Neonatal interleukin-12 capacity is associated with variations in allergen-specific immune responses in the neonatal and postnatal periods

Molecular Determinants of the Early Life Immune Response to COVID-19 Infection and Immunization

Clinical manifestations from primary COVID infection in children are generally less severe as compared to adults, and severe pediatric cases occur predominantly in children with underlying medical conditions. However, despite the lower incidence of disease severity, the burden of COVID-19 in children is not negligible. Throughout the course of the pandemic, the case incidence in children has substantially increased, with estimated cumulative rates of SARS-CoV-2 infection and COVID-19 symptomatic illness in children comparable to those in adults. Vaccination is a key approach to enhance immunogenicity and protection against SARS-CoV-2. Although the immune system of children is functionally distinct from that of other age groups, vaccine development specific for the pediatric population has mostly been limited to dose-titration of formulations that were developed primarily for adults. In this review, we summarize the literature pertaining to age-specific differences in COVID-19 pathogenesis and clinical manifestation. In addition, we review molecular distinctions in how the early life immune system responds to infection and vaccination. Finally, we discuss recent advances in development of pediatric COVID-19 vaccines and provide future directions for basic and translational research in this area.

Suppression of Allergic Asthma by Loss of Function of Miz1-Mediated Th1 Skewing

Asthma is the most prevalent chronic respiratory disease worldwide. There is currently no cure, and it remains an important cause of morbidity and mortality. Here we report that lung-specific loss of function of the transcription factor c-Myc-interacting zinc finger protein-1 (Miz1) upregulates the pro-T helper 1 (Th1) cytokine interleukin 12 (IL-12). Upregulation of IL-12 in turn stimulates a Th1 response, thereby counteracting T helper 2 (Th2) response and preventing the allergic response in mouse models of house dust mite (HDM)- and ovalbumin (OVA)-induced asthma. Using transgenic mice expressing Cre under a cell-specific promoter, we demonstrate that Miz1 acts in lung epithelial cells and dendritic cells in asthma. Chromatin immunoprecipitation (ChIP) coupled with high-throughput DNA sequencing (ChIP-seq) or quantitative PCR (ChIP-qPCR) reveals the binding of Miz1 on the Il12 promoter indicating direct repression of IL-12 by Miz1. Additionally, histone deacetylase 1 (HDAC1) is recruited to the Il12 promoter in a Miz1-depdenent manner, suggesting epigenetic repression of Il12 by Miz1. Furthermore, Miz1 is upregulated in human asthmatic samples as well as in asthmatic mice. Our data together suggest that Miz1 is upregulated during asthma, which in turn promotes asthma pathogenesis by preventing Th1 skewing through the transcriptional repression of IL-12.

Longitudinal analyses of development of the immune system during the first five years of life in relation to lifestyle

BACKGROUND

Changes in immune cell composition during the immunological window within the first years after birth are not fully understood, especially the effect that different lifestyles might have on immune cell functionality.

METHODS

Peripheral blood mononuclear cells from mothers and their children at birth and at two anvd five years were analyzed by mass cytometry. Immune cell composition and functionality was analyzed according to family lifestyle (anthroposophic and non-anthroposophic).

RESULTS

We found no significant differences in the proportions of major immune lineages between anthroposophic and non-anthroposophic children at each time point, but there were clear changes over time in the proportions of mononuclear leukocytes, especially in B-cells and T lymphocytes. Phenotypic distances between cord blood and maternal blood were high at birth but decreased sharply the first two years, indicating strong phenotypic convergence with maternal cells. We found that children exhibited similar stimulation responses at birth, but subsequently segregated into two discrete functional trajectories. Trajectory 1 was associated with a decrease in tumor necrosis factor alpha (TNFa) production by CD4⁺ T- and NK-cells, while Trajectory 2 depicted an increase in the production of IL-2 and interferon gamma (INFg) by T-cells. In both trajectories, there was an increase in IL-17A production by T-cells resulting in prominent differences at five years of age.

CONCLUSIONS

This exploratory study suggests that leukocyte frequencies and cell phenotypes change with age in the same way across all children, while functional development follows one of two discrete trajectories that largely segregate by family lifestyle, supporting the hypothesis that early environmental exposures imprint immune cell function which may contribute to IgE sensitization. Our results also support that the first two years are critical for the environmental exposures to imprint the immune cells. Further studies with larger sample sizes are required to validate our findings.

Molecular evolution of genes encoding allergen proteins in the peanuts genus Arachis: Structural and functional implications

Food allergies are severe immune responses to plant and animal products mediated by immunoglobulin E (IgE). Peanuts (Arachis hypogaea L.) are among the top 15 crops that feed the world. However, peanuts is among the "big eight food allergens", and allergies induced by peanuts are a significant public health problem and a life-threatening concern. Targeted mutation studies in peanuts demonstrate that single residue alterations in these allergen proteins could result in substantial reduction in allergenicity. Knowledge of peanut allergen proteins is confined to the allotetraploid crop and its two progenitors. We explored frequencies and positions of natural mutations in the hyperallergenic homologues Ara h 2 and Ara h 6 in newly generated sequences for 24 Arachis wild species and the crop species, assessed potential mutational impact on allergenicity using immunoblots and structural modeling, and evaluated whether these mutations follow evolutionary trends. We uncovered a wealth of natural mutations, both substitutions and gaps, including the elimination of immunodominant epitopes in some species. These molecular alterations appear to be associated with substantial reductions in allergenicity. The study demonstrated that Ara h 2 and Ara h 6 follow contrasting modes of natural selection and opposing mutational patterns, particularly in epitope regions. Phylogenetic analysis revealed a progressive trend towards immunodominant epitope evolution in Ara h 2. The findings provide valuable insight into the interactions among mutations, protein structure and immune system response, thus presenting a valuable platform for future manipulation of allergens to minimize, treat or eliminate allergenicity. The study strongly encourages exploration of genepools of economically important plants in allergenicity research.

Partner social support during pregnancy and the postpartum period and inflammation in 3-month-old infants

Prenatal social stress "programs" offspring immune activity in animal models, but how the prenatal social environment affects human offspring inflammation is not known. Here, we test associations between prenatal partner support quality, i.e. positive/helpful support, negative/upsetting support, and their interaction, and infant inflammatory markers. A sample of 113 women from the Alberta Pregnancy Outcomes and Nutrition (APrON) cohort were followed from early pregnancy to 3-months postpartum. Partner support quality was measured during pregnancy and the postpartum period. Three-month-old infant blood samples were assayed for inflammatory markers, i.e., adaptive immune markers IFNγ, IL12p70 and IL10. The prenatal positive-by-negative partner support interaction predicted infant IFNγ, IL12p70, and IL10, p's<.035, independent of covariates and postpartum partner support. When negative partner support was high, high positive support predicted higher infant IFNγ, IL12p70, and IL10. As such, partner support during pregnancy that is both highly negative/upsetting and also highly positive/helpful predicted adaptive immunity markers in infants at 3 months of age.

Decreased allergy incidence in children supplemented with E. coli O83:K24:H31 and its possible modes of action

The growing knowledge of the key role of microbiota in the maturation of neonatal immune system suggests that manipulation of microbiota could be exploited in hampering allergy development. In this study, Escherichia coli O83:K24:H31 (EcO83) was administered to newborns that were followed prospectively. Several immunological characteristics (cytokines, specific IgE, total T regulatory cells (Treg) and subpopulation of natural Treg (nTreg) and induced Treg (iTreg)) were tested in peripheral blood of 8-year-old children. Incidence of allergic disease was decreased in EcO83 supplemented children and significantly elevated levels of IL-10 and IFN-ɣ were detected in serum of EcO83 supplemented children. Probiotic supplementation did not influence the numbers of the total Treg population but their functional capacity (intracellular expression of IL-10) was significantly increased in children supplemented with EcO83 in comparison to non-supplemented children. Morover, decreased proportion of iTreg was present in peripheral blood of non-supplemented in comparison to EcO83 supplemented children. Finally, stimulation of cord blood cells with EcO83 promoted both gene expression and secretion of IL-10 and IFN-ɣ suggesting that beneficial effect of EcO83 in prevention of allergy development could be mediated by promotion of regulatory responses (by IL-10) and Th1 immune response (by IFN-ɣ).

Different capacity of in vitro generated myeloid dendritic cells of newborns of healthy and allergic mothers to respond to probiotic strain E. coli O83:K24:H31

Allergic diseases belong to one of the most common diseases with steadily increasing incidence even among young children. There is an urgent need to identify a prognostic marker pointing to increased risk of allergy development enabling early preventive measures introduction. It has been shown that administration of selected probiotic strains or mixtures could prevent allergy development. In our study, we have tested the capacity of probiotic strain Escherichia coli O83:K24:H31 (E. coli O83) to promote dendritic cell (DC) maturation and polarisation of immune responses. Increased presence of activation marker CD83 was observed on DC stimulated by E. coli O83 and DC of newborns of allergic mothers have significantly more increased cell surface presence of CD83 in comparison to children of healthy mothers. Increased gene expression and secretion of IL-10 was detected in DC stimulated with E. coli O83 being higher in DC of newborns of healthy mothers in comparison to allergic ones. Generally, increased presence of intracellular cytokines (IL-4, IL-13, IFN-gamma, IL-17A, IL-22, IL-10) was detected in CD4+ T cells cocultured with DC of children of allergic mothers in comparison to healthy ones. E. coli O83 primed DC significantly increased IL-10 and IL-17A in CD4 T cells of newborns of healthy mothers in comparison to the levels detected in CD4 T cells cocultured with control non-stimulated DC. We can conclude E. coli O83 induces dendritic cell maturation and IL-10 production in DC. Newborns of allergic mothers have generally increased reactivity of both DC and CD4 T cells which together with decreased capacity of DC of newborns of allergic mothers to produce IL-10 could support inappropriate immune responses development after allergen encounter.

A longitudinal study of natural antibody development to pneumococcal surface protein A families 1 and 2 in Papua New Guinean Highland children: a cohort study

BACKGROUND

Pneumococcal surface protein A (PspA), a conserved virulence factor essential for Streptococcus pneumoniae attachment to upper respiratory tract (URT) epithelia, is a potential vaccine candidate for preventing colonisation.

METHODS

This cohort study was conducted in the Asaro Valley in the Eastern Highlands Province of Papua New Guinea, of which Goroka town is the provincial capital. The children included in the analysis were participants in a neonatal pneumococcal conjugate vaccine trial (ClinicalTrials.gov NCT00219401) that was conducted between 2005 and 2009. We investigated the development of anti-PspA antibodies in the first 18 months of life relative to URT pneumococcal carriage in Papua New Guinean infants who experience one of the earliest and highest colonisation rates in the world. Blood samples and nasopharyngeal swabs were collected from a cohort of 88 children at ages 3, 9, and 18 months to quantify immunoglobulin G (IgG) levels to PspA families 1 and 2 using an enzyme-linked immunosorbent assay and to determine URT carriage.

RESULTS

Seventy-three per cent (64/88) of infants carried S. pneumoniae at age 3 months; 85 % (75/88) at 9 months, and 83 % (73/88) at 18 months. PspA-IgG levels declined between ages 3 and 9 months (p < 0.001), then increased between 9 and 18 months (p < 0.001). At age 3 months, pneumococcal carriers showed lower PspA1-IgG levels (geometric mean concentration [GMC] 602 arbitrary units [AU]/ml, 95 % confidence interval [CI] 497-728) than non-carriers (GMC 1058 AU/ml [95 % CI 732-1530]; p = 0.008), while at 9 months, PspA1- and PspA2-IgG levels were significantly higher in carriers (PspA1: 186 AU/ml, 95 % CI 136-256; PspA2: 284 AU/ml, 95 % CI 192-421) than in non-carriers (PspA1 87 AU/ml, 95 % CI 45-169; PspA2 74 AU/ml, 95 % CI 34-159) (PspA1: p = 0.037, PspA2: p = 0.003).

CONCLUSION

Our findings confirm that PspA is immunogenic and indicate that natural anti-PspA immune responses are acquired through exposure and develop with age. PspA may be a useful candidate in an infant pneumococcal vaccine to prevent early URT colonisation.

High breast milk IL-1β level is associated with reduced risk of childhood eczema

BACKGROUND

We recently demonstrated a dual effect of breastfeeding with increased risk of eczema and decreased risk of wheezing in early childhood by increasing breastfeeding length. We hypothesize that immune mediators in breast milk could explain such association either through a direct effect or as a surrogate marker of maternal immune constitution.

OBJECTIVE

To investigate the possible association between cytokine and chemokine levels in breast milk and development of eczema and recurrent wheeze during early childhood.

METHODS

Levels of 19 pro-inflammatory and immunoregulatory cytokines and chemokines were measured in 223 breast milk samples from mothers in the Copenhagen Prospective Study on Asthma in Childhood2000 (COPSAC) high-risk birth cohort. Eczema and recurrent wheeze at the age of 0-3 years were prospectively diagnosed by COPSAC physicians adherent to predefined validated algorithms. Association analyses were performed by Cox regression adjusting for potential confounding factors and by multivariable principal component analysis.

RESULTS

Increased IL-1β in breast milk (≥ 0.7 pg/mL) was associated with more than a halved risk of eczema before age three (aHR = 0.41; 95% CI = 0.24-0.68; P < 0.001), which remained significant after false discovery rate adjustment (P = 0.008). The principal component analysis confirmed that a mediator pattern dominated by high levels of IL-1β, IL-17A, and CCL17 and low levels of CXCL1 and TSLP in breast milk protected against eczema (aHR = 0.82; 95% CI = 0.68-0.98; P = 0.03). No associations were observed for recurrent wheeze.

CONCLUSIONS AND CLINICAL RELEVANCE

Elevated breast milk IL-1β level was associated with decreased risk of early childhood eczema suggesting either a direct protective effect of IL-1β or IL-1b acting as a proxy for a healthy maternal immune system protecting high-risk offspring from eczema.

Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal.

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.

Challenges in vaccination of neonates, infants and young children

All neonates, infants and young children receive multiple priming doses and booster vaccinations in the 1st and 2nd year of life to prevent infections by viral and bacterial pathogens. Despite high vaccine compliance, outbreaks of vaccine-preventable infections are occurring worldwide. These data strongly argue for an improved understanding of the immune responses of neonates, infants and young children to vaccine antigens and further study of the exploitable mechanisms to achieve more robust and prolonged immunity with fewer primary and booster vaccinations in the pediatric population. This review will focus on our recent work involving infant and young child immunity following routine recommended vaccinations. The discussion will address vaccine responses with respect to four areas: (1) systemic antibody responses, (2) memory B-cell generation, (3) CD4 T-cell responses, and (4) APC function.

Ontogeny of early life immunity

The human immune system comprises cellular and molecular components designed to coordinately prevent infection while avoiding potentially harmful inflammation and autoimmunity. Immunity varies with age, reflecting unique age-dependent challenges including fetal gestation, the neonatal phase, and infancy. Here, we review novel mechanistic insights into early life immunity, with an emphasis on emerging models of human immune ontogeny, which may inform age-specific translational development of novel anti-infectives, immunomodulators, and vaccines.

Ontogeny of Toll-like and NOD-like receptor-mediated innate immune responses in Papua New Guinean infants

Studies addressing the ontogeny of the innate immune system in early life have reported mainly on Toll-like receptor (TLR) responses in infants living in high-income countries, with little or even no information on other pattern recognition receptors or on early life innate immune responses in children living under very different environmental conditions in less-developed parts of the world. In this study, we describe whole blood innate immune responses to both Toll-like and nucleotide-binding oligomerization domain (NOD)-like receptor agonists including the widely used vaccine adjuvant ‘alum’ in a group of Papua New Guinean infants aged 1–3 (n = 18), 4–6 (n = 18), 7–12 (n = 21) and 13–18 (n = 10) months old. Depending on the ligands and cytokines studied, different age-related patterns were found: alum-induced IL-1β and CXCL8 responses were found to significantly decline with increasing age; inflammatory (IL-6, IL-1β, IFN-γ) responses to TLR2 and TLR3 agonists increased; and IL-10 responses remained constant or increased during infancy, while TNF-α responses either declined or remained the same. We report for the first time that whole blood innate immune responses to the vaccine adjuvant alum decrease with age in infancy; a finding that may imply that the adjuvant effect of alum in pediatric vaccines could be age-related. Our findings further suggest that patterns of innate immune development may vary between geographically diverse populations, which in line with the ‘hygiene hypothesis’ particularly involves persistence of innate IL-10 responses in populations experiencing higher infectious pressure.

Breastfeeding modulates neonatal innate immune responses: a prospective birth cohort study

BACKGROUND

Neonatal Toll-like receptor (TLR) responses are biased toward Th2-polarizing responses at birth and rapidly mature toward more balanced responses during the first month of life. Postnatal TLR maturation may be guided by environmental exposure.

AIMS

To determine the environmental determinants of neonatal TLR function.

MATERIALS AND METHODS

A prospective birth cohort study was performed in 291 healthy term neonates. Mode of delivery, breastfeeding, birth month, siblings, pets and parental smoking were analyzed in relation to neonatal innate immune parameters at the age of 1 month. Whole blood concentrations of innate immune cells were measured by flow cytometry. In vitro TLR-mediated cytokine production was determined by ELISA.

RESULTS

Breastfeeding was the major determinant of neonatal innate immunity, associated with 5 (31%) of neonatal innate immune parameters, of which the association with TLR7-mediated IL-10 production was most significant (76 pg/ml in breastfed neonates vs. 293 pg/ml in formula-fed neonates, p = 0.001). Of innate immune variables, TLR3-mediated IL-12p70 production was highly associated with environmental exposures (pets, breastfeeding and mode of delivery), whereas TLR9-mediated cytokine responses were not associated with any environmental factor.

CONCLUSION

Neonatal innate immune responses are differentially modulated by environmental exposure in the first month of life. The protective effect of breastfeeding against subsequent infections and atopy might be explained by its innate immune modulatory effects in the first month of life.

Early life exposure to genistein and daidzein disrupts structural development of reproductive organs in female mice

In mice, exposure to isoflavones (ISO), abundant in soy infant formula, during the first 5 d of life alters structural and functional development of reproductive organs. Effects of longer exposures are unknown. The study objective was to evaluate whether exposure to a combination of daidzein and genistein in the first 10 compared to 5 d of life results in greater adverse effects on ovarian and uterine structure in adult mice. Thirteen litters of 8-12 pups were cross-fostered and randomized to corn oil or ISO (2 mg daidzein + 5 mg genistein/kg body weight/d) for the first 5 or 10 d of life. The 10-d protocol mimicked the period when infants are fed soy protein formula (SPF) but avoids the time when suckling pups can consume mother's diet. Body and organ weights, and histology of ovaries and uteri were analyzed. There were no differences in the ovary or uterus weight, number of ovarian follicles, number of multiple oocyte follicles, or percent of ovarian cysts with 5 or 10 d ISO intervention compared to respective controls. The 10-d ISO group had higher body weights from 6 d to 4 mo of age and a higher percent of hyperplasia in the oviduct than the respective control. Lower number of ovarian corpus lutea and a higher incidence of abnormal changes were reported in the uteri of both ISO groups compared to their respective controls. Five and 10-d exposure to ISO had similar long-lasting adverse effects on the structure of ovaries and uterus in adult mice. Only the 10-d ISO exposure resulted in greater body weight gain at adulthood.

Emerging pathways in asthma: innate and adaptive interactions

BACKGROUND

Allergic asthma is a complex and chronic airway inflammatory disorder, and the prevalence of asthma has increased. Adaptive antigen-dependent immunity is a classical pathway of asthmatic pathology. Recent studies have focused on innate antigen-independent immunity in asthma.

SCOPE OF REVIEW

This review discusses updated research associating innate immunity with allergic asthma. We focus on innate molecules (Toll-like receptors and nucleotide-binding oligomerization domain-like receptors) and review studies regarding innate and adaptive interactions in allergic responses (surfactant protein D, lipopolysaccharide, and early life immune responses). We also highlight new emerging concepts in the field applicable to innate immunity and asthma.

MAJOR CONCLUSIONS

Innate immunity plays a key role in asthma. Understanding innate and adaptive interactions provide significant information in asthmatic research. Innate molecules not only contribute to classical pulmonary defense, but also modulate inflammatory responses. Emerging concepts in the analysis of the microbiome, microRNA and autophagy may provide new insights in searching therapeutic targets.

GENERAL SIGNIFICANCE

Finding specific mechanisms of innate and/or adaptive immunity in asthma are timely goals for further research. Integration of bioinformatics and systems biology tools, particularly in relation to microbiome analysis, may be helpful in providing an understanding to allergic immune responses. This article is part of a Special Issue entitled Biochemistry of Asthma.

EBI3 deficiency leads to diminished T helper type 1 and increased T helper type 2 mediated airway inflammation

Despite extensive investigation of the signals required for development of T helper type 1 (Th1) and type 2 (Th2) immune responses, the mechanisms involved are still not well-defined. A critical role for Epstein-Barr virus-induced gene 3 (EBI3) in these responses has been proposed. EBI3, initially discovered as a transcriptionally activated gene in Epstein-Barr virus-infected B lymphocytes, codes for a subunit of the cytokine interleukin-27 (IL-27). While initial studies suggested that it had an important role in promoting Th1 responses, subsequent studies have revealed that EBI3 receptor signalling influences a variety of immune cell types and can inhibit both Th1 and Th2 responses. In the present study, we evaluated EBI3(-/-) mice for their ability to mount both Th1-mediated and Th2-mediated airway inflammatory responses. The EBI3(-/-) mice sensitized by exposure to inhaled ovalbumin plus a high dose of lipopolysaccharide, which normally results in Th1 responses in wild-type (WT) mice, instead developed Th2 type airway inflammation, with increased numbers of eosinophils. The EBI3(-/-) mice that were exposed to inhaled ovalbumin with a low dose of lipopolysaccharide, which induces Th2 responses in WT mice, showed a marked enhancement of these responses, with increased airway eosinophils, increased serum IgE levels and increased levels of Th2 cytokines (IL-4, IL-5 and IL-13) in culture supernatants of mediastinal lymph node cells. Increased production of Th2 cytokines was also seen when naive CD4(+) T cells from EBI3(-/-) mice were stimulated in vitro compared with cells from WT mice. These results provide the first evidence that EBI3 may play an inhibitory role in allergic asthma development.

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.

Cord blood versus age 5 mononuclear cell proliferation on IgE and asthma

BACKGROUND

Fetal immune responses following exposure of mothers to allergens during pregnancy may influence the subsequent risk of childhood asthma. However, the association of allergen-induced cord blood mononuclear cell (CBMC) proliferation and cytokine production with later allergic immune responses and asthma has been controversial. Our objective was to compare indoor allergen-induced CBMC with age 5 peripheral blood mononuclear cell (PBMC) proliferation and determine which may be associated with age 5 allergic immune responses and asthma in an inner city cohort.

METHODS

As part of an ongoing cohort study of the Columbia Center for Children's Environmental Health (CCCEH), CBMCs and age 5 PBMCs were cultured with cockroach, mouse, and dust mite protein extracts. CBMC proliferation and cytokine (IL-5 and IFN-gamma) responses, and age 5 PBMC proliferation responses, were compared to anti-cockroach, anti-mouse, and anti-dust mite IgE levels, wheeze, cough, eczema and asthma.

RESULTS

Correlations between CBMC and age 5 PBMC proliferation in response to cockroach, mouse, and dust mite antigens were nonsignificant. Cockroach-, mouse-, and dust mite-induced CBMC proliferation and cytokine responses were not associated with allergen-specific IgE at ages 2, 3, and 5, or with asthma and eczema at age 5. However, after adjusting for potential confounders, age 5 cockroach-induced PBMC proliferation was associated with anti-cockroach IgE, total IgE, and asthma (p < 0.05).

CONCLUSION

In contrast to allergen-induced CBMC proliferation, age 5 cockroach-induced PBMC proliferation was associated with age 5 specific and total IgE, and asthma, in an inner-city cohort where cockroach allergens are prevalent and exposure can be high.

Parental characteristics, somatic fetal growth, and season of birth influence innate and adaptive cord blood cytokine responses

BACKGROUND

Immunologic responses at birth likely relate to subsequent risks for allergic diseases and wheezing in infancy; however, the influences of parental characteristics and prenatal factors on neonatal immune responses are incompletely understood.

OBJECTIVE

This study investigates potential correlations between urban parental, prenatal, and perinatal factors on innate and adaptive stimuli-induced cytokine responses.

METHODS

Five hundred sixty and 49 children of parents with and without allergic disease or asthma, respectively, were enrolled into a prospective birth cohort study (Urban Environment and Childhood Asthma). Cord blood mononuclear cells were incubated with innate and adaptive immune stimuli, and cytokine responses (ELISA) were compared with season of birth, parental characteristics, in utero stressors, and fetal growth.

RESULTS

Many cytokine responses varied by season of birth, including 2-fold to 3-fold fluctuations with specific IFN-alpha and IFN-gamma responses. Birth weight was inversely associated with IFN-gamma responses to respiratory syncytial virus (R = -0.16), but positively associated with IL-8 responses to a variety of innate stimuli (R = 0.08-0.12). Respiratory syncytial virus-induced cytokine responses were 21% to 54% lower in children of mothers with asthma. Cytokine responses were generally lower in babies born to parents with allergy/asthma.

CONCLUSIONS

Innate cytokine responses are associated with parental allergic or airway disease, somatic fetal growth, ethnicity, and season of birth. Collectively, these findings suggest that urban prenatal exposures and familial factors affect the development of the fetal immune system.

Fish Oil Supplementation in Pregnancy Lowers F2-isoprostanes in Neonates at High Risk of Atopy

The anti-inflammatory properties of n-3 polyunsaturated fatty acids (n-3 PUFA) have suggested a potential role of these nutrients in dietary modification for prevention of allergic disease in early life. As oxidative stress is known to modify antigen presenting cell (APC) signalling and resulting immune responses, we examined the effects of maternal n-3 PUFA supplementation in pregnancy on markers of oxidative stress and APC function in neonates at high risk of allergy. Eighty-three pregnant atopic women were randomised to receive 4 g daily of either fish oil (n = 40) or olive oil (n = 43) capsules in a controlled trial from 20 weeks gestation until delivery. Plasma (cord blood) and urinary F2-isoprostanes were measured as markers of lipid peroxidation. Cord erythrocyte fatty acids and markers of APC function (HLA-DR expression and cytokine responses) were measured and related to levels of plasma F2-isoprostanes. Maternal fish oil supplementation lowered plasma (p < 0.0001) and urinary (p = 0.06) F2-isoprostanes. HLA-DR expression on APC was not different between the groups. In multiple regression analysis, 28.8% of the variance in plasma F2-isoprostanes was explained by positive relationships with erythrocyte arachidonic acid (AA) and monocyte HLA-DR expression and a negative relationship with erythrocyte eicosapentaenoic acid (EPA). This study shows that maternal supplementation with fish oil can attenuate neonatal lipid peroxidation. Clinical follow-up of these infants will help to determine if there are sustained effects on postnatal oxidative stress and expression of allergic disease.

Total IL-12 levels are increased in paediatric atopic dermatitis: correlations with age and disease severity

Alterations in the immune response play an important role in the pathogenesis of atopic dermatitis (AD). We evaluated the role of Th1/Th2 cytokine imbalance in paediatric AD and its progression towards other allergic manifestations. The levels of total interleukin (IL)-12 (p70+p40), IL-12 p70 and soluble CD30 (sCD30) were measured in paediatric patients affected by AD and in age-matched, non-atopic subjects (controls). The serum levels of total IL-12 and sCD30 were higher in patients than in controls (p=0.003 and p=0.053, respectively). Total IL-12 and sCD30 were also particularly increased in patients with severe disease. Serum levels of total IL-12 were negatively correlated with patient age (p=0.001): they were significantly higher in patients younger than 30 months, as compared to age-matched controls and to older patients and controls. Total IL-12 and sCD30 production were not significantly correlated with disease outcomes (atopic march) or with a family history of atopy. Our data show that total IL-12 levels are strongly associated with Th2 activation and severe disease in children with AD. The increased production of total IL-12 at an early age might indicate a different immune modulation and suggests the possibility of new therapeutic approaches for allergic diseases, in particular AD, early in childhood.

Effects of interleukin-12 and interleukin-15 on measles-specific T-cell responses in vaccinated infants

Understanding the infant host response to measles vaccination is important because of their increased mortality from measles and the need to provide effective protection during the first year of life. Measles-specific T and B-cell responses are lower in infants after measles vaccination than in adults. To define potential mechanisms, we investigated age-related differences in measles-specific T-cell proliferation, CD40-L expression, and IFN-gamma production after measles immunization, and the effects of rhIL-12 and rhIL-15 on these responses. Measles-specific T-cell proliferation and mean IFN-gamma release from infant PBMCs were significantly lower when compared with responses of vaccinated children and adults. Infant responses increased to ranges observed in children and adults when both rhIL-12 and rhIL-15 were added to PBMC cultures. Furthermore, a significant rise in T-cell proliferation and IFN-gamma release was observed when infant PBMCs were stimulated with measles antigen in the presence of rhIL-12 and rhIL-15 compared to measles antigen alone. CD40-L expression by infant and adult T cells stimulated with measles antigen was comparable, but fewer infant CD40-L(+) T cells expressed IFN-gamma. These observations suggest that lower measles-specific T-cell immune responses elicited by measles vaccine in infants may be due to diminished levels of key cytokines.

Airway inflammatory responses to oxidative stress induced by prolonged low-dose diesel exhaust particle exposure from birth differ between mouse BALB/c and C57BL/6 strains

The authors used BALB/c and C57BL/6 mouse strains to search for genetically based differences in response to prolonged (6 months) low-dose (100 microg/m3) diesel exhaust particle (DEP) exposure from birth in terms of airway inflammatory responses. Histopathological assessment showed that inflammatory cells infiltrated the perivascular areas only in C57BL/6 mice. The count of DEP-laden alveolar macrophages in bronchoalveolar lavage (BAL) fluid was significantly greater in BALB/c mice (P < .05) than in C57BL/6 mice. The lymphocyte and eosinophil count in BAL fluid was significantly greater in C57BL/6 mice (P < .05) than in BALB/c mice. Immunoglobulin (Ig) IgG1 and IgG2 levels in serum, and the monocyte chemoattractant protein (MCP)-1 level in BAL fluid were significantly greater in BALB/c mice than in C57BL/6 mice. The interleukin (IL)-12 level in BAL fluid was significantly greater in C57BL/6 mice than in BALB/c mice, but the IL-13 level in BAL fluid was significantly less in BALB/c mice than in C57BL/6 mice. Glutathione S-transferase (GST) mRNA expression and protein production in lung tissues were significantly lower in C57BL/6 mice than in BALB/c mice, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) level in the lung tissues were significantly greater in C57BL/6 mice than in BALB/c mice. In conclusion, prolonged low-dose DEP exposure induces airway inflammatory responses that differ remarkably among mouse strains; these differences are caused by differences in the host defense response to the oxidative stress induced by DEP exposure and may be useful in the development of biomarkers.

Interleukin-12 peripheral blood levels in asthmatic children

Interleukin-12 (IL-12) was measured in 45 asthmatic children aged 3 to 16 years. The assessments were performed on 20 children during an episode of acute exacerbation and on 25 children during remission. There was no significant difference between the mean IL-12 level during exacerbation (1.63 ± 2.08 pg/mL) and during remission (0.88 ± 0.56 pg/mL) (p = .83). A positive, but insignificant, correlation was found between forced expiratory volume in 1 second and IL-12 (p = .634). IL-12 levels were significantly lower in children with a positive family history of asthma (1.13 ± 1.78 pg/mL) compared with those without (1.31 ± 1.06 pg/mL) (p < .012), supporting the theory that the gene-environment interactions affect the immune responses. IL-12 peripheral blood levels had no detectable impact on the course of established asthma in the study population.

Lung CD11c+ cells from mice deficient in Epstein-Barr virus-induced gene 3 (EBI-3) prevent airway hyper-responsiveness in experimental asthma

Epstein-Barr virus-induced gene (EBI)-3 codes for a soluble type 1 cytokine receptor homologous to the p40 subunit of IL-12 that is expressed by antigen-presenting cells following activation. Here, we analyzed the functional role of EBI-3 in a murine model of asthma associated with airway hyper-responsiveness (AHR) in ovalbumin-sensitized mice. Upon allergen challenge, EBI-3-/- mice showed less severe AHR, decreased numbers and degranulation of eosinophils and a significantly reduced number of VCAM-1+ cells in the lungs as compared to wild-type littermates. We thus analyzed lung CD11c+ cells before and after allergen challenge in these mice and found that before allergen challenge, lung CD11c+ cells isolated from EBI-3-/- mice express markers of a more plasmacytoid phenotype without releasing IFN-alpha as compared to those from wild-type littermates. Moreover, allergen challenge induced the development of myeloid CD11c+ cells in the lungs of EBI-3-/- mice, which released increased amounts of IL-10 and IL-12 while not expressing IFN-alpha. Finally, inhibition of EBI-3 expression in lung DC could prevent AHR in adoptive transfer studies by suppressing mediator release of effector cells into the airways. These results indicate a novel role for EBI-3 in controlling local immune responses in the lungs in experimental asthma.

Translational mini-review series on Toll-like receptors: Toll-like receptor ligands as novel pharmaceuticals for allergic disorders

Characterization of the Toll-like receptor (TLR) family and associated signalling pathways provides a key molecular basis for our understanding of the relationship between exposure to microbial products and susceptibility to immune-mediated disorders. Indeed, ligation of TLR controls innate and adaptive immune responses by inducing synthesis of pro- as well as anti-inflammatory cytokines and activation of effector as well as regulatory lymphocytes. TLRs are therefore considered as major targets for the development of vaccine adjuvants, but also of new immunotherapies. Herein, we review the potential of TLR ligands as a novel class of pharmaceuticals for the prevention or treatment of allergic disorders.

T-cell responses to allergens

The allergic response in human beings is engineered by CD4(+) T lymphocytes, which secrete T(H)2 cytokines in response to activation by allergen-derived peptides. Although T(H)2 cells have been well characterized, defining the properties of allergen-specific T cells has proved challenging in human beings because of their low frequency within the T-cell repertoire. However, recent studies have provided insight into the molecular signature of long-lived human memory T(H)2 cells, which are allergen-specific. T-cell responses directed against allergens develop in early life and are heavily influenced by the type and dose of allergen, and possibly coexposure to microbial products. These responses are susceptible to suppression by regulatory T cells. This article highlights recent advances in the characterization of allergen-specific memory T(H)2 cells and discusses the heterogeneous nature of regulatory T cells and possible mechanisms of action. The relevance of T-cell epitope mapping studies to understanding the unique nature of T-cell responses to different allergens, as well as to peptide vaccine development, is reviewed. Experimental techniques and approaches for analyzing allergen-specific T cells and identifying novel T-cell epitopes are described that may lead to new T-cell-based therapies.

Antenatal risk factors, cytokines and the development of atopic disease in early childhood

Atopic diseases are complex entities influenced by an array of risk factors, including genetic predisposition, environmental allergens, antenatal exposures, infections and psychosocial factors. One proposed mechanism by which these risk factors contribute to the development of atopic disease is through changes in the production of T helper cell type 1 (Th1) and T helper cell type 2 (Th2) cytokines. The objectives of this review are to discuss antenatal exposures that are associated with paediatric atopic diseases, to discuss the influence of the intrauterine environment on neonatal immune responses, to provide an overview of the Th1 and Th2 pathways and how they relate to atopic disease, and to summarise our current understanding of the association between cytokine responses in cord blood and the development of atopic disease in early childhood.

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.

Defective antigen-presenting cell function in human neonates

Immaturity of the immune system has been suggested as an underlying factor for the high rate of morbidity and mortality from infections in newborns. Functional impairment of neonatal T cells is frequently quoted as the main underlying mechanism for such immaturity. However, recent studies suggest that neonatal antigen-presenting cells (APCs) also exhibit functional alterations, which could lead to secondary defects of adaptive T-cell responses. In this review, we summarize what is known on the functionality of APC at birth and during early childhood. Compared to adults, neonatal APCs display markers of immaturity and produce low levels of cytokines. Multiple factors could be involved in neonatal APC alteration, such as intrinsic immaturity, defective interaction between APCs and T cells and regulatory T-cell-mediated inhibition. Characterization of the relative contribution of each mechanism is clearly needed to better understand the functional capability of the neonatal immune system.

Increased secretion of leukemia inhibitory factor by immature airway smooth muscle cells enhances intracellular signaling and airway contractility

Airway smooth muscle cells (ASMC) play a major role in airway inflammation, hyperresponsiveness, and obstruction in asthma. However, very little is known regarding the relation between inflammatory mediators and cytokines and immature ASMC. The aim of this study was to evaluate 1) the secretion of leukemia inhibitory factor (LIF) (an IL-6 family neurotrophic cytokine) by ASMC; 2) intracellular calcium concentration ([Ca(2+)](i)) signaling; and 3) the effect of LIF on mast cell chemotaxis and rat airway contractility. Immature and adult human ASMC were cultured. ELISA and real-time PCR were performed to assess LIF protein secretion and mRNA production, [methyl-(3)H]thymidine incorporation to quantify ASMC DNA synthesis, a Boyden chamber to evaluate the effect of LIF on mast cell chemotaxis, microspectroflurimetry using indo-1 (at baseline and after stimulation bradykinin, U-46619, histamine, and acetylcholine, in the presence or absence of LIF or TNF-alpha) for [Ca(2+)](i) signaling, and isolated rat pup tracheae to determine the effect of LIF on airway contractility to ACh. TNF-alpha-stimulated immature ASMC produce more LIF mRNA and protein than adult ASMC, although this cytokine induces a moderate increase in DNA synthesis (+20%) in adult ASMC only. Human recombinant LIF exerts no chemotactic effect on human mast cells. In immature ASMC, ACh-induced [Ca(2+)](i) response was enhanced twofold after incubation with LIF, whereas TNF-alpha increased the [Ca(2+)](i) to U-46619 threefold. In TNF-alpha-exposed adult ASMC, [Ca(2+)](i) responses to ACh were of greater magnitude (sixfold increase) than in immature ASMC. Human recombinant LIF increased contractility to ACh by 50% in immature, isolated rat tracheae. Stimulated immature human ASMC greatly secrete LIF, thus potentially contributing to neuroimmune airway inflammation and subsequent remodeling. Increased LIF secretion enhances airway reactivity and [Ca(2+)](i) signaling.

Fish oil supplementation of lactating mothers affects cytokine production in 2 1/2-year-old children

n-3 PUFA influence immune functioning and may affect the cytokine phenotype during development. To examine whether maternal fish oil supplementation during lactation could modify later immune responses in children, 122 lactating Danish mothers with a fish intake below the population median were randomized to groups supplemented for the first 4 mon of lactation with 4.5 g/d of fish oil (equivalent to 1.5 g/d of n-3 long-chain PUFA) or olive oil. Fifty-three mothers with a fish intake in the highest quartile of the population were also included. The FA composition of erythrocyte membranes was measured at 4 mon and at 2 1/2 yr. Plasma immunoglobulin E (IgE) levels and cytokine production in lipopolysaccharide-stimulated whole-blood cultures were determined at 2 1/2 yr. Erythrocyte n-3 PUFA at 4 mon were higher in infants from the fish oil group compared with the olive oil group (P < 0.001) but were no longer different at 2 1/2 yr. The median production of lipopolysaccharide-induced interferon gamma (IFN-gamma) in the fish oil group was fourfold higher than that in the olive oil group (P = 0.034), whereas interleukin-10 (IL-10) production was similar. The IFN-gamma/IL-10 ratio was twofold higher in the fish oil group (P = 0.019) and was positively correlated with 20:5n-3/20:4n-6 in erythrocytes at 4 mon (P = 0.050). The percentages of atopic children and plasma IgE were not different in the two groups, but the study was not designed to look at atopy. Cytokine responses and erythrocyte FA composition in children of mothers with a high fish intake were intermediate in comparison with those in the randomized groups. Fish oil supplementation during lactation resulted in increased in vitro IFN-gamma production in the children 2 yr after the supplementation was given, which may reflect a faster maturation of the immune system.

Increased levels of tumor necrosis factor-alpha and decreased levels of interleukin-12 p 70 in tracheal aspirates, within 2 hrs after birth, are associated with mortality among ventilated preterm infants

OBJECTIVE

To determine the association of antibacterial interleukin (IL)-12 p 70 levels as well as the pathogen-induced proinflammatory cytokine response in tracheal aspirate (TA) to respiratory failure and mortality among ventilated preterm infants.

DESIGN

A prospective observational clinical cohort study with measurements of cytokine levels and microbial cultures of TA from ventilated preterm neonates. Interleukin (IL)-1 beta, IL-8, IL-6, IL-10, IL-12 p 70, and tumor necrosis factor (TNF)-alpha were measured in TA within 2 hrs of birth, and comorbidity characteristics were recorded prospectively. The association between cytokine levels in TA and neonatal mortality was determined, with correction for comorbidity factors by means of multivariate stepwise logistic regression.

SETTING

A single tertiary neonatal intensive care unit at the University Hospital of Antwerp, Belgium.

PATIENTS

One hundred forty-one neonates born before a gestational age of 31 wks and who required ventilation were enrolled in the study; 31 (22%) died and 37 (26%) had airway colonization.

MEASUREMENTS AND MAIN RESULTS

The airway colonization rate was significantly greater among deceased neonates (45% vs. 21%; chi-square, 7.4; p=.007). Neonates who died had a significantly lower IL-12 p 70 cytokine level (6 pg/mL vs. 11 pg/mL; p<.05) in their TA. Neonates with a low IL-12 p 70 cytokine level had more pronounced respiratory failure (significantly higher oxygenation index, higher degree of radiologic respiratory distress syndrome, higher critical index for babies score, and more surfactant use). Multivariate analysis revealed that, after correction for severity of disease by critical index for babies score, the degree of intraventricular hemorrhage (odds ratio, 5.0 [95% confidence interval, 2.6-9.7]), low IL-12 p 70 levels (odds ratio, 4.9 [95% confidence interval, 2.1-11.7]), and high TNF-alpha levels in TA (odds ratio, 3.5 [95% confidence interval, 1.6-7.5]) were significantly associated with neonatal mortality.

CONCLUSIONS

Pathogen-induced excessive production of the proinflammatory cytokine TNF-alpha and lack of antibacterial IL-12 p 70 response in the TA are associated with increased neonatal mortality among ventilated preterm infants.

Modification of dendritic cell function as a tool to prevent and treat allergic asthma

Atopic asthma is a chronic inflammatory disease of the airways, characterized by airway hyperreactivity and mucus hypersecretion that result in intermittent airway obstruction. This chronic inflammation is the result of an aberrant Th2-mediated response to innocuous environmental proteins. The prevalence of this disease has increased dramatically in the industrialized world in the last decades. Current treatment is mainly based on pharmacological interventions, which control the disease but are not curative. Although the etiology is not completely understood, it becomes increasingly clear that dendritic cells play an important role in both the sensitization phase and maintenance of the disease. In this review, we explore the different possibilities to exploit dendritic cell vaccines in order to prevent the development of (or inhibit established) atopic asthma.

Hope for the hygiene hypothesis: when the dirt hits the fan

The hygiene hypothesis was developed in response to data suggesting that the increase in allergic diseases as well as asthma was secondary to a reduced exposure to infectious stimuli. Indeed, the epidemiologic changes, resulting in an increase in atopic disease, have been impressive and intriguing. Furthermore, although there clearly is a genetic component to atopic diseases, genetics cannot account for a marked increase in the incidence and prevalence of allergic manifestations within a few generations. Thus, environmental factors have been suggested as responsible for the changing prevalence. There are two--not mutually exclusive--possibilities, namely, that substances that promote atopy have been added to the environment or that factors that provided protection from allergic disease were lost from the environment. Both outdoor and indoor pollution, along with a long list of other environmental factors, have been proposed. It is of interest that in many developed countries, certain types of pollution have decreased, whereas the prevalence of atopic disease has increased. In this review, we have explored a detailed analysis of a large number of studies that have focused on this issue and suggest that, although the hygiene hypothesis has merit, the stimuli responsible for the new epidemiology remain enigmatic.

Dexamethasone inhibits maturation and alters function of monocyte-derived dendritic cells from cord blood

Critically ill infants are treated with dexamethasone (Dx) and other glucocorticoids to reduce inflammation and to promote lung and cardiac function. The neonatal immune system is immature, so neonatal dendritic cells (DCs) might be especially sensitive to glucocorticoid-mediated immunosuppression. To test this, we compared Dx treatment of monocyte-derived DCs from cord (CB) and adult blood (AB). Dx decreased CD1a levels on both AB and CB DCs. CB-treated cells also exhibited decreased expression of CD83 and increased expression of CD14, alterations not observed in AB DCs. Characteristic immature endocytic activity was sustained and enhanced in Dx-treated CB DCs, whereas AB DCs matured normally. Maintenance of endocytosis corresponded with CD14 expression. Dx markedly increased CB DC IL-10, a T cell helper 2 (Th2)-preferential cytokine, while reducing IL-12, a counterbalancing Th1 cytokine. AB DCs were also affected, but increases in IL-10 and decreases in IL-12 were more modest. Dx treatment also inhibited DC-induced T cell proliferation, but CB DCs were inhibited more. In short, neonatal DCs seemed to be especially sensitive to the immunosuppressive effects of Dx as indicated by altered phenotype, endocytic function, ability to stimulate T cells, and cytokine shift favoring Th2. These alterations in DC function are consistent with an increased risk for certain infections and atopic diseases.

Indoor air quality and human health: truth vs mass hysteria

Indoor air quality is an important issue, because anything we breathe can potentially affect our health. To determine if there is a real health risk, well-designed scientifically valid studies must be performed. Although much attention has focused on sick building syndrome, chemical sensitivities, and mycotoxicosis, there actually is very little evidence that these conditions have an adverse effect on human health. In contrast, real health issues have been shown to exist regarding indoor air triggers of allergies and asthma. Outdoor allergens are difficult to avoid because the pollen grains we encounter outdoors, which are the size that can cause allergies, are windborne and can travel for miles. However, indoor allergens can cause severe allergic symptoms and may also have a priming effect on an individual’s susceptibility to simultaneous or subsequent exposure of other outdoor allergens. Therefore, it is important to minimize exposure to indoor allergens. Determination of individual susceptibility can be paired with knowledge of the patient’s indoor exposure pattern to produce a customized management plan of avoidance, which can be used in conjunction with pharmacological treatment of allergies and asthma, as well as immunotherapy.

In search for predictive factors for atopy in human cord blood

Since early prevention is regarded as an important corner stone in the management of atopic diseases, the identification of reliable markers detecting individuals at risk are of major interest. Therefore, many efforts have been made to unravel reliable predictors for atopy which might identify children at risk and allow the initiation of preventive strategies at an early stage. In the past, much scientific energy has been forced in particular on the development of as noninvasive methods as possible to reach this goal. It is obvious that the identification of markers for atopy at the earliest time of life - namely immediately after birth - represents one of the most attractive attempts. In consequence various studies have been initiated to address this issue investigating markers for atopy in cord blood. Most of them have been geared to our current knowledge about cellular and soluble factors which are dysregulated in adolescent atopic individuals. Although the findings of these studies will improve our knowledge about the initial evolution of atopy, several parameters evaluated did not show any association or have led to almost conflicting results. In order to provide an up-date about the current developments in this field, recent research findings on predictive factors for atopy in cord blood are summarized in the following synopsis.

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.

Dendritic cells retrovirally overexpressing IL-12 induce strong Th1 responses to inhaled antigen in the lung but fail to revert established Th2 sensitization

It has been postulated that low-level interleukin (IL)-12 production of antigen-presenting cells is associated with the risk of developing atopic asthma. To study the relationship between IL-12 production capacity of dendritic cells (DCs) and development of T helper type 2 (Th2) responses in the lung, we genetically engineered DCs to constutively overexpress bioactive IL-12. Retrovirally mediated overexpression of IL-12 in DCs strongly polarized naive ovalbumin (OVA)-specific CD4+ T cells toward Th1 effector cells in vitro. After intratracheal injection, OVA-pulsed IL-12-overexpressing DCs failed to induce Th2 responses in vivo and no longer primed mice for Th2-dependent eosinophilic airway inflammation upon OVA aerosol challenge, readily observed in mice immunized with sham-transfected, OVA-pulsed DCs. Analysis of a panel of cytokines and chemokines in the lung demonstrated that the lack of Th2 sensitization was accompanied by increased production of the Th1 cytokine interferon-gamma (IFN-gamma), chemokines induced by IFN-gamma, and the immunoregulatory cytokine IL-10. When Th2 priming was induced using OVA/alum prior to intratracheal DC administration, DCs constitutively expressing IL-12 were no longer capable of preventing eosinophilic airway inflammation and even enhanced it. These data show directly that high-level expression of IL-12 in DCs prevents the development of Th2 sensitization. Enhancing IL-12 production in DCs should be seen as a primary prevention strategy for atopic disorders. Enhancing IL-12 production in DCs is less likely to be of benefit in already Th2-sensitized individuals.

The increased prevalence of allergy and the hygiene hypothesis: missing immune deviation, reduced immune suppression, or both?

Allergic atopic disorders, such as rhinitis, asthma, and atopic dermatitis, are the result of a systemic inflammatory reaction triggered by type 2 T helper (Th2) cell-mediated immune responses against 'innocuous' antigens (allergens) of complex genetic and environmental origin. A number of epidemiological studies have suggested that the increase in the prevalence of allergic disorders that has occurred over the past few decades is attributable to a reduced microbial burden during childhood, as a consequence of Westernized lifestyle (the 'hygiene hypothesis'). However, the mechanisms by which the reduced exposure of children to pathogenic and nonpathogenic microbes results in enhanced responses of Th2 cells are still controversial. The initial interpretation proposed a missing immune deviation of allergen-specific responses from a Th2 to a type 1 Th (Th1) profile, as a result of the reduced production of interleukin-12 and interferons by natural immunity cells which are stimulated by bacterial products via their Toll-like receptors. More recently, the role of reduced activity of T regulatory cells has been emphasized. The epidemiological findings and the experimental evidence available so far suggest that both mechanisms may be involved. A better understanding of this question is important not only from a theoretical point of view, but also because of its therapeutic implications.