Age-related T cell responses to allergens in childhood

BACKGROUND: T cell priming, as determined by allergen-induced proliferative responses, is believed to occur principally in early childhood in both atopic and non-atopic infants under the influence of multiple factors including environmental allergen exposure. It is considered that T cell priming with expansion of Th2 cells is a crucial factor in the development of atopic disease. OBJECTIVE: To examine T cell priming to commonly encountered allergens in childhood in relation to age. METHODS: In a cross-sectional study T cell proliferation in relation to age was examined for three common allergens, ovalbumin (OVA), house dust mite (HDM) and rye grass pollen (RYE), in atopic and non-atopic children. The effect of age on Th1 (IFN-gamma) and Th2 (IL-5 and IL-13) cytokine production in response to these allergens was investigated to examine the possibility of immune deviation with time. RESULTS: A significant increase in T cell proliferation with age was observed with RYE among atopic children only. However, the same was not observed with the two other allergens studied (i.e. OVA and HDM). In addition, RYE-induced (but not HDM or OVA) cytokine production showed an increased Th2 deviation with age as reflected in the increasing IL-5/IFN-gamma and IL-13/IFN-gamma ratios only among the atopic subjects with rye grass pollen sensitivity. CONCLUSION: These findings suggest that grass pollen sensitivity in childhood is accompanied by a progressive accumulation of allergen-primed T cells and progressive deviation of the allergen-induced cytokine response towards a Th2 response in atopic subjects throughout childhood.     

Polyclonal and allergen-induced cytokine responses in children with elevated immunoglobulin E but no atopic disease

BACKGROUND: Reduced Th1 and elevated Th2 cytokine responses are considered to be a principal mechanism in the generation of the inflammation leading to the manifestations of atopic disease in the skin of atopic dermatitis and in the airways of asthma. If reduced Th1 and elevated Th2 responses are principal determinants of the manifestation of atopic disease it might be expected that subjects with established disease would exhibit differences in their cytokine profiles as compared with atopic patients without clinical disease. OBJECTIVE: To determine whether asymptomatic atopic children exhibit a cytokine imbalance similar to that seen in patients with established atopic disease or if they behave like non-atopic controls. Cytokine responses in a group of children with elevated IgE but no clinical manifestations of disease, atopic children with established disease and non-atopic controls were compared. METHODS: We examined allergen-induced (house dust mite, HDM, rye grass pollen and RYE) cytokine responses in parallel with polyclonal (staphylococcal enterotoxin B, SEB) cytokine responses in a group of children with elevated serum IgE levels without current or past evidence of atopic disease (median age 6.6 years) and compared these with a non-atopic control group (median age 6.5 years) and a group of children with atopic disease (median age 6.7 years). RESULTS: Symptomatic atopic children had reduced SEB-induced IFN-gamma and increased SEB-induced IL-4 and IL-5 as compared with non-atopic controls. In contrast, SEB-induced IFN-gamma, IL-4 and IL-5 production in asymptomatic atopics was not significantly different from the non-atopic control subjects. Allergen-induced Th1 (IFN-gamma) and Th2 (IL-5 and IL-13) cytokine production was increased in both symptomatic atopics and asymptomatic atopics when compared with non-atopic controls. CONCLUSION: The defect in polyclonally induced IFN-gamma production was associated with the clinical manifestation of atopic disease but not the atopic stateper se. This suggests that the global reduction in IFN-gamma is the key determinant of the development of overt atopic disease. In contrast, elevated allergen-induced Th2 cytokine responses in children related to the atopic state per se irrespective of the presence of clinical atopic disease.     

Selective development of a strong Th2 cytokine profile in high-risk children who develop atopy: risk factors and regulatory role of IFN-γ, IL-4 and IL-10

BACKGROUND: The immunological processes in early life and their relation to allergic sensitization leading to a Th2 cytokine profile are still not well understood. OBJECTIVE: To analyse the environmental and genetic risk factors and immunological responses at birth in relation to the development of atopic disease at 12 months of age in a longitudinal study of high-risk children. METHODS: High-risk children were followed from birth till 12 months of age. Mononuclear cells obtained at birth and 6 and 12 months thereafter were analysed for their proliferative and cytokine responses after polyclonal and allergen-specific stimulation. RESULTS: At 12 months of age 25% children had developed an atopic disease. Two atopic parents, parental smoking and atopic dermatitis of at least one of the parents were significant risk factors. In cord blood of newborns who developed atopy, an increased percentage of CD4+CD45RO+ cells and an increased polyclonal-stimulated proliferation were observed. Furthermore, an impaired allergen-induced, but not polyclonal-stimulated IFN-gamma production was found, suggesting a regulatory defect. At 6 and 12 months of age, a strong Th2 profile (characterized by increased levels of IL-4, IL-5, and IL-13) after both polyclonal and, to a lesser extent, allergen-specific stimulation was found in the children developing atopy. Allergen-induced IL-10 production at 12 months of age was only observed in the non-atopic children. CONCLUSION: Our data indicate that the first 6 months of life represent a critical time window for the initiation of immunological changes resulting in the development of atopy. The selective development of a Th2 cytokine profile in high-risk children who develop atopy is due to increased production of Th2 cytokines, possibly caused by impaired allergen-induced IFN-gamma production in the neonatal period. Furthermore, the decreased allergen-induced IL-10 levels observed in the atopic children at 12 months of age may result in a lack of down-regulation of the inflammatory process.     

"Bystander" amplification of PBMC cytokine responses to seasonal allergen in polysensitized atopic children

BACKGROUND: Atopic children show increased expression and production of the Th2-associated cytokines IL-4, IL-5, IL-13, and IL-9 from PBMCs after stimulation with allergen, but it has previously not been clearly determined whether the Th2-cytokine production is restricted to the inhalant allergen the child is sensitized to, and whether perennial or seasonal allergens induce different cytokine responses. Our purpose was to determine whether in vitro Th2 cytokine production is specific to the sensitizing allergen, and to compare the cytokine responses to a perennial and a seasonal allergen in monosensitized and polysensitized children. METHODS: Using semiquantitative RT-PCR, we analyzed the expression of the cytokines IL-4, IL-5, IL-13, IL-9, IL-10, and IFN-gamma after stimulation of PBMCs with house-dust-mite (HDM) or ryegrass allergen. The cells were sampled from groups of 6-year-old children sensitized to either HDM (n=20) or ryegrass (n=24), or to both allergens (n=20), as well as from a nonatopic group (n=20). RESULTS: After stimulation with HDM allergen, PBMCs from children sensitized only to HDM expressed increased mRNA levels of the Th2 cytokines, but not of IL-10 and IFN-gamma, whereas ryegrass stimulation did not result in increased cytokine expression. PBMCs from children sensitized to HDM and ryegrass expressed increased Th2 cytokines after stimulation with either of the two allergens. In contrast, PBMCs from children sensitized only to ryegrass did not express increased levels after stimulation with either of the allergens. CONCLUSIONS: The expression of Th2 cytokines after in vitro stimulation of PBMCs from atopic children is specific to the sensitizing allergen, indicating that atopic status per se does not affect the type of T-cell response. In addition, T cells specific to seasonal allergens circulate in the blood out of season only if the child is concomitantly sensitized to a perennial allergen.     

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

BACKGROUND AND OBJECTIVES: A reduced capacity of antigen presenting cells (APC) to provide pro-T helper 1 (Th1) signals, such as IL-12, to T cells during early life may be implicated in the development of T helper 2 (Th2)-mediated allergic disease. In this study we examined the relationships between the capacity for IL-12 responses in the neonatal period and atopic risk (family allergy), in vitro T cell responses to allergens, and the subsequent development of allergic disease at 6 years. METHODS: The capacity of circulating neonatal (and maternal) APC to produce IL-12 p70 in response to LPS (and IFN-gamma) stimulation was assessed in a group of 60 children with previously well-characterized immune responses to allergens and atopic outcomes. The IL-12 responses were compared with allergen-induced lymphoproliferation (to house dust mite (HDM) ovalbumin (OVA), cat and beta-lactoglobulin (BLG)) and IL-13 and IFN-gamma cytokine responses (to OVA, HDM and phytohaemaglutinin (PHA)) in the neonatal and postnatal periods. IL-12 responses were also compared according to atopic risk and atopic outcomes (doctor-diagnosed asthma, eczema, food allergies and sensitization as evidenced by skin prick testing) at 6 years clinical follow-up. RESULTS: Maternal peripheral blood mononuclear cells (PBMC) synthesized significantly greater amounts of IL-12 than neonatal PBMC, though within maternal-infant pairs IL-12 responses were significantly correlated (r = 0.4, P = 0.019). Moreover, neonatal IL-12 responses were positively correlated with neonatal allergen proliferation for HDM (r = 0.6, P < 0.0001), OVA (r = 0.55, P < 0.0001), cat (r = 0.5, P = 0.003) and BLG (r = 0.55, P = 0.001), but negatively correlated with neonatal IL-13 responses to both allergens tested (HDM: r = - 0.4, P = 0.03 and OVA: r = - 0.5, P = 0.001). Both neonatal and maternal IL-12 responses were positively correlated with postnatal IFN-gamma responses to HDM at 12, 18 and 24 months of age (responses after age of 2 years were not assessed). There was no relationship between atopic risk and IL-12 capacity in the neonatal period, but there was a (non-significant) trend for neonatal IL-12 responses to be lower in the high-risk children who developed clinical allergy at 6 years (compared with the low risk group) although the number in this analysis was small. CONCLUSIONS: Reduced APC IL-12 production in the perinatal period was associated with reduced T cell activation (lymphoproliferation), stronger neonatal Th2 responses, and weaker Th1 responses to allergen in the postnatal period. This supports the notion that variations in APC function in early life may contribute to altered allergen-specific cytokine responses associated with later allergy.     

IL-13 production by allergen-stimulated T cells is increased in allergic disease and associated with IL-5 but not IFN-gamma expression.

Interleukin-13 (IL-13) shares many, but not all, of the properties of the prototypic T-helper type 2 (Th2) cytokine IL-4, but its role in allergen-driven T-cell responses remains poorly defined. We hypothesized that allergen stimulation of peripheral blood T cells from patients with atopic disease compared with non-atopic controls results in elevated IL-13 synthesis in the context of a 'Th2-type' pattern. Freshly isolated peripheral blood mononuclear cells (PBMC) obtained from sensitized atopic patients with allergic disease, and non-atopic control subjects, were cultured with the allergens Phleum pratense (Timothy grass pollen) or Dermatophagoides pteronyssinus (house dust mite) and the non-allergenic recall antigen Mycobacterium tuberculosis purified protein derivative (PPD). Supernatant concentrations of IL-13, along with IL-5 and interferon-gamma (IFN-gamma) (Th2- and Th1-type cytokines, respectively) were determined by enzyme-linked immunosorbent assay (ELISA). Allergen-induced IL-13 and IL-5 production by T cells from patients with allergic disease was markedly elevated (P = 0.0075 and P = 0.0004, respectively) compared with non-atopic controls, whereas IFN-gamma production was not significantly different. In contrast to allergen, the prototypic Th1-type antigen M. tuberculosis PPD induced an excess of IFN-gamma over IL-13 and IL-5 production, and absolute concentrations of cytokines were not affected by the presence or absence of atopic disease. Addition of exogenous recombinant IFN-gamma or IL-12, cytokines known to inhibit Th2-type responses, significantly inhibited allergen-driven production of both IL-13 and IL-5, but not T-cell proliferation, whereas exogenous IL-4 did not significantly affect production of IL-13 or IL-5. We conclude that allergen-specific T cells from atopic subjects secrete elevated quantities of IL-13 compared with non-atopic controls, in the context of a Th2-type pattern of cytokine production.     

Atopic dermatitis in young children is associated with impaired interleukin-10 and interferon-γ responses to allergens, vaccines and colonizing skin and gut bacteria

BACKGROUND: A significant proportion of children with food allergy and more severe forms of atopic dermatis (AD) go on to develop persistent forms of allergic disease such asthma. Defining immune dysregulation in these children will be of great value in understanding disease pathogenesis. OBJECTIVE: In this study we characterized the immune responses of young infants (6-18 months of age) with moderate-to-severe AD (a modified SCORAD>or=25) and compared these (n=53) with responses of non-allergic children with no history of dermatitis or sensitization of the same age (n=20). METHODS: Mononuclear cell cytokine responses to allergens (egg ovalbumin (OVA), beta-lactoglobulin (BLG), house dust mite (HDM)), vaccines (tetanus toxoid (TT), diphtheria toxoid (DT)), intestinal flora (heat-killed Lactobacillus species (HKLB)), heat-killed Staphylococcus aureus (HKSA), S. aureus enterotoxin B (SEB) and mitogen (phytohaemaglutinin (PHA)) were compared in children with AD with unaffected children. RESULTS: Children with AD had significantly lower spontaneous (unstimulated) production of regulatory cytokine IL-10 (P<0.001), as well as IFN-gamma (P<0.001) and TNF-alpha (P<0.001) compared with the unaffected children. After allowing for differences in baseline levels IL-10 responses to virtually all stimuli (food allergens (P=0.003), vaccines P=0.01, intestinal flora (heat-killed Lactobacillus species (HKLB), P=0.005) and skin flora (heat-killed Staphylococcus aureus (HKSA), P=0.003)) were also significantly attenuated in children with AD. The only exception was HDM, to which responses were stronger in children with AD [P=0.05]. Although there were no significant correlations between HDM IgE and HDM cytokine responses at this age, T-helper type 2 (Th2) IL-5 (P=0.014) and IL-13 (P=0.004) responses to HDM were significantly more frequent in the children with AD. However, while children with AD showed significantly attenuated Th1 IFN-gamma responses to food allergens (OVA, P=0.007 and BLG, P<0.001) and vaccines (DT, P=0.008 and TT, P<0.001), these children showed no difference in Th1 IFN-gamma responses to HDM or microbial agents (HKSA and HKLB). CONCLUSION: A increase in propensity for Th2 responses to aeroallergens in children with AD is associated with early impaired production of IL-10 regulatory cytokine to a broad range of environmental stimuli including foods, intestinal flora, S. aureus, and vaccines.     

Specific patterns of responsiveness to microbial antigens staphylococcal enterotoxin B and purified protein derivative by cord blood mononuclear cells are predictive of risk for development of atopic dermatitis

BACKGROUND: Mononuclear cells from children with active atopic dermatitis (AD) have been reported to be hyper-responsive to certain microbial stimuli, in particular staphylococcal enterotoxin B (SEB). However, it is not known whether this responsiveness is acquired during disease development, or is inherent. We investigated this question in a cohort of children at high risk of atopy followed prospectively from birth to age 3 years. We asked whether their cord blood mononuclear cell (CBMC) cytokine responses to SEB, to an unrelated microbial stimulus purified protein derivative (PPD), or to common allergens, were predictive of risk for subsequent AD development during infancy. METHODS: Children at high risk of developing atopy were randomly selected from an ongoing prospective cohort. Cord blood was collected at birth. The children were seen at 6 months, 1, 2 and 3 years and examined for the development of AD. IFN-gamma, IL-5, IL-10 and IL-13 production by CBMC cultured in the presence of SEB, PPD, PHA, house dust mite (HDM) allergen, ovalbumin (OVA) and cat allergen was determined. RESULTS: SEB-induced IL-5 production by CBMC was elevated in children who developed AD at 6 months (P = 0.01) and 2 years (P = 0.009). PPD-induced IL-5 responses were also elevated in CBMC from children who developed AD at 6 months, 2 years and 3 years (P = 0.05, P = 0.06 and P = 0.06, respectively), as were PPD-induced IL-10 responses (P = 0.05 at 1 years, P = 0.007 at 2 years, P = 0.003 at 3 years) and corresponding IFN-gamma responses (P = 0.05 at 6 months, P = 0.003 at 2 years, P = 0.0004 at 3 years). Increased IL-10 responses to HDM allergen were also observed throughout the observation period in CBMC from children who developed AD. CONCLUSION: Children who develop infantile AD appear to have a predisposition to respond to SEB in a Th2-dominant manner involving selective stimulation of IL-5 production. The increased IL-10 and IFN-gamma induced in response to PPD by children with AD may point to additional intrinsic differences in responses to microbial stimuli between those at high vs. those at low risk for AD, which merit more detailed investigations.     

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

BACKGROUND: High genetic risk (HR) of atopy among unstratified populations of infants is associated with attenuated IFN-gamma responses. However, the role of IFN-gamma in progression from HR status to active disease is less clear. OBJECTIVE: To identify immune function markers in neonates with HR that are associated with positive atopic outcomes at 2 years. METHODS: Cord blood mononuclear cells (CBMCs) were collected from 175 children with HR and cryopreserved. The children were assessed for atopy by skin prick at 0.5 and 2 years. CBMCs were thawed and stimulated with allergens and mitogens PHA and staphylococcal enterotoxin B (SEB), and cytokine responses were determined. RESULTS: No correlations were observed between allergen-specific CBMC responses and atopic outcomes. In contrast, sensitization was strongly associated with polyclonal IFN-gamma responses to both PHA (P=.002) and SEB (P=.005), and also with SEB-induced IL-5 (P =.05), IL-10 (P =.02), and IL-13 (P =.01). Logistic regression analysis identified elevated PHA-induced IFN-gamma and SEB-induced IL-13 responses as the strongest independent predictors of atopy development. Cell separation studies confirmed CD8+ T cells as the source of approximately 90% of IFN-gamma production. CONCLUSIONS: IFN-gamma produced by CD8+ T cells may synergize with T(H)2 cytokines in driving atopy development in children with HR.     

Polyclonal and allergen-induced cytokine responses in adults with asthma: resolution of asthma is associated with normalization of IFN-gamma responses

BACKGROUND: Atopic disease is associated with skewing of immune responses away from a T(H)1 toward a T(H)2 profile. Previous studies have implicated this cytokine imbalance in the development of disease. However, it is not known whether normalization of this imbalance is conversely associated with disease resolution. OBJECTIVE: To further delineate the role of reduced T(H)1 and increased T(H)2 cytokine production in the pathogenesis of atopic disease and to determine whether disease resolution is associated with alteration of cytokine profiles, we investigated cytokine responses in a cohort of adult patients with asthma followed from childhood. METHODS: A cohort of wheezy children and control subjects aged 7 to 10 years were recruited from 1964 to 1967. Subjects were reevaluated every 7 years to monitor the outcome of childhood asthma. At the 42-year follow-up, 89 subjects from this cohort were evaluated for mitogen and house dust mite (HDM)-induced T(H)1 (IFN-gamma) and T(H)2 (IL-4, IL-5, and IL-13) cytokine responses. Cytokine responses were compared in patients with ongoing asthma, patients with resolved asthma, and control subjects. RESULTS: Patients with severe ongoing asthma had significantly reduced HDM-induced IFN-gamma production compared with that of control subjects and patients with resolved asthma. In contrast, HDM-induced IFN-gamma production in patients with resolved asthma was equivalent to that seen in control subjects. Patients with ongoing and resolved asthma produced significantly higher levels of IL-5 in response to HDM compared with that seen in control subjects, with levels being equivalent in patients with active and resolved asthma. HDM-induced IL-13 production was significantly increased in the patients with resolved asthma when compared with that seen in the control subjects. PHA-induced cytokine responses did not parallel HDM-induced responses. CONCLUSION: Patients with persistent and severe atopic asthma have a reduced HDM-induced T(H)1 response, whereas those with resolved asthma do not. This suggests that reduced HDM-induced IFN-gamma production might be an important factor contributing to ongoing severe asthma and that normalization of allergen-induced T(H)1 responses might be important for disease resolution. The finding that all subjects with a history of asthma displayed increased HDM-induced T(H)2 (IL-5 and IL-13) cytokine responses, irrespective of the presence or absence of asthma, suggests that increased T(H)2 responses reflect the presence of the atopic state per se rather than being specifically linked to asthma.     

Allergen-induced Th1 and Th2 cytokine secretion in relation to specific allergen sensitization and atopic symptoms in children

BACKGROUND: Allergic diseases are believed to be due to T helper (Th)2-like immunity to allergens in affected tissues, and immune responses to allergens are characterized by a cross-regulation between Th1 and Th2 cells. Atopic individuals may develop IgE antibodies to only one or more allergens. However, the mechanisms behind sensitization to a specific allergen, e.g. why an individual develops IgE to cat but not birch, are not known. Our aim was to study birch- and cat-induced Th1 and Th2 cytokine secretion in children who were sensitized to birch but not to cat, and vice versa. MATERIALS AND METHODS: The subjects in the study were 60 12-year-old children. Seventeen of the children were sensitized (skin prick test and circulating IgE positive) to birch but not cat, 13 were sensitized to cat but not birch, 11 were sensitized both to birch and cat, and 19 children were skin prick test and circulating IgE negative. Forty-six children had a history of atopic symptoms, and 42 of them had current symptoms. Peripheral blood mononuclear cells were separated from venous blood and stimulated with cat or birch allergen. The levels of IL-4, IL-5, IL-9, IL-10, IL-13 and IFN-gamma in the cell supernatants were analysed by ELISA. RESULTS: Sensitized children produced more of the Th2 cytokines IL-4, IL-5, IL-9 and IL-13 than non-sensitized atopic and non-atopic children in response to stimulation with the allergen they were sensitized to. High levels of the Th2 cytokines IL-4 and IL-5 and low levels of the anti-inflammatory cytokine IL-10 were associated with atopic symptoms, and high cat-induced IL-9 levels with asthma. CONCLUSIONS: The Th2 cytokines IL-4, IL-5, IL-9 and IL-13 were all commonly detected in sensitized children after stimulation with the specific, in contrast to an unrelated, allergen. Atopic symptoms were associated with increased levels of IL-4 and IL-5 and tended to be associated with low levels of IL-10, and asthma with high cat-induced IL-9 levels.     

PHA-induced IL-12Rβ2 mRNA expression in atopic and non-atopic children

BACKGROUND: IL-12 is a strong inducer of Th1 responses. Stimulation via the CD2 receptor increases IFN-gamma production and enhances the responsiveness of activated T-cells to IL-12, possibly due to an up-regulation of the signal transducing beta(2) chain of the IL-12 receptor (IL-12R beta(2)). Atopic children have a reduced Th1-like immunity and a reduced CD2 expression. Our hypothesis is that atopic individuals have a reduced function of the CD2 pathway, causing reduced responsiveness to IL-12 and decreased IFN-gamma production. OBJECTIVE: The aim was to study the mRNA expression of the IL-12R beta(2) chain, after stimulation via the CD2 pathway in peripheral blood mononuclear cells (PBMC), of atopic and non-atopic children, and to investigate correlations to the production of Th1 and Th2 cytokines. MATERIALS AND METHODS: The study included 23 skin prick test positive, and 9 non-sensitized, 12-year-old children. PBMC were stimulated for 24 h with phytohemagglutinin (PHA) (2 microg/mL), which stimulates T cells through the CD2 pathway. Expression of IL-12R beta(2) mRNA was analysed by quantitative real time PCR and the cytokine production was detected with ELISA. RESULTS: Atopic and non-atopic children had similar baseline expression of IL-12R beta(2) mRNA, whereas PHA-induced IL-12R beta(2) mRNA expression was lower in atopic than in non-atopic children. The PHA-induced IL-12R beta(2) mRNA expression correlated well with the PHA-induced IFN-gamma production and with the IFN-gamma/IL-4 ratio. CONCLUSION: PBMC from atopic children expressed less IL-12R beta(2) mRNA than non-atopic children after stimulation via the CD2 pathway (PHA). This may indicate a reduced capacity to respond to Th1-inducing stimuli in atopic children.     

Allergen-induced cytokine production, atopic disease, IgE, and wheeze in children

BACKGROUND: The early childhood allergen-induced immune responses associated with atopic disease and IgE production in early life are not well understood. OBJECTIVE: We assessed the relationship of allergen-induced cytokine production by PBMCs to both atopic disease and to IgE increase in a cohort of children with a parental history of allergy or asthma (n = 112) at a median of 2 years of age. We examined cockroach (Bla g 1)-induced, house dust mite (Der f 1)-induced, and cat (Fel d 1)-induced cytokine secretion, including secretion of IFN-gamma, IL-13, IL-10, and TNF-alpha. We investigated whether distinct cytokine patterns associated with atopic disease can be detected in immune responses of children. METHODS: PBMCs were isolated, and allergen-induced cytokine secretion was analyzed by means of ELISA. Atopic disease was defined as physician- or nurse-diagnosed eczema or hay fever. Increased IgE was defined as an IgE level of greater than 35 U/mL to dust mite, cockroach, cat, and egg white or a total IgE level of 60 U/mL or greater. RESULTS: Compared with children without atopic disease, children with atopic disease had lower Der f 1 (P =.005) and Bla g 2 (P =.03) allergen-induced IFN-gamma levels. Compared with children without increased IgE (n = 95), those with increased IgE (n = 16) had higher Der f 1-induced (P =.006) and Fel d 1-induced (P =.005) IL-13 levels and lower Bla g 2-induced (P =.03) IFN-gamma levels. Compared with children with neither atopic disease nor repeated wheeze, children with both atopic disease and repeated wheeze had lower levels of allergen-induced IFN-gamma (P =.01 for Der f 1 and P =.02 for Bla g 2) cytokine secretion. CONCLUSION: In young children at risk for asthma or allergy, decreased allergen-induced IFN-gamma secretion is associated with atopic disease and, in some cases, with increased IgE levels. Increased allergen-induced IL-13 secretion is most strongly associated with early life increase of IgE.     

Cellular immune responses to ovalbumin and house dust mite in egg-allergic children

BACKGROUND: Although IgE-mediated food (egg) allergy is typically lost with age the underlying immune mechanisms are not understood, particularly in relation to the development of persistent IgE-mediated aeroallergen sensitivity. METHODS: Lymphoproliferation and cytokine responses (IL-5, IL-10, IL-13 and IFN-gamma) to house dust mite (HDM) allergen and egg ovalbumin (OVA) were assessed using peripheral blood mononuclear cells (PBMC) from children aged 6 months to 5 years (n = 59) with acute IgE-mediated egg allergy (urticaria and angiedema or anaphylaxis), as confirmed by positive skin prick testing (SPT). Of these 46 had positive SPT on the day of blood collection and 13 had outgrown egg allergy (negative SPT and successful egg challenge). Where possible, responses were compared with previous data from nonallergic children of similar ages (n = 107). RESULTS: Transient lymphoproliferative responses to OVA were seen in both egg-allergic and nonallergic children, but were more marked and more prolonged in egg-allergic children. Younger egg-allergic children (< 18 months) showed a mixed Th0 cytokine response to OVA, with readily detectable IFN-gamma, IL-5, IL-13 IL-10. Although IL-13 and IL-5 responses (OVA) correlated in younger egg-allergic children, there was a dissociation of these Th2 responses with age. Loss of clinical reactivity to egg was associated with almost complete loss of IL-5 responses and OVA-specific lymphoproliferation. Although IL-13 levels tended to be lower with age, this was not significant. Strong IFN-gamma and IL-10 responses to OVA persisted in older children after loss of OVA-specific lymphoproliferation. Lymphoproliferative responses to HDM also developed earlier in egg-allergic children compared with nonallergic children. Th1 (IFN-gamma) responses to HDM were largely below detection prior to 18 months of age, but increased significantly with age. In egg-allergic children Th2 (IL-5, IL-13) HDM responses also progressively increased with age. At 3 years of age almost all egg-allergic children had positive SPT to HDM and positive lymphoproliferative responses to HDM, with strong Th1 and Th2 (Th0) cytokine production. CONCLUSIONS: IL-5 responses (rather than IL-13) responses most closely reflected clinical food allergy, with dissociation of IL-5 and IL-13 responses in older and egg-tolerant children. In this population, food and aeroallergen sensitivity was not associated with inability to produce IFN-gamma, but rather with mixed Th2 and Th1 (Th0) responses. Strong IL-10 and IFN-gamma responses where associated with the development of tolerance, suggesting persistent 'regulatory' populations of OVA-specific T cells, rather than clonal deletion of OVA responsive T-cells.     

Immune responses to birch in young children during their first 7 years of life

BACKGROUND: The character of immune responses to allergens during the first years of life may decide whether the individual will become tolerant or develop allergy later in life. OBJECTIVE: To study the development of immune responses to the seasonal inhalant allergen birch over the first 7 years of life. METHODS: Blood samples were obtained from 21 children who were followed prospectively from the second to the seventh pollen season of life. Birch-induced cytokine production and IgG subclass antibodies to rBet v 1 were analysed with ELISA, mRNA expression with real time PCR, IgE antibodies to birch with Magic Lite and birch-induced mononuclear cell proliferation with 3H-thymidine incorporation. RESULTS: Birch-induced IFN-gamma and IL-10 production increased with age, both in atopic and non-atopic children, while birch-induced IL-13 production decreased. The two children who were sensitized and developed clinical allergy to birch showed persistent IL-4 and IL-5 production and IL-9 mRNA expression, as well as Th2-associated IgG4 responses. Transient Th2-like responses were observed among the other children. Proliferative responses and IgG1 antibodies were seen in all children. CONCLUSIONS: Immune responses to birch can be demonstrated in all children, during the first 7 years of life, regardless of atopic status. A transient early Th2-like response is down-regulated after the fourth pollen season, except in children who develop clinical allergy to the particular allergen.     

Superantigen concomitantly induces Th1 cytokine genes and the ability to shut off their expression on re-exposure to superantigen

Superantigens, exemplified by staphylococcal enterotoxin B (SEB), are the strongest known inducers of a cellular immune response; they elicit the production of excessive amounts of Th1 cytokines, IL-2, IFN-gamma and TNF, leading to toxic shock. We show that increasing doses of SEB cause not only a greater induction but also a more rapid cessation of IL-2 gene expression. Remarkably, exposure of human PBMC to a second dose of SEB, even at concentrations 10- or 100-fold lower than the initial inducing dose and even within 2 h after the first exposure to SEB, resulted in an immediate and essentially complete shutoff of the induced IL-2 and IFN-gamma mRNA expression. The shutoff response was observed when primary induction of IL-2 and IFN-gamma gene expression was by SEB but not when it was by phytohemaggutinin-P. Signaling by a superantigen thus results not only in a vigorous induction of Th1 cytokine genes but concomitantly induces the ability to shut off their expression upon re-exposure to superantigen. Without induction of this negative control mechanism, the cellular immune response to a superantigen would be even more pronounced.     

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

BACKGROUND: A reduction in microbial burden during infancy when allergen-specific memory is evolving has become a prominent explanation for the allergy epidemic. OBJECTIVE: We sought to determine whether probiotic dietary supplementation in the first 6 months of life could modify allergen- and vaccine-specific immune responses. METHODS: Two hundred and thirty-one pregnant women with a history of allergic disease and positive allergen skin prick test (SPT) were recruited into a randomized-controlled trial. The infants received either a probiotic (3 x 10(9)Lactobacillus acidophilus LAVRI-A1; Probiomics) or placebo (maltodextrin alone) daily for the first 6 months of life, given independent of feeding methods. One hundred and seventy-eight children completed the study; blood samples were available from 60 children in the placebo group and 58 children in the probiotic group. Infant cytokine (IL-5, IL-6, IL-10, IL-13, TNF-alpha or TGF-beta) responses to tetanus toxoid (TT), house dust mite (HDM), ovalbumin (OVA), beta-lactoglobulin (BLG), Staphylococcus enterotoxin B (SEB) and phytohaemaglutinin (PHA) were measured at 6 months of age. RESULTS: Children who received the probiotics showed reduced production of IL-5 and TGF-beta in response to polyclonal (SEB) stimulation (P=0.044 and 0.015, respectively). They also demonstrated significantly lower IL-10 responses to TT vaccine antigen compared with the placebo group (P=0.03), and this was not due to any differences in vaccination. However, there were no significant effects of probiotics on either Type 1 (Th1) or Type 2 (Th2) T helper cell responses to allergens or other stimuli. The only other effects observed were for reduced TNF-alpha and IL-10 responsiveness to HDM allergens in children receiving probiotics (P=0.046 and 0.014, respectively). CONCLUSIONS: In summary, although we did not see any consistent effects on allergen-specific responses, our study suggests that probiotics may have immunomodulatory effects on vaccine responses. The significance and clinical relevance of this need to be determined in further studies.     

Patterns of food allergen-specific cytokine production by T lymphocytes of children with multiple allergies

BACKGROUND: The contribution of different T cell subsets to the overall measured cytokine response to food allergens is largely unexplored. METHOD: The patterns of cytokine production of peripheral blood-derived T cells after allergen stimulation were studied in 22 children with multiple food allergies and in 20 non-allergic children as controls, using flow cytometry. RESULTS: Proportions of T cells of food-sensitized children spontaneously secreting IFN-gamma and IL-10 (without antigen stimulation) were lower than non-atopic children and adult controls (P相似文献   

Epicutaneous sensitization with superantigen induces allergic skin inflammation

BACKGROUND: Atopic dermatitis (AD) is characterized by skin infiltration with eosinophils and lymphocytes and expression of Th2 cytokines in acute skin lesions. The skin of patients with AD is frequently colonized with enterotoxin-secreting strains of Staphylococcus aureus. Staphylococcal enterotoxins have been implicated in the exacerbations of the inflammatory skin lesions in patients with AD. OBJECTIVE: We sought to determine whether epicutaneous (EC) sensitization of mice with staphylococcal enterotoxin B (SEB) results in allergic skin inflammation. METHODS: BALB/c mice were EC-sensitized with SEB. Their skin was examined for allergic inflammation and cytokine expression, and their splenocytes were examined for cytokine secretion in response to SEB. RESULTS: EC sensitization with SEB elicited a local, cutaneous, inflammatory response characterized by dermal infiltration with eosinophils and mononuclear cells and increased mRNA expression of the Th2 cytokine IL-4 but not of the Th1 cytokine IFN-gamma. EC-sensitized mice mounted a systemic Th2 response to SEB evidenced by elevated total and SEB-specific IgG1 and IgE. Although EC sensitization with SEB resulted in selective depletion of SEB-specific T-cell receptor Vbeta8+ cells from the spleen and sensitized skin, splenocytes from SEB-sensitized mice secreted relatively more IL-4 and less IFN-gamma than did saline-sensitized controls, consistent with Th2 skewing of the systemic immune response to the superantigen. CONCLUSION: These results suggest that EC exposure to superantigens skews the immune response toward Th2 cells, leading to allergic skin inflammation and increased IgE synthesis that are characteristic of AD.     

IL-10 and TGF-beta cooperate in the regulatory T cell response to mucosal allergens in normal immunity and specific immunotherapy

The regulation of normal and allergic immune responses to airborne allergens in the mucosa is still poorly understood, and the mechanism of specific immunotherapy (SIT) in normalizing the allergic response to such allergens is currently not clear. Accordingly, we have investigated the immunoregulatory mechanism of both normal and allergic responses to the major house-dust mite (HDM) and birch pollen allergens--Dermatophagoides pteroynyssinus (Der p)1 and Bet v 1, respectively--as well as the immunologic basis of SIT to HDM in rhinitis and asthma patients. In normal immunity to HDM and birch pollen, an allergen-specific peripheral T cell suppression to Der p 1 and Bet v 1 was observed. The deviated immune response was characterized by suppressed proliferative T cell and Th1 (IFN-gamma) and Th2 (IL-5, IL-13) cytokine responses, and increased IL-10 and TGF-beta secretion by allergen-specific T cells. Neutralization of cytokine activity showed that T cell suppression was induced by IL-10 and TGF-beta during SIT and in normal immunity to the mucosal allergens. In addition, SIT induced an antigen-specific suppressive activity in CD4(+) CD25(+) T cells of allergic individuals. Together, these results demonstrate a deviation towards a regulatory/suppressor T cell response during SIT and in normal immunity as a key event for the healthy immune response to mucosal antigens.