Determinants of neonatal IgE level: parity, maternal age, birth season and perinatal essential fatty acid status in infants of atopic mothers

A machine-learning exploration of the exposome from preconception in early childhood atopic eczema, rhinitis and wheeze development

BACKGROUND

Most previous research on the environmental epidemiology of childhood atopic eczema, rhinitis and wheeze is limited in the scope of risk factors studied. Our study adopted a machine learning approach to explore the role of the exposome starting already in the preconception phase.

METHODS

We performed a combined analysis of two multi-ethnic Asian birth cohorts, the Growing Up in Singapore Towards healthy Outcomes (GUSTO) and the Singapore PREconception Study of long Term maternal and child Outcomes (S-PRESTO) cohorts. Interviewer-administered questionnaires were used to collect information on demography, lifestyle and childhood atopic eczema, rhinitis and wheeze development. Data training was performed using XGBoost, genetic algorithm and logistic regression models, and the top variables with the highest importance were identified. Additive explanation values were identified and inputted into a final multiple logistic regression model. Generalised structural equation modelling with maternal and child blood micronutrients, metabolites and cytokines was performed to explain possible mechanisms.

RESULTS

The final study population included 1151 mother-child pairs. Our findings suggest that these childhood diseases are likely programmed in utero by the preconception and pregnancy exposomes through inflammatory pathways. We identified preconception alcohol consumption and maternal depressive symptoms during pregnancy as key modifiable maternal environmental exposures that increased eczema and rhinitis risk. Our mechanistic model suggested that higher maternal blood neopterin and child blood dimethylglycine protected against early childhood wheeze. After birth, early infection was a key driver of atopic eczema and rhinitis development.

CONCLUSION

Preconception and antenatal exposomes can programme atopic eczema, rhinitis and wheeze development in utero. Reducing maternal alcohol consumption during preconception and supporting maternal mental health during pregnancy may prevent atopic eczema and rhinitis by promoting an optimal antenatal environment. Our findings suggest a need to include preconception environmental exposures in future research to counter the earliest precursors of disease development in children.

Long-Chain Polyunsaturated Fatty Acid Status at Birth and Development of Childhood Allergy: A Systematic Review

The associations of fetal fatty acids status to immune-related health parameters later in life are unclear. Our aim is to collect all available information on the relationship between fatty acid status at birth and allergy in childhood. Systematic literature search was performed on Ovid MEDLINE, Cochrane Library, and Embase. The search retrieved 897 articles without duplicates; 14 articles remained after excluding those that did not fit into our inclusion criteria. When the dichotomous parameter of suffering or not from allergic condition in childhood was analyzed, cord blood eicosapentaenoic acid (EPA) values proved to be significantly lower in allergic than non-allergic children in four comparisons from three studies. When the linear parameters of odds ratios and relative risks for allergy were taken into consideration, high cord blood EPA, but also high docosahexaenoic acid (DHA) and high total n-3 long-chain polyunsaturated fatty acid values were associated to clinically relevant reduction (at least 38%) in eight comparisons from five studies. Within the cord blood samples, higher EPA, docosapentaenoic acid, and DHA values were significantly and negatively associated in eight correlation analyses from three studies with laboratory parameters considered to reflect allergic trait. The data reported here may provide information for defining optimal fatty acid intakes for pregnant women.

Association between maternal age at delivery and allergic rhinitis in schoolchildren: A population-based study

Background

Some studies have shown associations of maternal age at delivery with asthma and food allergy in offspring. However, the relationship between maternal age at delivery and allergic rhinitis is largely unclear. This study aimed to investigate the association between maternal age at delivery and allergic rhinitis in a population sample of Asian children, and to explore potential effect modifiers.

Methods

A total of 1344 singleton-birth children (763 boys, 56.8%; mean age, 6.4 years) participating in the Longitudinal Investigation of Global Health in Taiwanese Schoolchildren (LIGHTS) cohort were evaluated by a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and interviewed by pediatricians. Allergic sensitization was determined by using Phadiatop Infant. Multiple logistic regression models with covariates adjustment were performed to investigate the association of maternal age at delivery with allergic rhinitis and allergic sensitization in offspring.

Results

Among 1344 study children, 793 (59%) had physician-diagnosed allergic rhinitis. Advanced maternal age at delivery (≥40 years) was significantly associated with increased odds of allergic rhinitis (adjusted odds ratio [AOR] = 4.58, 95% confidence interval [CI]: 1.90–11.03) and allergic sensitization (AOR = 2.86, 95% CI: 1.13–7.22) in offspring. A sex-stratified analysis revealed that the association of advanced maternal age with allergic rhinitis was statistically significant only in female offspring (AOR = 7.02, 95% CI: 1.89–26.14). Stratified analyses by birth order or environmental tobacco smoke exposure during pregnancy did not reveal any significant differences.

Conclusion

Advanced maternal age at delivery was associated with increased risk of allergic rhinitis in Asian children, probably more pronounced among girls.

Mechanism for initiation of food allergy: Dependence on skin barrier mutations and environmental allergen costimulation

BACKGROUND

Mechanisms for the development of food allergy in neonates are unknown but clearly linked in patient populations to a genetic predisposition to skin barrier defects. Whether skin barrier defects contribute functionally to development of food allergy is unknown.

OBJECTIVE

The purpose of the study was to determine whether skin barrier mutations, which are primarily heterozygous in patient populations, contribute to the development of food allergy.

METHODS

Mice heterozygous for the filaggrin (Flg)ft and Tmem79ma mutations were skin sensitized with environmental and food allergens. After sensitization, mice received oral challenge with food allergen, and then inflammation, inflammatory mediators, and anaphylaxis were measured.

RESULTS

We define development of inflammation, inflammatory mediators, and food allergen-induced anaphylaxis in neonatal mice with skin barrier mutations after brief concurrent cutaneous exposure to food and environmental allergens. Moreover, neonates of allergic mothers have increased responses to suboptimal sensitization with food allergens. Importantly, responses to food allergens by these neonatal mice were dependent on genetic defects in skin barrier function and on exposure to environmental allergens. ST2 blockade during skin sensitization inhibited the development of anaphylaxis, antigen-specific IgE, and inflammatory mediators. Neonatal anaphylactic responses and antigen-specific IgE were also inhibited by oral pre-exposure to food allergen, but interestingly, this was blunted by concurrent pre-exposure of the skin to environmental allergen.

CONCLUSION

These studies uncover mechanisms for food allergy sensitization and anaphylaxis in neonatal mice that are consistent with features of human early-life exposures and genetics in patients with clinical food allergy and demonstrate that changes in barrier function drive development of anaphylaxis to food allergen.

Relationship of Cord Blood Immunoglobulin E and Maternal Immunoglobulin E with Birth Order and Maternal History of Allergy in Albanian Mother/Neonate Pairs

BACKGROUND

Previous studies reported that familial factors such as birth order and mothers atopy might influence cord blood levels and development of allergies.

AIM

The aim of the study was to evaluate the relationship of cord blood IgE and maternal IgE with birth order and mothers history of allergy in Albanian mother/neonate pairs.

MATERIAL AND METHODS

Study population represented 291 mother-infant pairs. Mothers were interviewed with a questionnaire for personal history of allergy and pregnancy history whereas serum IgE levels were determined using sandwich IRMA assay.

RESULTS

The mean level of cIgE in neonates with detectable levels was 1.59 (n = 78). No significant difference in means of cIgE was found between first born and later born neonates (p = 0.232) and between neonates of mothers with a negative and positive history of allergy (p = 0.125). Also, no significant difference was found between means of mIgE by birth order, whereas there was a significant difference of mIgE between mothers with and without a history of allergy (p = 0.01). In a group of neonates with detectable cIgE levels, maternal IgE levels were moderately correlated with cIgE levels.

CONCLUSION

Cord blood IgE is not affected by birth order and mothers history of allergy, whereas mothers IgE are affected by the history of allergy but not by birth order.

Effect of season of birth on cord blood IgE and IgE at birth: A systematic review and meta-analysis

BACKGROUND

Elevated cord blood IgE is important on the pathway to allergic disease. The association between season of birth and infant cord blood IgE is not well-established. Study findings differ on which birth season is associated with higher cord blood IgE risk and its magnitude. We conducted a systematic review and meta-analysis of studies on season of birth and cord blood IgE.

METHODS

We searched Medline, Web of Science, Scopus and ProQuest Health databases, and reviewed reference lists of articles that met the inclusion criteria. All included studies measured IgE as a binary variable using various cut-off values. We performed multivariate-random-effects meta-analysis to handle an exposure with multiple categories of Season of Birth.

RESULTS

Our search identified 275 records and 10 had sufficient data to be included in a meta-analysis. Relative to summer, winter birth had the greatest odds of high IgE (≥ 0.1IU/ml), meta-analysis OR = 1.24 (95%CI: 1.01-1.52). A similar OR, was found for IgE ≥ 0.5 IU/ml, OR = 1.30 (95%CI: 0.99-1.71).

CONCLUSIONS

A winter season of birth was associated with statistically significant higher odds of elevated cord blood IgE at cut-off ≥ 0.1IU/ml but borderline at cut-off ≥ 0.5IU/ml. This winter effect is likely to be a marker for a range of other environmental exposures during specific stages of pregnancy, such as aeroallergen exposures, maternal infections and vitamin D levels. Further research is required to support our finding and to identify the exact mechanisms that lead to the winter season of birth effect on circulating IgE levels, as this may have implications for allergic disease prevention.

Reduced Maternal Erythrocyte Long Chain Polyunsaturated Fatty Acids Exist in Early Pregnancy in Preeclampsia

The present prospective study examines proportions of maternal erythrocyte fatty acids across gestation and their association with cord erythrocyte fatty acids in normotensive control (NC) and preeclamptic pregnancies. We hypothesize that maternal fatty acid status in early pregnancy influences fetal fatty acid stores in preeclampsia. 137 NC women and 58 women with preeclampsia were included in this study. Maternal blood was collected at 3 time points during pregnancy (16-20th weeks, 26-30th weeks and at delivery). Cord blood was collected at delivery. Fatty acids were analyzed using gas chromatography. The proportions of maternal erythrocyte α-linolenic acid, docosahexaenoic acid, nervonic acid, and monounsaturated fatty acids (MUFA) (p < 0.05 for all) were lower while total n-6 fatty acids were higher (p < 0.05) at 16-20th weeks of gestation in preeclampsia as compared with NC. Cord 18:3n-3, 22:6n-3, 24:1n-9, MUFA, and total n-3 fatty acids (p < 0.05 for all) were also lower in preeclampsia as compared with NC. A positive association was observed between maternal erythrocyte 22:6n-3 and 24:1n-9 at 16-20th weeks with the same fatty acids in cord erythrocytes (p < 0.05 for both) in preeclampsia. Our study for the first time indicates alteration in maternal erythrocyte fatty acids at 16th weeks of gestation which is further reflected in cord erythrocytes at delivery in preeclampsia.

Maternal preeclampsia and childhood asthma in the offspring

BACKGROUND

Preeclampsia is a possible risk factor for childhood asthma in the offspring. Our aim was to find whether preeclampsia is associated with childhood asthma. We also aimed to study whether a possible association can be explained by factors shared by siblings.

METHODS

All eligible live singletons born in Denmark during 1993-2007 were identified (N = 923,533), and the occurrence of preeclampsia during the index pregnancy was determined. The children were followed from their 3rd birthday to the first hospitalization, outpatient contact or prescription for asthma, emigration, death, their 18th birthday, or the end of 2010, whichever came first. We carried out a nested case-control and a case-sibling study with density sampling to estimate incidence rate ratio (IRR) of asthma as a function of maternal preeclampsia, using conditional logistic regression.

RESULTS

A total of 115,522 asthma cases were identified during 1996-2010. In the case-control analysis, the overall IRR of asthma for those exposed to maternal preeclampsia was 1.19 (95% confidence interval (CI): 1.15, 1.24). The IRRs for asthma according to early and late onset preeclampsia were 1.88 (95% CI: 1.67, 2.11) and 1.14 (95% CI: 1.10, 1.19). In the case-sibling analysis, the corresponding IRRs were 1.06 (95% CI: 0.98, 1.14), 1.15 (95% CI: 1.02, 1.29), and 1.02 (95% CI: 0.93, 1.11), respectively.

CONCLUSIONS

Early onset preeclampsia was associated with an increased risk of asthma in the offspring, but part of this association may be due to confounding by factors shared by siblings.

Birth after preeclamptic pregnancies: association with allergic sensitization and allergic rhinoconjunctivitis in late childhood; a historically matched cohort study

Background

The development of allergic sensitization and allergic disease may be related to factors during intrauterine life, but the role of maternal preeclampsia is not known.

We studied if maternal preeclampsia is associated with long-term allergic sensitization, allergic rhinoconjunctivitis, atopic dermatitis, asthma and with altered lung function in late childhood.

Methods

617 children participated in a 1:2 matched and controlled historical cohort study; 230 born after preeclamptic pregnancies and 387 born after normotensive pregnancies. Specific IgE in serum and lung function were measured at the age of 12.8 years and questionnaires on maternal and adolescent data were completed at the ages of 10.8 years (girls) and 11.8 years (boys), and at 12.8 years (both genders). The association between birth after preeclampsia and the main outcome measures allergic sensitization, allergic rhinoconjunctivitis, atopic dermatitis, asthma and lung function in late childhood were analysed with multiple regression analyses, including possible confounders.

Results

Severe maternal preeclampsia was associated with high level allergic sensitization (sum of specific IgE in serum ≥ 3.9 kU/l; the 25 percentile for all children being sensitized); odds ratio (OR): 3.79; 95% confidence interval (CI): (1.54, 9.32); p = 0.015 and with allergic rhinoconjunctivitis in offspring; OR: 2.22, 95% CI: (1.19, 4.14), p = 0.047. Preeclampsia was not associated with atopic dermatitis, asthma or altered lung function in late childhood.

Conclusion

Maternal preeclampsia was associated with allergic sensitization and allergic rhinoconjunctivitis in offspring in late childhood, but not with other atopic diseases.

T cell subsets in cord blood are influenced by maternal allergy and associated with atopic dermatitis

BACKGROUND

This study aimed to investigate the influence of maternal allergy on cord blood regulatory and effector T cells and to evaluate their role as a predictor of atopic dermatitis (AD) during the first 2 yr of life.

METHODS

Seventy mother-infant pairs were recruited in this prospective birth cohort study (21 allergic and 49 non-allergic mothers). Cord blood samples were collected and assayed for the percentage of regulatory T cells (Treg), interferon-γ (IFN-γ), and interleukin-4 (IL-4) producing T cells (Th1 and Th2, respectively) using flow cytometry. Experiments were undertaken to assess the function of cord blood CD4(+) CD25(+) CD127(-) Treg cells by cell proliferation and cytokine responses. Their offspring at the age of 2 yr old were evaluated by dermatologists to determine whether they had AD.

RESULTS

During the first 2 yr of life, 15.7% of the children developed a physician-diagnosed AD. A significantly increased percentage of Th2 cell was observed in cord blood of newborns with maternal allergy. Treg/Th2 ratio significantly decreased among the offspring of allergic mothers. Treg cell-associated suppression of Th2 response was attenuated in Der p1-stimulated CD4(+) CD25(-) T cells from the offspring of allergic mothers. Children with reduced Th1/Th2 (p = 0.001, OR = 0.37) and Treg/Th2 (p = 0.001, OR = 0.47) ratio in cord blood had a higher risk of developing AD.

CONCLUSION

Maternal allergic status is associated with increased percentage of IL-4(+) CD4(+) T cells and a reduced Treg/Th2 ratio in cord blood at their children's birth, which may predispose to an increased risk for developing AD.

Pollen exposure in pregnancy and infancy and risk of asthma hospitalisation - a register based cohort study

Background

A seasonal effect of month of birth and risk of allergic disease has been suggested by numerous studies. Few studies have directly measured pollen exposures at different points during pregnancy and in early life, and assessed their effects on risk of respiratory disease outcomes.

Methods

Pollen exposure was calculated for the first and last 12 weeks of pregnancy and the first 12 weeks of infancy for all children conceived by women residing in Stockholm, Sweden, between 1988 and 1995. Hospital admission data for respiratory conditions in the first year of life was also collected.

Results

Out of 110,381 children, 940 had been hospitalised for asthma by 12-months of age. Pollen levels showed both marked seasonal variations and between year differences. Exposure to high levels of pollen in the last 12 weeks of pregnancy was associated with an increased risk of asthma hospitalisation (aOR = 1.35, 95% CI = 1.07-1.71 for highest quartile versus remaining infants). Exposure to high levels of pollen in the first three months of life was associated with a reduced risk (aOR = 0.76, 95% CI = 0.59-0.98) but only in children of heavy smoking mothers.

Conclusions

High levels of pollen exposure during late pregnancy were somewhat unexpectedly associated with an elevated risk of hospitalisation for asthma within the first year of life.

Exposure to air pollution in critical prenatal time windows and IgE levels in newborns

The objective of this study was to analyze the mechanisms by which exposure to ambient air pollutants influences respiratory health may include altered prenatal immune development. To analyze associations between elevated cord serum Immunoglobulin E (IgE) levels and maternal air pollution exposure during each month of gestation. Total cord serum IgE was determined by the CAP system and mothers' total IgE levels by nephelometry for 459 births in the Czech Republic from May 1994 to mid-January 1997. Concentrations of polycyclic aromatic hydrocarbons (PAHs) and particulate matter <2.5 microns in diameter (PM(2.5) ) were measured in ambient air, and arithmetic means were calculated for each gestational month. Log binomial regression models were used to estimate prevalence ratios (PR) for elevated cord serum IgE (≥0.9 IU/ml) adjusting for district of residence, year of birth, and in further models, for maternal IgE (a surrogate for atopy) and gestational season. Heterogeneity by maternal atopy status was evaluated for associations of air pollution and of cigarette smoke. In adjusted models, PAH and PM(2.5) exposures in the second month of gestation were each associated with a lower prevalence of elevated cord serum IgE. For an average increase of 100 ng/m(3) of PAHs, the PR was 0.69 (95% confidence interval (CI): 0.50, 0.95); for 25 μg/m(3) increase in PM(2.5) , the PR was 0.77 (95% CI: 0.55, 1.07). Conversely, exposures later in gestation were associated with a higher prevalence of elevated cord IgE: in the fifth month, the PR for PAH exposure was 1.64 (95% CI: 1.29, 2.08), while for PM(2.5) in the sixth month, it was 1.66 (95% CI: 1.30, 2.13). In analyses stratified by maternal atopy, air pollutants were associated with altered cord serum IgE only among neonates with non-atopic mothers. Similarly, an association of cigarette smoke with elevated cord serum IgE was found only in non-atopic mothers. PAHs and PM(2.5) , constituents of both ambient air pollution and cigarette smoke, appear to influence fetal immune development, particularly among infants whose mothers are not atopic.

The effect of CD14 C159T polymorphism on in vitro IgE synthesis and cytokine production by PBMC from children with asthma

BACKGROUND

Even though the genotype at the promoter region of the CD14 molecule is known to affect the atopic phenotypes, the cellular and molecular basis of this association is largely unknown.

OBJECTIVE

To investigate the effect of lipopolysaccharide (LPS) on IgE production and cytokine profile by peripheral blood mononuclear cells (PBMC) obtained from asthmatic children with the TT and the CC genotypes at position -159 of the CD14 gene.

METHODS

Peripheral blood mononuclear cells from asthmatic children with alternative genotypes at CD14 C159T locus were stimulated with 2 and 200 ng/ml LPS in vitro. The IgE, IgG and, IgM response was determined by ELISA and Ig έ-germline, IgG, and IgM transcription by real-time PCR. A cluster of cytokines was measured by cytometric bead array.

RESULTS

Asthmatic children with the TT genotype but not those with the CC genotype responded with increased IgE synthesis and germline transcription to LPS stimulation. There were no genotype-related differences in IgG and IgM. TT but not the CC genotype was associated with significantly increased interleukin (IL)-4/IL-12 and IL-4/interferon-gamma (IFN-γ) ratios in the culture supernatant. There were no genotype-related differences in IL-1β, IL-7, IL-10, IL-13, IL-17A, granulocyte colony stimulating factor, granulocyte macrophage colony stimulating factor, monocyte chemotactic protein, and tumor necrosis factor alpha.

CONCLUSION

Peripheral blood mononuclear cells from asthmatic children with the TT genotype at position -159 of the CD14 gene make more IgE than those with the CC genotype following LPS stimulation because of increased germline transcription and have an augmented Th2 cytokine profile.

Prediction of atopy in the first year of life using cord blood IgE levels and family history

We assessed correlations of total and specific cord-blood IgE (cIgE) levels with allergic symptoms in the first year of life. cIgE levels were determined by an immunoassay test in full-term neonates. This is a prospective study in which a questionnaire was used after birth, and at 6 and 12 months of age. We used multiple logistic regression models to assess the association between the family history of atopy and the incidence of allergy. The infants were divided in to groups based on the cIgE level (Group 1 < 0.1 IU/ml, n = 65; Group 2 0.1-0.5 IU/ml, n = 63; Group 3 > 0.5 IU/ml, n = 45). We found the symptoms of atopy in 26 children in Group 1 (40%), 30 (47.6%) in Group 2, and 17 (37.7%) in Group 3; the percentage of atopic diseases was in significantly different among the three groups. No association between a high total cIgE and specific cIgE with atopy family history and the outcome of atopic diseases was discovered. We conclude that neither total nor specific cIgE level with atopy family history can be used as an indicator to single out high risk infants.

Pre-eclampsia, placental abruption and increased risk of atopic sensitization in male adolescent offspring

PROBLEM

The aim of this study was to investigate maternal pre-eclampsia (PE), placental abruption (PA) and atopy among offspring.

METHOD OF STUDY

Obstetric data was recorded from 378 women who were included into the Caesarean delivery birth cohort during 1990-1992. When their children were 15-17 years old skin prick tests (SPTs) and inhalant allergen-specific (IAS) immunoglobulin E (IgE) were determined among offspring.

RESULTS

Adolescents whose mothers had either PE or PA at the time of delivery had more atopy and especially more severe atopy as measured by the incidence of SPTs positive for > or = 5 allergens (RR: 4.28, 95% CI: 1.54-11.92; P < 0.005) and elevated IAS IgE levels (> or = 1.0 kU/L) (RR: 4.27, 95% CI: 1.08-16.99; P < 0.039). This increased risk was particularly observed in male adolescents.

CONCLUSION

Maternal PE and PA were associated with an increased risk of severe atopy, especially in male adolescent offspring.

Maternal diet during pregnancy and allergic sensitization in the offspring by 5 yrs of age: a prospective cohort study

To examine the effect of maternal diet during pregnancy on allergic sensitization in the offspring by 5 yrs of age. The Finnish type 1 Diabetes Prediction and Prevention Nutrition Study. A population-based cohort study with 5-yr follow-up. A total of 931 children with human leukocyte antigen-conferred susceptibility to type 1 diabetes for whom maternal pregnancy food frequency questionnaire data and allergen-specific immunoglobulin E measurement at 5 yrs were available. Increasing maternal consumption of citrus fruits [odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.05-1.25] and total fruit (OR = 1.36, 95% CI = 1.09-1.70) were positively associated with sensitization to inhalant allergens, after adjustment for potential confounders. Maternal intake of vitamin D (OR = 0.56, 95% CI = 0.35-0.91) was inversely associated with sensitization to food allergens. Maternal consumption of citrus fruits during pregnancy may increase the risk to allergic sensitization in the offspring, whereas vitamin D intake may have a beneficial effect. Further studies are required to define more closely the putative effect of maternal intake of polyunsaturated fatty acids on development of allergic diseases in the offspring.

Risk factors and prevalence of asthma in schoolchildren in Castellon (Spain): a cross-sectional study

BACKGROUND

Research on potential risk factors of asthma can enhance our understanding of geographic differences and inform decisions on preventive strategies.

METHODS

In 2002, a cross-sectional population-based study was carried out in the area of Castellon (Spain), following the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III methodology. Asthma symptoms and related risk factor questionnaires were completed by parents of 6-7 year-old schoolchildren. Logistic regression was used in the analysis.

RESULTS

Participation rate was 88 % (4492 of 4872 schoolchildren). Prevalence of wheeze in the past year, asthma ever, and physician-diagnosed asthma were 8 %, 7 % and 6 %, respectively. Risk factors independently associated with all three asthma case definitions were history of bronchitis or pneumonia, allergic rhinitis, family members with atopic disease, and residing in an industrialised area. Risk factors for asthma ever and physician-diagnosed asthma were male sex, atopic eczema and presence of a dog at home; exclusive breast-feeding and the presence of another animal (not a dog or cat) were protective factors. Maternal age was inversely related to physician-diagnosed asthma. Residence in an area of heavy truck traffic and the father smoking at home were associated with asthma ever. Risk factors for wheeze in the past year were low social class, history of sinusitis and the father smoking at home.

CONCLUSIONS

Environmental factors are related to the presence of asthma. Preventive measures should be directed to improving air pollution, promoting breast-feeding and reducing smoking in the home.

Maternal country of birth and previous pregnancies are associated with breast milk characteristics

Populations in high infectious exposure countries are at low risk of some immune-mediated diseases such as Crohn's disease and allergy. This low risk is maintained upon immigration to an industrialized country, but the offspring of such immigrants have a higher immune-mediated disease risk than the indigenous population. We hypothesize that early life exposures in a developing country shape the maternal immune system, which could have implications for the offspring born in a developed country with a low infectious load. The aim of this study was to investigate if exposures in childhood (indicated by country of origin) and subsequent exposures influence immunologic characteristics relevant to stimulation of offspring. Breast milk components among 64 mothers resident in Sweden, 32 of whom immigrated from a developing country, were examined using the ELISA and Cytometric Bead Array methods. Immigrants from a developing country had statistically significantly higher levels of breast milk interleukin-6 (IL-6), IL-8 and transforming growth factor-beta1. A larger number of previous pregnancies were associated with down-regulation of several substances, statistically significant for soluble CD14 and IL-8. The results suggest that maternal country of birth may influence adult immune characteristics, potentially relevant to disease risk in offspring. Such a mechanism may explain the higher immune-mediated disease risk among children of migrants from a developing to developed country. Older siblings may influence disease risk through the action of previous pregnancies on maternal immune characteristics.

Allergies and childhood leukemia

A majority of studies to date have reported an inversed association between allergies and childhood leukemia. However, this association is likely an indirect one and may represent some shared underlying immune mechanisms that have been explained in the context of the "hygiene hypothesis", which has been thought to play an important role in the development of both allergies and childhood leukemia. This review focuses on what we know so far about the role of various immune cells (Th1, Th2, T regulatory and Th17 cells) in the development of allergies and how they may potentially be related to the etiology of childhood leukemia. In addition, the utilities of genetic and molecular studies to disentangle the association between allergies and childhood leukemia and to elucidate the biological mechanisms are also discussed.

Maternal employment in child-care institutions and the risk of infant wheeze and atopic dermatitis in the offspring

It has been proposed that exposure to infections and microbes protects against atopic diseases, but epidemiological data has so far been conflicting. We hypothesized that maternal exposure to infections and microbes before or during pregnancy would be of particular importance. To test this hypothesis, we studied the incidence of wheezing and atopic dermatitis (AD) in infants of mothers employed in child-care institutions - and thus presumably being highly exposed to infections and microbes - compared with infants of mothers not so employed. A total of 31471 mother-child pairs enrolled in the Danish National Birth Cohort were followed prospectively. Information on wheezing episodes, AD, maternal employment, and other variables were collected by interview at 12 and 30 wk of gestation, and 6 and 18 months of age, and by linkage to the Danish Medical Birth Register and the Child-care Database. The relative risk was estimated in Cox proportional hazard models. Analyses were stratified by sibling status (first born or not), as older siblings are likely to be a significant source of infectious agents. The adjusted relative risks of wheeze, recurrent wheeze and AD was 1.14 (95% CI: 0.96-1.37), 1.37 (95% CI: 1.05-1.77), and 1.03 (95% CI: 0.81-1.31), respectively, for first-born infants of mothers employed in child-care institutions compared with infants of mothers not so employed. There was no effect of maternal employment in child-care institutions among infants with older siblings. In conclusion, the results did not support the hypothesis that maternal microbial exposure before or during pregnancy as reflected by maternal employment in child-care institutions protects the offspring against infant wheeze and AD.

The prevalence of preterm birth and season of conception

Preterm birth is a major obstetric problem. An exploration of the season of conception in relation to preterm birth may provide direction in the search for risk factors. We conducted a retrospective cohort study of 82 213 singleton livebirths (20-45 weeks' gestation) to 61,630 women at Magee-Womens Hospital, Pittsburgh, PA, from 1995 to 2005. Conception was estimated based on gestational age determined by best obstetric estimate. Fourier series analysis was used to model seasonal trends. Spontaneous preterm birth at <37 weeks was associated with conception season (P < 0.05). The peak prevalence occurred among conceptions in winter and spring (peaking February 23 at 6.9%), with an average trough among late summer/early autumn conceptions (August 25 at 6.2%). The pattern for spontaneous preterm birth <32 weeks was similar (P < 0.05), with the peak on March 13 (1.7%), and nadir on September 12 (1.4%). Results were similar when indicated preterm births were included. These seasonal changes may increase our insight into the role of exposures with seasonal periodicity in the pathophysiology of preterm birth.

Asthma prevalence, family size, and birth order

BACKGROUND

Asthma prevalence may be reduced in large families. The hygiene hypothesis suggests that older siblings protect their younger siblings from asthma through a modulating effect on the still-maturing immune system. If the hygiene hypothesis is correct, asthma prevalence should be inversely related to birth order. The objective of this study was to examine the relationship between asthma prevalence, and family size and birth order.

METHODS

The medical records of 531,116 Israeli military conscripts were reviewed. The association between number of children in the family and the prevalence of asthma, and between birth order and the prevalence of asthma was assessed. Odds ratios for asthma by birth order and family size, adjusted for each other, were calculated.

RESULTS

Asthma was diagnosed in 26,833 male subjects (8.6%) and 15,079 female subjects (6.9%). Asthma prevalence was inversely related to the number of children in the family (p < 0.001). Among subjects who were the only child in the family, the prevalence of asthma was 7.3%. The prevalence increased to 8.95% among subjects from families with three siblings, and then progressively decreased as the number of siblings increased, and reached a trough of 0.58% in conscripts from families of 15 to 20 siblings. Asthma prevalence was similar for all birth orders.

CONCLUSIONS

In families with four or more children, asthma prevalence is inversely related to the number of children in the family. Asthma prevalence is similar for all birth orders. The similar asthma prevalence for all birth orders challenges the hygiene hypothesis as the mechanism for the decreased asthma prevalence in large families.

Impact of diet on the immunological microenvironment of the pregnant uterus and its relationship to allergic disease in the offspring--a review of the recent literature

Medical progress has reduced the mortality from infectious diseases in most countries, but allergic diseases have become more prevalent worldwide over the same period, especially in industrialized countries. This has prompted speculation that modern lifestyles have altered the relationship between heredity and environment so as to promote development of an atopic phenotype when exposure to infection decreases. A healthy uterine microenvironment is known to favor Th2 lymphocyte development. However, some evidence suggests that persistence of the Th2 pattern of immunity directs the developing organism's immune response towards a long-lasting atopic phenotype. Even though the outcome also depends on other factors (such as infection, functional state of the intestinal microflora, and exposure to environmental allergens at times critical to development), it seems that the immune system during the perinatal period is responsive to interventions that are no longer effective in adulthood. We have reviewed the literature accessible through Medline to identify recent advances in the prevention of allergic disease through interventions in the fetal-maternal relationship. Diet seems to have a significant impact on the immunological profile of the pregnant uterus, as well as on the postnatal development of allergic disease in the offspring, as suggested by the effects of probiotic bacteria and by manipulations of the dietary content of polyunsaturated fatty acids and antioxidants. This highlights the need for further studies, in order to define the best intervention methods, the most appropriate time interval and the individuals who will most likely benefit from them.

Early life circumstances and atopic disorders in childhood

The prevalence of childhood atopic disorders has risen dramatically in the last decades of the past century. Risk factors for the development of these disorders have been studied extensively. This review focuses on the role of early life risk factors such as pre-natal development, perinatal circumstances, birth order and childhood vaccinations.

Does paternal antigen-induced secretion of interleukin-10 by T regulatory cells mediate the birth order effect?

Childhood allergy constitutes a significant burden of disease in the Western world. The prevalence of this condition is highest in first born children, an as yet unresolved phenomenon called the "birth order effect". The hygiene hypothesis attempted to explain this differential risk by stating that less exposure to microbial agents at an early age of first born children would result in reduced activation of the immune system and subsequent polarization towards a Th2 phenotype. However, no conclusive evidence for or against the hygiene hypothesis has been found so far. Another, not necessarily conflicting, theory states that the birth order effect is already established during prenatal life and that the fetal-maternal interaction changes during successive pregnancies. Combining this theory with research on preeclampsia, another disease originating in pregnancy and also related to birth order, could suggest clues about the mechanisms underlying the birth order effect. Recent research on preeclampsia showed that preeclamptic women have higher levels of pro-inflammatory IL-6 and lower paternal antigen-induced secretion of IL-10 compared to normal pregnant women, indicating a lower number or lower functional activity of T regulatory (Treg) cells. These Treg cells play an important role in maintaining tolerance to fetal antigens in pregnancy and they are found in high numbers at the maternal-fetal interface. We hypothesize that nulliparous women have a lower activity of Treg cells specific to paternal antigens compared to parous women, either in peripheral blood or in the decidua (maternal part of the fetal-maternal interface). If this hypothesis is true, this would mean that the allergen suppressor mechanism of Treg cells is sub-optimal in first born children. This would explain at least a part of the mechanism of the birth order effect and would give us directions for developing preventive measures to prevent possibly 30% of future childhood allergies.

Association between sibship size and allergic diseases in the Glasgow Alumni Study

BACKGROUND

Recent epidemiological studies consistently report an inverse association between sibship size and allergic disease, but evidence from individuals born before the 1980s is inconsistent. As information on relative permanence of this finding may offer clues to its biological explanation, the association between sibship size and allergic disease in individuals born between 1918 and 1952 was investigated.

METHODS

Cross sectional surveys conducted by the Student Health Service at the University of Glasgow (1948-68) provided data on 14 140 men and women aged 16-30 years at the time of examination. The main outcome measures studied were self-reported asthma, eczema-urticaria, and hay fever.

RESULTS

A total of 1677 individuals (11.9%) provided a positive history of at least one of the three allergic diseases: 457 (3.2%) asthma, 594 (4.2%) eczema-urticaria, and 885 (6.3%) hay fever. Compared with those without siblings (reference odds ratio = 1), the odds ratios (95% confidence intervals) for having any allergic disease among those with one, two or three siblings were 0.86 (0.75 to 0.99), 0.80 (0.69 to 0.93), and 0.70 (0.60 to 0.83), respectively (p(trend)<0.001). Increasing birth order and low socioeconomic position in childhood were associated with a lower risk of allergy. Adjustment for birth order, year of birth, age, sex, socioeconomic position in childhood, and family history of allergy did not materially alter the results.

CONCLUSIONS

There is a robust inverse association between sibship size and allergic disease even among people born in the first half of the 20th century. These results favour relatively time-independent explanations for this phenomenon (such as the hygiene hypothesis or parity related changes in the intrauterine environment) over new environmental exposures.

The effect of polymorphisms at the CD14 promoter and the TLR4 gene on asthma phenotypes in Turkish children with asthma

BACKGROUND

Endotoxin, with its potential to enhance type 1 immunity, is a significant player in the hygiene hypothesis. The combined effects of the genetic variants of various molecules in the endotoxin response pathway on asthma related phenotypes are largely unknown.

OBJECTIVE

To investigate the effects of the genetic variants of CD14 and TLR4 genes on asthma phenotypes in a large number of asthmatic children.

METHODS

613 asthmatic children were genotyped at the CD14-C159T, TLR4-A896G and TLR4-C1196T loci. IgE, eosinophil numbers and FEV1 were compared in 327 children who were not on any controller medications and were symptom free. Multivariate logistic regression was used to determine the factors associated with total IgE.

RESULTS

Among children with atopic asthma, total IgE levels were significantly different among the three genotypes in the co-dominant model [CC: 435 kU/l (interquartile range: 146-820); CT: 361 (140-710); TT 204 (98-435), P = 0.035]. TT genotype was significantly and independently associated with lower IgE levels (OR: 0.5 95%; CI = 0.28-0.90, P = 0.021). Both TLR4-A896G and TLR4-C1196T polymorphisms were more frequent in the mild asthma group with atopy (P = 0.032, 0.018, respectively). The combined effects of the genetic variants in CD14 and TLR4 genes did not improve the observed associations.

CONCLUSION

Our study demonstrates that the CD14-C159T promoter variant influences total IgE levels and also indicates that the T allele has a more profound effect on total IgE in children with atopic asthma. Polymorphisms in the TLR4 gene may be associated with milder forms of disease in atopic asthmatics in the population studied.

The asthma epidemic and our artificial habitats

Background

The recent increase in childhood asthma has been a puzzling one. Recent views focus on the role of infection in the education of the immune system of young children. However, this so called hygiene hypothesis fails to answer some important questions about the current trends in asthma or to account for environmental influences that bear little relation to infection.

Discussion

The multi-factorial nature of asthma, reflecting the different ways we tend to interact with our environment, mandates that we look at the asthma epidemic from a broader perspective. Seemingly modern affluent lifestyles are placing us increasingly in static, artificial, microenvironments very different from the conditions prevailed for most part of our evolution and shaped our organisms. Changes that occurred during the second half of the 20th century in industrialized nations with the spread of central heating/conditioning, building insulation, hygiene, TV/PC/games, manufactured food, indoor entertainment, cars, medical care, and sedentary lifestyles all seem to be depriving our children from the essential inputs needed to develop normal airway function (resistance). Asthma according to this view is a manifestation of our respiratory maladaptation to modern lifestyles, or in other words to our increasingly artificial habitats. The basis of the artificial habitat notion may lie in reduced exposure of innate immunity to a variety of environmental stimuli, infectious and non-infectious, leading to reduced formulation of regulatory cells/cytokines as well as inscribed regulatory pathways. This could contribute to a faulty checking mechanism of non-functional Th2 (and likely Th1) responses, resulting in asthma and other immuno-dysregulation disorders.

Summary

In this piece I discuss the artificial habitat concept, its correspondence with epidemiological data of asthma and allergy, and provide possible immunological underpinning for it from an evolutionary perspective of health and disease.