Parity among atopic and non-atopic mothers

A temporary Th2 skewed immunity is essential for a successful outcome of pregnancy. It is also a hallmark of atopic disease. We recorded the number of siblings to 3667 children in relation to maternal atopy. In all, 65% of the allergic and 56% of the non-allergic mothers had more than one child (p < 0.001). These data support a hypothesis that the atopic genotype may be associated with an increased likelihood for a successful outcome of pregnancy and thus from an evolutionary point of view compensate for the less efficient host defence against microbial infections associated with this type of immunity.     

Hygiene levels in a contemporary population cohort are associated with wheezing and atopic eczema in preschool infants

Background: The hygiene hypothesis states that insufficient exposure to certain infectious agents during childhood increases the risk of developing asthma and atopic diseases. Improvements in hygiene levels may be partly responsible for this decline in exposure. Aims: To assess whether hygiene levels in infancy are associated with wheeze and/or atopic eczema, independent of a number of possible confounding factors. Methods: Data were gathered from the Avon Longitudinal Study of Parents and Children (ALSPAC). Parental self completion questionnaires provided symptom data on infant wheeze and atopic eczema at 0–6 months and 30–42 months, respectively. A simple hygiene score was derived using questionnaire responses at 15 months, which ranged from least hygienic to most hygienic. Multivariable logistic regression models analysed the effect of hygiene scores on health outcomes, while adjusting for a number of important confounding variables. Results: Increasing hygiene scores were independently associated with wheezing (OR = 1.04; 95% CI: 1.00 to 1.08) and atopic eczema (OR = 1.04; 95% CI: 1.01 to 1.07) between 30 and 42 months, but not in the first six months. The odds ratio was higher for atopic eczema if the rash was reported to have become sore and oozy (OR = 1.09; 95% CI: 1.02 to 1.16). Conclusions: High levels of hygiene at 15 months of age were independently associated with wheeze and atopic eczema reported between 30 and 42 months, and there was an increased risk for children with more severe eczema during this period. The importance of hygiene in public health should not be dismissed; however, the creation of a sterile environment through excessive cleanliness may potentially be harmful to the immune system.     

Hygiene levels in a contemporary population cohort are associated with wheezing and atopic eczema in preschool infants.

BACKGROUND: The hygiene hypothesis states that insufficient exposure to certain infectious agents during childhood increases the risk of developing asthma and atopic diseases. Improvements in hygiene levels may be partly responsible for this decline in exposure. AIMS: To assess whether hygiene levels in infancy are associated with wheeze and/or atopic eczema, independent of a number of possible confounding factors. METHODS: Data were gathered from the Avon Longitudinal Study of Parents and Children (ALSPAC). Parental self completion questionnaires provided symptom data on infant wheeze and atopic eczema at 0-6 months and 30-42 months, respectively. A simple hygiene score was derived using questionnaire responses at 15 months, which ranged from least hygienic to most hygienic. Multivariable logistic regression models analysed the effect of hygiene scores on health outcomes, while adjusting for a number of important confounding variables. RESULTS: Increasing hygiene scores were independently associated with wheezing (OR = 1.04; 95% CI: 1.00 to 1.08) and atopic eczema (OR = 1.04; 95% CI: 1.01 to 1.07) between 30 and 42 months, but not in the first six months. The odds ratio was higher for atopic eczema if the rash was reported to have become sore and oozy (OR = 1.09; 95% CI: 1.02 to 1.16). CONCLUSIONS: High levels of hygiene at 15 months of age were independently associated with wheeze and atopic eczema reported between 30 and 42 months, and there was an increased risk for children with more severe eczema during this period. The importance of hygiene in public health should not be dismissed; however, the creation of a sterile environment through excessive cleanliness may potentially be harmful to the immune system.     

Reduced IL-2-induced IL-12 responsiveness in atopic children

Atopy may be associated with a reduced T-cell function particularly regarding maturation of T helper 1 (Th1) responses. We hypothesized that atopic children may have a reduced capacity to up-regulate the β₂ subunit of the interleukin-12 (IL-12) receptor (IL-12Rβ₂, the signal-transducing component). The study included 38 children followed from birth to the age of 7 years. Twenty one had a cumulative history of atopic disease, whereas 17 had none. Sixteen out of 21 children also had atopic symptoms within the past year (current), out of whom 10 children had atopic airway symptoms. The expression of IL-12Rβ₂ mRNA was analyzed by quantitative real-time PCR and the secretion of interferon-γ (IFN-γ), IL-5 and IL-10 was assessed by enzyme-linked immunosorbent assay (ELISA). Children with current atopic airway symptoms and high levels of total IgE up-regulated IL-12Rβ₂ mRNA expression less than non-atopic children with low IgE levels after IL-2 stimulation. This was accompanied by a low IL-2- and IL-12-induced IFN-γ production, possibly reflecting the reduced capacity of atopic children to up-regulate the IL-12 receptor. As IL-2 is needed to initiate and sustain immune responses and IL-12 promotes Th1 responses, this may contribute to the Th2-skewed pattern in atopic children.     

Das Th1/Th2-Paradigma bei allergischen Asthma bronchiale

The incidence of allergic asthma, which is characterized by chronic airway inflammation and airway hyperreactivity, has increased dramatically in the last two decades and is present in as many as 10% of individuals in industrialized nations. Allergic asthma is caused by an inappropriate immune response to common aero-allergens in genetically predisposed individuals. The central role in this immune response is played by CD4⁺ T helper(Th)2 cells. Through the release of cytokines like interleukin (IL)-4, IL-13, and IL-5, Th2 cells orchestrate the recruitment and activation of mast cells, eosinophils and basophils and induce the production of IgE by B cells. While Th2 cells promote airway inflammation in asthma, interferon (IFN)-γ producing Th1 cells are proposed to protect against allergic disease by dampening the activity of Th2 effector cells. Accordingly, new therapeutic strategies aim at inhibition of Th2 cells and promotion of Th1 cells. Recent studies demonstrated that Th1 cells are not always able to inhibit Th2 cell-mediated disease and can even be unexpectedly harmful. These studies indicate that the Th1/Th2 paradigm is more complex than initially appreciated and that suppression of allergic inflammation and Th2 activity may depend – at least in part – on cells other than Th1 lymphocytes.     

围生期感染与儿童哮喘

支气管哮喘是儿童时期最常见的慢性非感染性呼吸系统疾病,最近的流行病学和临床研究表明,哮喘的发病率和细菌感染呈明显的负相关,并提出了卫生假说.但是哮喘通常发病于生命早期,出生前后暴露内毒素或其他细菌产物可以降低儿童哮喘的发病率,其机制可能是围生期感染影响了T细胞的分化过程和Th2细胞因子以及转录因子的变化;内毒素耐受和肺发育的改变也参与了儿童哮喘的预防和发生.     

Immunotherapy as a disease modifier

Immunotherapy was formerly the treatment of allergic disease by repeated exposure to allergen. Other approaches to immune modulation have emerged using new knowledge of T cell function. The so-called hygiene hypothesis argues that alterations in our environment have resulted in a failure of the immune system to develop normally, such that excessive Th2 type responses to antigen exposures occur. These observations have prompted therapies designed to promote a shift from Th-2 to Th-1 responses. These therapies include bacterial vaccines and stimulation of the immune system with Toll like receptor ligands or bacterial nucleotide immunostimulatory sequences (CpG motifs). Traditional desensitization immunotherapy is being re-examined and anti-IgE therapy is also enjoying a measure of success.     

Ontogeny of T-helper 1 and T-helper 2 cytokine production in childhood

Compared to adults, infants and young children demonstrate differences in their immune response, indicating that there is maturation or change over time and it is probable that this may be reflected in cytokine production. Cytokine responses have been demonstrated to be different in atopic and non-atopic individuals. In this study, we examined T-helper 1 (Th1) (interferon-γ[IFN-γ]) and T-helper 2 (Th2) (interleukin [IL]-4, IL-5, and IL-13) cytokine release from atopic and non-atopic children in response to the staphylococcal superantigen, staphylococcal enterotoxin B (SEB). In non-atopic and atopic children, IFN-γ, IL-4, and IL-5 release was significantly related to age. Non-atopic children younger than 2 years of age were found to have significantly reduced Th2 (IL-4, IL-5, and IL-13) responses when compared with older, non-atopic children. Atopic children had a reduced IFN-γ response when compared with non-atopics in early childhood; however, the decreased IFN-γ response seen in early childhood did not persist after 10 years. These age-related changes in cytokine production provide further support for the concept that cytokine deviations may determine the natural history of atopic disease during early childhood. In addition, the present study indicates the necessity of age-matched controls when examining children for both Th1 (IFN-γ) and Th2 (IL-4) cytokine release.     

Association between neopterin in cord blood, urinary neopterin in early childhood and the development of atopic dermatitis, asthma and hay fever.

It is generally accepted that the increased prevalence of atopic disease is due to a disturbed balance of T-helper (Th)1/Th2-type immunity. Upon stimulation by the Th1-type cytokine interferon (IFN)-gamma, human monocytes/macrophages release large amounts of neopterin. Thus, the determination of neopterin concentrations is an indirect measure of the levels of IFN-gamma and allows us to monitor Th1-type immune response. We evaluated whether neopterin concentrations in the neonatal cord blood could be a valuable marker predicting atopic disease in early childhood and whether there is a difference in actually determined urinary neopterin concentrations in children with and without atopic disease. Five hundred and five children born during 1997-1999 were enrolled, with cord blood neopterin data available at birth. The International study of asthma and allergies in childhood (ISAAC) questionnaire was used to assess the prevalence of wheezy bronchitis (asthma), atopic dermatitis and allergic rhinitis. Morning urinary samples were collected and urinary neopterin concentration was measured by high-pressure liquid chromatography. By the average age of 6 yr, the prevalence of atopic disease in the last 12 months was 31%. There was no significant correlation between cord blood and urinary neopterin concentrations at age 6 yr, and between cord blood neopterin and later atopic disease. Urinary neopterin concentrations were significant lower in children with a family history of atopic disease (p = 0.02). In this study, cord blood neopterin concentration was not a predictor for atopic disease in early childhood. Family history of atopic disease was associated with lower urinary neopterin levels at age 6 yr, which might mirror a Th1/Th2 imbalance.     

益生菌在过敏性疾病中的应用及作用机制

益生菌通过促进树突状细胞释放细胞因子,改变Th1/Th2平衡,使免疫反应向Th1细胞方向进行,抑制Th2细胞反应,从而增强宿主的免疫功能.研究表明益生菌在特异性皮炎、哮喘及过敏性鼻炎等IgE相关过敏性疾病的预防和治疗中发挥一定的作用,但由于过敏性疾病的病因复杂、诱因众多,目前益生菌对其作用尚无一致的结论,需进一步进行循证医学研究.     

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.     

Expression of the T-cell markers CD2 and CD28 in healthy and atopic children during the first 18 months of life

Atopy may be associated with a reduced T-cell function early in life, particularly regarding maturation of Th1 responses. The T-cell surface molecules CD2 and CD28 are involved in important T-cell activation pathways. Stimulation via the CD2 receptor increases the responsiveness to interleukin (IL)-12, which is a potent inducer of Th1 responses, whereas CD28 stimulation is critical for Th2 differentiation. Our aim was to prospectively study the expression of the cell-surface markers CD2 and CD28 on T-cells in relation to development of atopic disease. Children (n = 172) were followed from birth to 18 months and the cumulative history of atopic disease was recorded. Blood samples were obtained at birth and at 18 months, and in a subgroup of 78 infants also at 3, 6 and 12 months. Flow cytometry was used to analyze the T-cell markers CD2 and CD28, the latter also within the subsets of T-helper (CD4+) and T-cytotoxic (CD8+) cells. At 18 months, 31 children had and 118 did not have atopic symptoms. At this age, skin prick test (SPT) positive children with atopic symptoms with or without an atopic family history (AFH) showed a lower expression of CD2 mode fluorescence intensity (FI) as well as a lower proportion of CD2+ cells, as compared with non-sensitized children with neither atopic symptoms nor AFH. This was accompanied by a higher expression of CD28 FI on CD2+CD8+CD28+ cells. No significant differences were seen at time points before 18 months, although the proportion of CD2+ tended to be low also earlier in life. In conclusion, the observed reduced expression of CD2 in atopic infants may support previous findings that atopy is associated with a reduced CD2 function. The high CD28 FI in SPT positive children with atopic symptoms may possibly be a consequence of a TH2-skewed immune system.     

Effects of probiotics on the prevention of atopic dermatitis

Atopic dermatitis (AD) is an immune disorder that is becoming increasingly prevalent throughout the world. The exact etiology of AD remains unknown, and a cure for AD is not currently available. The hypothesis that appropriate early microbial stimulation contributes to the establishment of a balanced immune system in terms of T helper type Th1, Th2, and regulatory T cell (Treg) responses has led to the use of probiotics for the prevention and treatment of AD in light of various human clinical studies and animal experiments. Meta-analysis data suggests that probiotics can alleviate the symptoms of AD in infants. The effects of balancing Th1/Th2 immunity and enhancing Treg activity via the interaction of probiotics with dendritic cells have been described in vitro and in animal models, although such an effect has not been demonstrated in human studies. In this review, we present some highlights of the immunomodulatory effects of probiotics in humans and animal studies with regard to their effects on the prevention of AD.     

Understanding asthma pathogenesis: linking innate and adaptive immunity

PURPOSE OF REVIEW: Treatment and even prevention of allergic asthma will require a detailed understanding of disease pathogenesis and in particular identification of factors that govern T-helper type 2 (Th2) immunity. This review defines the priming and differentiation steps necessary to develop antiallergen Th2 immunity and highlights recently identified stimuli that satisfy these requirements. RECENT FINDINGS: Striking discoveries in innate immunity have advanced our understanding of how adaptive immune responses are initiated, yet only recently have these principles been applied to allergic disease. Signaling through certain innate immune receptors, the toll-like receptors (TLR) have been shown to modulate Th2-mediated disease in animal models. The dendritic cell has emerged as the central player in the intricate interplay between the adaptive and innate systems of immunity. Recent studies have also uncovered alternative pathways of initiating allergen sensitization that depend entirely on adaptive, rather than innate immune, triggers. SUMMARY: The adaptive immune system cannot initiate a response without the "permission" of the innate immune system, and this holds true for Th2 responses to aeroallergens, although induction of Th2 immunity in response to TLR signaling varies with the type and dose of TLR ligand. However, under conditions of ongoing Th2 inflammation, the adaptive immune system can act as its own adjuvant and provide the necessary activating signals to initiate an immune response to foreign protein antigens. This may be the mechanism underlying the clinically observed phenomenon of polysensitization in atopic patients and provides another therapeutic target in asthma.     

Soluble CD30 and CD23 in cord blood are not related to atopy in early childhood

Atopic disease, including atopic dermatitis (AD), is associated with a T-helper 2 (Th2)-dependent immune response. The cytokine receptor CD30 appears to be preferentially expressed on, and its soluble form (sCD30) released by, Th2 cells. Therefore, sCD30 may be a potential marker for atopic disorders. The aim of this study was to test the hypothesis that the sCD30 level in cord blood could be used to predict the development of atopy or AD in early childhood. In a case-control study, levels of sCD30, as well as soluble low-affinity immunoglobulin E (IgE) receptor (sCD23), interleukin-4 (IL-4) and IgE, were measured in cord blood in 35 children who subsequently developed allergic sensitization and AD before the age of three, and the results were compared to those of 35 matched children without a history of atopy. There was no difference in cord blood levels of sCD30 between controls (32.5 U/ml; 19.7–80.1) and children with subsequent atopy and AD (32.2 U/ml; 22–75.9) (median; quartiles). The concentration of sCD30 showed no relation to the levels of total IgE, sCD23 or IL-4. Levels of sCD23 were similar in children with subsequent atopy (60.2 U/ml; 44.5–76.8) and controls (55.2 U/ml; 38.3–72.5), whereas IL-4 was detectable in 10 of the atopic children and in only two of the controls (p < 0.05). In conclusion, cord blood levels of sCD30 or sCD23 do not seem to be related to the subsequent development of atopy or AD at the age of three.     

Imbalanced cytokine secretion in newborns

In adults, a balance between Th1 and Th2 cytokine networks has been proposed to be associated with a healthy status. Newborn babies are reported to express Th2-type immune reactions. Further, the impaired protection of newborn babies against infections has been attributed to a deficient secretion of interferon gamma (IFN-gamma) and interleukin-10 (IL-10). Using IFN-gamma and IL-10 as surrogate markers of Th1 and Th2 orientation, we compared the patterns of IFN-gamma and IL-10 secretion by peripheral blood mononuclear cells between 52 healthy newborns and 35 adults. The baseline secretion of IFN-gamma in adults was similar to that of newborns. The lipopolysaccharide-stimulated IFN-gamma secretion was higher in newborns than in adults, whereas the concanavalin-A-stimulated IFN-gamma secretion was higher in adults. The unstimulated and stimulated IL-10 secretion was significantly lower in newborns than in adults. Using a threshold level of 1,000 pg/ml, we classified neonates and adults on the basis of their stimulated IL-10 and IFN-gamma secretion. Four different groups were identified: IL-10-oriented secretion, IFN-gamma- oriented secretion, balanced high secretion, and balanced low secretion. Only 25% of the neonates had a high IL-10 and a high IFN-gamma secretion as compared with 77% of the adults. Eight percent of the newborns, but none of the adults, had a low secretion of both cytokines. Thirty-six percent of the neonates, but only 5% of the adults, had a high IL-10 and a low IFN-gamma secretion. Thirty-one percent of the neonates and 18% of the adults had a high IFN-gamma secretion, but a low IL-10 secretion. We conclude that neonates have an immature IL-10 and IFN-gamma response as compared with adults. However, individual neonates may have a mature cytokine secretion, whereas others may have a Th1- or a Th2-directed immune response.     

Atopy as a minimal immunodeficiency?

Despite impressive recent advances in the understanding of the chemical and cellular bases of the reaginic response, the pathogenesis of atopic diseases still remains a matter of speculation. The frequent finding of atopic diseases in some primary immunodeficiencies such as selective IgA deficiency and the Wiskott-Aldrich syndrome offers a unique opportunity for studying the immune mechanisms underlying the genesis of atopy. Recent studies in subjects with selective IgA deficiency have challenged the well known hypothesis that atopy is the result of defective immune exclusion by the secretory immune system. A number of immunological features found in the primary immunodeficiencies associated with atopic disorders suggest that defective homeostatic mechanisms regulating reaginic responses may play a major role in the pathogenesis of atopy. A thorough analysis of these disease combinations may help to generate new working hypotheses concerning the immune pathogenesis of atopic diseases.     

Novel approaches to the nutritional management of the allergic infant

The increased prevalence of atopic diseases, i.e. atopic eczema, allergic rhinitis and asthma, has been described as the epidemic of the 21st century in Western societies. New approaches in the fight against allergic diseases are clearly called for, the target being the persistence of the allergic responder pattern beyond infancy. The advantage afforded by elimination diets lies in the silencing of specific allergic inflammation induced by an offending food. Novel nutritional approaches, beyond the treatment of food allergies, have recently attracted research interest subsequent to the identification of the immunomodulatory potential of specific dietary compounds. Dietary lipids as immunomodulators may prevent allergic sensitization by down-regulating inflammatory response whilst protecting the epithelial barrier. Probiotic bacteria have been shown to reinforce the different lines of gut defence: immune exclusion, immune elimination and immune regulation. On this basis, the strategy against allergic disease proposed here is based on the administration of tolerogenic gut-processed peptide fragments of a specific protein, in addition to the use of specific dietary compounds such as fatty acids and antioxidants, and introducing a microbial stimulus for the immature immune system by means of cultures of beneficial live micro-organisms characteristic of the healthy infant gut microbiota.     

Novel approaches to the nutritional management of the allergic infant

The increased prevalence of atopic diseases, i.e. atopic eczema, allergic rhinitis and asthma, has been described as the epidemic of the 21st century in Western societies. New approaches in the fight against allergic diseases are clearly called for, the target being the persistence of the allergic responder pattern beyond infancy. The advantage afforded by elimination diets lies in the silencing of specific allergic inflammation induced by an offending food. Novel nutritional approaches, beyond the treatment of food allergies, have recently attracted research interest subsequent to the identification of the immunomodulatory potential of specific dietary compounds. Dietary lipids as immunomodulators may prevent allergic sensitization by down-regulating inflammatory response whilst protecting the epithelial barrier. Probiotic bacteria have been shown to reinforce the different lines of gut defence: immune exclusion, immune elimination and immune regulation. On this basis, the strategy against allergic disease proposed here is based on the administration of tolerogenic gut-processed peptide fragments of a specific protein, in addition to the use of specific dietary compounds such as fatty acids and antioxidants, and introducing a microbial stimulus for the immature immune system by means of cultures of beneficial live micro-organisms characteristic of the healthy infant gut microbiota.     

Risk factors for allergy

Host factors involved in the risk for allergy are heredity, sex, race and age, with heredity being by far the most important. Exposure to allergens has been identified as an influential environmental factor, whereas passive smoking and pollution may act as an adjuvant. The atopic mother may – during pregnancy – add to an atopy-prone environment. Whereas respiratory infections are associated with attacks of bronchial asthma, infections in early life might play a role in the protection against atopy by preferential stimulation of a Th1 response, with mutual down-regulation of the Th2 response. Conclusion Recognition of the risk factors for allergy is important in order to select the factors that could be modified for individuals at risk and in order to identify those factors of which the modulation could evolve in general preventive measures. Received: 8 June 1998 / Accepted in revised form: 16 July 1998