Genetic 'risk' for atopy is associated with delayed postnatal maturation of T-cell competence

Household size, T regulatory cell development, and early allergic disease: a birth cohort study

BACKGROUND

Children born to larger households have less allergic disease. T regulatory cell (Treg) development may be a relevant mechanism, but this has not been studied longitudinally.

OBJECTIVE

We aim to (i) describe how prenatal and postnatal environmental factors are associated with Treg development and (ii) investigate whether serial Treg measures predict allergic outcomes at 1 year of age.

METHODS

A birth cohort (n = 1074) with information on prenatal and postnatal early life factors. Both naïve Treg (nTreg) and activated Treg (aTreg) cell populations (as a proportion of CD4⁺ T cells) were available in 463 infants at birth (cord blood), 600 at 6 months, and 675 at 12 months. 191 infants had serial measures. Measures of allergic status at 12 months were polysensitization (sensitization to 2 or more allergens), clinically proven food allergy, atopic eczema, and atopic wheeze.

RESULTS

Infants born to larger households (3 or more residents) had higher longitudinal nTreg proportions over the first postnatal year with a mean difference (MD) of 0.67 (95% CI 0.30-1.04)%. Higher nTreg proportions at birth were associated with a reduced risk of infant allergic outcomes. Childcare attendance and breastfeeding were associated with higher longitudinal nTreg proportions (MD 0.48 (95% CI 0.08-0.80)%.

CONCLUSION

Multiple prenatal and postnatal microbial factors are associated with nTreg and aTreg development. Larger household size was associated with higher nTreg at birth which in turn was associated with reduced allergic sensitization and disease at 12 months of age.

Galectin-1 secreted by bone marrow-derived mesenchymal stem cells mediates anti-inflammatory responses in acute airway disease

The hallmarks of allergic airway disease (AAD) include infiltration of inflammatory cells into the bronchoalveolar space. Bone marrow derived mesenchymal stem cells (BMSCs) show anti-inflammatory properties in AAD. In addition, galectin-1 (Gal-1) is a lectin significantly upregulated upon inflammation and is also known to mediate potential anti-inflammatory responses. We hypothesized that BMSCs regulated inflammatory responses by secretion of Gal-1 during AAD pathogenesis. BMSCs were isolated from murine femurs and tibiae and adoptively transferred into an ovalbumin-induced AAD mouse model. Knockdown of Gal-1 in BMSCs was performed using shRNA. Flow cytometry, ELISAs, and immunohistology were performed to analyze inflammatory responses in mice, and a Transwell system was used to establish an in vitro co-culture system of lung epithelial cells (MLE-12) and BMSCs. Administration of BMSCs significantly upregulated Gal-1 expression upon inflammation and decreased infiltration of inflammatory cells and secretion of proinflammatory cytokines in vivo. In addition, we showed that this function was mediated by reduced activation of the MAPK p38 signaling pathway. Similar observations were found using an in vitro lipopolysaccharide-induced model when MLE-12 cells were co-cultured with BMSCs. Gal-1 secretion by BMSCs alleviated inflammatory responses observed in AAD and hence provides a promising therapeutic alternative to AAD patients insensitive to conventional drug treatments.

Training the Fetal Immune System Through Maternal Inflammation-A Layered Hygiene Hypothesis

Over the last century, the alarming surge in allergy and autoimmune disease has led to the hypothesis that decreasing exposure to microbes, which has accompanied industrialization and modern life in the Western world, has fundamentally altered the immune response. In its current iteration, the “hygiene hypothesis” suggests that reduced microbial exposures during early life restricts the production and differentiation of immune cells suited for immune regulation. Although it is now well-appreciated that the increase in hypersensitivity disorders represents a “perfect storm” of many contributing factors, we argue here that two important considerations have rarely been explored. First, the window of microbial exposure that impacts immune development is not limited to early childhood, but likely extends into the womb. Second, restricted microbial interactions by an expectant mother will bias the fetal immune system toward hypersensitivity. Here, we extend this discussion to hypothesize that the cell types sensing microbial exposures include fetal hematopoietic stem cells, which drive long-lasting changes to immunity.

Whole-Cell Pertussis Vaccination and Decreased Risk of IgE-Mediated Food Allergy: A Nested Case-Control Study

BACKGROUND

Rates of food allergy have increased markedly in Australia and other high- income countries in recent years. On the basis of ecological observations, and the known immunologic characteristics of whole-cell pertussis (wP) compared with acellular pertussis (aP) vaccines, we hypothesized that wP vaccination in infancy protects against the development of food allergy.

OBJECTIVE

To determine whether infants who receive wP in infancy were less likely to develop IgE-mediated food allergy than those who received aP.

METHODS

Retrospective cohort-nested case-control study of Australian children born in the period 1997 to 1999, the period of transition from using wP-containing to aP-containing vaccines. Children diagnosed with IgE-mediated food allergy were individually matched to 10 controls by date of birth, socioeconomic decile, and jurisdiction of birth. The odds ratio of vaccination with wP versus aP among cases and matched controls was calculated using conditional logistic regression.

RESULTS

The odds ratio of receiving the first dose as wP (rather than aP) among cases of food allergy compared with controls was 0.77 (95% CI, 0.62-0.95). The results of secondary analyses (any dose as wP vs aP-only, and wP-only vs aP-only) were broadly similar.

CONCLUSIONS

Australian infants who received wP vaccines were less likely to be diagnosed with food allergy in childhood than contemporaneous children who received aP vaccines. If a protective effect is confirmed in a randomized controlled trial, wP or mixed wP and aP vaccination schedules could form part of an effective strategy for combating the rise in food allergies.

An immune gate of depression - Early neuroimmune development in the formation of the underlying depressive disorder

The prevalence of depression worldwide is increasing from year to year and constitutes a serious medical, economic and social problem. Currently, despite multifactorial risk factors and pathways contributing to depression development, a significant aspect is attributed to the inflammatory process. Cytokines are considered a factor activating the kynurenine pathway, which leads to the exhaustion of tryptophan in the tryptophan catabolite (TRYCAT) pathway. This results in the activation of potentially neuroprogressive processes and also affects the metabolism of many neurotransmitters. The immune system plays a coordinating role in mediating inflammatory process. Beginning from foetal life, dendritic cells have the ability to react to bacterial and viral antigens, stimulating T lymphocytes in a similar way to adult cells. Cytotoxicity in the prenatal period shapes the predisposition to the development of depression in adult life. Allostasis, i.e. the ability to maintain the body's balance in the face of environmental adversity through changes in its behaviour or physiology, allows the organism to survive but its consequences may be unfavourable if it lasts too long. As a result, Th lymphocytes, in particular T helper 17 cells, which play a central role in the immunity of the whole body, contribute to the development of both autoimmune diseases and psychiatric disorders including depression, as well as have an impact on the differentiation of T CD4+ cells into Th17 cells in the later development of the child's organism, which confirms the importance of the foetal period for the progression of depressive disorders.

Epigenetic dysregulation of naive CD4+ T-cell activation genes in childhood food allergy

Food allergy poses a significant clinical and public health burden affecting 2–10% of infants. Using integrated DNA methylation and transcriptomic profiling, we found that polyclonal activation of naive CD4+ T cells through the T cell receptor results in poorer lymphoproliferative responses in children with immunoglobulin E (IgE)-mediated food allergy. Reduced expression of cell cycle-related targets of the E2F and MYC transcription factor networks, and remodeling of DNA methylation at metabolic (RPTOR, PIK3D, MAPK1, FOXO1) and inflammatory genes (IL1R, IL18RAP, CD82) underpins this suboptimal response. Infants who fail to resolve food allergy in later childhood exhibit cumulative increases in epigenetic disruption at T cell activation genes and poorer lymphoproliferative responses compared to children who resolved food allergy. Our data indicate epigenetic dysregulation in the early stages of signal transduction through the T cell receptor complex, and likely reflects pathways modified by gene–environment interactions in food allergy.

Immunoglobulin E (IgE)-mediated food allergy is a major issue that affects 2–10% of infants. Here the authors study the epigenetic regulation of the naive CD4+ T cell activation response among children with IgE-mediated food allergy finding epigenetic dysregulation in the early stages of signal transduction through the T cell receptor complex.

The mechanism or mechanisms driving atopic asthma initiation: The infant respiratory microbiome moves to center stage

Developments over the last 5 to 10 years, principally from studies on comprehensively phenotyped prospective birth cohorts, have highlighted the important role of viral respiratory tract infections during infancy and early childhood, particularly those occurring against a background of pre-existing sensitization to perennial aeroallergens, in driving the development of early-onset atopic asthma. Although debate surrounding the mechanism or mechanisms governing this causal pathway remains intense, demonstration of the capacity of pretreatment with anti-IgE antibody to blunt seasonal virus-associated asthma exacerbations in children provides strong support for the underlying concept. However, emerging data appear set to further complicate this picture. Notably, a combination of culture-based studies and complementary population-wide bacterial metagenomic data suggests that parallel host-bacteria interactions during infancy might play an additional role in modulating this causal pathway, as well as contributing independently to pathogenesis. These and related issues surrounding development of immune competence during the crucial early postnatal period, when these pathways are maximally active, are discussed below.

Elucidation of pathways driving asthma pathogenesis: development of a systems-level analytic strategy

Asthma is a genetically complex, chronic lung disease defined clinically as episodic airflow limitation and breathlessness that is at least partially reversible, either spontaneously or in response to therapy. Whereas asthma was rare in the late 1800s and early 1900s, the marked increase in its incidence and prevalence since the 1960s points to substantial gene × environment interactions occurring over a period of years, but these interactions are very poorly understood (1-6). It is widely believed that the majority of asthma begins during childhood and manifests first as intermittent wheeze. However, wheeze is also very common in infancy and only a subset of wheezy children progress to persistent asthma for reasons that are largely obscure. Here, we review the current literature regarding causal pathways leading to early asthma development and chronicity. Given the complex interactions of many risk factors over time eventually leading to apparently multiple asthma phenotypes, we suggest that deeply phenotyped cohort studies combined with sophisticated network models will be required to derive the next generation of biological and clinical insights in asthma pathogenesis.

Maternal and postnatal dietary probiotic supplementation enhances splenic regulatory T helper cell population and reduces peanut allergen-induced hypersensitivity responses in mice

Neonatal to early childhood is the critical period for establishing a balance of T helper 1 (Th1) versus T helper 2 (Th2) cellular immunity within the gut, which is strongly influenced by the source and establishment of gut microflora. Probiotic administration has been shown to attenuate Th2-biased cellular immunity and predisposition to food allergies. To test this hypothesis we provided ad libitum a probiotic-supplemented (Primalac 454 Feed Grade Microbials) or control diet to lactating dams with suckling pups and weaned pups until 10 weeks of age. Weaned mice were sensitized/challenged with peanut extract, saline or adjuvant at 6, 8 and 10 weeks of age. At 3, 6, 8 and 10 weeks, fecal samples were collected for microbial analysis, while blood samples were analyzed for total plasma IgE levels. At termination (10 weeks of age), splenic T lymphocyte population subtypes were determined using FACS analysis and Th1/Th2/Th17 gene expression by PCR array. Mice given the probiotic-supplemented diet had significantly enhanced probiotic fecal counts compared to controls at 3, 6, 8 and 10 weeks. Moreover, mice fed the probiotic-supplemented diet had enhanced splenic naturally occurring T regulatory cell populations, and reduced splenic gene expression of allergic mediator IL-13 compared to controls. These results provide evidence that early probiotic supplementation may provide host protection to hypersensitivity reactions to food allergens by attenuating food allergen inflammatory responses.

Asthma and the immune response to MMR vaccine viruses in Somali immigrant children: a cross-sectional retrospective cohort study

Background:

According to the ‘hygiene hypothesis’, an increase in microbial exposure in childhood leads to a T-helper cell 1 (Th1) predominant immune response and protection against asthma and atopic conditions.

Aims:

To assess the prevalence of asthma and other atopic conditions in Somali immigrants and to determine the humoral immune response to the measles, mumps, and rubella (MMR) vaccine viruses in Somali immigrants with asthma.

Methods:

A retrospective cohort study was conducted in Olmsted County, Minnesota. Study subjects were Somali immigrants who were born and lived in Africa during childhood and immigrated to the USA. The subjects had participated in a previous MMR vaccine study. Asthma was ascertained using predetermined asthma criteria after a thorough medical record review. An atopic condition was determined from physician-diagnosed ICD codes. Virus-specific IgG levels in response to the MMR vaccine viruses were determined using an enzyme immunoassay.

Results:

Of the 62 eligible subjects, 33 (53%) were female and 29 (47%) were male; 10 (16%) had asthma and 22 (35%) had other atopic conditions. There was no difference in the rubella (p=0.150) and measles (p=0.715) virus-specific IgG levels between the subjects with and without asthma. Mumps virus-specific IgG antibody levels were lower in those with asthma than in those without asthma (mean±SE 2.08±0.28 vs. 3.06±0.14, p=0.005).

Conclusions:

Our study results may not support the hygiene hypothesis. In addition, the previously reported abnormal T-cell development in Caucasian children with atopy can be considered even in Somali immigrants.

Persistent effects of maternal smoking during pregnancy on lung function and asthma in adolescents

RATIONALE

The extent to which maternal smoking in pregnancy (MSP) has persisting effects on respiratory health remains uncertain and the mechanisms involved are not fully understood. Alterations in immune function have been proposed as a mechanism contributing to respiratory disease.

OBJECTIVES

To determine whether MSP increases risk of respiratory disorders in adolescence and, if so, whether this occurs by decreased lung function, altered immune function, and/or enhanced atopy.

METHODS

Data on spirometry, bronchial responsiveness, respiratory symptoms, total and allergen-specific IgE and IgG4, immune function, and inflammatory markers were obtained from 1,129 participants in the 14-year follow-up of the Western Australian Pregnancy (Raine) Cohort and related to MSP using regression analyses.

MEASUREMENTS AND MAIN RESULTS

MSP was reported for 21.0% (237 of 1,129) of participants, with 92 (8.1%) reporting current smoking. MSP was associated with some altered immune measures at age 14. MSP was strongly related to reduced lung function in current nonsmokers (forced expiratory flow midexpiratory phase [FEF25-75%], P = 0.016; FEV1/FVC, P = 0.009) and increased risk for current asthma (odds ratio [OR], 1.84; 95% confidence interval [CI], 1.16-2.92; P = 0.01), current wheeze (OR, 1.77; 95% CI, 1.14-2.75; P = 0.011), and exercise-induced wheeze (OR, 2.29; 95% CI, 1.37-3.85; P = 0.002), but not for bronchial hyperresponsiveness or atopy. Adjustment for immune measures and/or lung function in multivariate models did not greatly alter these associations and the increased risks for asthma and wheeze were not modified by sex, atopy, or maternal history of asthma or atopy.

CONCLUSIONS

MSP increases risk of asthma and wheezing in adolescence; mechanisms go beyond reducing lung function and exclude altering immune function or enhancing atopy.

The neonatal susceptibility window for inhalant allergen sensitization in the atopically predisposed canine asthma model

Allergic asthma often begins in early life and, although many risk factors have been enumerated, the specific factors that initiate disease progression in an individual remain unclear. Using our dog model of early life allergen inhalation, we tested the hypothesis that the atopically biased neonatal immune system would exhibit tolerance to ragweed if allowed to mature normally before exposure or artificially through innate immune stimulation with early life exposure. Dogs were subjected to a series of inhalational ragweed exposures from 1 to 20 weeks old, with or without inhalation of a Toll-like receptor 4 (TLR4) agonist (CRX-527), or from 13 to 31 weeks old. Serum allergen-specific antibody response was assessed at 4, 8 and 20 weeks after the last sensitizing exposure. At 24 or 35 weeks old, airway hyper-responsiveness to methacholine and ragweed challenges and pulmonary inflammation by bronchoalveolar lavage were tested 1 and 4 days after ragweed challenge at 28 or 39 weeks old. Allergen-free immune maturation resulted in no airway hyper-responsiveness and very little ragweed-specific IgE relative to the control group, but eosinophilia developed upon ragweed challenge. TLR4 agonism yielded no airway hyper-responsiveness, but a strong airway neutrophilia developed upon ragweed challenge. Our data indicate that an atopic predisposition creates a critical window in which allergen exposure can lead to an asthmatic phenotype. Allergen-free immune maturation may lead to allergen tolerance. TLR4 agonism before early life allergen exposure may abrogate the development of allergen-specific bronchonconstriction, but allergen-specific pulmonary inflammation remains a strong concern.

How aluminum adjuvants could promote and enhance non-target IgE synthesis in a genetically-vulnerable sub-population

Aluminum-containing adjuvants increase the effectiveness of vaccination, but their ability to augment immune responsiveness also carries the risk of eliciting non-target responses, especially in genetically susceptible individuals. This study reviews the relevant actions of aluminum adjuvants and sources of genetic risk that can combine to adversely affect a vulnerable sub-population. Aluminum adjuvants promote oxidative stress and increase inflammasome activity, leading to the release of IL-1β, IL-18, and IL-33, but not the important regulatory cytokine IL-12. In addition, they stimulate macrophages to produce PGE₂, which also has a role in regulating immune responses. This aluminum-induced cytokine context leads to a T(H)2 immune response, characterized by the further release of IL-3, IL-4, IL-5, IL-9, IL-13, and IgE-potentiating factors such as sCD23. Genetic variants in cytokine genes, such as IL-4, IL-13, IL-33, and IL-18 influence the response to vaccines in children and are also associated with atopy. These genetic factors may therefore define a genetically-vulnerable sub-population, children with a family history of atopy, who may experience an exaggerated T(H)2 immune response to aluminum-containing vaccines. IL-4, sCD23, and IgE are common factors for both atopy and the immune-stimulating properties of aluminum adjuvants. IL-4 is critical in the production of IgE and total IgE up-regulation. IL-4 has also been reported to induce the production of sCD23 and trigger resting sIgM+, sIgD+ B-cells to switch to sIgE+ B-cells, making them targets for IgE-potentiating factors. Further, the actions of IgE-potentiating factors on sIgE+ B-cells are polyclonal and unrestricted, triggering their differentiation into IgE-forming plasma cells. These actions provide a mechanism for aluminum-adjuvant promotion and enhancement of non-target IgE in a genetically vulnerable sub-population. Identification of these individuals may decrease the risk of adverse events associated with the use of aluminum-containing vaccines.

Analysis of cyt0kine gene expression in stimulated T cells of small children by semi-quantitative PCR

Only limited amounts of peripheral blood samples can be obtained from small children. Therefore, a polymerase chain reaction (PCR) aided analysis of cytokine gene expression by PBMC or T cells is a valuable tool. We present a combination of procedures to obtain an accurate estimation of the expression of the cytokines IL-4 and IFN-γ. This can be performed on T cells purified from blood samples of up to 5 ml in volume from children aged 0–4 years with allergic asthma and atopic dermatitis. This procedure includes multiple sampling of PCR products to determine the linear phase of the PCR; inter-experiment correction using a helper T-cell clone, expressing both IL-4 and IFN-γ; interpatient correction by comparing the expression of a housekeeping gene (HPRT); and finally the development of specific software to analyse densitometric data obtained by scanning photographs of agarose gels, separating PCR products. In this way it is possible to study cytokine gene expression from a very small amount of material.

Asthma as a chronic disease of the innate and adaptive immune systems responding to viruses and allergens

Research on the pathogenesis of asthma has traditionally concentrated on environmental stimuli, genetic susceptibilities, adaptive immune responses, and end-organ alterations (particularly in airway mucous cells and smooth muscle) as critical steps leading to disease. The focus of this cascade has been the response to allergic stimuli. An alternative scheme suggests that respiratory viruses and the consequent response of the innate immune system also drives the development of asthma as well as related inflammatory diseases. This conceptual shift raises the possibility that sentinel cells such as airway epithelial cells, DCs, NKT cells, innate lymphoid cells, and macrophages also represent critical components of asthma pathogenesis as well as new targets for therapeutic discovery. A particular challenge will be to understand and balance the innate as well as the adaptive immune responses to defend the host against acute infection as well as chronic inflammatory disease.

Influence of asthma epidemiology on the risk for other diseases

Asthma is a multifactorial chronic disease affecting a significant proportion of people in the United States and worldwide. Numerous laboratory and epidemiological studies have attempted to understand the etiology and underlying mechanisms of asthma and to identify effective therapies. However, the impact of asthma on the risk for other diseases has drawn little attention. This paper discusses the potential effects of asthma as a risk factor for other diseases, explores the potential mechanisms, and reviews the implications of the findings to clinical practice, public health, and research.

T-cell activation genes differentially expressed at birth in CD4+ T-cells from children who develop IgE food allergy

BACKGROUND

Presymptomatic immaturity in neonatal T-cell function is a consistent antecedent of allergic disease, including reduced responsiveness to polyclonal activation.

METHODS

To elucidate the underlying mechanisms, we examined for differences in T-cell gene expression in longitudinal samples collected at birth and at 1 year of age in children with (n = 30) and without IgE-mediated food allergy (n = 30). We employed a low-level soluble anti-CD3 stimulus to activate the T-cell receptor (TCR) and surveyed gene expression by DNA microarray in purified CD4(+) T-cells. Allergen-specific responses were assessed in parallel functional studies.

RESULTS

At birth, the allergic group showed a reduced number of genes up regulated in response to anti-CD3 treatment on the microarray and a reduced lympho proliferative capacity, suggesting clear differences in T-cell signalling pathways. Polymerase chain reaction (PCR) validation of candidate genes confirmed significantly lower expression of a number of genes in the allergic group including RELB, NFKB2, LIF and FAS. By 12 months of age, there were marked changes in the anti-CD3 response in all infants, culminating in upregulation of cytokine genes (IL-5, IL-13, IL-17 and IL-22). Neonatal differences were no longer apparent. Instead, the allergic group, all symptomatic by this age, showed differential expression of T-cell lineage pathways including GATA-3, MAL and FcER1 in unstimulated T-cells. Allergen stimulation induced significantly higher cytokines production (IL-5, IL-13 and IFNγ) in the allergic group.

CONCLUSION

Although transient, suboptimal neonatal T-cell activation pathways that signal through the NF-κB complex may affect the developmental transition of T-cell phenotypes in the periphery shortly after birth and may increase the risk of food allergy.

Can we prevent food allergy by manipulating the timing of food exposure?

Prevention of food allergies by maternal and infant feeding practices serves as a simple, inexpensive approach to address the growing number of subjects with food allergies in comparison with any emerging interventional therapies for existing food allergies, such as oral immunotherapy. This article provides a careful evaluation of the rationale and existing data on the effect of timing of the introduction of food allergens (during pregnancy, lactation, and early childhood) on the development of specific food allergies.

T regulatory cells in childhood asthma

Asthma is a chronic disease of the airways, most commonly driven by immuno-inflammatory responses to ubiquitous airborne antigens. Epidemiological studies have shown that disease is initiated early in life when the immune and respiratory systems are functionally immature and less able to maintain homeostasis in the face of continuous antigen challenge. Here, we examine the cellular and molecular mechanisms that underlie initial aeroallergen sensitization and the ensuing regulation of secondary responses to inhaled allergens in the airway mucosa. In particular, we focus on how T-regulatory (Treg) cells influence early asthma initiation and the potential of Treg cells as therapeutic targets for drug development in asthma.

Antibiotic exposure by 6 months and asthma and allergy at 6 years: Findings in a cohort of 1,401 US children

Many studies have reported that antibiotic use may be associated with increased risk of childhood asthma. Respiratory tract infections in small children may be difficult to distinguish from early symptoms of asthma, and studies may have been confounded by "protopathic" bias, where antibiotics are used to treat early symptoms of asthma. These analyses of a cohort including 1,401 US children assess the association between antibiotic use within the first 6 months of life and asthma and allergy at 6 years of age between 2003 and 2007. Antibiotic exposure was associated with increased risk of asthma (adjusted odds ratio = 1.52, 95% confidence interval (CI): 1.07, 2.16). The odds ratio if asthma was first diagnosed after 3 years of age was 1.66 (95% CI: 0.99, 2.79) and, in children with no history of lower respiratory infection in the first year of life, the odds ratio was 1.66 (95% CI: 1.12, 3.46). The adverse effect of antibiotics was particularly strong in children with no family history of asthma (odds ratio = 1.89, 95% CI: 1.00, 3.58) (P(interaction) = 0.03). The odds ratio for a positive allergy blood or skin test was 1.59 (95% CI: 1.10, 2.28). The results show that early antibiotic use was associated with asthma and allergy at 6 years of age, and that protopathic bias was unlikely to account for the main findings.

The hygiene hypothesis revisited: role of materno-fetal interactions

For 20 years, the hygiene hypothesis has dominated attempts to explain the increasing prevalence of allergic disease. A causal link between maternal innate immune response during pregnancy and disease protection in the offspring was recently demonstrated. Central to this was a systemically diffused signal that downregulated Toll-like receptor expression in placental tissues. Herein we develop the hypothesis that maternal systemic regulatory mechanisms operational during pregnancy could impact allergic disease risk of the offspring, depending on the type of inflammatory response from which they originate. Classic microbial-derived, mild, subacute inflammation provides a protective signal, whereas allergic inflammation provides a negative one. Mild, subacute inflammation of pregnant women leads to systemically diffused signals manifest in the gestation-associated tissues and by the fetus and newborn as a dampened inflammatory response. The converse is true if the mother has allergic inflammation during pregnancy. In both cases, these impact on development of the airways and of balanced immune function at birth and in early postnatal life. Thus, we seem to be at the dawn of a new incarnation of the hygiene hypothesis in which the pregnant woman's inflammatory response is crucial to determining the child's likelihood of developing allergic disease.

Neonatal immune function and inflammatory illnesses in later life: lessons to be learnt from the developing world?

With the emergence of allergic and autoimmune diseases in populations that have started to transit to a western lifestyle, there has been an increasing interest in the role of environmental factors modulating early immune function. Yet, most of the information concerning neonatal immune function has been derived from studies in westernized countries. We postulate that comparative studies of early immune development in children born under conditions that are typical for a westernized vs. that of a still more traditional setting will provide a crucial insight into the environmental-driven immunological mechanisms that are responsible for the world-wide rise in inflammatory disorders. In this review, we summarize the current understanding of early-life immune function in humans in general and the literature on some major lifestyle factors that may influence neonatal immune function and potentially the risk for disease in later life. An understanding of the mechanisms of 'prenatal/early-life programming' in populations living in traditional compared with modern societies is crucial to develop strategies to prevent a further rise in 'western diseases' such as allergic disorders. Indications exist that prenatal conditioning of the innate immune system by low-grade inflammatory responses is key to inducing more tightly regulated postnatal adaptive immune responses.

Dendritic cells interact with CD4 T cells in intestinal mucosa

Absence of lymph nodes in nonmammalian species, expression of MHCII by APCs in the periphery, and the recent findings that T cells can change their polarization status after presentation in the lymph nodes imply a role for MHCII-mediated presentation outside the organized lymphoid tissue. This study shows that MHCII(+) ECs and DCs from the intestinal mucosa of the pig can present antigen to T cells in vitro. In vivo, APCs colocalize with T cells in pig and mouse intestinal mucosa. In the pig, endothelium is involved in these interactions in neonates but not in adults, indicating different roles for stromal and professional APCs in the neonate compared with the adult. The ratio of expression of DQ and DR MHCII locus products was lower on ECs than on other mucosal APCs, indicating that the two types of cells present different peptide sets. Adult nonendothelial APCs expressed a higher ratio of DQ/DR than in neonates. These results suggest that mucosal DCs can present antigen locally to primed T cells and that stromal APCs are recruited to these interactions in some cases. This raises the possibility that local presentation may influence T cell responses at the effector stage after initial presentation in the lymph node.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: the role of infections in allergy: atopic asthma as a paradigm

Earlier iterations of the 'hygiene hypothesis', in which infections during childhood protect against allergic disease by stimulation of the T helper type 2 (Th2)-antagonistic Th1 immunity, have been supplanted progressively by a broader understanding of the complexities of the underlying cellular and molecular interactions. Most notably, it is now clear that whole certain types of microbial exposure, in particular from normal gastrointestinal flora, may provide key signals driving postnatal development of immune competence, including mechanisms responsible for natural resistance to allergic sensitization. Other types of infections can exert converse effects and promote allergic disease. We review below recent findings relating to both sides of this complex picture.

A role for the atopy-associated gene PHF11 in T-cell activation and viability

Polymorphisms within plant homeodomain finger protein 11 (PHF11) are associated with total IgE, allergic asthma and eczema. PHF11 is a transcriptional co-activator of the Th1 effector cytokine genes, interleukin-2 (IL2) and interferon-γ (IFNG), co-operating with nuclear factor kappa B (NF-κB). The involvement with NF-κB led us to test whether PHF11 might have a broader function in T-cell activation and viability. We show that PHF11 is abundant in the cytoplasm of T-cells and imported into the nucleus of activated T-cells. Consistent with its presence in the nucleus, PHF11 was recruited to the IFNG promoter and over-expression of PHF11 increased the binding of NF-κB to the IFNG promoter and IFNG gene transcription. Over-expression of PHF11 did not increase IL2 gene transcription, suggesting some specificity in promoter recognition. In contrast, small-interfering RNA knock-down of PHF11 decreased transcription of both IFNG and IL2 and led to decreased CD28 cell-surface expression and reduced NF-κB nuclear import and DNA binding. Knock-down of PHF11 also decreased cell viability and was accompanied by reduced expression of GIMAP4 and 5 genes required for T-cell differentiation, viability and homeostasis. Therefore, in addition to its earlier identified function in regulating Th1 cytokine gene expression, we now show that PHF11 has a broader function in contributing to T-cell activation and viability.

Ageing and its possible impact on mucosal immune responses

The development, structural diversification, and functional maturation of mammalian immunologic repertoire at mucosal surfaces and the systemic lymphoid tissue is a remarkably dynamic and continuous process, which begins in early fetal life and eventually culminates in variable degree of senescence or cellular death with advancing age. This brief overview will highlight the status of our current understanding of the ontogeny of mucosal immunologic response. The role of mucosal microflora and other environmental macromolecules in the regulation of mucosal immunity relative to the process of ageing will also be reviewed.

Probiotics for allergic respiratory diseases--putting it into perspective

Respiratory allergies include allergic rhinitis, sinusitis and asthma. Increasing attention on pathogenesis of allergic airway diseases has given rise to "atopic march" hypothesis i.e. clinical features of atopic eczema occur first and precede the development of asthma and allergic rhinitis. The "hygiene hypothesis" proposes that the increase in allergic diseases reflects a decrease in infections during childhood. Clinical trials also suggest that the exposure to microbes through the gastrointestinal tract powerfully shapes immune function. Probiotics are live organisms which exert a beneficial effect in the prevention as well as treatment of allergic diseases through modification of immune system of host via gut ecosystem. Intestinal microbiota differs in infants who later develop allergic diseases, and feeding probiotics to infants at risk has been shown to reduce their rate of developing eczema. This has prompted studies of feeding probiotics in prevention as well as treatment of respiratory allergy. We hereby discuss the status of probiotics in respiratory allergy.

Silent mysteries: epigenetic paradigms could hold the key to conquering the epidemic of allergy and immune disease

Epigenetic mechanisms provide new insights into how environmental changes may mediate the increasing propensity for complex immune diseases such as allergic disease. There is now strong evidence that early environmental exposures play a key role in activating or silencing genes by altering DNA and histone methylation, histone acetylation and chromatin structure. These modifications determine the degree of DNA compaction and accessibility for gene transcription, altering gene expression, phenotype and disease susceptibility. While there is already evidence that a number of early environmental exposures are associated with an increased risk of allergic disease, several new studies indicate in utero microbial and dietary exposures can modify gene expression and allergic disease propensity through epigenetic modification. This review explores the evidence that immune development is under clear epigenetic regulation, including the pattern of T helper (Th)1 and Th2 cell differentiation, regulatory T cell differentiation, and more recently, Th17 development. It also considers the mechanisms of epigenetic regulation and early immune defects in allergy prone neonates. The inherent plasticity conferred by epigenetic mechanisms clearly also provides opportunities for environmental strategies that can re-programme gene expression for disease prevention. Identifying genes that are differentially silenced or activated in relation to subsequent disease will not only assist in identifying causal pathways, but may also help identify the contributing environmental factors.

Soothing signals: transplacental transmission of resistance to asthma and allergy

The progressive rise in the prevalence of allergic diseases since the 1970s is widely attributed to diminished exposure to microbial stimuli, resulting in dysregulated immune functions during early life. Most studies investigating the mechanism behind this phenomenon have focused on postnatal microbial exposure. But emerging evidence suggests that such programming may also occur in the developing fetus as a result of microbial stimulation of the pregnant mother.

Pathogenic mechanisms of allergic inflammation: atopic asthma as a paradigm

Prospective studies tracking birth cohorts over periods of years indicate that the seeds for atopic asthma in adulthood are sewn during early life. The key events involve programming of functional phenotypes within the immune and respiratory systems which determine long-term responsiveness to ubiquitous environmental stimuli, particularly respiratory viruses and aeroallergens. A crucial component of asthma pathogenesis is early sensitization to aeroallergens stemming from a failure of mucosal tolerance mechanisms during the preschool years, which is associated with delayed postnatal maturation of a range of adaptive and innate immune functions. These maturational defects also increase risk for severe respiratory infections, and the combination of sensitization and infections maximizes risk for early development of the persistent asthma phenotype. Interactions between immunoinflammatory pathways stimulated by these agents also sustain the disease in later life as major triggers of asthma exacerbations. Recent studies on the nature of these interactions suggest the operation of an infection-associated lung:bone marrow axis involving upregulation of FcERlalpha on myeloid precursor populations prior to their migration to the airways, thus amplifying local inflammation via IgE-mediated recruitment of bystander atopic effector mechanisms. The key participants in the disease process are airway mucosal dendritic cells and adjacent epithelial cells, and transiting CD4(+) effector and regulatory T-cell populations, and increasingly detailed characterization of their roles at different stages of pathogenesis is opening up novel possibilities for therapeutic control of asthma. Of particular interest is the application of genomics-based approaches to drug target identification in cell populations of interest, exemplified by recent findings discussed below relating to the gene network(s) triggered by activation of Th2-memory cells from atopics.

Potential association between allergic diseases and pertussis infection in schoolchildren: results of two cross-sectional studies seven years apart

BACKGROUND

In this study, we aimed to investigate the relationship between pertussis infections and allergic diseases in two cross-sectional questionnaire-based surveys carried out in 1997 and 2004. We also measured serum level of antibody to B. pertussis.

MATERIAL AND METHODS

Two cross-sectional, questionnaire-based surveys were carried out in 1997 (n = 3164) and 2004 (n = 3728). 361 cases and 465 controls were recruited from both surveys. The skin tests were performed using standardised extracts. The level of pertussis specific IgG was measured in 136 allergic and 168 non-allergic children.

RESULTS

We found that allergic diseases prevalence was significantly higher in the children suffering from pertussis infections (22.3 % fi rst and 8.8 % second survey) compared to children who did not suffer from pertussis infections (6.6 % fi rst and 4.5 % second survey) (p = 0.001 and p = 0.035, respectively). Asthma prevalence was also significantly higher in children suffering from pertussis infection (37.6 % fi rst and 26.2 % second survey) compared to children who did not suffer from pertussis (7.4 % fi rst and 5.0 % second survey) (p = 0.001 and p = 0.001, respectively). However, the mean serum levels of anti-pertussis IgG were similar in allergic and non-allergic groups (p > 0.05).

CONCLUSION

Although pertussis antibody levels in atopic and non-atopic children were similar to each other, pertussis infection still seemed to have a significant effect on the development of atopic diseases.

Lower levels of plasmacytoid dendritic cells in peripheral blood are associated with a diagnosis of asthma 6 yr after severe respiratory syncytial virus bronchiolitis

Plasmacytoid dendritic cells (pDC) play a crucial role in antiviral immunity and promoting Th1 polarization, possibly protecting against development of allergic disease. Examination of the relationship between peripheral blood plasmacytoid DC levels and manifestations of asthma and atopy early in life. We have isolated peripheral blood mononuclear cells (PBMC) from 73 children (mean age +/- SD: 6.6 +/- 0.5 yr old) participating in the RSV Bronchiolitis in Early Life (RBEL) study. Flow cytometry was performed on PBMC detecting DC surface-markers: Blood Dendritic Cell Antigens (BDCA) 1, 3, and 2 which identify myeloid type 1, type 2, and plasmacytoid cells, respectively. Total serum IgE, peripheral eosinophil count, and allergy skin tests were documented. About 45% (n = 33) of study participants had physician-diagnosed asthma by 6 yr of age. These children had significantly lower quantities (mean +/- SD) of plasmacytoid DC than their non-asthmatic counterparts (1020 +/- 921 vs. 1952 +/- 1170 cells per 10(6) PBMC, p = 0.003). We found significantly lower numbers of myeloid dendritic cells in children with asthma (3836 +/- 2472 cells per 10(6) PBMC) compared with those without asthma (4768 +/- 2224 cells per 10(6) PBMC, p = 0.02); however, this divergence was not significant after adjusting for covariates of age, gender, race, skin test reactivity, smoke exposure, and daycare attendance. We did not identify any direct association between DC levels and markers of atopy: skin test reactivity, peripheral eosinophilia, and IgE level. Children who are diagnosed with asthma after severe RSV bronchiolitis appear to have a relative deficiency of plasmacytoid DC in peripheral blood.

Probiotics during weaning reduce the incidence of eczema

A reduced microbial load early in life has been suggested to be linked to the increasing prevalence of allergic diseases in the industrialized world. Some studies have indicated that probiotics may be effective in the prevention of eczema. In vitro studies indicate that probiotics have immunomodulatory effects. In the present study, we evaluated the effects of feeding Lactobacillus F19 during weaning on the incidence of eczema and Th1/Th2 balance. In a double-blind, placebo-controlled randomized intervention trial, infants were fed cereals with (n = 89) or without Lactobacillus F19 (n = 90) from 4 to 13 months of age. We assessed the cumulative incidence of eczema at 13 months of age. The ratio of interferon-gamma (IFN-gamma) to interleukin 4 (IL4) mRNA expression levels in polyclonally stimulated peripheral blood T cells was used as a proxy for immune balance. Total and specific IgE serum levels were also assessed. The cumulative incidence of eczema at 13 months was 11% (4-17%, 95% CI) and 22% (13-31%, 95% CI) in the probiotic and placebo groups, respectively (p < 0.05). The number needed to treat was 9 (6.5-11.5, 95% CI). At 13 months of age, the IFN-gamma/IL4 mRNA ratio was higher in the probiotic compared with the placebo group (p < 0.05). In contrast, there were no differences between groups in serum concentrations of IgE. In summary, feeding Lactobacillus F19 during weaning could be an effective tool in the prevention of early manifestation of allergy, e.g., eczema. The higher Th1/Th2 ratio in the probiotic compared with the placebo group suggests enhancing effects of Lactobacillus F19 on the T cell-mediated immune response.

Allergic bronchopulmonary aspergillosis after infliximab therapy for sarcoidosis: a potential mechanism related to T-helper cytokine balance

We report a case of allergic bronchopulmonary aspergillosis (ABPA) that occurred in a man receiving infliximab for systemic sarcoidosis. His symptoms associated with ABPA were temporally related to his infliximab infusions. We suspect that infliximab disrupted the T-helper (Th) type 1-Th2 lymphocyte balance such that Th2 cytokines were left relatively unopposed, promoting the development of ABPA.

Maternal cytokine production during pregnancy and the development of childhood wheezing and allergic disease in offspring three years of age

Allergic diseases are multifactorial; they develop from complex interactions between genes and the environment. The immunological bias toward atopy and asthma might be established during in utero development of the fetal immune system. We prospectively investigated the association between maternal cytokine changes during pregnancy and the development of childhood wheezing and atopy at three years of age. Blood samples from 90 pregnant women were assayed for TNF-alpha, TGF-beta, IFN-gamma, IL-4, IL-6, and IL-2 at 18 weeks of gestation and at 6 weeks after delivery. Telephone interviews were performed and a questionnaire administered to assess wheezing and allergic disease in the children. The serum total IgE and specific IgE to eggs, milk and dust mites were measured. Maternal IFN-gamma, TNF-alpha and TGF-beta levels significantly decreased during pregnancy compared to the levels after delivery. However, the IL-4 levels did not change. Maternal TNF-alpha and IFN-gamma levels were decreased both before and after delivery in children with reported wheezing. Individual maternal IL-4 levels, before delivery, were higher than after delivery in the children that developed wheezing. There were no significant differences in maternal cytokine levels between children with and without asthma. In children with atopy, the maternal IFN-gamma /IL-4 ratio, during the first trimester, had a tendency to decrease compared to the children without atopy, whereas the maternal IL-2 levels at 6 weeks after delivery were increased. A first pregnancy showed higher concentrations of IL-4 before and after delivery than did women with multiple pregnancies. Maternal cytokine levels begin to change toward a Th2 immunity starting in the first trimester. A stronger Th2 immune response during the first trimester of pregnancy is associated with childhood wheezing and atopy at three years of age, and a first pregnancy.

Suppression of allergic airway inflammation and IgE responses by a class I restricted allergen peptide vaccine

CD8 T cells are known to deviate CD4 T-cell responses from Th2 toward Th1. Reduction of Th2 cytokines and increased interferon-gamma ameliorates allergic airway disease. We have developed a novel approach to the suppression of allergic airway inflammation, by designing a MHC class I-restricted allergen peptide vaccine, which induces potent and long-lived CD8 T-cell responses. Vaccination of C57BL/6 mice before allergen sensitization completely prevented allergen-specific immunoglobulin E (IgE) antibody responses. Vaccination after sensitization failed to suppress IgE, but inhibited accumulation of eosinophils and neutrophils in airways after subsequent allergen challenge. Vaccination suppressed Th2 airway infiltration and enhanced the lung Th1 response without inducing excessive CD8 cellular infiltration or interleukin-17, and the combination of class I peptide with adjuvant was more effective than adjuvant alone. Airway hyperreactivity was prevented by vaccination in an allergen-specific fashion. Class I peptide vaccines might therefore represent a robust and long-lasting immunotherapeutic strategy in allergic disease.