Reduced IFNgamma production in response to IL-12 stimulation and/or reduced IL-12 production in atopic patients

Host defense against Neospora caninum infection via IL-12p40 production through TLR2/TLR3-AKT-ERK signaling pathway in C57BL/6 mice

Neospora caninum is an intracellular parasite which can cause neosporosis and significant economic losses in both dairy and beef industries worldwide. A better understanding of the immune response by host cells against N. caninum could help to design better strategies for the prevention and treatment of neosporosis. Although previous studies have shown TLR2/TLR3 were involved in controlling N. caninum infection in mice, the precise mechanisms of the AKT and MAPK pathways controlled by TLR2/TLR3 to regulate N. caninum-induced IL-12p40 production and the role of TLR2/TLR3 in anti-N. caninum infection in bovine macrophages remain unclear. In the present study, TLR2^-/- mice displayed more parasite burden and lower level of IL-12p40 production compared to TLR3^-/- mice. N. caninum could activate AKT and ERK signaling pathways in WT mouse macrophages, which were inhibited in TLR2^-/- and TLR3^-/- mouse macrophages. In N. caninum-infected WT mouse macrophages, AKT inhibitor or AKT siRNA could decrease the phosphorylation of ERK. AKT or ERK inhibitors reduced the production of IL-12p40 and increased the number of parasites. The productions of ROS, NO, and GBP2 were significantly reduced in TLR2^-/- and TLR3^-/- mouse macrophages. Supplementation of rIL-12p40 inhibited N. caninum proliferation and rescued the productions of IFN-γ, NO, and GBP2 in WT, TLR2^-/-, and TLR3^-/- mouse macrophages. In bovine macrophages, the expressions of TLR2, TLR3, and IL-12p40 mRNA were significantly enhanced by N. caninum, and N. caninum proliferation was inhibited by TLR2/TLR3 agonists. Taken together, the proliferation of N. caninum in mouse macrophages was controlled by the TLR2/TLR3-AKT-ERK signal pathway via increased IL-12p40 production, which in turn lead to the productions of NO, GBP2, and IFN-γ during N. caninum infection. And in bovine macrophages, TLR2 and TLR3 contributed to inhibiting N. caninum proliferation via increased IL-12p40 production.

Biological characteristics of intestinal IgE and gut diseases

Immunoglobulin E (IgE), a crucial protective substance for the intestinal tract, plays an important role in gut immunity. IgE is secreted by plasma cells in the submucosal lamina propria upon antigenic invasion and, together with certain cytokines and immune cells, is involved in the regulation of gastrointestinal immunity in normal or abnormal conditions via the high affinity IgE receptor (FcεR I) and low affinity IgE receptor (CD23⁺). In this paper, we review the structure, synthetic transport, secretory regulation, receptor classification, and function of intestinal IgE as well as the related gut diseases.

Effects of dioxins on the quantitative levels of immune components in infants

Dioxins (polychlorinated dibenzo-p-dioxin (PCDD)=polychlorinated dibenzofuran (PCDF)) and polychlorinated biphenyls (PCBs) are potentially hazardous compounds and have structural similarity with thyroid hormones. Animal studies have demonstrated that PCDDs, PCDFs and PCBs can alter immune functions. However, in humans it is not yet elucidated whether dioxins contained in breast milk have any effects on the immune functions in infants. To investigate the effects of dioxins on the immune system, we compared the quantitative levels of immune components between a breast-fed group and bottle-fed group, in which dioxin concentration is almost zero. Ratios of immune cells, such as CD4= and CD8= T-lymphocytes, as well as B-lymphocytes (CD19= and/or CD20=) and NK cells (CD16=, CD56=) in peripheral blood lymphocytes, serum immunoglobulin level, and level of specific IgE antibody to allergens in the venous blood at 12 months of age were assessed in a subgroup of 281 infants. The relationship of post-natal dioxin exposure via breast feeding with the ratio of immunological markers and the level of humoral antibodies up to 12 month of age was not demonstrated. In conclusion, it would appear that the content of dioxins in breast milk in the Japanese general population is not enough to induce any change in theses-examined immunological parameters during the first year of life, although long-term effects remain to be evaluated.

Reduced IFN-γ receptor expression and attenuated IFN-γ response by dendritic cells in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is characterized by a predominance of T(H)2 immune reactions but weaker T(H)1 immune responses in acute skin lesions.

OBJECTIVES

To evaluate whether enhanced T(H)2 immunity in patients with AD might impair T(H)1 immune responses by affecting the IFN-γ responsiveness of antigen-presenting cells, we investigated IFN-γ receptor and IL-4 receptor α chain expression, IFN-γ signaling, and the expression of IFN-γ-responsive mediators in dendritic cells (DCs) and their precursors from patients with AD compared with those from healthy subjects.

METHODS

Skin biopsy specimens were obtained and both monocytes and monocyte-derived dendritic cells (MoDCs) from patients with AD (n = 86) and control subjects (n = 84) were analyzed by means of flow cytometry, real-time PCR, ELISA, and HPLC.

RESULTS

We observed lower IFN-γ receptor II expression combined with higher IL-4 receptor α chain expression on epidermal DCs, monocytes, and MoDCs from patients with AD. Induction of IFN-γ-inducible factors, such as interferon regulatory factor 1, interferon-inducible protein 10, and indoleamine 2,3-dioxygenase, was attenuated in IFN-γ-pulsed MoDCs from patients with AD. Weaker signal transducer and activator of transcription 1 activation mirrored by lower phosphorylated signal transducer and activator of transcription 1 levels in response to IFN-γ stimulation could be observed in epidermal DCs, monocytes, and MoDCs from patients with AD.

CONCLUSION

Impaired IFN-γ signaling together with attenuated IFN-γ responses in DCs and their precursor cells might contribute to the T(H)2 bias in patients with AD.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

Hypothermia augments NF-kappaB activity and the production of IL-12 and IFN-gamma

BACKGROUND

The differentiation of Th1 and Th2 is strictly regulated by humoral and cellular factors. The imbalance between Th1 and Th2 is considered to be the pathogenesis of allergic and autoimmune disorders. It is important to elucidate the effect of environmental factors, such as temperature, on the expression of cytokines of Th1 and Th2.

METHODS

We investigated the expression of IFN-gamma, IL-4, IL-5, IL-10 and IL-12 from LPS- or PHA-stimulated PBMCs at 30 degrees C or 37 degrees C using ELISA and Real-time PCR. We measured the change of NF-kappaB activity at 30 degrees C or 37 degrees C with LPS stimulation using the reporter gene assay.

RESULTS

IFN-gamma production from LPS-stimulated PBMCs at 30 degrees C was up-regulated compared with 37 degrees C. IL-5 and IL-10 production from PHA-stimulated PBMCs at 30 degrees C were down-regulated compared with 37 degrees C. This augmented IFN-gamma production was caused by the up-regulation of IL-12 production from CD14+ blood monocytes. Both IL-12 mRNA and IL12 protein at 30 degrees C were up-regulated compared with 37 degrees C. NF-kappaB, the key molecule for the expression of IL-12, was also augmented at 30 degrees C compared with 37 degrees C.

CONCLUSIONS

Hypothermia up-regulated the expression of IL-12 and IFN-gamma due to the augmented NF-kappaB activity. It is suggested that hypothermia modifies the pattern of cytokine gene expression.

Hev b 6.01 and Hev b 5 induce pro-inflammatory cytokines and chemokines from peripheral blood mononuclear cells in latex allergy

BACKGROUND

Hev b 6.01 (prohevein) and Hev b 5 [acidic natural rubber latex (NRL) protein] are major IgE-binding allergens in NRL allergy.

OBJECTIVE

To examine allergen-specific cytokine and chemokine responses in NRL-allergic patients.

METHODS

Fourteen NRL-allergic patients and 10 healthy controls participated in the study. Hev b 6.01 and Hev b 5 were purified under non-denaturating conditions by chromatographic methods. Specific IgE antibodies were measured by ELISA and proliferation of peripheral blood mononuclear cells (PBMC) by (3)H-thymidine incorporation assay. Allergen-specific induction of cytokine and chemokine mRNA in PBMC was measured by real-time PCR and protein levels by ELISA. Surface expression of chemokine receptors was analysed by flow cytometry.

RESULTS

Twelve (86%) NRL-allergic patients had positive skin prick test reactions and IgE antibodies against Hev b 6.01, but less than 30% responded to Hev b 5. Cell proliferation against Hev b 6.01, but not against Hev b 5, was significantly increased. Both allergens elicited significantly higher expression of pro-inflammatory and T-helper type 2 cytokines (TNF, IL-12p40, IL-13) and chemokines (CCL3, CCL4, CCL20) in the NRL-allergic patients than in controls. Interestingly, mRNA expression of the regulatory cytokine TGF-beta1 was reduced, whereas IL-10 expression was enhanced after allergen stimulations in patients with NRL allergy. Finally, the NRL-allergic patients showed increased CCR4 expression on CD3(+)CD8(-) T cells and decreased CXCR3 expression on CD3(+)CD8(+) T cells.

CONCLUSION

Allergen-specific induction of cytokines and chemokines in PBMC and chemokine receptor expression on circulating T cells may contribute to the pathogenesis of NRL allergy.

Suppression of innate immune cytokines and interferon regulatory factor-1 by endogenous interferon-alpha in response to respiratory syncytial virus in neonate mononuclear cells

Respiratory syncytial virus (RSV) infections are extremely common in early childhood but are most severe in infants in the first few months of life. Unresponsive adaptive immunity and hyporesponsive innate immunity were previously found to be the typical responses of neonate mononuclear cells (MCs) to live RSV. Investigating the mechanism of innate immune hyporesponsiveness in neonate MCs to live RSV revealed that in contrast to the previously reported low expression of interferon (IFN)-gamma, IFN-alpha expression in response to live RSV was significantly greater than that observed in adult MCs. Inhibition of live RSV-induced IFN-alpha with anti-IFN-alpha antibodies in neonate MCs led to significant increases in innate cytokine [IFN-gamma, interleukin (IL)-12, IL-18 and tumor necrosis factor (TNF)-alpha] but not adaptive immune cytokine [IL-2] production. Although MCs from adults responded to live RSV with upregulation of interferon regulatory factor-1 (IRF-1) mRNA, IRF-1 mRNA in RSV-treated neonate MCs was not detectable. However, in the presence of anti-IFN-alpha antibodies, live RSV induced detectable IRF-1 mRNA expression in neonate MCs. These data support the possibility that the severity of early life RSV-induced illnesses may occur via a mechanism in which live RSV induces IFN-alpha that in turn leads to innate immune suppression in neonate MCs.

Adipokines in cord blood and risk of wheezing disorders within the first two years of life

BACKGROUND

Adipokines are involved in the regulation of many inflammatory processes and are present at very high concentrations in cord blood of term infants.

OBJECTIVE

We analysed data of a large prospective birth cohort study to examine whether adiponectin and leptin concentration in cord blood are determinants of wheezing disorders in children within the first 2 years of life.

METHODS

Seven hundred and forty mothers and their newborns were included in this analysis. Adiponectin and leptin concentrations were measured in cord blood. The cumulative incidence of physician-reported asthma or obstructive bronchitis was recorded during a 2-year follow-up.

RESULTS

During the first 2 years of life, asthma or obstructive bronchitis was reported by the caring paediatricians for 157 (19.6%) of the children. We found a strong interaction of cord blood adiponectin and history of atopic disease in the mother with respect to the risk of physician-reported asthma or obstructive bronchitis (P=0.006). Compared with children with cord blood levels in the middle quintile (reference category), the odds ratios for physician-reported asthma or obstructive bronchitis in the bottom quintile and top quintile were 0.14 [95% confidence interval (CI) 0.02-0.90] and 2.12 (95% CI 0.67-6.66), respectively (P for trend=0.0003), among children of mothers with a history of atopy. This association was independent of other established risk factors. Leptin levels in cord blood were not associated with risk of asthma or obstructive bronchitis.

CONCLUSIONS

In children of mothers with a history of atopy, concentrations of adiponectin in cord blood could play an important role in determining risk of wheezing disorders in early childhood.

Selective impairment of Toll-like receptor 2–mediated proinflammatory cytokine production by monocytes from patients with atopic dermatitis

BACKGROUND

The skin of patients with atopic dermatitis (AD) exhibits a striking susceptibility to infection with gram-positive bacteria and herpes simplex virus (HSV), which are known to stimulate Toll-like receptor (TLR) 2.

OBJECTIVE

We investigated whether TLR2-mediated proinflammatory cytokine production by monocytes is selectively impaired in patients with AD and, if so, whether high FcvarepsilonRI levels on the monocytes could be related to the impairment.

METHODS

The 2 subpopulations of monocytes, CD14(dim) proinflammatory and CD14(bright) classical monocytes, from patients with AD and healthy control subjects were stimulated to produce IL-1beta and TNF-alpha with phorbol 12-myristate 13-acetate/ionomycin, LPS (TLR4 ligand), or Pam3Cys (TLR2 ligand) for 4 hours, and simultaneous flow cytometric assessment of surface phenotype and intracellular cytokine synthesis was performed. Surface expression of TLR2, TLR4, and FcvarepsilonRI on the monocyte subpopulations was also assessed by means of flow cytometry.

RESULTS

TLR2-mediated IL-1beta and TNF-alpha production by either the CD14(dim) or CD14(bright) monocytes was found to be selectively impaired in patients with AD. The most remarkable reduction in TLR2-mediated proinflammatory cytokine production was observed in CD14(dim) monocytes expressing high FcvarepsilonRI levels from patients with AD. This reduction was restored by means of downregulation of their FcvarepsilonRI expression after preculture in the absence of IgE.

CONCLUSION

Monocytes, particularly the proinflammatory monocytes, from patients with AD are functionally defective in their capacity to produce proinflammatory cytokines on TLR2 stimuli in part because of the high levels of their FcvarepsilonRI expression.

CLINICAL IMPLICATIONS

This selective impairment of monocytes would explain why patients with AD are specifically susceptible to cutaneous staphylococcal and streptococcal and HSV infections.

mRNA expression and RNA editing (2451 C-to-U) of IL-12 receptor beta2 in adult atopic patients

Interleukin (IL)-12 activates T helper (Th) 1 cells to produce interferon (IFN)-gamma which inhibits atopic inflammation. IL-12 acts through interaction with its receptor, especially beta(2) subunit. In several studies, the low production of IFN-gamma in peripheral mononuclear cells of atopic patients on response to IL-12 stimulation has been reported. Therefore we investigated the IL-12 receptor beta(2) (IL-12R beta(2)) mRNA expression and RNA editing, nucleotide 2451 C-to-U conversion, to find the cause of low responsiveness to IL-12 in atopy. Quantitative real time PCR for mRNA expression and sequence analysis for RNA editing were performed in 80 atopic patients and 54 healthy controls. The expression of IL-12R beta(2) mRNA was significantly lower in atopic patients than healthy controls (p<0.05). In sequence analysis, RNA editing on nucleotide 2451 was not found from either atopic patients or healthy controls. In additional evaluation, there was no relationship between expression of IL-12R beta(2) mRNA and serum total IgE or blood eosinophil count. Reduced IL-12R beta(2) mRNA expression in atopic patients indicate the reduced capacity to respond to IL-12 which induce IFN-gamma production and this may contribute to Th2-skewed immune response in atopy.

Prevention of allergen-specific, Th2-biased immune responses in vivo: role of increased IL-12 and IL-18 responsiveness

The factors that control development of adaptive responses to exogenous Ag remain incompletely understood. An ability to selectively direct immunity toward a specific phenotype would be of clinical benefit in numerous immunological disorders. Administration of chemically modified allergen glutaraldehyde-polymerized OVA (OA-POL) leads to >90% reductions in murine IgE and >500-fold increases in IgG2c responses that develop upon subsequent immunization with native Ag. In the present study, we examine the mechanisms underlying this reorientation of the type 2 dominant response that would normally develop. Lack of endogenous IL-12 or IFN-gamma results in markedly reduced induction of IgG2c responses following OA-POL treatment, but only IFN-gamma(-/-) mice demonstrate reduced capacity to prevent IgE induction. This indicates that while both IL-12 and IFN-gamma are critical promoters of type 1 immunity, only IFN-gamma is required to maximally inhibit development of type 2 immune responses. Compared with OVA-immunized mice, CD69(+) T cells from OA-POL-immunized mice demonstrate elevated IL-12Rbeta(2), IL-18Ralpha, and IL-18Rbeta mRNA levels, as well as increased IFN-gamma production in response to rIL-12 or rIL-18 stimulation. Collectively, these data indicate that preventing induction of type 2 immune responses is critically dependent on altered T cell responsiveness to these cytokines. The finding that targeted, Ag-specific manipulation of IL-12 and IL-18 responsiveness can be used to shape the phenotype of the dominant immune response that develops suggests that specifically targeting IL-12 and IL-18 receptor expression may offer clinical options for clinical prophylaxis or intervention.

Inherited defects in the interferon-gamma receptor or interleukin-12 signalling pathways are not sufficient to cause allergic disease in children

T-helper (Th)2 cells, which produce the cytokines interleukins (IL)-4, IL-5 and IL-13, dominate T cell responses in allergic diseases. The Th1-type cytokines IL-12 and interferon-gamma (IFNgamma) are important in down-regulating Th2 responses to allergens. Patients with defects in the IL-12 receptor (IL-12R) or IFNgamma receptor (IFNgammaR) have abnormal responses to IL-12 or IFNgamma and a failure to produce normal levels of IFNgamma. Current paradigms of T-helper subset balance would predict a high prevalence of atopic illness in this group. We have studied a cohort of patients (n =29) with defects in these pathways to assess the prevalence of allergic disease. A questionnaire based on those developed for the International Study of Asthma and Allergy in Childhood (ISAAC) was used in conjunction with analysis of total and specific IgE to common aeroallergens. The prevalence of asthma, eczema and rhino-conjunctivitis (13.7%, 17.5% and 6.8% respectively) in this group was no higher than in comparable populations where prevalences of 13.9%, 7.9% and 13.5% are reported for asthma, eczema and rhinoconjunctivitis respectively. Patients with IFNgammaR defects had higher rates of clinical atopic illness than control populations and patients with IL-12R defects, with 28.5% prevalences for asthma and eczema, respectively. None of the patients suffered from severe clinical atopic disease. Defects in interferon-gamma receptor/interleukin-12 receptor responses are not sufficient to cause clinical allergic disease. Patients with defects in the interferon-gamma receptor pathway have a higher prevalence of high IgE and clinical atopic illness compared to control populations, supporting the concept that interferon-gamma receptor signalling plays a role in down-regulating type-2 cytokine responses.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Deficient translocation of c-Rel is associated with impaired Th1 cytokine production in T cells from atopic dermatitis patients

Decreased production of T helper type 1 (Th1) cytokines, such as interferon-gamma (IFN-gamma) or interleukin-2 (IL-2), is a hallmark of atopic diseases. While accessory signals from antigen-presenting cells may be missing, T cells themselves may be suppressed in their ability to produce substantial amounts of Th1 cytokines. We show, in this study, that T cell receptor (TCR)-activated T cells from atopic dermatitis (AD) patients proliferate less than control T cells and produce lower amounts of IFN-gamma and IL-2, but comparable amounts of IL-4. Because mice lacking the nuclear factor kappa B (NF-kappaB) transcription factors - p65 or c-Rel - show reduced Th1, but undisturbed Th2 responses, we investigated the role of c-Rel and p65 for Th1 cytokine production in T cells from healthy and severe AD patients. TCR-activated primary T cells from healthy donors treated with c-Rel antisense oligonucleotides produced lower levels of IL-2 and IFN-gamma and proliferated less efficiently than the corresponding control T cells. Moreover, transfection of primary T cells with c-Rel or p65 enhanced proliferation and production of IL-2 and IFN-gamma. Nuclear extracts of activated primary T cells from AD donors bound weakly to NF-kappaB-specific oligonucleotides, compared to extracts from healthy control T cells. Western blotting studies revealed that nuclear, but not cytosolic, extracts from T cells of AD patients lacked significant amounts of c-Rel and p65. T cell clones derived from AD patients failed to sufficiently translocate c-Rel and p65 into the nucleus following activation. Thus, impaired nuclear translocation of c-Rel and p65 may determine an impaired Th1 cytokine response in AD.

Low numbers of interleukin-12-producing cord blood mononuclear cells and immunoglobulin E sensitization in early childhood

BACKGROUND

Successful pregnancies are associated with skewing towards a Th2 cytokine profile. Cytokine responses to allergens can be detected in cord blood mononuclear cells (CBMC), suggesting allergen priming already in utero.

OBJECTIVE

To investigate the cytokine profile in CBMC after in vitro stimulation with allergens and to relate the responses to the outcome in terms of allergic disease at 2 years of age.

METHODS

CBMC were isolated from 82 children. The responses to ovalbumin (OVA), birch, cat and phytohaemagglutinin (PHA) were investigated by the ELISpot technique. The numbers of IFN-gamma-, IL-4- and IL-12-producing CBMC were counted for each stimulation. The children were followed prospectively; skin prick test (SPT) and RAST towards food and inhalant allergens were assessed at 24 months of age.

RESULTS

Sixteen (19.5%) children were classified as IgE sensitized (positive SPT; > or =3 mm and/or RAST; > or =0.35 kUA/L). The numbers of IL-12-producing CBMC after stimulation with birch, OVA and cat were lower among IgE-sensitized children, statistically significant for cat. IFN-gamma-producing cells, did not differ in numbers between the sensitized and non-sensitized children. Children who had atopic eczema/dermatitis syndrome (AEDS) during the observation (n=53) had significantly lower numbers of IFN-gamma-producing CBMC after stimulation with OVA and cat than their non-AEDS counterparts.

CONCLUSIONS

Although the numbers of infants in our study are limited our data suggest that a low number of IL-12-producing CBMC is associated with IgE sensitization during early childhood and that a reduced number of IFN-gamma-producing CBMC promotes the development of AEDS during the first 2 years of life.

Cytokines and transcription factors that regulate T helper cell differentiation: new players and new insights

The differentiation of naive CD4+ T cells into subsets of T helper cells is a pivotal process with major implications for host defense and the pathogenesis of immune-mediated diseases. Though the basic paradigm was discovered more than 15 years ago, new discoveries continue to be made that offer fresh insights into the regulation of this process. T helper (TH)1 cells produce interferon (IFN)-gamma, promoting cell-mediated immunity and control of intracellular pathogens. We now know that TH1 differentiation is regulated by transcription factors such as T-bet, Stat1, and Stat4, as well as cytokines such as IL-12, IL-23, IL-27, type I IFNs, and IFN-gamma. In contrast, TH2 cells produce IL-4, which promotes allergic responses and is important in host defense against helminths. The transcription factors Stat6, GATA-3, c-Maf, NFATs, and the cytokine IL-4 promote TH2 differentiation. These key regulators of TH differentiation are the subject of this review.

The biology of IL-12: coordinating innate and adaptive immune responses

Cytokines play critical roles in regulating all aspects of immune responses, including lymphoid development, homeostasis, differentiation, tolerance and memory. Interleukin (IL)-12 is especially important because its expression during infection regulates innate responses and determines the type and duration of adaptive immune response. IL-12 induces interferon-gamma (IFN-gamma) production by NK, T cells, dendritic cells (DC), and macrophages. IL-12 also promotes the differentiation of naïve CD4+ T cells into T helper 1 (Th1) cells that produce IFN-gamma and aid in cell-mediated immunity. As IL-12 is induced by microbial products and regulates the development of adaptive immune cells, IL-12 plays a central role in coordinating innate and adaptive immunity. IL-12 and the recently identified cytokines, IL-23 and IL-27, define a family of related cytokines that induce IFN-gamma production and promote T cell expansion and proliferation.

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 beta2 subunit of the interleukin-12 (IL-12) receptor (IL-12Rbeta2, 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-12Rbeta2 mRNA was analyzed by quantitative real-time PCR and the secretion of interferon-gamma (IFN-gamma), 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-12Rbeta2 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-gamma 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.

Cytokines and transcription factors that regulate T helper cell differentiation: new players and new insights

The differentiation of naive CD4+ T cells into subsets of T helper cells is a pivotal process with major implications for host defense and the pathogenesis of immune-mediated diseases. Though the basic paradigm was discovered more than 15 years ago, new discoveries continue to be made that offer fresh insights into the regulation of this process. T helper (TH)1 cells produce interferon (IFN)-gamma, promoting cell-mediated immunity and control of intracellular pathogens. We now know that TH1 differentiation is regulated by transcription factors such as T-bet, Stat1, and Stat4, as well as cytokines such as IL-12, IL-23, IL-27, type I IFNs, and IFN-gamma. In contrast, TH2 cells produce IL-4, which promotes allergic responses and is important in host defense against helminths. The transcription factors Stat6, GATA-3, c-Maf, NFATs, and the cytokine IL-4 promote TH2 differentiation. These key regulators of TH differentiation are the subject of this review.

The development of childhood asthma: lessons from the German Multicentre Allergy Study (MAS)

Epidemiological surveys have indicated that there has been a notable increase in the prevalence of both asthma and other allergic symptoms in children and young adults. Since it seems unlikely that genetic factors would contribute to the rising trend, environmental factors might play a major part in the development of childhood asthma. In a prospective birth-cohort study, we assessed the relevance of different exposures such as mite and cat allergen exposure, environmental tobacco smoke (ETS) exposure, early infectious diseases and vaccinations for the development of childhood asthma up to the age of 10 years. Data up to 7 years of age have been evaluated. Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 7 years were available for 939 children (72%). Assessments included repeated measurements of specific IgE to food and inhalant allergens, measurement of indoor allergen exposure at 6 months, 18 months and 3 years of age and yearly interviews by a paediatrician. At age 7 years, pulmonary function was tested and bronchial responsiveness was determined in 645 children. At age 7, the prevalence of wheezing in the past 12 months was 10% (94 out of 938), and 6.1% (57 out of 939) parents reported a doctor's diagnosis of asthma in their children. Sensitisation to indoor allergens was associated with asthma, wheeze and increased bronchial responsiveness. However, no relationship between early indoor allergen exposure and the prevalence of asthma, wheeze and bronchial responsiveness was seen. During the first 3 years of life, intra-uterine tobacco and consistent ETS exposure have an adjuvant effect on allergic sensitisation that is transient and restricted to children with a genetic predisposition for allergy. Children sensitised to any allergen early in life and sensitised to inhalant allergens by the age of 7 years were at a significantly increased risk of being asthmatic at this age (odds ratio (OR) = 10.12; 95% confidence interval (CI) = 3.81-26.88). Children with repeated episodes (> or =2) of runny nose before the age of 1 year were less likely to develop asthma by the age of 7 years (OR = 0.52; 95% CI = 0.29-0.92). Our data do not support the hypothesis that exposure to environmental allergens directly causes asthma in childhood but that induction of specific IgE responses and the development of childhood asthma are determined by independent factors. Indoor allergen avoidance is recommended as first line treatment in secondary and tertiary prevention; however, conclusions should be drawn with caution about the possible effect of primary preventative measures. Since allergic asthma seems to be a Th2-disease, immunomodulating factors such as early childhood infections, LPS-exposure or other factors influencing gene-environment interaction and individual susceptibility seem to be relevant for the development of childhood asthma.

Predominant expression of 950delCAG of IL-18R alpha chain cDNA is associated with reduced IFN-gamma production and high serum IgE levels in atopic Japanese children

BACKGROUND

We previously reported that serum IgE levels were negatively correlated with the amount of IFN-gamma produced by phytohemagglutinin-stimulated or IL-12-stimulated PBMCs and that one of the mechanisms of the pathogenesis of atopy was the reduced IFN-gamma production, which led to upregulated IgE production.

OBJECTIVE

IL-18 is also known to be a strong inducer of IFN-gamma production. However, it has not yet been determined whether IL-18 is associated with atopic disease.

METHODS

We investigated the response to IL-18 or IL-12 stimulation and the sequence of IL-18 receptor (IL-18R) alpha chain cDNA in 41 nonatopic controls and 39 atopic patients.

RESULTS

Serum IgE level was negatively correlated with IFN-gamma production by PBMCs stimulated with IL-18. The IL-18R alpha chain cDNA of atopic patients was sequenced. We identified a 3-base deletion of the IL-18R alpha chain cDNA (950delCAG ), which was generated by alternative splicing, as determined on the basis of genomic sequence data for the IL-18R alpha chain gene. PBMCs with the predominant expression of 950delCAG significantly showed the reduced IFN-gamma production after IL-18 stimulation. There was a significant difference in the expression pattern of the IL-18R alpha chain transcript between the atopic patients and the nonatopic controls.

CONCLUSION

According to these results, the dominant expression of the 950delCAG transcript of IL-18R alpha chain cDNA, which was associated with reduced IFN-gamma production by IL-18 stimulation and high serum IgE levels, is predisposition to some atopic diseases.

The childhood origins of asthma (COAST) study

Although asthma is probably a heterogeneous disease or syndrome, three factors and/or events consistently emerge for their ability to significantly influence asthma inception in the first decade of life: immune response aberrations, which appear to be defined best by the concept of cytokine dysregulation; lower respiratory tract infections, in particular respiratory syncytial virus (RSV); and some form of gene-environment interaction that needs to occur at a critical time-period in the development of the immune system or the lung. It remains to be firmly established, however, how any one or all of these factors, either independently or interactively, influence the development of childhood asthma. For example, cytokine dysregulation (T helper 1/T helper 2 imbalance) appears to track best epidemiologically with allergic diseases. As not everyone who undergoes allergic sensitization develops asthma, some other host-environment interaction must need to occur to target this chronic allergic inflammatory response to the lower airway. Some evidence suggests that this event might be an environmental insult in the form of a virus infection, particularly with RSV, which has a predilection for infecting, destroying, and/or in some way biologically altering lower airway epithelium. However, only a fraction of children develop recurrent wheezing following RSV infections, despite the fact that nearly all children have been infected at least once by 2 years of age. Thus, although RSV infections may have the potential of targeting the inflammatory response to the lower airway, they may only be able to do so during a vulnerable time-period during development of the immune system or lung. This developmental component may further reflect important gene-environment interactions that regulate both short- and long-term airway physiological alterations that manifest themselves clinically as childhood asthma. Efforts to determine and define the importance of these three factors to asthma pathogenesis are the focus and goal of the COAST (Childhood Origins of Asthma) project.

IFN-gamma production in response to IL-18 or IL-12 stimulation by peripheral blood mononuclear cells of atopic patients

BACKGROUND

Several studies have shown that interleukin (IL)-4 and interferon-gamma (IFN-gamma) are important for the regulation of immunoglobulin E (IgE) production and that IL-18 and IL-12 induce IFN-gamma.

OBJECTIVE

IFN-gamma production in response to IL-18 or IL-12 stimulation was investigated in peripheral blood mononuclear cells (PBMCs) of atopic patients with various levels of serum IgE.

METHODS

Cytokine production from PBMCs was measured following stimulation with a non-specific stimulator (phytohemagglutinin: PHA), IL-18 or IL-12 in 12 healthy controls and 26 atopic patients with various serum IgE levels.

RESULTS

IFN-gamma production by IL-18-stimulated PBMCs was positively correlated with IFN-gamma production by IL-12-stimulated PBMCs (P < 0.05). However some atopic patients showed discrepancy between the levels of IFN-gamma production stimulated by IL-12 and by IL-18.

CONCLUSIONS

The results shown here suggest the presence of abnormalities in the IL-12 and/or IL-18 signalling pathways, such as genetic defects in the atopic patients.