CD45RO, on TLR2 and TLR4 expression, on LPS binding and on interferon (IFN)-gamma release, by a microchemotaxis chamber, by flow cytometry and by enzyme-linked immunosorbent assay, respectively.

RESULTS

In vivo while rPar j 2 induced a positive skin reaction, 1-55 and 52-102 fragments did not. In vitro, while rPar j 2 increased both CD45RO expression and neutrophils chemotaxis in PBMC, both Par j 2 fragments did not. 1-55 fragment of Par j 2 upregulated both TLR2 and TLR4 expression and LPS binding, while the rPar j 2 and 52-102 fragment did not. Finally, 1-55 fragment of Par j 2 induced IFNgamma release, while the rPar j 2 and 52-102 fragment did not.

CONCLUSIONS

Hypoallergenic 1-55 fragment, upregulating innate immunity receptors and increasing IFNgamma, might re-orientate, in atopics, the immune system toward a physiologic balance between Th1 and Th2 responses.

CD48 is an allergen and IL-3-induced activation molecule on eosinophils

Eosinophils are involved in a variety of allergic, parasitic, malignant, and idiopathic disorders by releasing a variety of factors including specific granule proteins, lipid mediators, and proinflammatory and immunoregulatory cytokines and chemokines. In addition, they interact with various cell types in the inflamed tissue. Yet, the mechanism of eosinophil activation is still poorly understood. Recently, we described the expression and function of the CD2-subfamily of receptors and especially 2B4 on human eosinophils. In this study we focus on CD48, the high-affinity ligand of 2B4. CD48 is a GPI-anchored protein involved in cellular activation, costimulation, and adhesion, but has not been studied on eosinophils. We demonstrate that human eosinophils from atopic asthmatics display enhanced levels of CD48 expression and that IL-3 up-regulates CD48 expression. Furthermore, cross-linking CD48 on human eosinophils triggers release of eosinophil granule proteins. Assessment of CD48 expression in a murine model of experimental asthma revealed that CD48 is induced by allergen challenge and partially regulated by IL-3. Additionally, anti-IL-3 reduces CD48 expression and the degree of airway inflammation. Thus, CD48 is an IL-3-induced activating receptor on eosinophils, likely involved in promoting allergic inflammation.

Pulmonary distribution, regulation, and functional role of Trk receptors in a murine model of asthma

BACKGROUND

Neurotrophins have been implicated in the pathogenesis of asthma because of their ability to promote hyperreactivity of sensory neurons and to induce airway inflammation. Hyperreactivity of sensory nerves is one key mechanism of airway hyperreactivity that is defined as an abnormal reactivity of the airways to unspecific stimuli, such as cold air and cigarette smoke. Neurotrophins use a dual-receptor system consisting of Trk receptor tyrosine kinases and the structurally unrelated p75 neurotrophin receptor.

OBJECTIVE

The aim of this study was to characterize the distribution, allergen-dependent regulation, and functional relevance of the Trk receptors in allergic asthma.

METHODS

BALB/c mice were sensitized to ovalbumin. After provocation with ovalbumin or vehicle aerosol, respectively, Trk receptor expression was analyzed in lung tissue by means of fluorescence microscopy and quantitative RT-PCR. To assess the functional relevance of Trk receptors in asthma, we tested the effects of the intranasally administered pan-Trk receptor decoy REN1826. Allergic airway inflammation was quantified and lung function was measured by using head-out body plethysmography.

RESULTS

Trk receptors were expressed in neurons, airway smooth muscle cells, and cells of the inflammatory infiltrate surrounding the bronchi and upregulated after allergen challenge. Local application of REN1826 reduced IL-4 and IL-5 cytokine levels but had no effect on IL-13 levels or the cellular composition of bronchoalveolar lavage fluid cells. Furthermore, REN1826 decreased broncho-obstruction in response to sensory stimuli, indicating a diminished hyperreactivity of sensory nerves, but did not influence airway smooth muscle hyperreactivity in response to methacholine.

CONCLUSION

These results emphasize the important role of Trk receptor signaling in the development of asthma.

CLINICAL IMPLICATIONS

Our data indicate that blocking of Trk receptor signaling might reduce asthma symptoms.

Lipid transfer proteins in Parietaria judaica L. pollen grains: immunocytochemical localization and function

Parietariajudaica L. (Urticaceae) pollen is considered one of the most common causes of allergic respiratory symptoms in the Mediterranean area. The localization of lipid transfer proteins (LTPs) in P. judaica mature and hydrated-activated pollen grains was investigated applying a combination of transmission electron microscopy (TEM) with immunocytochemical methods. Our results show that the content of LTPs in P. judaica pollen grains changes during the process of hydration. The localization of judaica LTPs in the cytoplasm and in the lipid bodies associated with vacuoles demonstrated that LTPs represent primarily intracellular proteins. On the other hand, exposure of the pollen grains to germination medium induced the release of LTPs from the pollen grain. Thus, LTPs are cytoplasmic proteins that are secreted to become available for pollen-stigma interactions and probably induce the IgE antibody responses in allergic patients.

Plasma 9alpha,11beta-PGF2, a PGD2 metabolite, as a sensitive marker of mast cell activation by allergen in bronchial asthma

BACKGROUND

Prostaglandin D(2) (PGD(2)) is a major cyclooxygenase product generated by activated mast cells during an allergic response. Assessment of PGD(2) and its metabolites in patients with asthma has mostly been performed in urine, bronchoalveolar lavage fluid and induced sputum, whereas human plasma determinations have been performed only sporadically.

METHODS

In 32 patients with allergic asthma and 50 healthy non-allergic controls, baseline plasma and urinary levels of 9alpha,11beta-PGF(2), a primary PGD(2) metabolite, were assessed by gas chromatography/mass spectrometry. Serum tryptase levels were measured by fluoroenzyme immunoassay and urinary leukotriene E(4) (LTE(4)) by ELISA. In a subgroup of 10 asthmatics (randomly selected from the 32 study patients) in whom bronchial allergen challenges with specific allergens (Dermatophagoides pteronyssinus, n = 4, mixed grass pollens, n = 6) were carried out, measurements were taken both before and after provocation.

RESULTS

At baseline no significant differences between mean plasma and urinary levels of the PGD(2) metabolite and serum tryptase levels were found in asthmatics or controls. Asthmatic patients had significantly higher urinary LTE(4) levels. Allergen challenge resulted in a significant early increase in the mean plasma 9alpha,11beta-PGF(2) level and only a borderline but significant increase in the urinary 9alpha,11beta-PGF(2) level within 2 hours after provocation. The challenge did not produce statistically significant changes in serum tryptase levels. Urinary LTE(4) levels remained significantly increased 4 hours after provocation.

CONCLUSIONS

PGD(2) is actively involved in the early asthmatic response to allergens. Measurement of 9alpha,11beta-PGF(2) release into plasma rather than urine following allergen challenge is a sensitive marker of enhanced PGD(2) synthesis, most probably due to mast cell activation.

Influences of genetic and environmental factors on the concentration of the allergen Cry j 1 in sugi (Cryptomeria japonica) pollen

Pollen from sugi (Japanese cedar, Cryptomeria japonica D. Don), a forest tree species that is widely grown in Japan, causes serious allergic disease. The major allergens from sugi pollen, Cry j 1 and Cry j 2, have been isolated and characterized. It has been reported that Cry j 1 concentration in pollen varies considerably among trees. If Cry j 1 concentration is genetically controlled, the planting of trees with low Cry j 1 concentrations would reduce pollinosis. We investigated genetic and environmental effects on Cry j 1 concentration in eight clones growing at four sites. Concentrations of Cry j 1 in pollen were measured with a monoclonal antibody-based Enzyme Linked Immunosorbent Assay (ELISA). The Cry j 1 concentrations differed significantly among clones and sites, but the site x clone interaction was not significant, suggesting that the Cry j 1 concentration is controlled primarily by genetic factors. We examined correlations between Cry j 1 concentration and temperature and precipitation from July through February. Temperature was not significantly related to Cry j 1 concentration, whereas cumulative precipitation during the 8 months and mean daily precipitation in September showed significant negative correlations with Cry j 1 concentration.

Are rhinovirus-induced airway responses in asthma aggravated by chronic allergen exposure?

Airway inflammation in asthma may represent a favorable environment for respiratory viral infections, augmenting virus-induced exacerbations in asthma. We postulated that repeated low-dose allergen exposure preceding experimental rhinovirus 16 (RV16) infection increases the severity of RV-induced airway obstruction and inflammation. Thirty-six house dust mite-allergic patients with mild to moderate asthma participated in a three-arm, parallel, placebo-controlled, double-blind study. Patients inhaled a low dose of house dust mite allergen for 10 subsequent working days (Days 1-5 and 8-12) and/or were subsequently infected with RV16 (Days 15 and 16). Allergen exposure resulted in a significant fall in FEV1 (p < 0.001) and provocative concentration of histamine causing a 20% fall in FEV1 (p < 0.001) and an increase in exhaled nitric oxide (p < 0.001) and percentage of sputum eosinophils (p < 0.001). RV16 infection led to a fall in FEV1 (p = 0.02) and increases in the percentage of sputum neutrophils (p = 0.01), sputum interleukin-8 (p = 0.04), and neutrophil elastase (p = 0.04). Successive allergen exposure and RV16 infection had no synergistic or additive effect on any of the clinical or inflammatory outcomes. In conclusion, repeated low-dose allergen exposure and RV16 infection induce distinct inflammatory profiles within the airways in asthma without apparent interaction between these two environmental triggers. This suggests that preceding allergen exposure, at the used dose and duration, is not a determinant of the severity of RV-induced exacerbations in patients with mild to moderate asthma.

Impact of pollen on human health: more than allergen carriers?

The transfer of pollen from floral anther to recipient stigma is the critical reproductive event among higher plants--this is the botanical view of pollen. Proteins and glycoproteins from pollen can function as allergens, environmental molecules interacting with the human immune system to elicit an allergic response in susceptible individuals--this is how allergists and immunologists see pollen grains. Between 10 and 25% of the population now have symptoms of hay fever or allergic asthma and the incidence has more than doubled in the past three decades while the reason(s) for this increment are only hypothetical, but there is a multitude of them. Despite our natural focus on this impact of pollen on human health, pollen have to be considered in a larger context. First of all, to evaluate the bioavailability of allergens from pollen, we have to understand their function and their influence factors. Furthermore, pollen grains are not only releasing proteins eliciting specific immune responses, but they also liberate bioactive lipid mediators and this much more rapidly. And last but not least, recent observations indicate, that pollen do not only induce allergy and thus have a much broader impact on human health. This review is an attempt to favour this holistic view of pollen and their impact on human health.

Molecular characterization and allergenic activity of Lyc e 2 (beta-fructofuranosidase), a glycosylated allergen of tomato

Until now, only a small amount of information is available about tomato allergens. In the present study, a glycosylated allergen of tomato (Lycopersicon esculentum), Lyc e 2, was purified from tomato extract by a two-step FPLC method. The cDNA of two different isoforms of the protein, Lyc e 2.01 and Lyc e 2.02, was cloned into the bacterial expression vector pET100D. The recombinant proteins were purified by electroelution and refolded. The IgE reactivity of both the recombinant and the natural proteins was investigated with sera of patients with adverse reactions to tomato. IgE-binding to natural Lyc e 2 was completely inhibited by the pineapple stem bromelain glycopeptide MUXF (Man alpha 1-6(Xyl beta 1-2)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-3)GlcNAc). Accordingly, the nonglycosylated recombinant protein isoforms did not bind IgE of tomato allergic patients. Hence, we concluded that the IgE reactivity of the natural protein mainly depends on the glycan structure. The amino acid sequences of both isoforms of the allergen contain four possible N-glycosylation sites. By application of MALDI-TOF mass spectrometry the predominant glycan structure of the natural allergen was identified as MMXF (Man alpha 1-6(Man alpha 1-3)(Xyl beta 1-2)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-3) GlcNAc). Natural Lyc e 2, but not the recombinant protein was able to trigger histamine release from passively sensitized basophils of patients with IgE to carbohydrate determinants, demonstrating that glycan structures can be important for the biological activity of allergens.

Allergen-independent maternal transmission of asthma susceptibility

Maternal asthma is a risk factor for development of asthma in children, but mechanisms remain unclear. Offspring of asthmatic mother mice (sensitized and repeatedly exposed to OVA Ag) showed airway hyperresponsiveness and allergic pulmonary inflammation after an intentionally suboptimal OVA sensitization and exposure protocol that had little effect on normal offspring. Similar results were obtained when offspring of OVA-allergic mothers were exposed to an unrelated allergen, casein, indicating that the maternal effect is allergen independent and not transferred by OVA-specific Abs. Premating treatment with neutralizing anti-IL-4 Ab or reduction of maternal allergen exposure abrogated the maternal effect, showing a critical mechanistic role for IL-4 and suggesting an additional benefit of allergen avoidance.

The C-terminal segment of the 1,3-beta-glucanase Ole e 9 from olive (Olea europaea) pollen is an independent domain with allergenic activity: expression in Pichia pastoris and characterization

Several allergenic proteins, such as the 1,3-beta-glucanases, have been associated with plant defence responses. Ole e 9 (46 kDa) is a 1,3-beta-glucanase and major allergen from olive pollen, which is a principal cause of allergy in Mediterranean countries. Its C-terminal segment (101 amino acid residues) has been produced as a recombinant polypeptide in the yeast Pichia pastoris. The cDNA encoding the polypeptide was inserted into the plasmid vector pPICZalpha-A and overexpressed in KM71 yeast cells. The recombinant product was purified by size-exclusion chromatography followed by reversed-phase HPLC. Edman degradation, MS and CD were used to determine molecular properties of the recombinant polypeptide, which exhibited 16% alpha-helix and 30% beta-sheet as regular elements of secondary structure. Disulphide bridges of the molecule were determined at positions Cys-14-Cys-76, Cys-33-Cys-94 and Cys-39-Cys-48. The high IgE-binding capability of the recombinant C-terminal segment of Ole e 9 against sera from Ole e 9-sensitive individuals, which was determined by immunoblotting and ELISA inhibition, supported the proper folding of the polypeptide and the maintenance of antigenic properties that it exhibits as a part of the whole allergen. These data indicated that this portion of Ole e 9 constitutes an independent domain, which could be used to study its three-dimensional structure and function, as well as for clinical purposes such as diagnosis and specific immunotherapy. Since it shows sequence similarity with portions of 1,3-beta-glucanases from plant tissues and the Gas/Phr/Epd protein families involved in yeast morphogenesis, we suggest that this domain could play an equivalent functional role within these enzymes.

House dust mite Dermatophagoides farinae augments proinflammatory mediator productions and accessory function of alveolar macrophages: implications for allergic sensitization and inflammation

In this study, we examine the effects of Dermatophagoides farinae (Der f), a major source of airborne allergens, on alveolar macrophages (AMs), and we also test its contribution to allergic responses in mice. Der f activated NF-kappaB of AMs and, unlike OVA or LPS stimulation, up-regulated IL-6, TNF-alpha, and NO. In addition, it down-regulated antioxidants, but affected neither the expression nor production of IL-12. Der f-stimulated AMs expressed enhanced levels of costimulatory B7 molecules, supported T cell proliferation, and promoted Th2 cell development. The enhanced accessory function was suppressed by blockade mAbs to B7.2, IL-6, and TNF-alpha and by N-monomethyl-L-arginine, an NO synthase inhibitor, and N-acetylcysteine, a thiol antioxidant, whereas it was augmented by (+/-)-S-nitroso-N-acetylpenicillamine, an NO donor. Arg-Gly-Asp-Ser peptide and neo-glycoproteins galactose-BSA and mannose-BSA inhibited the Der f-induced IL-6 and TNF-alpha productions and enhanced accessory function of AMs. Der f was more potent than OVA for inducing pulmonary eosinophilic inflammation, NO, and serum allergen-specific IgG1 Ab production in mice. AMs from Der f-challenged mice expressed enhanced levels of B7 and augmented T cell proliferation ex vivo. In Der f-challenged mice, respiratory syncytial virus infection (5 x 10(5) pfu; 3 days before Der f instillation) augmented Der f-specific Ab production, whereas dexamethasone (50 mg/kg; 1 h before Der f instillation) diminished the allergic airway inflammation and Ab response. We conclude that AMs are sensitive targets for Der f and that the Der f-induced proinflammatory responses may represent an important mechanism in mediating the development of allergic sensitization and inflammation.

Skin as a route of exposure to protein allergens

Protein contact with skin is associated with a number of clinical conditions, including protein contact dermatitis and immunologic contact urticaria. This article reviews the clinical and other selected evidence that proteinaceous materials penetrate skin. It is concluded that whilst penetration of intact proteins through normal skin is extremely low and without consequence, any damage to the skin barrier may allow penetration. As a result, risk assessment for contact of protein with skin must take into account potential barrier impairment and thus the possibility of both the induction and the elicitation of allergic skin reactions.

Pollen and inhalant allergy

Anyone who suffers from hayfever will know what a serious problem allergies can be. In the long term, genetic technology may provide solutions in diagnosis, treatment and even avoidance. Eliminating allergens from pollen released by plants is technically feasible, but might this interfere with the natural processes of pollination?

Reasons for and costs of hospitalization for pediatric asthma: a prospective 1-year follow-up in a population-based setting

The aims of this study were to examine the frequency of, and the reasons for, emergency hospitalization for asthma among children. In addition, the costs of hospital treatment, preventive medication, and productivity losses of the caregivers were evaluated in a population-based setting during 1 year. Data on purchases of regular asthma medication were obtained from the Social Insurance Institution. In total, 106 (2.3/1000) children aged up to 15 years were admitted 136 times for asthma exacerbation to the Kuopio University Hospital in 1998. This represented approximately 5% of all children with asthma in the area. The trigger for the exacerbation was respiratory infection in 63% of the episodes, allergen exposure in 24%, and unknown in 13%. The age-adjusted risk for admittance was 5.3% in children on inhaled steroids, 5.8% in those on cromones, and 7.9% in those with no regular medication for asthma. The mean direct cost for an admission was $1,209 (median $908; range $454-6,812) and the indirect cost was $358 ($316; $253-1,139). The cost of regular medication for asthma was, on average, $272 per admitted child on maintenance. The annual total cost as a result of asthma rose eight-fold if a child on regular medication was admitted for asthma.

In vivo and in vitro techniques to determine the biological activity of food allergens

Methods for determination of the biological activity of food allergens comprise both determination of the allergenic potency, i.e. the capability to elicit an allergic reaction in an already sensitized individual, and the allergenic potential, i.e. the risk for sensitizing a hitherto non-allergic individual. Several methods are discussed for determination of potency including the double-blinded placebo-controlled food challenge, skin testing, in vitro effector cell assays such as basophil histamine release, and IgE-based techniques such as RAST and RAST inhibition. No reliable methods have yet been developed which can predict the allergenic potential of a food or a food allergen. The progress in the areas of stability studies and animal models for food allergy are discussed.

What establishes a protein as an allergen?

There is little known about the factors that determine the allergenicity of food proteins. Apparently, the ability of a food protein to induce an allergic response requires its presence in substantial amounts in the food supply, its durability during food processing, and its resistance to digestion in the gastrointestinal tract. In addition to the mode and degree of exposure, structural characteristics appear to play an important role for the capacity of a protein to modulate the immune response towards allergic reactions. Until now, however, there has been no indication for common structural characteristics of linear T cell or linear IgE (B cell) epitopes and the knowledge of structural characteristics of conformational IgE binding sites is very limited. Experimental data point only to certain surface areas of allergenic proteins which are important for IgE binding. Therefore, it is not possible to suggest any structural motif or conformational sequence pattern common to all allergenic proteins. Furthermore, glycosylation appears not to be a common critical determinant of allergenicity since food allergens comprise both glycoproteins and nonglycosylated proteins. Based on the few published three-dimensional structures of allergenic proteins including food proteins, one unifying feature of allergens appears to be their spherical shape. The three-dimensional structures of many more allergens have to be determined, however, to allow for a better understanding of the molecular basis of allergenicity. Most recently, new ideas have been introduced as to why certain biochemical or biologic functions such as enzymatic activities may predispose a protein to become an allergen. Proteolytically active allergens have been demonstrated to irritate the human mucosal surface, to enhance their own transmucosal uptake, and to augment IgE production. Therefore, the functional activity of some allergens may play a role among other factors in the process of sensitization and allergic responses.

Pathogenesis of atopic dermatitis (AD) and the role of allergic factors

OBJECTIVE

In this paper we will demonstrate that the exact pathogenesis of atopic dermatitis (AD) remains enigmatic, however the central defect is genetically determined, and the several dysfunctions we will highlight all point to a vicious cycle of allergen exposure, allergen-specific IgE production, and chronic Th2 cell stimulation. An important role is played by the late phase of IgE-mediated hypersensitivity, and evidence is accumulating that eosinophils actively participate in late phase-allergic reactions also in the skin.

OBSERVATIONS

AD is the first atopic disease to appear in the absolute sense: dendritic cells (DC) develop firstly in the skin and then in lung, in addition to homing receptors for T lymphocytes that are selective for skin localizations and not for lung. Among the DC, a primary role is reserved to Langerhans cells (LC) that express E-cadherin, a homophilic adhesion molecule that is prominently represented in epithelia. In addition keratinocytes and the interleukins (IL) they express are capable of activating a host of IgE-bearing cells.

CONCLUSION

Although much new information regarding the pathogenesis of AD has evolved over the past several years, the basic underlying etiology of this disorder remains elusive. Preventive measures are the only treatment for AD. We hope that the coming years will witness the development of new strategies for the treatment of AD, aimed at specific targets based on a thorough understanding of its pathogenesis.

Mechanisms and characteristics of airway sensitization to indoor allergens

The increasing prevalence of allergic respiratory diseases, and particularly of bronchial asthma, has been linked to changes induced by human activities in outdoor and indoor environments. People living in industrialized countries spend most of their time indoors: in private homes, offices and means of transport. Indoor environments are not a refuge from outdoor air pollution. Modern systems for energy saving such as insulated windows and doors reduce the indoor natural ventilation and consequently increase the rate of indoor humidity. These conditions may determine an increase in the level of indoor pollutants (tobacco smoke, gases produced by cooling processes etc.) and of allergens derived from mites, domestic animals and cockroaches. Upholstered furniture, wall-to-wall carpets, central heating systems and/or humidifiers may also contribute to the growth of mite populations. The increasing levels of exposure to pollutants and allergens in indoor environments represents a risk factor for the development of airway sensitization, especially if these materials are inhaled early in life. The major cat allergen Fel d 1 is considered an ubiquitous allergen, since it has been found in many indoor environments where a cat has never been kept. The clothing of cat owners seems to help spread Fel d 1 in cat-free environments. Sensitization to cockroach allergens is very common in patients living in urban areas where unhygenic conditions may favour the growth of cockroach populations. Monitoring of the levels of allergens and strategies of allergen and pollutant avoidance in indoor environments are the main ways to reduce the prevalence of respiratory allergies induced by these materials.

Interpreting atmospheric pollen counts for use in clinical allergy: allergic symptomology

BACKGROUND

Allergists generally consider atmospheric pollen counts to be an estimate of the antigenic challenge confronting allergic individuals. The nature of this challenge depends on the particular pollen types found in the atmosphere and also the airborne concentration of these pollen types. Both clinical experience and clinical investigations support these assumptions; however, a coherent system for relating pollen counts and allergic symptomology does not exist.

OBJECTIVE

This review article will systematically review the medical and technical literature concerning the clinical significance of atmospheric pollen counts.

DATA SOURCES

This review article will consider three independent bodies of literature: 1) data contrasting human exposure patterns with rooftop pollen counts; 2) data concerning dose-response relationships between atmospheric pollen counts and allergic symptomology; and 3) data concerning methods for indexing atmospheric pollen counts based on a pollen type's in vivo allergenicity and terminal velocity.

RESULTS

Three principal results emerged. First, rooftop pollen counts imperfectly approximate human exposure to atmospheric pollen. Differences in both the concentration and type of pollen encountered by humans can be expected to differ from samples obtained on rooftops. Second, allergic symptomology is positively correlated with atmospheric pollen counts. Investigations involving Betula (birch) pollen offer quantitative dose-response models. Complex, nonlinear relationships that seem to reflect both the priming effect and late-phase reactions exist. Last, atmospheric pollen counts can be indexed based on a contemporary application of Thommen's postulates. This system provides allergists with a means to estimate the clinical significance of various pollen types by combining data concerning in vivo allergenicity and terminal velocity.

CONCLUSIONS

These conclusions should allow allergists to judge the clinical significance of atmospheric pollen counts with greater sophistication than was previously possible.

The effects of roasting on the allergenic properties of peanut proteins

BACKGROUND

Because of the widespread use of peanut products, peanut allergenicity is a major health concern in the United States. The effect or effects of thermal processing (roasting) on the allergenic properties of peanut proteins have rarely been addressed.

OBJECTIVE

We sought to assess the biochemical effects of roasting on the allergenic properties of peanut proteins.

METHODS

Competitive inhibition ELISA was used to compare the IgE-binding properties of roasted and raw peanut extracts. A well-characterized in vitro model was used to test whether the Maillard reaction contributes to the allergenic properties of peanut proteins. The allergic properties were measured by using ELISA, digestion by gastric secretions, and stability of the proteins to heat and degradation.

RESULTS

Here we report that roasted peanuts from two different sources bound IgE from patients with peanut allergy at approximately 90-fold higher levels than the raw peanuts from the same peanut cultivars. The purified major allergens Ara h 1 and Ara h 2 were subjected to the Maillard reaction in vitro and compared with corresponding unreacted samples for allergenic properties. Ara h 1 and Ara h 2 bound higher levels of IgE and were more resistant to heat and digestion by gastrointestinal enzymes once they had undergone the Maillard reaction.

CONCLUSIONS

The data presented here indicate that thermal processing may play an important role in enhancing the allergenic properties of peanuts and that the protein modifications made by the Maillard reaction contribute to this effect.

Antisense-mediated silencing of a gene encoding a major ryegrass pollen allergen

Type 1 allergic reactions, such as hay fever and allergic asthma, triggered by grass pollen allergens are a global health problem that affects approximately 20% of the population in cool, temperate climates. Ryegrass is the dominant source of allergens because of its prodigious production of airborne pollen. Lol p 5 is the major allergenic protein of ryegrass pollen, judging from the fact that almost all of the individuals allergic to grass pollen show presence of serum IgE antibodies against this protein. Moreover, nearly two-thirds of the IgE reactivity of ryegrass pollen has been attributed to this protein. Therefore, it can be expected that down-regulation of Lol p 5 production can significantly reduce the allergic potential of ryegrass pollen. Here, we report down-regulation of Lol p 5 with an antisense construct targeted to the Lol p 5 gene in ryegrass. The expression of antisense RNA was regulated by a pollen-specific promoter. Immunoblot analysis of proteins with allergen-specific antibodies did not detect Lol p 5 in the transgenic pollen. The transgenic pollen showed remarkably reduced allergenicity as reflected by low IgE-binding capacity of pollen extract as compared with that of control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development, indicating that genetic engineering of hypoallergenic grass plants is possible.

The biological function of allergens: relevant for the induction of allergic diseases?

During the last 10 years an increasing number of allergens were identified and biochemically as well as immunologically characterized. More and more information on the primary structure of these molecules, revealed by recombinant technologies, became available. Furthermore for several allergens the biological functions could be elucidated. Most recently it was shown that beside IgE-binding capacity functional properties such as enzyme activity may contribute to the allergenicity and the induction of allergic inflammation. These findings could stimulate novel concepts in allergy prevention and therapy. This review summarizes recent data in this area.

Endogenous superallergen protein Fv induces IL-4 secretion from human Fc epsilon RI+ cells through interaction with the VH3 region of IgE

We investigated the mechanism whereby protein Fv (pFv), a human sialoprotein found in normal liver and largely released in the intestinal tract in patients with viral hepatitis, induces mediator release from basophils and mast cells and evaluated whether it also induces IL-4 synthesis and secretion in basophils. pFv is a potent stimulus for histamine and IL-4 release from purified basophils. Histamine and IL-4 secretion from basophils activated by pFv was significantly correlated (rs = 0.70; p < 0.001). There was also a correlation (rs = 0.58; p < 0.01) between the maximum pFv- and anti-IgE-induced IL-4 release from basophils. The average t1/2 for pFv-induced histamine release was lower (3.5+/-1.5 min) than for IL-4 release (79.5+/-8.5 min; p < 0.01). IL-4 mRNA, constitutively present in basophils, was increased after stimulation by pFv and was inhibited by cyclosporin A and tacrolimus. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released IL-4 in response to pFv and anti-IgE. The response to an mAb cross-linking the alpha-chain of Fc epsilon RI was unaffected by this treatment. Three human VH3+ monoclonal IgM concentration-dependently inhibited pFv-induced secretion of IL-4 and histamine from basophils and of histamine from human lung mast cells. In contrast, VH6+ monoclonal IgM did not inhibit the release of IL-4 and histamine induced by pFv. These results indicate that pFv, which acts as an endogenous superallergen, interacts with the VH3 domain of IgE to induce the synthesis and release of IL-4 from human Fc epsilon RI+ cells.

Dust mite proteolytic allergens induce cytokine release from cultured airway epithelium

Endogenous proteolytic enzymes have been shown to be potential sources of airway inflammation inducing proinflammatory cytokine release from respiratory epithelial cells; however, whether any of the exogenous proteases from important allergen sources such as the house dust mite present in our environment behave in a similar fashion is unclear. To this end, we have investigated whether the mite cysteine and serine proteolytic allergens, Der p 1 and Der p 9, respectively, induced cytokine production from primary human bronchial epithelial cells and from the epithelial cell line BEAS-2B. Cells were exposed to mite proteases, and cells or supernatants were assayed for cytokine release, cytokine mRNA expression, and modulation of intracellular calcium ion concentration. Both proteases induced concentration- and time-dependent increases in the release of granulocyte-macrophage (GM)-CSF, IL-6, and IL-8 as well as an increase in the expression of IL-6 mRNA. Cytokine release and mRNA expression were first observed at 8 h and 2 h after protease exposure, respectively. The minimum concentration of each protease that was required to stimulate GM-CSF, IL-6, and IL-8 release was approximately 10 ng/ml. Cytokine release was initiated by 1 to 2 h of protease exposure, although maximum concentrations were detected only after a 24-h incubation. IL-6, but not IL-8 and GM-CSF, was shown to be degraded by both proteases at concentrations of > 2 microg/ml. The proteases also stimulated changes in the intracellular calcium ion concentration. All mite protease-induced phenomena were inhibited using appropriate protease inhibitors. These results suggest that the proteolytic activity of an allergen may stimulate the release of proinflammatory cytokines from human bronchial epithelium.

Direct measurements of temperature and humidity in dust mite microhabitats

BACKGROUND

Up to 70% of atopic asthmatics have a positive skin test to the dust mite allergen Der p 1. Reduction of dust mite numbers by lowering room humidity control is one suggested technique for reducing dust mite allergen levels to clinically acceptable levels. Trials of this technique in temperate climates have reported mixed results. It has been speculated that one reason for this is that humidity changes in room ambient air are not tightly linked to humidity changes in the dust mite microenvironment (in the base of carpets, bedding, furniture etc.).

OBJECTIVE

To directly measure humidities and temperatures in dust mite microenvironments and compare these to ambient conditions, and so gather data on how the microclimates are influenced by room conditions and moisture and heat sources, such as an occupant in a bed.

METHODS

A special small humidity device has been developed which can discriminate humidity changes over distances of millimetres. With these devices microclimates have been measured in the base of carpets, in layers through bedding, and in furniture.

RESULTS

Measured base-of-carpet humidities were significantly higher than room humidities. Bedding relative humidities show complex behaviour according to the distance separation between the measuring point and the occupant. Immediately below the occupant, bed relative humidities fall when the person enters the bed. Similar behaviour is observed in a sofa.

CONCLUSION

Some dust mite microclimates have been shown to be very different from room conditions. Consequently, reduction of dust mite numbers and allergen levels cannot be guaranteed by the controlling of room humidities.

Endothelial gaps and adherent leukocytes in allergen-induced early- and late-phase plasma leakage in rat airways

Exposure of sensitized individuals to antigen can induce allergic responses in the respiratory tract, manifested by early and late phases of vasodilatation, plasma leakage, leukocyte influx, and bronchoconstriction. Similar responses can occur in the skin, eye, and gastrointestinal tract. The early-phase response involves mast cell mediators and the late-phase response is leukocyte dependent, but the mechanism of leakage is not understood. We sought to identify the leaky blood vessels, to determine whether these vessels contained endothelial gaps, and to analyze the relationship of the gaps to adherent leukocytes, using biotinylated lectins or silver nitrate to stain the cells in situ and Monastral blue as a tracer to quantify plasma leakage. Most of the leakage occurred in postcapillary venules (< 40-microns diameter), whereas most of the leukocyte migration (predominantly neutrophils) occurred in collecting venules. Capillaries and arterioles did not leak. Endothelial gaps were found in the leaky venules, both by silver nitrate staining and by scanning electron microscopy, and 94% of the gaps were distinct from sites of leukocyte adhesion or migration. We conclude that endothelial gaps contribute to both early and late phases of plasma leakage induced by antigen, but most leakage occurs upstream to sites of leukocyte adhesion.

Molecular regulation of plant cell wall extensibility

Gravity responses in plants often involve spatial and temporal changes in cell growth, which is regulated primarily by controlling the ability of the cell wall to extend. The wall is thought to be a cellulose-hemicellulose network embedded in a hydrated matrix of complex polysaccharides and a small amount of structural protein. The wall extends by a form of polymer creep, which is mediated by expansins, a novel group of wall-loosening proteins. Expansins were discovered during a molecular dissection of the "acid growth" behavior of cell walls. Expansin alters the rheology of plant walls in profound ways, yet its molecular mechanism of action is still uncertain. It lacks detectable hydrolytic activity against the major components of the wall, but it is able to disrupt noncovalent adhesion between wall polysaccharides. The discovery of a second family of expansins (beta-expansins) sheds light on the biological role of a major group of pollen allergens and implies that expansins have evolved for diverse developmental functions. Finally, the contribution of other processes to wall extensibility is briefly summarized.

More positive patch test reactions with larger test chambers? Results from a study group of the German Contact Dermatitis Research Group (DKG)

Test chambers of various sizes are commercially available for patch testing. Therefore, we asked the question whether the size of patch test chambers may affect allergic patch test reactions. A total of 495 patients were double tested synchronously with small and large Finn Chambers containing standard preparations of fragrance mix, wool wax alcohols, Kathon CG and formaldehyde. Double tests in 217 patients who had reacted with at least 1 allergic, questionable, or irritant reaction to 1 of these allergens were statistically evaluated. For each of the 4 allergens, a significantly higher number of stronger reactions was seen with the large chambers as compared to the small ones. It is concluded that large test chambers may be useful for detection of weak sensitizations to particular contact allergens.

Group I allergens of grass pollen as cell wall-loosening agents

Group I allergens are the major allergens of grass pollen, but their biological function is unknown. These proteins are shown here to be structurally related to expansins, which are able to induce extension (creep) of plant cell walls. Extracts of maize pollen possess potent expansin-like activity, as measured in wall extension and wall stress-relaxation assays. This activity is selective for grass cell walls and is, at least partly, due to the action of maize group I allergens. We propose that group I allergens facilitate invasion of the pollen tube into the maternal tissues by loosening the cell walls of the grass stigma and style. Additionally, the presence of related mRNAs in vegetative tissues of rice, Arabidopsis, and soybean implies that allergen homologs may function to loosen walls in growing vegetative tissues as well.

X-ray crystal structures of birch pollen profilin and Phl p 2

BACKGROUND

Type 1 allergy affects 20% of industrialized populations and thus represents a major health care issue. The symptoms of type 1 allergy, which include rhinitis, conjunctivitis, dermatitis and asthma, are elicited by the cross-linking of IgE receptors through polyvalent allergens. A detailed understanding of the cell surface phenomena and the rational development of new therapies require high-resolution structural information.

METHODS

The structures of two widespread allergens, birch pollen profilin (BPP) and Phl p 2 have been solved by multiple isomorphous replacement. Refinements are underway to 2.4 and 2.0 A, respectively. In addition, the IgE-reactive epitopes of BPP where identified by screening an epitope expression library with the serum IgE of an allergic individual.

RESULTS

BPP exhibits an alpha/beta-fold which is similar to the mammalian and amoeba profilins. The structure of Phl p 2 is a compact eight-stranded beta-barrel. Screening an epitope library of BPP identified three major epitopic regions involved in IgE binding, including the amino and carboxy-terminal alpha-helices. These regions also interact with the physiologically relevant ligands of profilin, actin and proline-rich peptides.

CONCLUSIONS

The distribution of IgE-binding sites on BPP allows for the productive interaction with IgE antibodies of different epitope specificities required for efficient signal transduction. These epitopes correspond to the most highly conserved regions of the profilin molecule and thus provide the molecular basis for allergen cross-sensitivity. Due to steric considerations, the involvement of these epitopic regions in the binding of physiologically relevant profilin ligands indicates that the native profilin is the species responsible for eliciting the allergic response. A comparison of the BPP and Phl p 2 structures shows that there is no preference for secondary structural elements in the allergic response. The detailed chemical and physical description of the major reactive epitopes provides a data base for the design of tight-binding monovalent ligands which can prevent receptor aggregation and thereby reduce the allergic response.

Allergen-induced recruitment of Fc epsilon RI+ eosinophils in human atopic skin

We have attempted to identify Fc epsilon RI+ eosinophils in cutaneous late-phase reaction in atopic subjects biopsied at 6, 24 and 48 h after the injection of either allergen or a diluent control. Compared to the diluent sites, allergen-injected sites had significantly increased numbers of eosinophils, peaking between 6 and 24 h, of which approximately 20-30% expressed mRNA for the alpha, beta, and gamma chains of Fc epsilon RI, as shown by in situ hybridization. Using either a monoclonal or a polyclonal anti-alpha chain antibody, the Fc epsilon RI alpha protein also co-localized to approximately 50-80% of eosinophils at all time points studied. We also observed a significant correlation (r = 0.89; p = 0.02) between the numbers of Fc epsilon RI+ (997+)/EG2+ eosinophils and the magnitude of the late-phase reaction. Thus, a significant proportion of eosinophils infiltrating the site of allergen-induced allergic tissue reactions in atopic subjects express Fc epsilon. RI. The findings show that high-affinity IgE receptors may play a role in eosinophil secretory processes in vivo.

IL-4 as a key factor influencing the development of allergen-specific Th2-like cells in atopic individuals

In the last years Th2-like cells, able to produce IL-4, IL-5, IL-6 and IL-10, have been shown to play an important role in the pathogenesis of allergic diseases. They are absolutely required for IgE production by B-cells and are expanded at the level of target tissues of atopic patients. Very recently, much attention has been focused on the genetic and environmental factors responsible for the differentiation and ongoing expansion of allergen-specific Th2-like cells in atopic subjects. In this review possible cellular sources of IL-4 in the primary, secondary and ongoing responses to allergens are discussed. In atopics, Th cell precursors themselves could be proposed as a main source of IL-4 in the primary responses to allergens. However, there is extensive evidence for the role of other cells such as mast cells, basophils and eosinophils as important sources of IL-4 the secondary and ongoing responses to allergens.