Importance of allergy in asthma: an epidemiologic perspective

The response of CD27+CD38+ plasmablasts, CD24hiCD38hi transitional B cells, CXCR5-ICOS+PD-1+ Tph, Tph2 and Tfh2 subtypes to allergens in children with allergic asthma

BACKGROUND

Allergic asthma is a type I allergic reaction mediated by serum Immunoglobulin E (IgE). B cell-mediated humoral immune response to allergens in the pathophysiology of allergic asthma have not been thoroughly elucidated. Peripheral helper T cells (Tph) and follicular helper T cells (Tfh) promote B cell differentiation and antibody production in inflamed tissues.

OBJECTIVE

To investigate the roles of B cell subsets, Tph cell subsets and Tfh cell subsets in allergic immune responses.

METHODS

Circulating B cell subsets, Tph cell subsets and Tfh cell subsets in 33 children with allergic asthma and 17 healthy children were analyzed using multicolor flow cytometry. The level of serum total IgE was also assessed.

RESULTS

Our study found that CD27+CD38+ plasmablasts and CD24hiCD38hi transitional B cells increased and were correlated with serum total IgE level, CD27- naive B cells and CD24hiCD27+ B cells decreased in children with allergic asthma. CXCR5- Tph, CXCR5-ICOS+ Tph, CXCR5-ICOS+PD-1+ Tph, CXCR5+ICOS+ Tfh and CXCR5+ICOS+PD-1+ Tfh increased in children with allergic asthma. Further analysis showed increased Tph2, Tph17, Tfh2 and Tfh17 subtypes while decreased Tph1 and Tfh1 subtypes in children with allergic asthma. Most interestingly, Tph2 or Tfh2 subtypes had a positive correlation with serum total IgE level.

CONCLUSION

Overall, these results provide insight into the allergens elicited B, Tph or Tfh cell response and identify heretofore unappreciated CD24hiCD38hi transitional B cells, CD24hiCD27+ B cells, CXCR5- Tph, CXCR5-ICOS+PD-1+ Tph, Tph2 subtypes and Tfh2 subtypes response to allergens.

Prenatal IgE as a Risk Factor for the Development of Childhood Neurodevelopmental Disorders

Background: Few studies have examined if maternal allergic disease is associated with an offspring's neurodevelopment. We hypothesized that Th-2 biased maternal immune function assessed as total serum immunoglobulin (Ig) E is associated with attention deficit hyperactivity disorder (ADHD). Methods: Data are from the Wayne County Health, Environment, Allergy, and Asthma Longitudinal Study (WHEALS), a racially and socioeconomically diverse birth cohort in metropolitan Detroit, Michigan. Maternal total IgE was measured prenatally and at 1-month postpartum. Child total IgE was assessed at birth, 6 months, and 2 years of age. ADHD diagnosis was based on the parental report at the 10-12-year study visits or medical chart abstraction. Total IgE was log2 transformed. Poisson regression models with robust error variance were used to calculate the risk ratios (RR). Inverse probability weighting was used to correct for potential bias due to a loss to follow-up and non-response. Results: Of the 636 maternal-child pairs in the analysis, 513 children were neurotypical and 123 had ADHD. Maternal prenatal total IgE was significantly associated with ADHD even after adjustment for potential confounders (RR = 1.08, 95% CI 1.03-1.13). Maternal and child IgE measures were positively and significantly correlated, but child total IgE was not associated with ADHD at any time point. Conclusions: Maternal prenatal IgE may influence neurodevelopment, but additional studies are needed to confirm and expand these findings.

Characterization of Severe Asthma Worldwide: Data From the International Severe Asthma Registry

BACKGROUND

Clinical characteristics of the international population with severe asthma are unknown. Intercountry comparisons are hindered by variable data collection within regional and national severe asthma registries. We aimed to describe demographic and clinical characteristics of patients treated in severe asthma services in the United States, Europe, and the Asia-Pacific region.

METHODS

The International Severe Asthma Registry retrospectively and prospectively collected data in patients with severe asthma (≥ 18 years old), receiving Global Initiative for Asthma (GINA) Step 5 treatment or with severe asthma remaining uncontrolled at GINA Step 4. Baseline demographic and clinical data were collected from the United States, United Kingdom, South Korea, Italy, and the Severe Asthma Web-based Database registry (including Australia, Singapore, and New Zealand) from December 2014 to December 2017.

RESULTS

We included 4,990 patients. Mean (SD) age was 55.0 (15.9) years, and mean (SD) age at asthma onset was 30.7 (17.7) years. Patients were predominantly female (59.3%) and white (72.6%), had never smoked (60.5%), and were overweight or obese (70.4%); 34.9% were at GINA Step 5; and 57.2% had poorly controlled disease. A total of 51.1% of patients were receiving regular intermittent oral corticosteroids, and 25.4% were receiving biologics (72.6% for those at GINA Step 5). Mean (SD) exacerbation rate was 1.7 (2.7) per year. Intercountry variation was observed in clinical characteristics, prescribed treatments, and biomarker profiles.

CONCLUSIONS

Using a common data set and definitions, this study describes severe asthma characteristics of a large patient cohort included in multiple severe asthma registries and identifies country differences. Whether these are related to underlying epidemiological factors, environmental factors, phenotypes, asthma management systems, treatment access, and/or cultural factors requires further study.

Whole Blood Cytokine Response to Local Traffic-Related Particulate Matter in Peruvian Children With and Without Asthma

This study sought to investigate if acute phase immune responses of whole blood from Peruvian children with controlled and uncontrolled asthma differed from children without asthma, following exposure to traffic-related particulate matter (TRPM). TRPM, including particulate matter from diesel combustion, has been shown to stimulate acute airway inflammation in individuals with and without asthma. For this study, a whole blood assay (WBA) was used to test peripheral whole blood samples from 27 children with asthma, and 12 without asthma. Participant blood samples were stimulated, ex vivo, for 24-h with an aqueous extract of TRPM that was collected near study area highways in Lima, Peru. All participant blood samples were tested against the same TRPM extract, in addition to purified bacterial endotoxin and pyrogen-free water, which served as positive and negative WBA controls, respectively. The innate and adaptive cytokine responses were evaluated in cell-free supernatants of the whole blood incubations. Comparatively similar levels were recorded for nine out of the 10 cytokines measured [e.g., – Interleukin (IL)-1β, IL-6, IL-10], regardless of study participant asthma status. However, IL-8 levels in TRPM-stimulated blood from children with uncontrolled asthma were diminished, compared to subjects without asthma (633 pg/ml vs. 1,023 pg/ml, respectively; p < 0.01); IL-8 responses for subjects with controlled asthma were also reduced, but to a lesser degree (799 pg/ml vs. 1,023 pg/ml, respectively; p = 0.10). These relationships were present before, and after, adjusting for age, sex, obesity/overweight status, C-reactive protein levels, and residential proximity to the study area’s major roadway. For tests conducted with endotoxin, there were no discernible differences in cytokine response between groups, for all cytokines measured. The WBA testing conducted for this study highlighted the capacity of the TRPM extract to potently elicit the release of IL-8 from the human whole blood system. Although the small sample size of the study limits the capacity to draw definitive conclusions, the IL-8 responses suggest that that asthma control may be associated with the regulation of a key mediator in neutrophil chemotaxis, at a systemic level, following exposure to PM derived from traffic-related sources.

Do chronic workplace irritant exposures cause asthma?

PURPOSE OF REVIEW

The present review summarizes the recent literature on the relation between chronic workplace irritant exposures and asthma, focusing on exposures of low to moderate levels. We discuss results from epidemiological surveys, potential biological mechanisms, and needs for further research. These aspects are largely illustrated by studies on exposure to cleaning products.

RECENT FINDINGS

Recent results from nine population-based and workplace-based epidemiological studies, mostly cross-sectional, found an increased risk of both new-onset and work-exacerbated asthma among participants exposed to moderate level of irritants and/or cleaning products.

SUMMARY

Evidence of a causal effect of chronic workplace irritant exposure in new-onset asthma remains limited, mainly because of a lack of longitudinal studies and the difficulty to evaluate irritant exposures. However, recent epidemiological studies strengthen the evidence of an effect of chronic exposure to irritants in work-related asthma. The underlying mechanism remains unknown but may be related to oxidative stress, neurogenic inflammation and dual irritant and adjuvant effects. However, disentangling chronic irritant effects from either acute irritant-induced asthma or immunological low molecular weight agent-induced asthma is difficult for some agents. Further research is needed to improve assessment of irritant exposures and identify biomarkers.

Atopic diseases and inflammation of the brain in the pathogenesis of autism spectrum disorders

Autism spectrum disorders (ASDs) affect as many as 1 in 45 children and are characterized by deficits in sociability and communication, as well as stereotypic movements. Many children also show severe anxiety. The lack of distinct pathogenesis and reliable biomarkers hampers the development of effective treatments. As a result, most children with ASD are prescribed psychopharmacologic agents that do not address the core symptoms of ASD. Autoantibodies against brain epitopes in mothers of children with ASD and many such children strongly correlate with allergic symptoms and indicate an aberrant immune response, as well as disruption of the blood-brain barrier (BBB). Recent epidemiological studies have shown a strong statistical correlation between risk for ASD and either maternal or infantile atopic diseases, such as asthma, eczema, food allergies and food intolerance, all of which involve activation of mast cells (MCs). These unique tissue immune cells are located perivascularly in all tissues, including the thalamus and hypothalamus, which regulate emotions. MC-derived inflammatory and vasoactive mediators increase BBB permeability. Expression of the inflammatory molecules interleukin (IL-1β), IL-6, 1 L-17 and tumor necrosis factor (TNF) is increased in the brain, cerebrospinal fluid and serum of some patients with ASD, while NF-kB is activated in brain samples and stimulated peripheral blood immune cells of other patients; however, these molecules are not specific. Instead the peptide neurotensin is uniquely elevated in the serum of children with ASD, as is corticotropin-releasing hormone, secreted from the hypothalamus under stress. Both peptides trigger MC to release IL-6 and TNF, which in turn, stimulate microglia proliferation and activation, leading to disruption of neuronal connectivity. MC-derived IL-6 and TGFβ induce maturation of Th17 cells and MCs also secrete IL-17, which is increased in ASD. Serum IL-6 and TNF may define an ASD subgroup that benefits most from treatment with the natural flavonoid luteolin. Atopic diseases may create a phenotype susceptible to ASD and formulations targeting focal inflammation of the brain could have great promise in the treatment of ASD.

Follicular helper T cells mediate IgE antibody response to airborne allergens

BACKGROUND

T_H2 cells have long been believed to play a pivotal role in allergic immune responses, including IgE antibody production and type 2 cytokine-mediated inflammation and pathology. A new T-cell subset, follicular helper T (T_FH) cells, is specialized in supporting B-cell maturation and antibody production.

OBJECTIVE

We sought to investigate the roles of T_FH cells in allergic immune responses.

METHODS

Naive mice were exposed to cytokines or natural allergens through the airways. Development of allergic immune responses was analyzed by collecting draining lymph nodes and sera and by challenging the animals. Cytokine reporter mice and gene-deficient mice were used to dissect the immunologic mechanisms.

RESULTS

We observed the development of IL-4-producing T_FH cells and T_H2 cells in draining lymph nodes after airway exposure to IL-1 family cytokines or natural allergens. T_FH and T_H2 cells demonstrated unique phenotypes, tissue localization, and cytokine responses. T_FH cells supported the sustained production of IgE antibody in vivo in the absence of other T-cell subsets or even when T_H2 cell functions were severely compromised. Conversely, conditional deficiency of the master regulator Bcl6 in CD4⁺ T cells resulted in a marked reduction in T_FH cell numbers and IgE antibody levels, but type 2 cytokine responses and eosinophilic inflammation in the airways remained unaffected.

CONCLUSION

T_FH cells play critical roles in the regulation of IgE antibody production. Allergic immune responses to airborne allergens likely involve 2 distinct subsets of IL-4-producing CD4⁺ T cells, namely T_FH and Th2 cells.

Pet ownership is associated with increased risk of non-atopic asthma and reduced risk of atopy in childhood: findings from a UK birth cohort

BACKGROUND

Studies have shown an inverse association of pet ownership with allergy but inconclusive findings for asthma.

OBJECTIVE

To investigate whether pet ownership during pregnancy and childhood was associated with asthma and atopy at the age of 7 in a UK population-based birth cohort.

METHODS

Data from the Avon Longitudinal Study of Parents and Children (ALSPAC) were used to investigate associations of pet ownership at six time points from pregnancy to the age of 7 with asthma, atopy (grass, house dust mite, and cat skin prick test) and atopic vs. non-atopic asthma at the age of 7 using logistic regression models adjusted for child's sex, maternal history of asthma/atopy, maternal smoking during pregnancy, and family adversity.

RESULTS

A total of 3768 children had complete data on pet ownership, asthma, and atopy. Compared with non-ownership, continuous ownership of any pet (before and after the age of 3) was associated with 52% lower odds of atopic asthma [odds ratio (OR) 0.48, 95% CI 0.34-0.68]. Pet ownership tended to be associated with increased risk of non-atopic asthma, particularly rabbits (OR 1.61, 1.04-2.51) and rodents (OR 1.86, 1.15-3.01), comparing continuous vs. non-ownership. Pet ownership was consistently associated with lower odds of sensitization to grass, house dust mite, and cat allergens, but rodent ownership was associated with higher odds of sensitization to rodent allergen. Differential effects of pet ownership on atopic vs. non-atopic asthma were evident for all pet types.

CONCLUSIONS AND CLINICAL RELEVANCE

Pet ownership during pregnancy and childhood in this birth cohort was consistently associated with a reduced risk of aeroallergen sensitization and atopic asthma at the age of 7, but tended to be associated (particularly for rabbits and rodents) with an increased risk of non-atopic asthma. The opposing effects on atopy vs. non-atopic asthma might be considered by parents when they are deciding whether to acquire a pet.

Risk factors for nonwork-related adult-onset asthma and occupational asthma: a comparative review

PURPOSE OF REVIEW

To identify the similarities and differences between nonwork-related adult-onset and occupational asthma from various literature sources published between 2010 and 2013, with respect to the epidemiology, phenotypic manifestations, and risk factors for the disease.

RECENT FINDINGS

The incidence of adult-onset asthma from pooled population studies is estimated to be 3.6 per 1000 person-years in men and 4.6 cases per 1000 person-years in women. In adults with new-onset asthma, occupational asthma is a common asthma phenotype. Work-related factors are estimated to account for up to 25% of adult cases of asthma and occupational asthma comprising about 16% of adult-onset asthma cases. The review finds that nonwork-related adult-onset asthma is a heterogenous entity and that environmental exposure factors (aside from occupational exposures) appear to have a lesser role than host factors when compared with occupational asthma.

SUMMARY

Large-scale general population studies are needed to identify the similarities and differences between nonwork-related adult-onset and occupational asthma, which may enable a better understanding of these entities and promote efforts towards holistic management approaches for these asthma phenotypes.

Adeno-associated virus-like particles as new carriers for B-cell vaccines: testing immunogenicity and safety in BALB/c mice

Adeno-associated viruses (AAVs) are established vectors for gene therapy of different human diseases. AAVs are assembled of 60 capsomers, which can be genetically modified, allowing high-density display of short peptide sequences at their surface. The aim of our study was to evaluate the immunogenicity and safety of an adeno-associated virus-like particle (AAVLP)-displayed B-cell peptide epitope taking ovalbumin (OVA) as a model antigen or allergen from egg, respectively. An OVA-derived B-cell epitope was expressed as fusion protein with the AAV-2 capsid protein of VP3 (AAVLP-OVA) and for control, with the nonrelated peptide TP18 (AAVLP-TP18). Cellular internalization studies revealed an impaired uptake of AAVLP-OVA by mouse BMDC, macrophages, and human HeLa cells. Nevertheless, BALB/c mice immunized subcutaneously with AAVLP-OVA formed similarly high titers of OVA-specific IgG1 compared to mice immunized with the native OVA. The extent of the immune response was independent whether aluminum hydroxide or water in oil emulsion was used as adjuvant. Furthermore, in mice immunized with native OVA, high OVA-specific IgE levels were observed, which permitted OVA-specific mast-cell degranulation in a β-hexosaminidase release assay, whereas immunizations with AAVLP-OVA rendered background IgE levels only. Accordingly, OVA-immunized mice, but not AAVLP-OVA immunized mice, displayed an anaphylactic reaction with a significant drop of body temperature upon intravenous OVA challenge. From this mouse model, we conclude that AAVLPs that display B-cell epitope peptides on their surface are suitable vaccine candidates, especially in the field of allergy.

Trends in the prevalence of asthma

The asthma epidemic of the last few decades may have peaked; studies suggest that the incidence and prevalence of asthma has decreased in some countries in the last few years, although other studies suggest continuing small increases in prevalence. Increasing awareness and changing diagnostic habits make precise evaluation of epidemiologic trends difficult in the absence of a gold-standard test for asthma, and on a global basis uncertainty persists. Trends in prevalence in some populations (eg, immigrants, farming communities) suggest both adverse and beneficial effects of specific environmental factors. Although the effects of indoor allergens, dampness, and mold and of outdoor air pollutants, especially traffic related, have traditionally dominated risk-factor research, more recent epidemiologic and clinical studies have focused on metabolic and nutritional factors, including maternal obesity and vitamin D levels, mode of delivery and its effect on the infant microbiome, fetal and infant growth, the psychosocial environment, and medication use by mother and infant. It is likely that changes in incidence and prevalence are due to multiple factors, each contributing a relatively small effect. Longitudinal studies from pregnancy through childhood to adulthood will yield greater insights into the complex pathways leading to asthma.

Cleaning and asthma characteristics in women

BACKGROUND

We aimed to assess the associations between occupational exposure to cleaning products, a gender-related exposure, and asthma characteristics, considering clinical, immunological and inflammatory aspects.

METHODS

Analyses were conducted in 391 women (73 with adult-onset asthma) from the follow-up of the Epidemiological Study on the Genetics and Environment of Asthma (EGEA). Occupational exposure to cleaning/disinfecting products was estimated using the asthma-specific job-exposure-matrix (44 women exposed).

RESULTS

Occupational exposures were associated with more symptomatic asthma (odds ratio (95% CI): 2.8(1.2-6.4)) and severe asthma (5.1(1.7-15.3)). An association was suggested for poorly controlled asthma (2.2(0.9-5.5)). Associations were observed for asthma without positive skin prick test (3.0(1.1-8.3)), with a low IgE level (2.8(1.2-6.2)), and with a low eosinophil count (3.2(1.5-7.1)).

CONCLUSIONS

Results strengthen the evidence of a deleterious role of cleaning products in asthma and are consistent with the hypothesis of non-allergic mechanisms in relation to workplace cleaning exposures.

Is a subtype of autism an allergy of the brain?

BACKGROUND

Autism spectrum disorders (ASDs) are characterized by deficits in social communication and language and the presence of repetitive behaviors that affect as many as 1 in 50 US children. Perinatal stress and environmental factors appear to play a significant role in increasing the risk for ASDs. There is no definitive pathogenesis, which therefore significantly hinders the development of a cure.

OBJECTIVE

We aimed to identify publications using basic or clinical data that suggest a possible association between atopic symptoms and ASDs, as well as evidence of how such an association could lead to brain disease, that may explain the pathogenesis of ASD.

METHODS

PubMed was searched for articles published since 1995 that reported any association between autism and/or ASDs and any one of the following terms: allergy, atopy, brain, corticotropin-releasing hormone, cytokines, eczema, food allergy, food intolerance, gene mutation, inflammation, mast cells, mitochondria, neurotensin, phenotype, stress, subtype, or treatment.

RESULTS

Children with ASD respond disproportionally to stress and also present with food and skin allergies that involve mast cells. Brain mast cells are found primarily in the hypothalamus, which participates in the regulation of behavior and language. Corticotropin-releasing hormone is secreted from the hypothalamus under stress and, together with neurotensin, stimulates brain mast cells that could result in focal brain allergy and neurotoxicity. Neurotensin is significantly increased in serum of children with ASD and stimulates mast cell secretion of mitochondrial adenosine triphosphate and DNA, which is increased in these children; these mitochondrial components are misconstrued as innate pathogens, triggering an autoallergic response in the brain. Gene mutations associated with higher risk of ASD have been linked to reduction of the phosphatase and tensin homolog, which inhibits the mammalian target of rapamycin (mTOR). These same mutations also lead to mast cell activation and proliferation. Corticotropin-releasing hormone, neurotensin, and environmental toxins could further trigger the already activated mTOR, leading to superstimulation of brain mast cells in those areas responsible for ASD symptoms. Preliminary evidence indicates that the flavonoid luteolin is a stronger inhibitor of mTOR than rapamycin and is a potent mast cell blocker.

CONCLUSION

Activation of brain mast cells by allergic, environmental, immune, neurohormonal, stress, and toxic triggers, especially in those areas associated with behavior and language, lead to focal brain allergies and subsequent focal encephalitis. This possibility is more likely in the subgroup of patients with ASD susceptibility genes that also involve mast cell activation.

Adolescent asthma self-management: patient and parent-caregiver perspectives on using social media to improve care

BACKGROUND

Self-management of asthma can now leverage new media technologies. To optimize implementation they must employ a consumer-oriented developmental approach. This study explored benefits of and barriers to improved asthma self-management and identified key elements for the development of a digital media tool to enhance asthma control.

METHODS

Between August 2010 and January 2011, 18 teens with asthma and 18 parent-caregivers participated in semistructured in-depth interviews to identify mechanisms for improving asthma self-management and propose characteristics for developing a digital media tool to aid such efforts.

RESULTS

Teens and caregivers enumerated physician-recommended strategies for asthma management as well as currently employed strategies. Both groups thought of a potential digital media solution as positive, but indicated specific design requirements for such a solution to have utility. Whereas most participants perceived mobile platforms to be viable modes to improve asthma self-management, interest in having social networking capabilities was mixed.

CONCLUSIONS

A digital media product capable of tracking conditions, triggers, and related asthma activities can be a core element of improved asthma control for youth. Improved asthma control will help decrease school absenteeism.

The "missing link" in autoimmunity and autism: extracellular mitochondrial components secreted from activated live mast cells

Autoimmune diseases continue to increase, but the reason(s) remain obscure and infections have not proven to be major contributors. Mast cells are tissue immune cells responsible for allergies, but have been increasingly shown to be involved in innate and acquired immunity, as well as inflammation. This involvement is possible because of their ability to release multiple mediators in response to a great variety of triggers. We recently published that activation of mast cells is accompanied by mitochondrial fission and translocation to the cell surface from where they secrete at least ATP and DNA outside the cell without cell damage. These extracellular mitochondrial components are misconstrued by the body as "innate pathogens" leading to powerful autocrine and paracrine auto-immune/auto-inflammatory responses. We also showed that mitochondrial DNA is increased in the serum of young children with autism spectrum disorders (ASD), a condition that could involve "focal brain allergy/encephalitits". Blocking the secretion of extracellular mitochondrial components could present unique possibilities for the therapy of ASD and other autoimmune diseases. Unique formulation of the flavonoid luteolin offers unique advantages.

Work related asthma. A causal analysis controlling the healthy worker effect

OBJECTIVES

The healthy worker effect usually leads to underestimation of the association between occupational exposure and asthma. The role of irritants in work-related asthma is disputed. We estimated the effect of occupational exposure on asthma expression in a longitudinal study, using marginal structural modelling to control for the healthy worker effect.

METHODS

Analyses included 1284 participants (17-79 years, 48% men) from the follow-up (2003-2007) of the French Epidemiological study on the Genetics and Environment of Asthma (case-control study). Age at asthma onset, periods with/without attacks over lifetime and occupational history were recorded retrospectively. Exposures to known asthmagens, irritants or low level of chemicals/allergens were evaluated through a job-exposure matrix. The job history was reconstructed into 5-year intervals.

RESULTS

Thirty-one per cent of subjects had ever been exposed to occupational asthmagens. Among the 38% of subjects who had asthma (ever), presence of attacks was reported in 52% of all time periods. Using standard analyses, no association was observed between exposure to known asthmagens (OR (95% CI): 0.99 (0.72 to 1.36)) or to irritants/low level of chemicals/allergens (0.82 (0.56 to 1.20)) and asthma attacks. Using a marginal structural model, all associations increased with suggestive evidence for known asthmagens (1.26 (0.90 to 1.76)), and reaching statistical significance for irritants/low level of chemicals/allergens (1.56 (1.02 to 2.40)).

CONCLUSIONS

The healthy worker effect has an important impact in risk assessment in work-related asthma studies. Marginal structural models are useful to eliminate imbalances in exposure due to disease-driven selection. Results support the role of irritants in work-related asthma.

Lifestyle changes and childhood asthma

In recent decades there have been marked increases in asthma prevalence in Western countries. More recently, asthma prevalence has peaked, or even begun to decline, in Western countries, but many low and middle income countries are now beginning to experience increases in prevalence (although there is no evidence of increases in prevalence in India to date). "Established" risk factors for asthma cannot account for the global prevalence increases, or the international patterns that have been observed, or the recent declines in prevalence in some Western countries. It seems that as a result of the "package" of changes in the intrauterine and infant environment that are occurring with "Westernization", we are seeing an increased susceptibility to the development of asthma and/or allergy. There are a number of elements of this "package" including changes in maternal diet, increased fetal growth, smaller family size, reduced infant infections and increased use of antibiotics and paracetamol, and immunization, all of which have been (inconsistently) associated with an increased risk of childhood asthma, but none of which can alone explain the increases in prevalence. It is likely that the "package" is more than the sum of its parts, and that these social and environmental changes are all pushing the infants' immune systems towards an increased risk of asthma.

Asthma and rhinitis: what is the relationship?

PURPOSE OF REVIEW

Asthma and rhinitis are commonly associated and they influence their respective control. New observations have contributed to better understand how to assess those conditions and how they influence each other.

RECENT FINDINGS

Recent studies found that not only the intensity, but also the duration of rhinitis could be correlated with the development of asthma and possibly its remission. The measure of exhaled nitric oxide (FeNO) has been used to show the presence of lower airway inflammation in rhinitic patients, with or without asthma. Furthermore, it has been shown that allergic rhinitis could affect asthma control in children as in adults, and consequently suggested that allergic rhinitis and asthma should be concomitantly approached in regard to their diagnosis and treatment. Additional observations showed improvements in various asthma outcomes with the treatment of rhinitis.

SUMMARY

These new data confirm the strong link between asthma and rhinitis, the importance of their interactions, and the need to identify and treat rhinitis adequately in asthmatic patients.

Specific immunotherapy can greatly reduce the need for systemic steroids in allergic rhinitis

BACKGROUND

Worldwide, more than 400 million individuals have allergic rhinitis, which has a significant impact on the individual's general health. Most patients self-medicate with over-the-counter drugs, but severe cases need treatment with topical corticosteroids and/or immunotherapy (SCIT). Although the ARIA guidelines discourage the use of systemic corticosteroids, this treatment is often used by general practitioners.

AIMS

To investigate the use of systemic steroids to treat allergic rhinitis in Denmark and the role of SCIT as an alternative.

METHODS

A retrospective study based on Danish National Registry databases 1995-2009. Steroid use was defined as a minimum of one steroid injection during April-July for at least three consecutive years. SCIT treatment against grass (Phleum pratense), birch (Betula verrucosa) or both was included.

RESULTS

Overall, 39 173 individuals were treated with either SCIT or steroids; 93.1% received only steroids, and 6.9% received SCIT and/or steroids. The steroid-to-SCIT ratio was 14 : 1 (P < 0.0001). The mean annual steroid injections were 1.6 in the steroid-only group and 1.0 in the SCIT group (P < 0.0001). Of the SCIT-treated individuals, 84% did not need steroids after SCIT treatment (P < 0.0001). The hazard ratios of receiving steroids after SCIT against grass, birch or both were 0.65, 0.83 and 0.72, respectively (P < 0.0001), when compared with the steroids-only group. The maximum hazard reduction was obtained if patients responded well to SCIT treatment after one to 3 years.

CONCLUSIONS

Systemic steroid injections are still widely used to treat pollen allergy. Specific immunotherapy can greatly reduce the need for steroids.

Regulatory T cells and the control of the allergic response

The study of immune regulation and tolerance has been traditionally associated with self/nonself-discrimination. However, the finding that dominant tolerance, a model that puts in evidence the active role of regulatory T cells, can develop to nonself-antigens suggests that the imposition of tolerance can be context dependent. This paper reviews the emerging field of acquired immune tolerance to non-self antigens, with an emphasis on the different subsets of induced regulatory T cells that appear to specialize in specific functional niches. Such regulatory mechanisms are important in preventing the onset of allergic diseases in healthy individuals. In addition, it may be possible to take advantage of these immune regulatory mechanisms for the induction of tolerance in cases where pathological immune responses are generated to allergens occurring in nature, but also to other immunogens such as biological drugs developed for medical therapies.