Atopy and the human IL-4 receptor alpha chain

Safety, Pharmacokinetics and Preliminary Efficacy of IL4-Rα Monoclonal Antibody AK120 in Both Healthy and Atopic Dermatitis Subjects: A Phase I, Randomized, Two-Part, Double-Blind, Placebo-Controlled, Dose-Escalation, First-In-Human Clinical Study

INTRODUCTION

Interleukin-4 (IL-4) and interleukin-13 (IL-13) are two essential cytokines involved in the T helper 2 (Th2)-mediated inflammatory response to diseases, such as atopic dermatitis (AD). AK120 is a humanized immunoglobulin G subclass 4 (IgG4) monoclonal antibody (mAb) directed against the IL-4 receptor alpha (IL-4Rα) subunit shared by the IL-4 and IL-13 receptor complexes. This mAb inhibits the signaling of the IL-4 and IL-13 cytokines.

METHODS

The study consisted of two parts. Part 1 was a single ascending dose (SAD) study with five cohorts (receiving 15, 50, 150, 300 or 600 mg of AK120, respectively) of healthy subjects; part 2 was a multiple ascending dose (MAD) study with four cohorts (receiving AK120 at doses of 300 mg once every 2 weeks [Q2W], 300 mg once weekly [QW], 150 mg QW or 75 mg QW) of subjects with AD. A total of 81 subjects (40 in part 1, 41 in part 2) were enrolled in the study.

RESULTS

The compound was safe and well tolerated in both a SAD up to 600 mg in healthy subjects and in a MAD from 75 to 600 mg in subjects with AD. The exposure of AK120 increased in an approximately dose-dependent manner upon subcutaneous dosing. The levels of the biomarkers serum thymus and activation-regulated chemokine ligand 17 (TARC/CCL17) and immunoglobulin E decreased from baseline after AK120 administration, indicating the inhibition of the IL-4/IL-13 signaling pathways. AK120 showed improved Eczema Area and Severity Index (EASI) scores, and the proportion of subjects with Investigator Global Assessment (IGA) score 0/1 increased after AK120 treatment.

CONCLUSIONS

AK120 exhibited an acceptable safety profile in healthy and AD subjects, and showed preliminary efficacy. These findings support the continued investigation of AK120 for treating AD.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identification number: NCT04256174.

Effects of korean red ginseng extract for the treatment of atopic dermatitis-like skin lesions in mice

Atopic dermatitis (AD) is an allergic, inflammatory skin disease characterized by chronic eczema and mechanical injury to the skin, caused by scratching. Korean red ginseng (RG) has diverse biological activities, but the molecular effects of RG on allergic diseases, like AD, are unclear. The present study was designed to investigate whether RG inhibits 1-chloro-2,4-dinitrobenzene (DNCB)-induced AD in a mouse model. DNCB was applied topically on the dorsal surface of Balb/c mice to induce AD-like skin lesions. We observed the scratching behavior and examined the serum IgE level and interleukin (IL)-4 and IL-10 in splenocytes compared with dexamethasone. We also evaluated the DNCB-induced mitogen-activated protein kinases (MAPKs), NF-κB, and Ikaros activities after RG treatment using reverse transcriptase-polymerase chain reaction, Western blotting, and ELISA. Our data showed that the topical application of RG significantly improved the AD-like skin lesions and scratching behavior. RG decreased not only the mRNA expression of IL-4 and IL-10, but also the secretion of IL-4 protein and serum IgE in mice. Additionally, RG treatment decreased the DNCB-induced MAPKs activity and subsequent Ikaros translocation irrespective of NF-κB. We suggest that RG may be useful as a therapeutic nutrition for the treatment of AD.

Current concepts of IgE regulation and impact of genetic determinants

Immunoglobulin E (IgE) mediated immune responses seem to be directed against parasites and neoplasms, but are best known for their involvement in allergies. The IgE network is tightly controlled at different levels as outlined in this review. Genetic determinants were suspected to influence IgE regulation and IgE levels considerably for many years. Linkage and candidate gene studies suggested a number of loci and genes to correlate with total serum IgE levels, and recently genome-wide association studies (GWAS) provided the power to identify genetic determinants for total serum IgE levels: 1q23 (FCER1A), 5q31 (RAD50, IL13, IL4), 12q13 (STAT6), 6p21.3 (HLA-DRB1) and 16p12 (IL4R, IL21R). In this review, we analyse the potential role of these GWAS hits in the IgE network and suggest mechanisms of how genes and genetic variants in these loci may influence IgE regulation.

The differences in the involvements of loci of promoter region and Ile50Val in interleukin-4 receptor α chain gene between atopic dermatitis and Japanese cedar pollinosis

BACKGROUND

Atopic dermatitis (AD) and Japanese cedar pollinosis (JCP) are common chronically allergic diseases associated with the activation of T-helper 2 cells. Recent studies have shown that polymorphisms in the genes for IL-4 receptor α chain (IL4RA) may contribute to susceptibility of AD and JCP, although the differences in the involvements of loci of IL4RA gene between AD and JCP are unclear. In this study, we investigated the role of polymorphisms in IL-4RA gene in conferring susceptibility to the development of AD and/or JCP using a family analysis and an association analysis in a Japanese population.

METHODS

Five polymorphisms in the IL-4RA gene, C-3223T, T-1914C, T-890C, Ile50Val and Glu375Ala, have been genotyped using PCR-based methods in 75 trios families, including 15 AD families, 30 JCP families, and 30 families with combination of AD and JCP in the family analysis. Forty-five AD, 60 JCP and 125 control children constituted the association study.

RESULTS

The transmission disequilibrium test showed that the allele of Ile50 was significantly transmitted to children with JCP alone (p < 0.05). Haplotype analysis showed that the -3223T/Ile50 haplotype was preferentially transmitted to both AD (p < 0.01) and JCP children (p < 0.01), while that the C-3223/Ile50 haplotype was preferentially transmitted to only JCP children (p < 0.01). The association study showed that -3223T and haplotype of -3223T/Ile50 were associated with AD children, but not with JCP. Ile50 was associated with both AD and JCP.

CONCLUSIONS

Our data suggest that -3223T and the -3223T/Ile50 haplotype were risk factors for AD. Ile50 allele seems to be involved in both JCP and AD. Interactions of the IL-4RA loci may play a role both conferring susceptibility and modulating severity of AD.

Genetics of asthma: potential implications for reducing asthma disparities

Although genetic factors may partly explain the differences in asthma prevalence, morbidity, and mortality among ethnic groups in the United States, few studies of the genetics of asthma have included members of ethnic minority groups. Only one genome-wide linkage analysis of asthma and/or asthma-related phenotypes (conducted by the Collaborative Study on the Genetics of Asthma) has included any members of ethnic minority populations. The interpretation of the findings of genetic association studies of asthma in ethnic minority groups is complicated by reduced statistical power due to small sample sizes; the failure to correct for multiple comparisons; a lack of homogeneity of the populations studied with regard to area of residence, ancestral background, and/or country of origin; a lack of measurement of relevant environmental exposures; and (for case-control studies of genetic association) a lack of detection and control of potential population stratification. Genetic studies may improve our understanding of asthma and lead to new methods to prevent, diagnose, and treat this disease. Limited study of asthma genetics in ethnic minority populations is unacceptable, as it may prevent these groups from benefiting from future developments in asthma management and thus widen existing disparities in asthma care. Future genetic association studies of asthma among ethnic minorities in the United States should include large samples of populations that have been adequately defined with regard to area of residence, self-designated ancestry, and country of origin. These studies should also include an adequate assessment of potentially relevant environmental exposures and (for case-control association studies) population stratification.

In utero exposure to environmental tobacco smoke potentiates adult responses to allergen in BALB/c mice

BACKGROUND

Fetal stress has been linked to adult atherosclerosis, obesity, and diabetes. Epidemiology studies have associated fetal exposure to maternal smoking and postnatal exposure to environmental tobacco smoke (ETS) with increased asthma risk.

OBJECTIVE

We tested the hypothesis, in a mouse model of asthma, that in utero ETS exposure alters airway function and respiratory immune responses in adults.

METHODS

Pregnant Balb/c mice were exposed daily to ETS or HEPA-filtered air (AIR). Offspring inhaled aerosolized ovalbumin (OVA) or saline in weeks 7-8. Regardless of whether they inhaled OVA or saline, mice were sensitized by OVA injections in weeks 11 and 13 followed by OVA aerosol challenge in weeks 14-15. At three time points, we assessed OVA-specific serum immunoglobins, bronchoalveolar lavage cells and cytokines, lung and nasal histopathology, and airway hyperresponsiveness (AHR).

RESULTS

At 6 weeks, we found no significant differences between in utero ETS and AIR mice. At 10 weeks, following OVA aerosol, ETS mice displayed greater AHR than AIR mice (alpha = 0.05), unaccompanied by changes in histopathology, cytokine profile, or antibody levels. At 15 weeks, mice that had inhaled saline in weeks 7-8 developed airway inflammation: eosinophilia (alpha = 0.05), interleukin-5 (alpha = 0.05), and AHR (alpha = 0.05) were greater in ETS mice than in AIR mice. Mice that had inhaled OVA in weeks 7-8 demonstrated no airway inflammation after sensitization and challenge.

CONCLUSION

In utero ETS exposure exacerbates subsequent adult responses to initial allergen exposure.

Genetic and respiratory tract risk factors for aspergillosis: ABPA and asthma with fungal sensitization

Allergic bronchopulmonary aspergillosis (ABPA) is a Th2 allergic hypersensitivity lung disease due to bronchial colonization of Aspergillus fumigatus that affects 1-2% of asthmatic and 7-9% of cystic fibrosis (CF) patients. We hypothesize that genetic risk factors predispose these patients to develop ABPA. We previously reported HLA-DR2 and DR5 restriction as a risk factor for the development of ABPA. We further propose that HLA-DR restriction is necessary but not sufficient for the development of ABPA. Recently, we reported that IL-4Rα single nucleotide polymorphisms (SNP) and in particular the ile75val SNP in the IL-4 binding region is another risk factor and is associated with increased sensitivity to IL-4 stimulation. It has been reported that the combination of IL-4Rα and IL-13 SNP, ile75val/arg110gln, is associated with more severe asthma. In preliminary studies, we have observed increased frequency of this combination in ABPA asthmatic and CF patients. Another genetic risk factor reported by Brouard et al. is the -1082 GG genotype in the IL-10 promoter in CF patients for the colonization of A. fumigatus and development of ABPA. This genotype was associated with increased plasma IL-10 levels, and perhaps may be associated with increased skewing of Th2 Aspergillus responses rather than down-regulation of inflammatory responses. We hypothesize that increased sensitivity of IL-4 mediated activities secondary to polymorphisms IL-4R in conjunction of other polymorphisms such as IL-13 and IL-10 in conjunction with HLA-DR2/DR5 restriction to Aspergillus antigens in ABPA patients result in increased B-cell activity, monocyte/dendritic cell phenotype that skews Th2 responses, and skewing of Aspergillus-specific Th2 cells. This model system may be applicable to other fungi such as Alternaria and Cladosporium which is associated with increased asthma severity.

Cytokines, allergy, and asthma

PURPOSE OF REVIEW

This review examines recent articles on the relationship of cytokines to allergy and asthma with particular emphasis on immune mechanisms involved in disease development in early life.

RECENT FINDINGS

It was previously proposed that reduced microbial exposure in early life is responsible for a shift of the Th1/Th2 balance in the immune system towards the proallergenic Th2 response. This Th1/Th2 imbalance results in the clinical expression of allergy and/or asthma. In recent years, accumulating data from mice and humans have identified Th2 cytokines [interleukin (IL)-4, IL-13, and IL-5] as major contributors to allergy and asthma. Interestingly, the Th1 cytokine interferon-gamma has recently been shown to act concurrently with Th2 cytokines in maintaining the chronic inflammatory response in allergic diseases, particularly in asthmatic airways. Most recently, evidence suggests that suppression of T-regulatory cells may contribute to the underlying immune mechanisms involved in allergy and asthma.

SUMMARY

An enhanced Th2 immune response and the elaboration of cytokines such as IL-4, IL-13, and IL-5 contribute to the induction of allergy and asthma. Interferon-gamma, a Th1 cytokine, acts in conjunction with Th2 (IL-4, IL-13, and IL-5) in maintaining chronic allergic inflammation. The mechanisms leading to an enhanced Th2 response are still controversial. Th2-dominated immune responses may result from immune suppression of T-regulatory cells as well as Th1 cells. Understanding early-life immune mechanisms responsible for atopic diseases, specifically how cytokines of T-regulatory cells act to balance the Th1 and Th2 immune response, continues to be a fruitful area of research.

The genetics of atopic dermatitis: recent findings and future options

Atopic dermatitis (AD) is a chronic pruritic skin disease affecting up to 15% of children in industrialized countries. AD belongs to the group of allergic disorders that include food allergy, allergic rhinitis, and asthma. A multifactorial background for AD has been suggested, with genetic as well as environmental factors influencing disease development. Genome-wide screens for AD have been completed in four different populations to date. Interestingly, the susceptibility regions identified for AD show little overlap with asthma susceptibility regions, suggesting that, at least in part, separate genes might be involved in the pathogenesis of the different atopic disorders. Instead, some of the identified regions overlap with susceptibility regions for psoriasis, another chronic skin disease. Thus, genes expressed in the skin might play an important role in AD pathogenesis, in addition to genes influencing atopic diatheses. Although no veritable "AD gene" has been identified by positional cloning to date, examples from other complex genetic disorders such as asthma show that this goal is likely to be reached in the near future. Candidate gene studies, on the other hand, have identified 19 genes that were shown to be associated with AD in at least one study. The results of genome-wide screens as well as candidate gene studies are evaluated here in detail.

Exposure of adult mice to environmental tobacco smoke fails to enhance the immune response to inhaled antigen

Epidemiologic evidence supports a role for environmental tobacco smoke (ETS) in the occurrence and severity of allergies/asthma. However, neither the precise combination of ETS and allergen exposure nor the mechanism (or mechanisms) by which these factors interact and contribute to asthma induction is known. Animal model studies have failed to establish a convincing relationship between ETS exposure and asthma induction, perhaps because of methodological inadequacies. Here, we tested the hypothesis that ETS inhalation would provoke an asthmatic response by overcoming normal airway tolerance to inhaled antigens. Our protocol combined daily ETS exposure with nose-only sensitization to ovalbumin. Three strains of mice were tested, each with a different level of susceptibility to airway hypersensitivity. Immunological responses were assessed by immunoglobulin production. Airway inflammation was assessed by bronchoalveolar lavage differentials and lung histopathology. Airway hyperresponsiveness was determined by methacholine challenge. The mice produced ovalbumin-specific antibodies following ovalbumin exposure in a strain-dependent manner. Only the A/J mice produced detectable levels of ovalbumin-specific immunoglobulin (Ig) E. Both A/J and BALB/c mice produced ovalbumin-specific IgG1 antibodies. The C57Bl/6 mice did not produce detectable levels of antibodies. The A/J mice also exhibited airway inflammation following ovalbumin exposure. Neither the C57Bl/6 nor the BALB/c mice exhibited signs of airway inflammation. Exposure to ETS failed to enhance ovalbumin-specific antibody production, airway inflammation, or hyperresponsiveness. Together these results indicate that ETS exposure accompanied by nose-only allergen sensitization fails to overcome aerosol tolerance in adult mice.

Effects of common atopy-associated amino acid substitutions in the IL-4 receptor alpha chain on IL-4 induced phenotypes

The human IL-4 receptor alpha chain gene (IL4R) is highly polymorphic and controversial reports have been published with respect to the association of different single nucleotide polymorphisms (SNPs) with atopy markers. Here we analyzed the functional and associational relevance of common IL4R coding SNPs. Transfection of B cell lines expressing the IL-4R variant V75+R576 did not result in enhanced IL-4 induced CD23 expression compared to cell lines expressing the wild type IL-4R alpha chain. Transfection of the IL-4R variant P503 into a murine T cell line did not influence IL-4 induced T-cell proliferation compared to wild type constructs. Analysis of six IL4R coding SNPs (I75V, E400A, C431R, S436L, S503P, Q576R) and common haplotypes (frequency >/=0.05%) in blood donors (n=300) did not indicate a significant association with elevated serum IgE level. Moreover, the most informative IL4R coding SNPs (I75V, C431R, Q576R) and related two- and three-point haplotypes (frequency >/=0.05%) were analyzed in a second, extended group of blood donors (n=689). Again, no significant association with elevated serum IgE was detectable. We conclude that common coding SNPs in the IL4R gene are unlikely to contribute significantly to increased IgE levels and variations outside the coding region may influence atopy susceptibility.

Immunopathogenesis of allergic bronchopulmonary aspergillosis in cystic fibrosis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity lung disease mediated by an allergic late-phase inflammatory response to Aspergillus fumigatus antigens. ABPA is characterized by markedly elevated Aspergillus-specific and total IgE levels and eosinophilia, and manifested by wheezing, pulmonary infiltrates, and bronchiectasis and fibrosis, which afflict asthmatic and cystic fibrosis (CF) patients. We propose that ABPA develops in genetically susceptible CF patients due to HLA-DR2 and DR5 restriction, increased sensitivity to IL-4 stimulation, and increased A. fumigatus allergen-specific Th2 CD4+ T-cell-mediated responses. In addition, A. fumigatus proteases play a role in facilitation of antigen transport across the epithelial cell layer by damaging the epithelial integrity and by a direct interaction with epithelial cell surface receptors, resulting in pro-inflammatory cytokine production and corresponding inflammatory responses.

Differential activation of signal transducer and activator of transcription 6 in B cells from allergic children and their non-allergic siblings

BACKGROUND

The germline (GL) epsilon promoter is regulated by IL-4 and is essential for class switching to IgE. IL-4-induced gene expression is largely mediated through activation of latent transcription factor STAT6 (signal transducer and activator of transcription 6).

OBJECTIVE

We investigated whether increased levels of IgE in allergic individuals may be associated with alteration in the level or activation of STAT6 and subsequent increase in GL epsilon promoter activity.

METHODS

Electrophoretic mobility shift assay and Western blotting assays were used to investigate the level of expression and activation of STAT6 in Epstein-Barr virus (EBV)-transformed B cell lines from children with birch pollen allergy and their non-allergic siblings. The activity of the GL epsilon promoter was tested in a transient transfection assay.

RESULTS

STAT6 was expressed at the same level in all B cell lines tested. In two out of five sibling pairs STAT6 was activated by IL-4 more efficiently in the allergic individuals but in the three other pairs the opposite was found. In transient transfections, no difference in IL-4-induced GL epsilon promoter function was detected, although basal promoter activity varied between allergic and healthy siblings in two out of five pairs.

CONCLUSIONS

We demonstrate for the first time that upon IL-4 signalling STAT6 transcription factor activation differs in B cells from different individuals. Although we did not find any association between STAT6 activation and allergy, we do not exclude a possibility that stronger activation of this transcription factor is associated with an expression of allergic phenotype.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.

High contribution contrast between the genes of eosinophil peroxidase and IL-4 receptor α-chain in Japanese cedar pollinosis

BACKGROUND

Japanese cedar pollinosis is the most common form of hayfever in Japan in spring and has remarkably increased since 1960.

OBJECTIVE

We sought to clarify the candidate genes for cedar pollinosis using a case-control study.

METHODS

After diagnosing 351 subjects on the basis of an intradermal test, nasal provocation test, and questionnaire regarding nasal and conjunctival symptoms, we determined the blood-specific IgE values and genotypes of eosinophil peroxidase (EPO) and interleukin-4 receptor alpha-chain (IL4RA) in 145 patients with pollinosis and 206 healthy subjects, including 75 healthy subjects with higher specific IgE values.

RESULTS

We found significant differences in the frequencies of Pro358Leu in EPO and of Ile50Val and Glu375Ala in IL4RA between patients and healthy subjects. There was a significantly higher frequency of 358Leu in EPO in patients than in healthy subjects showing a higher specific IgE value. In contrast, we recognized significant changes in the prevalence of Ile50Val and Glu375Ala in IL4RA in healthy subjects with a normal IgE value compared with those in healthy subjects with a higher specific IgE value. The relationship between EPO polymorphisms and the onset of symptoms was exactly opposite that for IL4RA.

CONCLUSIONS

These results suggest that Pro358Leu in EPO is strongly involved in the development of cedar pollinosis. Ile50Val and Glu375Ala in IL4RA seem to be related to cedar pollen sensitization. Subjects with Ile50 or Glu375 might develop cedar pollinosis with increased exposure to cedar pollen.

Comparative analysis of mononuclear cell surface markers in atopic processes--a preliminary study

Atopic disorders are driven by the Th2 cell subset. We have determined the expression of costimulatory molecules and cell surface markers on peripheral CD4+ T cells and antigen presenting cells, in different atopic diseases, and we have also tried to correlate the expression of these markers with the severity of the disease. Cells from patients with atopic and contact dermatitis, mild or severe asthma, and symptomatic and non-symptomatic atopic rhinitis were analyzed by flow cytometry. Our results showed that CD30, CD124, and CD152 expression on CD4+ T cells was significantly higher in atopic dermatitis than in contact dermatitis patients (p < 0.05). It was interesting to observe that the cell surface expression of CD80 in T and B cells from atopic dermatitis patients was not enhanced as opposed to the other atopic diseases we analyzed. Our results suggest that there are differences in the immune mechanisms involved in the different atopic diseases, and that expression of CD30 in CD4+ T cells might be a marker of disease activity in atopic dermatitis.

Present status on the genetic studies of asthma

Asthma, one of the most common chronic diseases, is a complex and heterogeneous disorder. The results of genome screens for asthma-related traits in 11 different populations identified at least 18 regions of the genome that probably house asthma/atopy genes. The most consistently replicated regions are on chromosomes 2q, 5q, 6p, 12q and 13q. Positional cloning projects are ongoing in laboratories around the world to identify the asthma susceptibility loci in these regions. In addition, many candidate genes have been associated with asthma phenotypes, such as the genes in the IL-4/IL-13 pathway.

Asthma and IL-4 receptor alpha gene variants

Linkage of allergy to chromosome 16 has been described in several studies, together with a positive association with interleukin 4 receptor alpha gene variants. Our aim was to replicate these findings in a sample of German and Swedish families recruited through sib-pairs affected by bronchial asthma. None of the markers showed linkage with the main phenotype of asthma or with total serum IgE. Seropositivity to D. pteronyssinus showed borderline significance in a region flanking the IL4Ralpha location. Single nucleotide polymorphisms (SNPs) leading to the protein exchanges I50V, E375A, C406R, S478P and Q551R in the IL-4 receptor alpha were examined for allele sharing in sibs with asthma. Multiple regression analysis was performed for association with total serum IgE and specific IgE. Allele sharing of IL4Ralpha SNPs in asthmatic children was not significantly increased for any of the examined SNPs except for the intracytoplasmatic polymorphism 551R (0.79 vs. 0.84 expected, P = 0.044). The variants 50V, 478P and 551R were associated with slightly increased, and 375A and 406R with decreased total IgE levels, all at a non-significant level. None of the examined IL4Ralpha variants were correlated to asthma severity. In summary, a single gene effect of IL4Ralpha variants or any other gene on chromosome 16 could not be shown in this selected population of children with asthma. As there could be interactions with multiple genetic and environmental factors, IL4Ralpha could still be involved in asthma pathogenesis.

IL-4 receptor alpha chain genetic polymorphism and total IgE levels in the English population: two-locus haplotypes are more informative than individual SNPs

The IL-4RA locus encodes for the alpha chain of the IL-4 receptor, and is both a functional and positional candidate gene for atopy and allergic disease. Recently Ober et al. have shown that the study of haplotypes at multiple loci in the IL-4RA gene could be more informative than the separate study of single nucleotide polymorphisms (SNPs). One hundred and fifty subjects affected by atopic asthma and 150 healthy control subjects were studied in the English population (Oxford district). Subjects and controls were genotyped for the Ile50Val, Ser478Pro and Gln551Arg polymorphism of the IL-4 receptor alpha chain. The distribution of haplotypes 50-478 shows a highly significant association with IgE levels. In particular, the haplotype Val50/Pro478 is much less frequent in subjects with IgE levels > 100 U mL-1 than in those with IgE levels < 100 U mL-1. Furthermore, the distribution of haplotype 50-551 shows a weak association with IgE levels that is lacking for 478-551 haplotypes. A lower frequency of the Val50/Pro478 haplotype is also observed among asthmatic subjects as compared to healthy controls. With regard to individual SNPs (50 478 and 551), no significant association has been observed with IgE levels or with asthma, thus confirming the higher informative value of the haplotype analysis as compared to separate study on SNPs.

Regulation of IL-13 production by histamine in cloned murine T helper type 2 cells

Histamine affects the balance of T helper type 1 (Th1) and T helper type 2 (Th2) cytokines by shifting cytokine production from a Th1 to a Th2 pattern. Interleukin-13 (IL-13) is an important autacoid mediator that has been implicated in the development of allergic disease. This study was designed to investigate the mechanisms of regulation of IL-13 by histamine in Th2 cells. D10.G4.1 cells, a murine Th2 cell line, were treated with histamine (10(-8)-10(-4) M) and then activated with PMA (phorbol 12 myristate 13-acetate) plus ionomycin or alphaCD3. Levels of IL-13 production were then measured by enzyme-linked immunosorbent assay (ELISA) and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Cells were pretreated with histamine receptor antagonists pyrilamine, ranitidine, cimetidine and thioperamide to determine the involvement of histamine receptors. Cells were also pretreated with protein kinase A (PKA) inhibitors N-[2-(methylaminoethyl)]-5-isoquinoline-sulfonamide (H-8) and Rp-diastereomer of adenosine cyclic 3'5'-phosphorothionate (Rp-cAMPS), and Janus kinase-signal transducer and activator of transcription (Jak-STAT) inhibitor tyrphostin AG490 prior to the addition of histamine. H-8 is an inhibitor of the catalytic subunit of PKA while Rp-cAMPS is an inhibitor of the regulatory subunit of PKA. Tyrphostin is an inhibitor of Jak2, Jak3, STATI, STAT3 and STAT5. Finally, cells were pretreated with IL-12, a monokine known to repress STAT6 DNA binding. We found that histamine dose-dependently enhanced IL-13 secretion and mRNA levels in Th2 cells via H1 and H2 receptors. Pretreatment of cells with H-8, Rp-cAMPS and tyrphostin prevented histamine-induced secretion and transcription of IL-13. Likewise, pretreatment of Th2 cells with IL-12 also reversed histamine's effects on IL-13 secretion from stimulatory to inhibitory. These observations suggest a role for PKA and the Jak-STAT pathway in histamine-mediated elevation of IL-13 secretion and transcription.

Current concepts on the genetics of asthma

Asthma is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having small effects. Numerous asthma and atopy loci have been reported in studies demonstrating associations and/or linkage of the asthma-associated phenotypes, atopy, elevated IgE levels, and bronchial hyperresponsiveness to alleles of microsatellite markers and single nucleotide polymorphisms within specific cytokine/chemokine and IgE regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. This review compiles the evidence that supports linkage and associations to the various genetic loci and candidate genes. Whereas significant progress has been made in the field of asthma genetics in the past decade, the roles of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype remain to be determined.

Regulation of allergic airways inflammation by cytokines and glucocorticoids

Cytokines mediate the allergic inflammatory response of the airways, and glucocorticosteroids ameliorate allergy symptoms by regulating cytokine expression. Recent studies provide insight into the manner by which cytokines work together to mediate allergic airway disease. Real progress has also been gained in our understanding of subcellular mechanisms of allergic inflammation, particularly the role of transcription factors in regulating the expression of specific cytokine profiles and the differentiation of the TH2 subset. This article provides an update of recently reported findings in this field and highlights emerging concepts of allergic inflammation.