Association of interleukin-2 and interferon-gamma production by blood mononuclear cells in infancy with parental allergy skin tests and with subsequent development of atopy

The intersect of genetics, environment, and microbiota in asthma-perspectives and challenges

In asthma, a significant portion of the interaction between genetics and environment occurs through microbiota. The proposed mechanisms behind this interaction are complex and at times contradictory. This review covers recent developments in our understanding of this interaction: the "microbial hypothesis" and the "farm effect"; the role of endotoxin and genetic variation in pattern recognition systems; the interaction with allergen exposure; the additional involvement of host gut and airway microbiota; the role of viral respiratory infections in interaction with the 17q21 and CDHR3 genetic loci; and the importance of in utero and early-life timing of exposures. We propose a unified framework for understanding how all these phenomena interact to drive asthma pathogenesis. Finally, we point out some future challenges for continued research in this field, in particular the need for multiomic integration, as well as the potential utility of asthma endotyping.

Childhood Asthma Inception and Progression: Role of Microbial Exposures, Susceptibility to Viruses and Early Allergic Sensitization

Inappropriate responses to respiratory viruses, especially rhinovirus, and early allergic sensitization are the strongest contributors to the inception and persistence of early onset asthma. The ORMDL3 asthma locus in chromosome 17q seems to exert its effects by increasing susceptibility to human rhinovirus in early life. Being raised on animal farms is highly protective against the development of asthma, and this protective effect is mediated by exposure to microbes. Two trials in high-risk young children, one to prevent wheezing lower respiratory tract illness using bacterial lyophilizates and another using anti-immunoglobulin E to prevent asthma progression, are already under way.

Methylene-tetrahydrofolate reductase contributes to allergic airway disease

Rationale

Environmental exposures strongly influence the development and progression of asthma. We have previously demonstrated that mice exposed to a diet enriched with methyl donors during vulnerable periods of fetal development can enhance the heritable risk of allergic airway disease through epigenetic changes. There is conflicting evidence on the role of folate (one of the primary methyl donors) in modifying allergic airway disease.

Objectives

We hypothesized that blocking folate metabolism through the loss of methylene-tetrahydrofolate reductase (Mthfr) activity would reduce the allergic airway disease phenotype through epigenetic mechanisms.

Methods

Allergic airway disease was induced in C57BL/6 and C57BL/6^Mthfr-/- mice through house dust mite (HDM) exposure. Airway inflammation and airway hyperresponsiveness (AHR) were measured between the two groups. Gene expression and methylation profiles were generated for whole lung tissue. Disease and molecular outcomes were evaluated in C57BL/6 and C57BL/6^Mthfr-/- mice supplemented with betaine.

Measurements and main results

Loss of Mthfr alters single carbon metabolite levels in the lung and serum including elevated homocysteine and cystathionine and reduced methionine. HDM-treated C57BL/6^Mthfr-/- mice demonstrated significantly less airway hyperreactivity (AHR) compared to HDM-treated C57BL/6 mice. Furthermore, HDM-treated C57BL/6^Mthfr-/- mice compared to HDM-treated C57BL/6 mice have reduced whole lung lavage (WLL) cellularity, eosinophilia, and Il-4/Il-5 cytokine concentrations. Betaine supplementation reversed parts of the HDM-induced allergic airway disease that are modified by Mthfr loss. 737 genes are differentially expressed and 146 regions are differentially methylated in lung tissue from HDM-treated C57BL/6^Mthfr-/- mice and HDM-treated C57BL/6 mice. Additionally, analysis of methylation/expression relationships identified 503 significant correlations.

Conclusion

Collectively, these findings indicate that the loss of folate as a methyl donor is a modifier of allergic airway disease, and that epigenetic and expression changes correlate with this modification. Further investigation into the mechanisms that drive this observation is warranted.

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.

Neonatal protein kinase C zeta expression determines the neonatal T-Cell cytokine phenotype and predicts the development and severity of infant allergic disease

BACKGROUND

Previous studies have demonstrated that reduced T-cell protein kinase C zeta (PKCζ) expression is associated with allergy development in infants born to atopic mothers. This study examined whether this relationship extends to a general population and addressed the basis for the association.

METHODS

A flow cytometry assay was developed for the measurement of T-cell PKCζ levels in PBMC, cord blood mononuclear cell and whole blood. Cord blood T-cell PKCζ levels were measured in 135 neonates, and allergic disease was evaluated by skin prick test and clinical examination at 12 months of age.

RESULTS

Allergic children (particularly those with eczema) had significantly lower neonatal T-cell PKCζ expression than nonallergic children (P < 0.001). PKCζ levels predicted allergic disease with optimal specificity of 86% and sensitivity of 54%. The sensitivity was increased in the children of allergic mothers, who had significantly lower PKC levels than the children of nonallergic mothers. Cord blood PKCζ levels did not affect T-cell maturation in culture as assessed by CD45RA/RO expression, but low PKCζ expression was associated with reduced capacity for IFNγ production by matured T cells. Low cord blood PKC expression was further associated with increased IL-13 responses at 6 months.

CONCLUSIONS

The findings suggest a potential role for the use of PKCζ levels in cord blood T cells as a presymptomatic test to predict allergy risk in children, particularly offspring of allergic mothers, and that the basis of this relationship is related to cytokine patterns in mature T cells.

Cord blood cellular proliferative response as a predictive factor for atopic dermatitis at 12 months

Since the risk of developing allergic disease increases in individuals exposed to allergens previously, even during the neonatal period, the immunologic status of a fetus may be important in the subsequent development of allergy. We evaluated the fetal factors to predict atopic dermatitis (AD) at 12 months in 412 infants of a COhort for Childhood Origin of Asthma and Allergic Diseases (COCOA) in the general Korean population. Cord blood mononuclear cells (CBMCs) were stimulated with ovalbumin and phytohemagglutinin and cellular proliferative response and concentrations of interleukin-13 and interferon-γ, were measured. The risk of developing AD was greater in boys than girls (OR 1.97, 95% CI 1.26-3.09), infants delivered by cesarean section than vaginally (OR 1.93, 95% CI 1.14-3.26) and infants with than without parental history of AD (OR 2.34, 95% CI 1.29-4.24). The CBMC proliferative response to phytohemagglutinin stimulation was higher in infants with than without AD (P = 0.048), but no difference was observed in ovalbumin-stimulated cells (P = 0.771). Risk factors for the development of AD at 12 months include male gender, delivery by cesarean section and parental history of AD. Increased CBMC proliferative response to phytohemagglutinin stimulation may predict the development of AD at 12 months.

Allergic sensitization frequency and wheezing differences in early life between black and white children

Asthma is more common in black children than in white children. Allergic sensitization has been shown to be associated with increased likelihood of asthma. This study was designed to determine whether there are racial differences in the allergens to which children are sensitized in the Detroit metropolitan area and determine whether sensitization was associated with wheeze outcomes. Pregnant women were recruited for the Wayne County Health, Environment, Allergy, and Asthma Longitudinal Study birth cohort to follow the health of their children in the Detroit metropolitan area. Specific IgE (sIgE) was measured for Alternaria, cat, cockroach, dog, Dermatophagoides farinae, short ragweed, timothy grass, egg, milk, and peanut in blood samples from the children at age 2 years. A positive allergen sIgE was defined as ≥0.35 IU/mL. Mothers reported their child's race and completed interviews at age 2 years about characteristics of wheezing episodes in their child (frequency, medication, acute care, or emergency department visit). Black children (n = 384) were more likely than white children (n = 180) to have been positive for each of the allergens tested and also tended to have positive responses to a greater number of allergens (four or more allergens: 9.2% versus 3.5%). Children who had two or more positive sIgEs (adjusted odds ratio [aOR] = 2.68; 95% 95% confidence interval [CI], 1.33, 5.46) or three or more positive sIgEs (aOR = 2.67, 95% CI, 1.19, 6.01) were more likely to have wheezed four or more times in the last 12 months. Racial differences in sensitization at this young age may contribute to the racial difference in asthma prevalence at later ages.

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.

Cord blood derived CD4+ CD25(high) T cells become functional regulatory T cells upon antigen encounter

Background: Upon antigen exposure, cord blood derived T cells respond to ubiquitous environmental antigens by high proliferation. To date it remains unclear whether these “excessive” responses relate to different regulatory properties of the putative T regulatory cell (Treg) compartment or even expansion of the Treg compartment itself.

Methods: Cord blood (>37 week of gestation) and peripheral blood (healthy controls) were obtained and different Treg cell subsets were isolated. The suppressive potential of Treg populations after antigen exposure was evaluated via functional inhibition assays ([³H]thymidine incorporation assay and CFSE staining) with or without allergen stimulation. The frequency and markers of CD4⁺CD25^highFoxP3⁺ T cells were characterized by mRNA analysis and flow cytometry.

Results: Cord blood derived CD4⁺CD25^high cells did not show substantial suppressor capacity upon TCR activation, in contrast to CD4⁺CD25^high cells freshly purified from adult blood. This could not be explained by a lower frequency of FoxP3⁺CD4⁺CD25^highcells or FOXP3 mRNA expression. However, after antigen-specific stimulation in vitro, these cells showed strong proliferation and expansion and gained potent suppressive properties. The efficiency of their suppressive capacity can be enhanced in the presence of endotoxins. If T-cells were sorted according to their CD127 expression, a tiny subset of Treg cells (CD4⁺CD25⁺CD127^low) is highly suppressive even without prior antigen exposure.

Conclusion: Cord blood harbors a very small subset of CD4⁺CD25^high Treg cells that requires antigen-stimulation to show expansion and become functional suppressive Tregs.

Neonatal cytokine profile in the airway mucosal lining fluid is skewed by maternal atopy

RATIONALE

Heredity from mother or father may impact differently in complex diseases, such as atopy. Maternal atopy is a stronger risk factor than paternal atopy for the development of atopy in the offspring. We hypothesized that mother's and father's atopy would have a differential imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates.

OBJECTIVES

To study parental atopic imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates.

METHODS

Eighteen cytokines and chemokines were quantified in nasal mucosal lining fluid in 309 neonates from the novel unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohort.

MEASUREMENTS AND MAIN RESULTS

Maternal, but not paternal, atopic status (asthma, hay fever, or eczema with or without sensitization) was associated with general down-regulation of all 18 mediators assessed by principal component analysis (overall P = 0.015).

CONCLUSIONS

Maternal atopy, but not paternal atopy, showed a strong linkage with a suppressed mucosal cytokine and chemokine signature in asymptomatic neonates, suggesting imprinting by the maternal milieu in utero or perinatal life.

Evidence for a causal relationship between allergic sensitization and rhinovirus wheezing in early life

RATIONALE

Aeroallergen sensitization and virus-induced wheezing are risk factors for asthma development during early childhood, but the temporal developmental sequence between them is incompletely understood.

OBJECTIVE

To define the developmental relationship between aeroallergen sensitization and virus-induced wheezing.

METHODS

A total of 285 children at high risk for allergic disease and asthma were followed prospectively from birth. The timing and etiology of viral respiratory wheezing illnesses were determined, and aeroallergen sensitization was assessed annually for the first 6 years of life. The relationships between these events were assessed using a longitudinal multistate Markov model.

MEASUREMENTS AND MAIN RESULTS

Children who were sensitized to aeroallergens had greater risk of developing viral wheeze than nonsensitized children (hazard ratio [HR], 1.9; 95% confidence interval [CI], 1.2-3.1). Allergic sensitization led to an increased risk of wheezing illnesses caused by human rhinovirus (HRV) but not respiratory syncytial virus. The absolute risk of sensitized children developing viral wheeze was greatest at 1 year of age; however, the relative risk was consistently increased at every age assessed. In contrast, viral wheeze did not lead to increased risk of subsequent allergic sensitization (HR, 0.76; 95% CI, 0.50-1.1).

CONCLUSIONS

Prospective, repeated characterization of a birth cohort demonstrated that allergic sensitization precedes HRV wheezing and that the converse is not true. This sequential relationship and the plausible mechanisms by which allergic sensitization can lead to more severe HRV-induced lower respiratory illnesses support a causal role for allergic sensitization in this developmental pathway. Therefore, therapeutics aimed at preventing allergic sensitization may modify virus-induced wheezing and the development of asthma.

Epigenetics and prenatal influences on asthma and allergic airways disease

Uterine life is arguably the most critical time in developmental programming, when environmental exposures may have the greatest potential to influence evolving fetal structure and function. There has been substantial progress in understanding the epigenetic mechanisms through which environmental exposures can permanently alter the expression of fetal genes and contribute to the increasing propensity for many complex diseases. These concepts of "developmental origins" of disease are being applied across virtually all fields of medicine, and emerging epigenetic paradigms are the likely mechanism behind the environment-driven epidemic of asthma and allergic disease. Here, we examine the epigenetic regulation of immune development and the early immune profiles that contribute to allergic risk. In particular we review new evidence that key environmental exposures, such as microbial exposure, dietary changes, tobacco smoke, and pollutants, can induce epigenetic changes in gene expression and alter disease risk. Although most of these factors have already been clearly implicated in epidemiologic studies of asthma and allergic disease, new studies investigating the mechanisms of these effects may provide new avenues for using these pathways for disease prevention.

Can multiple doses of BCG vaccine protect against asthma?

OBJECTIVE

To compare BCG vaccination involving a single intradermal dose and that involving multiple doses, one given with the multiple puncture technique, in terms of the protective effect against the subsequent onset of asthma.

METHODS

A retrospective cohort study involving 2,311 individuals having received the BCG vaccine. The patients were classified according to the number of doses of BCG vaccine administered (one; two; or three or more). The minimum follow-up period in order to determine whether there was any protective effect of BCG vaccination regarding the diagnosis of asthma was 10 years.

RESULTS

The sample included 1,317 individuals (56.99%) who had received only one BCG dose, 644 (27.87%) who had received two doses, and 350 (15.14%) who had received three or more doses. The number of patients diagnosed with asthma among those who had received one dose, two doses and three or more doses was, respectively, 216 (16.40%), 107 (16.61%) and 50 (14.28%). There were no significant differences among the groups.

CONCLUSIONS

In the study sample, the prevalence of asthma among individuals having received multiple doses of the BCG vaccine was no different than that observed among those having received a single dose.

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.

Severe Asthma in Children: Insights from the National Heart, Lung, and Blood Institute's Severe Asthma Research Program

Severe asthma in children is a complicated disorder characterized by ongoing symptoms and persistent airway inflammation despite treatment with high doses of inhaled and oral corticosteroids. Although knowledge of asthma and its associated mechanisms has increased substantially over the past decade, significant gaps remain about the determinants of severe asthma in children and the progression of the disorder across the lifespan. This review highlights recent insights into severe asthma in children derived from the National Heart, Lung, and Blood Institute's Severe Asthma Research Program (SARP), with an emphasis on age-specific findings and differences from severe asthma in adults. While the existence of a true severe asthma phenotype in children is subject to some debate, given the results of SARP and other investigators, we conclude that there is indeed a subgroup of children with severe asthma who have extreme morbidity and differentiating clinical features that are identifiable very early in life. However, unlike adults with severe asthma, children with severe asthma are more likely to fall in a more narrow cluster that is characterized by marked atopy and reversible airflow obstruction. While SARP has advanced knowledge of severe asthma in children, considerable gaps remain for which additional studies are needed.

Reduced IFN-gamma- and enhanced IL-4-producing CD4+ cord blood T cells are associated with a higher risk for atopic dermatitis during the first 2 yr of life

The aim of this study was to analyse whether altered cytokine production by cord blood (CB) T cells is of relevance regarding the development of allergic diseases during the first 2 yr of life independent from known or suspected risk factors for allergy. Within an ongoing birth cohort study (Life style - Immune System - Allergy; LISA) the cytokine production of PMA/ionomycin-stimulated CB cells was measured by intracellular cytokine staining. Data of 98 children from Leipzig and Munich with complete information on cytokine production at birth and allergic outcomes during the first 2 yr were analysed. Statistical analysis was performed using a regression model adjusted for gender, month of birth, parental history of atopy, parental education, exposure to environmental tobacco smoke, maternal smoking during pregnancy, renovation activities during pregnancy, pet ownership and study centre. During the first 2 yr of life, 17.3% of the children developed a physician-diagnosed atopic dermatitis. Children with reduced frequencies of interferon-gamma (IFN-gamma)-producing CD4(+) T cells in the CB (1st quartile) had a higher risk to develop atopic dermatitis (adjusted OR 5.16, 95% CI: 1.04-25.6). Furthermore, a high percentage of interleukin (IL)-4-producing T cells in CB in children from the Leipzig cohort were associated with an increased risk for atopic dermatitis (adjusted OR 8.92, 95% CI: 1.40-56.93 for the 90th percentile). CD8(+) cytokine-producing CB T cells had no relation to increased risk for atopic dermatitis. Low amounts of IFN-gamma and high amounts of IL-4-producing T cells at birth may enhance the risk of subsequent development of atopic dermatitis.

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.

Plasmacytoid dendritic cells during infancy are inversely associated with childhood respiratory tract infections and wheezing

BACKGROUND

It has been proposed that immune dysfunction during early childhood plays an important role in asthma pathogenesis. However, it is not known specifically whether changes in dendritic cells (DCs) during infancy antedate the development of respiratory tract infections, asthma, and related clinical phenotypes.

OBJECTIVES

We sought to assess the association between the level of blood DCs during the first year and the subsequent development of respiratory tract infections, wheezing, and allergic sensitization.

METHODS

A community-based cohort of children with a family history of atopy was followed to age 5 years. Children were monitored intensively for respiratory tract infections. History of wheeze and asthma was collected annually, atopy was documented at 5 years, and flow cytometry was used to identify DC subsets in blood samples collected when children were well.

RESULTS

Levels of plasmacytoid DCs (pDCs) during infancy were inversely correlated with symptoms of lower respiratory tract infections, parent-reported wheezing, and the cumulative rate of physician-diagnosed asthma up to age 5 years. These relationships were independent of atopy, as determined by allergy skin test results and total and specific IgE levels. In contrast, levels of myeloid DCs were not associated with respiratory tract infections, asthma, or wheezing but were associated with total IgE levels at age 5 years.

CONCLUSION

In children with a family history of atopy, relative deficiency of circulating pDCs during infancy appears to be a risk factor for more frequent and more severe respiratory tract infections, wheezing, and a diagnosis of asthma. Infants with higher numbers of pDCs are protected against these outcomes.

Early markers of allergic disease in a primary prevention study using probiotics: 2.5-year follow-up phase

BACKGROUND

We previously reported that a Lactobacillus acidophilus probiotic strain (LAFTI) L10/LAVRI-A1) given for the first 6 months of life increased the risk of allergen sensitization at 1 year of age.

METHODS

To assess the effects on subsequent allergic outcomes, 153 children from the initial prevention cohort (n = 178) were reviewed at 2.5 years of age. Clinical outcomes were assessed in relation to (i) probiotic supplementation; and (ii) immune function previously assessed at 6 months of age.

RESULTS

Supplementation with this probiotic did not reduce the risk of dermatitis at 2.5 years (31/74, 42%) compared with that in placebo group (25/76, 34%). There was no significant reduction in any other allergic disease or allergen sensitization. Inhalant sensitization at 2.5 years (n = 29) was associated with higher proportions of circulating CD4+ CD25+ regulatory T-cell populations (P = 0.005) and higher allergen-induced FOXP3 levels (P = 0.003) at 6 months. This was also seen in children with dermatitis. Children with dermatitis at 2.5 years also had significantly lower toll-like receptor 4 lipopolysaccharide responses at 6 months of age (IL-12 P = 0.04, IL-6 P = 0.039) and lower polyclonal (PHA) responses (IFN-gamma P = 0.005, IL-10 P = 0.001, and IL-6 P = 0.001). Children who had previously received the probiotic had fewer gastrointestinal infections in the preceding 18 months (P = 0.023).

CONCLUSION

The LAFTI L10 probiotic strain did not have any significant effect on allergy outcomes. Allergic children showed a number of early differences in immune function including altered regulatory T-cell markers and innate immune function.

Children with egg allergy have evidence of reduced neonatal CD4(+)CD25(+)CD127(lo/-) regulatory T cell function

BACKGROUND

The role of regulatory T (Treg) cells in allergic predisposition is not known.

OBJECTIVE

This study compared the frequency and function of cord blood Treg cells from nonallergic children (n = 18) with those from children who have egg allergy (n = 15) in the first year of life.

METHODS

CD4(+) effector T cells and autologous antigen-presenting cells isolated from cord blood mononuclear cells were cocultured with or without CD4(+)CD25(+)CD127(lo/-) Treg cells, and cytokine responses to staphylococcal endotoxin B were assessed after 48 hours.

RESULTS

The addition of Treg cell populations to cord blood mononuclear cell cultures resulted in significant reduction in IL-10 (P = .002), IL-13 (P = .012), and IFN-gamma (P < .001) production. Consistent with other reports, effector CD4(+) T-cell responses (IFN-gamma and IL-13) tended to be lower in the allergic group. These neonates showed less significant Treg cell-associated suppression of IFN-gamma (P = .015) compared with that seen in the nonallergic group (P = .001). The allergic group was also less likely (44%) to show Treg cell-associated suppression of IFN-gamma effector responses compared with that seen in the nonallergic group (78%, P = .015). The magnitude of suppression (change in IFN-gamma level when CD4(+)CD25(+)CD127(lo/-) Treg cells were added to responding effector T-cell cultures) was significantly lower in the allergic group (P = .004). There were no between-group differences in the circulating CD4(+)CD25(+)CD127(lo/-) Treg cells (as a percentage of cord blood T cells) or in the FOXP3 expression of these cells.

CONCLUSION

This study confirms the presence and activity of Treg cells in cord blood and provides preliminary evidence of differences in neonates who progress to allergic disease in the first year of life.

Cytokine levels in supernatants of whole blood and mononuclear cell cultures in adults and neonates reveal significant differences with respect to interleukin-13 and interferon-gamma

Findings regarding cytokine levels in neonates and their impact on the development of allergic diseases are controversial. This might be attributed to different laboratory approaches. To compare cytokine levels in supernatants of whole blood (WB) and mononuclear cell (MC) cultures in response to unspecific and allergen specific stimuli. A total population of n = 25 healthy full-term neonates and n = 25 adults was recruited. WB was diluted 1 in 5 and incubated with phytohaemagglutinine (PHA; 20 mug/ml) and the cows' milk protein betalactoglobulin (BLG) for 24 and 120 h. In parallel, cord blood mononuclear cells (CBMC) and peripheral blood mononuclear cells (PBMC) were isolated, and cells were cultured with PHA and BLG in the same concentrations in a medium supplemented with fetal calf serum (FCS) and in a serum- free medium (only PBMC from adults). The cytokines interferon-gamma (IFN-gamma), interleukin-10 (IL-10), and IL-13 in the cell culture supernatants were measured using the ELISA technique. IFN-gamma and IL-10 levels in response to PHA in supernatants of MC of neonates were significantly lower compared to that in adults (p < 0.05, Wilcoxon two-sample test). IL-13 levels were significantly higher in response to PHA in neonates. In adults, only levels of IL-10 were significantly correlated in WB and PBMC cultures (PHA: r(S) 0.6; p = 0.002; BLG: r(S) 0.54; p = 0.005). In neonates, IL-10 (PHA: r(S) 0.77; p < 0.001; BLG: r(S) 0.63; p < 0.001) and IFN-gamma (PHA: r(S) 0.48; p = 0.02; BLG: r(S) 0.4; p < 0.047) were significantly correlated. Supernatants of PBMC cultured with an FCS-supplemented medium showed a significant lower IFN-gamma release (PHA 1297 pg/ml; BLG 2762 pg/ml) compared to serum-free cell cultures (PHA 6592.5 pg/ml, p < 0.0001; BLG 14228 pg/ml, p = 0.04). IFN-gamma and IL-13 levels in WB and MC supernatants revealed significant differences. Our data indicate the need for thoroughly defined and standardized culture conditions for the detection of in vitro cytokine levels.

[Association between asthma and viral infections]

A pesar de que las infecciones respiratorias virales son el factor asociado con más frecuencia con la expresión del asma (independientemente del fenotipo, edad y fase de la historia natural asmática en la cual la infección ocurre) y de la fuerte asociación temporal existente entre las infecciones y las crisis obstructivas/asmáticas, el rol de los virus en la patogénesis del asma no está aún bien dilucidado. Los factores que explicarían esta conexión son heterogéneos y, a veces, contradictorios. Probablemente las alteraciones en la función y tamaño de la vía aérea, la desregulación (congénita y adquirida) del tono de la vía aérea, las alteraciones en la respuesta inmunitaria a las infecciones y las variantes genéticas en dicha respuesta sean los cuatro mecanismos principales implicados en la asociación entre las infecciones respiratorias virales y el posterior desarrollo del asma o sibilancias en los niños. Futuras estrategias terapéuticas y de prevención deberían considerar estos mecanismos.

Fetal cord blood: aspects of heightened immune responses

Neonatal immune responses have been associated with the development of atopy in childhood. We assessed in cord blood mononuclear cells (CBMC) whether increased allergen/mitogen-induced lymphoproliferation (LP) is associated with pro-allergic Th2 cytokine IL-13 or Th1 cytokine IFN-gamma secretion. We determined whether LP to one allergen is related to heightened lymphocyte function to other allergens/mitogen. CBMC from 135 neonates were stimulated with house dust mite (Derf1), cockroach, ovalbumin, or mitogen. LP to one allergen was associated with significantly increased LP to other allergens/mitogen. Increased Derf1-LP was associated with increased Derf1-induced IL-13 secretion (r = 0.21, p = 0.01). After adjusting for neonatal gender, race, and maternal smoking, Derf1-LP remained associated with Derf1-IL-13 (OR 3.08, 95% CI 1.56-6.10). Increased mitogen-induced proliferation was associated with increased mitogen-induced IL-13 secretion (r = 0.37, p < 0.001). For some individuals, a predisposition to a heightened immune response is already evident at birth. Whether this phenotype results in atopy in childhood warrants further investigation.

Low IFN-gamma production in the first year of life as a predictor of wheeze during childhood

BACKGROUND

Diminished cytokine production in infancy has been associated with an increased risk for allergen sensitization and early-life wheeze.

OBJECTIVE

We sought to assess the effect of low cytokine production in the first year of life on the development of wheeze through age 13 years.

METHODS

Cytokine production (IFN-gamma and IL-2) by mitogen-stimulated mononuclear cells was determined from peripheral blood samples (9.4 months, n = 118) in a subset of healthy infants enrolled in the Tucson Children's Respiratory Study. The occurrence of wheeze during the previous year was ascertained at ages 2, 3, 6, 8, 11, and 13 years by means of questionnaire. Relative risk for wheeze was computed with generalized estimating equations.

RESULTS

The risk of wheezing between 2 and 13 years was significantly higher for subjects with low 9-month IFN-gamma production (relative risk, 2.29; 95% CI, 1.35-3.89) and borderline significant for those with intermediate IFN-gamma production (relative risk, 1.59; 95% CI, 0.95-2.68) compared with those who produced high levels of IFN-gamma (P value for linear association = .002). Nine-month IL-2 production was unrelated to wheeze. In relation to complex wheezing phenotypes, 9-month IFN-gamma production was inversely related to toddler wheeze (occurring only before age 6 years, P = .03) and chronic wheeze (occurring before and after age 6 years, P = .007) but not school-age wheeze (occurring only after age 6 years, P = .06).

CONCLUSION

The results suggest that characteristics of the immune system present during the first year of life can anticipate the likelihood of development of episodes of airway obstruction characterized by wheezing.

CLINICAL IMPLICATIONS

Immune susceptibility to asthma is established very early during postnatal life.

Protein kinase Cζ: A novel protective neonatal T-cell marker that can be upregulated by allergy prevention strategies

BACKGROUND

Variations in neonatal T-cell function have been associated with allergic disease.

OBJECTIVES

To examine the relationship between neonatal T-cell protein kinase (PKC) expression and subsequent allergic disease.

METHODS

T cells were purified from cord blood samples (n = 74) obtained from a cohort of mothers who received either 4 g/d fish oil or a placebo from 20 weeks of gestation. PKC expression was examined in relationship to supplementation, fatty acid levels, cytokine production, and allergic outcomes at 1 year and 2.5 years of age.

RESULTS

Neonatal T-cell PKCzeta expression was lower in children who had evidence of allergic disease at 1 year (P = .001) and 2.5 years (P = .052) of age. It was also lower in children with sensitization (positive skin prick test) at each age (P = .02 and P = .072, respectively). PKCzeta expression was inversely correlated to PKCalpha (r = -0.28; P = .025), which was strongly related to IL-5 responses to allergens (ovalbumin, r = 0.59; P = .003; dust mite, r = 0.52; P = .011) at 1 year of age. Fish oil supplementation was associated with significantly higher PKCzeta expression (P = .014), whereas most other isozymes were reduced by fish oil supplementation.

CONCLUSION

This is the first study to show that allergic disease is associated with altered expression of T-cell PKC isozymes in the neonatal period. It has also demonstrated that fish oil can modulate expression of PKC isozymes in a potentially favorable direction.

CLINICAL IMPLICATIONS

Protein kinase Czeta should be explored further as an early marker and potential target for disease prevention.

Prenatal fatty acid status and immune development: the pathways and the evidence

This review explores the effects of dietary long chain polyunsaturated fatty acids (LCPUFA) on various aspects of early immune development and their potential role in the development or the prevention of immune disease. Modern diets have become increasingly rich in n-6 LCPUFA and relatively n-3 LCPUFA deficient. These potentially "pro-inflammatory" dietary changes have clear implications for the immature and developing fetal immune system. It is now well known that immunological abnormalities precede the development of allergic disease and are frequently evident at birth or in the first months of life. This has lead to the hypothesis that potential effects of LCPUFA could be greatest in very early life before immune responses and clinical phenotype are established. Here we summarise the evidence that patterns of LCPUFA exposure in pregnancy can influence aspects of fetal immune in ways that are consistent with the immunological properties of these nutrients in adults. Specifically, human studies have shown that higher levels of n-3 LCPUFA are associated with reduction in neonatal oxidative stress, reduced production of inflammatory leukotienne B4 (LTB4) and altered T cell function. Inverse correlations between n-3 LCPUFA levels and neonatal T cell cytokine production, are consistent with adult studies showing reduction in T cell cytokine production with fish oil supplementation. At this stage the relevance of these effects in the prevention of disease is unclear. Although there have been no effects of postnatal fish oil supplementation (from 6 months of age) on allergy prevention, preliminary studies suggest possible merits in pregnancy and there are ongoing pregnancy intervention studies to address this more definitively.

Can allergic diseases be prevented prenatally?

Allergic diseases continue to increase in prevalence, and now affect over a third of the population in many countries. There is evidence that the increase in such diseases has its origins in early life exposures. Pregnancy or early childhood may therefore be critical periods for preventing the onset of allergic disease, and prenatal interventions are an attractive possibility for a population-based preventive approach. Here we review the data suggesting that prenatal exposures are important in the development of allergic disease, and that interventions during this time might be effective in prevention. We find evidence from both animal and human studies that prenatal interventions can influence the future development of allergic disease. There are a number of mechanisms through which such interventions may act to prevent allergic sensitization. We conclude that prenatal interventions have the potential to reduce the burden of allergic disease, and merit continued investigation. Further research in this area may lead to significant public health initiatives.

Evaluation of the effects of probiotic supplementation from the neonatal period on innate immune development in infancy

BACKGROUND

Activation of the innate immune system by microbial stimulation is believed to be critical for normal immune maturation, and there has been speculation that these pathways are important for inhibiting allergic-immune responses.

OBJECTIVE

To assess innate immune function following a 6-month supplementation with probiotic bacteria.

METHODS

Two hundred and thirty-one allergic, pregnant women were recruited into a randomized, controlled trial. The infants received either a probiotic (Lactobacillus acidophilus LAVRI-A1; Probiomics) or placebo (maltodextrin alone) daily for the first 6 months of life. Mononuclear cell samples were available from 118 infants. Functional responses to toll-like receptor (TLR) were assessed using ligands for TLR2 (Pansorbin) and TLR4/CD14 [lipopolysaccharide (LPS)] and measuring cytokine responses in the supernatants. Antigen-presenting cell function, as well as capacity for cytokine production (IL-12p70 and IL-10) was assessed.

RESULTS

Infants in the probiotic group did not demonstrate differences in innate immune function compared with those in the control group. No differences were seen when cytokine responses were examined following stimulation with Pansorbin (TLR2) or LPS (TLR4). Similarly, no differences were seen in the antigen-presenting capacity of these infants. The mean fluorescence intensities of human leucocyte antigen-DR (HLA-DR) on monocytes, B cells and dendritic cells (DC) subsets were not affected, nor were the percentage of circulating DC subsets affected by a 6-month supplementation with L. acidophilus LAVRI-A1.

CONCLUSIONS

Probiotic supplementation with L. acidophilus for the first 6 months of life did not alter early innate immune responses in this population at high risk of developing allergic disease.

Effects of probiotic supplementation for the first 6 months of life on allergen- and vaccine-specific immune responses

BACKGROUND

A reduction in microbial burden during infancy when allergen-specific memory is evolving has become a prominent explanation for the allergy epidemic.

OBJECTIVE

We sought to determine whether probiotic dietary supplementation in the first 6 months of life could modify allergen- and vaccine-specific immune responses.

METHODS

Two hundred and thirty-one pregnant women with a history of allergic disease and positive allergen skin prick test (SPT) were recruited into a randomized-controlled trial. The infants received either a probiotic (3 x 10(9)Lactobacillus acidophilus LAVRI-A1; Probiomics) or placebo (maltodextrin alone) daily for the first 6 months of life, given independent of feeding methods. One hundred and seventy-eight children completed the study; blood samples were available from 60 children in the placebo group and 58 children in the probiotic group. Infant cytokine (IL-5, IL-6, IL-10, IL-13, TNF-alpha or TGF-beta) responses to tetanus toxoid (TT), house dust mite (HDM), ovalbumin (OVA), beta-lactoglobulin (BLG), Staphylococcus enterotoxin B (SEB) and phytohaemaglutinin (PHA) were measured at 6 months of age.

RESULTS

Children who received the probiotics showed reduced production of IL-5 and TGF-beta in response to polyclonal (SEB) stimulation (P=0.044 and 0.015, respectively). They also demonstrated significantly lower IL-10 responses to TT vaccine antigen compared with the placebo group (P=0.03), and this was not due to any differences in vaccination. However, there were no significant effects of probiotics on either Type 1 (Th1) or Type 2 (Th2) T helper cell responses to allergens or other stimuli. The only other effects observed were for reduced TNF-alpha and IL-10 responsiveness to HDM allergens in children receiving probiotics (P=0.046 and 0.014, respectively).

CONCLUSIONS

In summary, although we did not see any consistent effects on allergen-specific responses, our study suggests that probiotics may have immunomodulatory effects on vaccine responses. The significance and clinical relevance of this need to be determined in further studies.

Pregnancy, but not the allergic status, influences spontaneous and induced interleukin-1beta (IL-1beta), IL-6, IL-10 and IL-12 responses

In this study, we investigated how pregnancy influences cytokine production in response to stimulation of the innate and the adaptive immune system, respectively. Peripheral blood mononuclear cells (PBMCs) from allergic (n = 44) and non-allergic (n = 36) women were collected at three time-points: during the third trimester, at delivery and at a non-pregnant state 2 years after delivery. The production of interleukin-1beta (IL-1beta), IL-6, IL-10 and IL-12 was measured by enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot assay (ELISPOT). The spontaneous cytokine production, and the response following stimulation with agents that primarily activate the adaptive part of the immune system [phytohaemagglutinin (PHA), allergen extracts from cat and birch], or lipopolysaccharide (LPS) that activate innate immunity was measured in vitro. There was a significantly higher spontaneous in vitro production of IL-1beta, IL-6 and IL-10 by PBMCs during pregnancy than 2 years after pregnancy, and this was not affected by the allergic status of the women. Conversely, in PHA-stimulated cell cultures there was a lower production of IL-10 and IL-12 during pregnancy than 2 years after pregnancy. LPS-induced IL-6 levels were significantly lower in PBMCs obtained during pregnancy than at 2 years after pregnancy. In addition, we made the interesting observation that in allergic women total immunoglobulin E (IgE) levels were significantly lower 2 years after pregnancy compared to the levels during pregnancy. Taken together, our results indicate that while atopic allergy in women does not have a substantial effect on cytokine production, pregnancy has an obvious effect on the immune system in terms of cytokine production as well as on the total IgE levels.

Relationship between maternal and child cytokine responses to allergen and phytohaemagglutinin 2 years after delivery

Little is known at present about the relation between parental and child cytokine profiles. In this study we aimed to investigate the cytokine profile of 2-year-old children and their corresponding mothers, 2 years after delivery. Peripheral blood mononuclear cells (PBMC) were isolated from IgE-sensitized (n=15) and non-esitized (n=58) 2-year-old children and their mothers. The responses to ovalbumin, cat and phytohaemagglutinin (PHA) were investigated using the enzyme-linked immunospot (ELISpot) technique. Interferon (IFN)-gamma-, interleukin (IL)-4-, IL-10- and IL-12-producing cells were enumerated. At 2 years of age, IgE-sensitized children exhibited increased numbers of IL-4-producing cells in response to PHA and also showed an increase in IL-10- and IL-12-producing cells to allergen that was more pronounced in response to ovalbumin than to cat. A statistically significant increase in the numbers of IFN-gamma-, IL-10- and IL-12-producing cells to the allergens, but not to PHA, was found in the mothers of IgE-sensitized children irrespective of their own atopic status. IgE levels and cytokine responses were correlated between the mothers and their children, indicating that cytokine responses to both allergen and PHA might be governed by genetic factors. We speculate that the increased cytokine response to allergen, as opposed to the allergic status of the mother, might be a better predictor and/or a risk factor for the child to develop IgE-sensitization in early life.

Viral infections, cytokine dysregulation and the origins of childhood asthma and allergic diseases

BACKGROUND

The origins of asthma and allergic disease begin in early life for many individuals. It is vital to understand the factors and/or events leading to their development.

METHODS

The Childhood Origins of Asthma project evaluated children at high risk for asthma to study the relationships among viral infections, environmental factors, immune dysregulation, genetic factors, and the development of atopic diseases. Consequently wheezing illnesses, viral respiratory pathogen identification, and in vitro cytokine response profiles were comprehensively evaluated from birth to 3 years of age, and associations of the observed phenotypes with genetic polymorphisms were investigated.

RESULTS

For the entire cohort, cytokine responses did not develop according to a strict T helper cell 1 or T helper cell 2 polarization pattern during infancy. Increased cord blood mononuclear cell phytohemagglutin-induced interferon-gamma responses of mononuclear cells were associated with decreased numbers of moderate to severe viral infections during infancy, especially among subjects with the greatest exposure to other children. In support of the hygiene hypothesis, an increased frequency of viral infections in infancy resulted in increased mitogen-induced interferon-gamma responses at 1 year of age. First year wheezing illnesses caused by respiratory viral infection were the strongest predictor of subsequent third year wheezing. Also, genotypic variation interacting with environmental factors, including day care, was associated with clinical and immunologic phenotypes that may precede the development of asthma.

CONCLUSIONS

Associations between clinical wheezing, viral identification, specific cytokine responses and genetic variation provide insight into the immunopathogenesis of childhood asthma and allergic diseases.

Prevalence of atopic diseases and the use of topical corticosteroids. Is there any connection?

The prevalence of atopic diseases (atopic dermatitis, bronchial asthma, allergic rhinitis) has considerably increased for the last 40 years. This tendency has coincided with the beginning of the epoch of the use of the topical corticosteroids, which have a potent immunomodulation action. This fact itself as well as a number of research results has allowed to formulate the following hypothesis: the use of topical corticosteroids in children of early age contributes to the increase of prevalence of atopic diseases in the developed countries. The offered hypothesis can explain lower prevalence of atopic diseases in rural areas and in children from families with the anthroposophic life style. In other side this hypothesis also capable to give explanation of increased level of atopic diseases among people with high socioeconomic level and in children from 1 child families. It is of a note that corticosteroids use in developing countries is limited due to economic reasons and active use of complementary medicine. If the proposed hypothesis is correct, a revision of the therapeutic approaches is necessary concerning the attitude towards application of topical corticosteroids in children suffering from various forms of eczema. The direct proof of this hypothesis can be found during prospective studies.

Immune dysregulation in allergic respiratory disease: the role of T regulatory cells

Although earlier research focused on the role of the polarity of T helper cell signalling as the defining factor in immune responses, it is now recognised that other cells with regulatory properties have a more key role. It has been recently proposed that allergic disease may result from an inappropriate balance between regulatory cells (including but not limited to CD4+ CD25+ T regulatory cells) and T helper type 2 (Th2) effector cells. In the airways, a number of other cells also have important regulatory effects on local immune responses, including epithelial cells and airway dendritic cells (DC). Allergic respiratory disease appears to be the culmination of both local epithelial dysfunction and generalised immune dysregulation resulting in Th2 propensity (atopic predisposition). Although these processes are related they also appear to occur independently. This review examines evolving models of allergy pathogenesis, including the newly recognised role of diverse groups of regulatory cells. Increasing rates of allergic disease (and other immune diseases) suggest that environmental changes may be having fundamental effects on common regulatory pathways. Understanding these influences and their mechanism of action could lead to strategies to prevent disease.

Allergic diseases and asthma in relation to serum immunoglobulins and salivary immunoglobulin A in pre-school children: a follow-up community-based study

BACKGROUND

We have previously reported an association between low IgA and allergic manifestations in early childhood (0-2 years) and have now followed our cohort for an additional 2 years.

OBJECTIVE

To evaluate in a longitudinal community-based cohort study the association between maturation of Ig production and allergic manifestations in the first 4 years of life.

METHODS

A cohort of 161 randomly selected children was followed from birth to the age of 42-48 months and evaluated at 18-23 months (EV1; n = 179) and again at the age of 42-48 months (EV2; n = 161). Diagnoses were made with the help of a clinical questionnaire, physical examination and skin prick tests (SPTs) to 10 common allergens. Serum immunoglobulins were measured at EV1 and EV2, and salivary IgA (sal-IgA) at EV2.

RESULTS

Serum IgA, IgE, IgG1, IgG2 and IgG4 increased from 2 to 4 years of age (P < 0.001) and their levels showed close correlations (P < or = 0.01 for most comparisons). Children with one or more positive SPTs had lower serum IgA (P = 0.004) and IgG4 (P = 0.05) at EV2 than those who did not respond, and children who developed allergic rhinitis between EV1 and EV2 had low sal-IgA (P = 0.006) and IgG3 (P < 0.05) at EV2. Atopic eczema was associated with low sal-IgA at EV2, and children who developed eczema between EV1 and EV2 had significantly lower sal-IgA than those who recovered after EV1 (P = 0.02).

CONCLUSION

Allergic manifestations in predisposed children may be influenced by the rate of maturation of immunological components that counteract sensitization or inhibit effector mechanisms of allergy.

Gene-environment interaction effects on the development of immune responses in the 1st year of life

Asthma is a common disease that results from both genetic and environmental risk factors. Children attending day care in the 1st year of life have lower risks for developing asthma, although the mechanism for this "day care" effect is largely unknown. We investigated the interactions between day care exposure in the 1st 6 mo of life and genotypes for 72 polymorphisms at 45 candidate loci and their effects on cytokine response profiles and on the development of atopic phenotypes in the 1st year of life in the Childhood Onset of Asthma (COAST) cohort of children. Six interactions (at four polymorphisms in three loci) with "day care" that had an effect on early-life immune phenotypes were significant at P<.001. The estimated false-discovery rate was 33%, indicating that an estimated four P values correspond to true associations. Moreover, the "day care" effect at some loci was accounted for by the increased number of viral infections among COAST children attending day care, whereas interactions at other loci were independent of the number of viral infections, indicating the presence of additional risk factors associated with day care environment. This study identified significant gene-environment interactions influencing the early patterning of the immune system and the subsequent development of asthma and highlights the importance of considering environmental risk factors in genetic analyses.

Understanding the origin of asthma and its relationship to breastfeeding

Asthma is a chronic disease of the lung that has been increasing at an alarming rate in industrialized countries around the world over the last few decades. Although considerable progress has been made in our understanding of the underlying pathogenesis of the disease, the exact causes of the increasing prevalence are unknown. Studies suggest that most asthma develops in early childhood and that environmental factors present early in life may be crucial in the development of disease. One potential explanation for the recent epidemic referred to as the "hygiene hypothesis" postulates that factors that have resulted in a reduction in exposure to microbial products and/or infections in the western world may be contributing to this rise in disease prevalence. As early life influences are known to play an important role in establishment of asthma, studies have focused on the interface between mother and child that occurs during gestation and through breastfeeding. In this regard, the body of evidence regarding the relationship between breastfeeding and asthma indicates benefit but with the potential for risk. While providing population-level protection from infections and atopy in infancy and early childhood, breastfeeding might also pose an increased risk of atopic asthma among children with asthmatic mothers. In order to put this controversy in context, we discuss our current understanding of asthma pathogenesis, current theories on the factors driving the rising prevalence of asthma, and then discuss the potential influence of breastfeeding on asthma pathogenesis.

Inhalation of low-dose endotoxin favors local T(H)2 response and primes airway phagocytes in vivo

BACKGROUND

We previously reported that inhalation of 5 mug of endotoxin (30,000 endotoxin units [EU]) induced airway neutrophilia and decreased phagocytosis by airway monocytes, macrophages, and neutrophils. Conversely, we recently reported that very low doses of endotoxin, which are not associated with neutrophil influx, enhance response to allergen in the nasal and bronchial airway.

OBJECTIVE

We sought to determine whether endotoxin (0-10,000 EU) at doses that do not induce airway neutrophilia prime airway phagocyte function, alter expression of relevant cell-surface receptors (membrane-bound CD14 [mCD14] and CD11b/CR3), and cause induction of a T(H)2 cytokine profile in the airway.

METHODS

Thirteen nonallergic healthy volunteers were challenged on separate occasions with escalating doses of Clinical Center Reference Endotoxin (CCRE; 0, 2500, 5000, and 10,000 EU), with 9 volunteers completing the entire dose range. Sputum cells and fluid-phase components were recovered 6 hours after challenge. Sputum inflammatory cells were analyzed by means of flow cytometry for mCD14 and CD11b expression and immune function (phagocytosis of IgG-opsonized zymosan particles).

RESULTS

At all doses of CCRE, there was no increase in airway neutrophils relative to that caused by saline. However, inhalation of 10,000 EU enhanced phagocytosis (monocytes and macrophages), upregulated expression of CD11b and mCD14 (monocytes and neutrophils), and increased IL-13 levels, whereas IFN-gamma levels were significantly decreased.

CONCLUSION

The 10,000-EU dose of CCRE is subthreshold for inducing airway neutrophilia but primes phagocyte function and cell-surface receptor expression in the presence of increased IL-13 and decreased IFN-gamma levels. We speculate that low-dose endotoxin challenge skews airway inflammation in a T(H)2 direction in vivo .

Diminished dendritic cell interleukin 10 production in atopic children

BACKGROUND

Diminished interleukin 10 (IL-10) and/or IL-12 production may contribute to the pathogenesis of asthma and atopy. Dendritic cells (DCs) produce these cytokines and have been implicated in the pathogenesis of these disorders.

OBJECTIVE

To determine whether DC IL-10 and/or IL-12 production is diminished in children aged 6 to 12 years with allergic rhinitis (AR) and with or without asthma.

METHODS

Monocyte-derived DCs were isolated from 20 subjects without AR or asthma (group 1), 20 subjects with AR without asthma (group 2), and 20 subjects with AR and asthma (group 3). Asthma was defined as a history of physician-diagnosed disease, and AR was defined as a positive history and positive puncture skin test responses (wheal > or = 5 mm) to relevant inhalant allergens. DCs were stimulated with either lipopolysaccharide (LPS) or diluent and cultured for 24 hours. Supernatants were assayed for IL-10 and IL-12 levels by enzyme-linked immunosorbent assay.

RESULTS

DC IL-10 production was diminished in groups 2 and 3 compared with group 1. Median LPS-induced IL-10 levels were 11.0 pg/mL in group 1, 6.1 pg/mL in group 2, and 1.5 pg/mL in group 3. The frequencies of subjects with detectable IL-10 levels were 85%, 20%, and 20% in groups 1, 2 and 3, respectively. Median LPS-induced IL-12 levels were similar in all groups.

CONCLUSIONS

These data support the hypothesis that atopic subjects have an intrinsic inability to up-regulate DC IL-10 production. Future studies in this area could lead to a better understanding of the pathogenesis of atopy.

High IFN-gamma production by CD8+ T cells and early sensitization among infants at high risk of atopy

BACKGROUND

High genetic risk (HR) of atopy among unstratified populations of infants is associated with attenuated IFN-gamma responses. However, the role of IFN-gamma in progression from HR status to active disease is less clear.

OBJECTIVE

To identify immune function markers in neonates with HR that are associated with positive atopic outcomes at 2 years.

METHODS

Cord blood mononuclear cells (CBMCs) were collected from 175 children with HR and cryopreserved. The children were assessed for atopy by skin prick at 0.5 and 2 years. CBMCs were thawed and stimulated with allergens and mitogens PHA and staphylococcal enterotoxin B (SEB), and cytokine responses were determined.

RESULTS

No correlations were observed between allergen-specific CBMC responses and atopic outcomes. In contrast, sensitization was strongly associated with polyclonal IFN-gamma responses to both PHA (P=.002) and SEB (P=.005), and also with SEB-induced IL-5 (P =.05), IL-10 (P =.02), and IL-13 (P =.01). Logistic regression analysis identified elevated PHA-induced IFN-gamma and SEB-induced IL-13 responses as the strongest independent predictors of atopy development. Cell separation studies confirmed CD8+ T cells as the source of approximately 90% of IFN-gamma production.

CONCLUSIONS

IFN-gamma produced by CD8+ T cells may synergize with T(H)2 cytokines in driving atopy development in children with HR.

Dietary prevention of allergic diseases in infants and small children. Part I: immunologic background and criteria for hypoallergenicity

The role of primary prevention of allergic diseases has been a matter of debate for the last 40 years. In order to shed some light into this issue, a group of experts of the Section of Pediatrics EAACI critically reviewed the existing literature on the subject. In this paper, the immunology of the fetus and newborn is reviewed as well as the post-natal development of the immune system. The influence of post-natal environment and breastfeeding on tolerance induction and sensitization are examined. Allergic diseases result from a strong relationship between genetic and environmental factors. Sensitization to food allergens occurs in the first year of life and cow's milk allergy is the first food allergy to appear in the susceptible infants. Hypoallergenicity of food formulas to be used is a critical issue both for treatment of cow's milk-allergic children and for prevention. Methods to document hypoallergenicity are discussed and evaluated in the preclinical and clinical steps.

High interleukin-13 production by phytohaemagglutinin- and Der p 1-stimulated cord blood mononuclear cells is associated with the subsequent development of atopic dermatitis at the age of 3 years

OBJECTIVE

The aim of our study was to conduct a prospective investigation into the potential association of cord blood proliferative response and cytokine production in response to various stimuli on the development of atopic dermatitis (AD) at the age of 3 years.

METHODS

Cord blood mononuclear cells (CBMC) from 40 healthy term neonates were isolated. The proliferative response of CBMC stimulated with IL-2, betalactoglobulin (BLG) and house dust mite allergen (Der p 1) was assessed by liquid scintillation counting and the stimulation index (SI) was calculated. The cytokines interleukin (IL-)13, interferon (IFN-)gamma, IL-10 and IL-18 in the cell culture supernatants in response to phytohaemagglutinin (PHA), Der p 1 and BLG were measured using the ELISA technique. After 3 years, symptoms of AD were obtained with a questionnaire completed by the parents.

RESULTS

We observed significantly higher IL-13 levels in response to PHA in children who subsequently developed symptoms of AD (S: median, 291 pg/mL) compared with asymptomatic children (No-S: 149 pg/mL; P=0.021, Wilcoxon test). Similarly, in response to Der p 1 significantly higher IL-13 levels were observed in symptomatic children (S: 168.6; No-S: 61.6 pg/mL; P=0.0084). In response to BLG, IL-13 levels were 287.2 (S) and 123.6 pg/mL (No-S; P=0.19). No significant differences were found when comparing the IFN-gamma levels in CBMC cultures stimulated with PHA (S: 10.2; No-S: 17.6 IU/L; P=0.78), Der p 1 (S: 307.6; No-S: 616.2 IU/L; P=0.2) or BLG (S: 18; No-S: 28.5 IU/L; P=0.83; Fig. 2). The IL-18 and IL-10 levels and the stimulation index in response to IL-2, BLG and Der p 1 showed no significant difference between children who subsequently developed symptoms of AD and asymptomatic children.

CONCLUSION

Our data suggest that enhanced IL-13 levels at birth are associated with the subsequent development of atopic symptoms at the age of 3 years.

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.

Reduced interferon gamma production and soluble CD14 levels in early life predict recurrent wheezing by 1 year of age

It is unknown whether reduced production of IFNgamma in early life, before any lower respiratory tract illness, is a risk factor for recurrent wheezing in infancy. We followed 238 infants prospectively from birth to 1 year of age. At birth and at 3 months of age, IFNgamma production from polyclonally stimulated peripheral blood mononuclear cells and soluble CD14 (sCD14) levels in plasma were measured. The odds of developing recurrent wheezing (assessed by questionnaire) in the first year of life were up to 4.5 times higher for children in the lowest quartile of IFNgamma production at 3 months (p = 0.0005) and 3.2 times higher for children in the lowest quartile of sCD14 levels at birth (p = 0.004) as compared with children in the other 3 combined quartiles of IFNgamma and sCD14, respectively. Findings were confirmed in the multivariate analysis. IFNgamma production at 3 months and sCD14 levels at birth were correlated (r = 0.188, p = 0.031). Our findings from a longitudinal cohort suggest that impaired IFNgamma production at 3 months and reduced plasma-sCD14 levels at birth significantly increase the risk of developing recurrent wheezing in the first year of life.

Maternal smoking in pregnancy alters neonatal cytokine responses

BACKGROUND

Maternal cigarette smoking in pregnancy is an important, common and avoidable exposure that has been linked with elevated cord blood (CB) immunoglobulin E levels and subsequent asthma and allergic disease in childhood. Despite this, there is still very little information about the immunological effects of maternal smoking on the fetus.

METHODS

This aim of this study was to compare cord blood mononuclear cell (CBMC) cytokine responses to allergens [ovalbumin (OVA) or house dust mite (HDM)] and mitogens [concanavalin A (ConA) or phytohemaglutinen (PHA)] in neonates whose mothers smoked throughout pregnancy (n = 17) with responses of neonates whose mothers never smoked (n = 40). Cell cultures were stimulated for 24 h and supernatants collected for cytokine detection by enzyme-linked immunosorbent assay [interleukin (IL)-13, IL-6, interferon (IFN)gamma and IL-10]. Cell pellets were also collected for cytokine mRNA detection (IL-5, IL-9, IFNgamma).

RESULTS

Maternal smoking in pregnancy was associated with significantly higher neonatal T helper type 2 (IL-13 protein) responses to both HDM (P = 0.01) and OVA (P = 0.035). These effects remained statistically significant after allowing for confounding factors, including the effects of maternal atopy. Similar trends were also seen for IL-9mRNA, IL-5mRNA and IL-6 responses, although these were not statistically significant. Although IFNgamma mRNA responses to PHA (P = 0.015) and ConA (P = 0.025) were lower if mothers smoked in pregnancy, there were no differences in neonatal (Th1) IFNgamma protein responses to allergens or mitogens.

CONCLUSIONS

These findings indicate that maternal cigarette smoking can modify aspects of fetal immune function and highlight the need for further studies in this area.