IL-4 and IL-5 mRNA and protein in bronchial biopsies from patients with atopic and nonatopic asthma: evidence against "intrinsic" asthma being a distinct immunopathologic entity

Evaluation of airway inflammation by quantitative Th1/Th2 cytokine mRNA measurement in sputum of asthma patients

BACKGROUND

Asthma is a chronic inflammatory disorder of the airways driven by T cell activation. Th2 cells and their cytokines are thought to play a role in the pathophysiology of allergic as well as non-allergic asthma.

METHODS

Airway cells were obtained by sputum induction from 15 healthy and 39 asthmatic individuals and the airway T cell cytokine profiles (interleukin (IL)-4, IL-5, IL-13, IL-10 and interferon (IFN)-gamma) at the mRNA level were studied by real time RT-PCR.

RESULTS

Asthma patients had increased expression of IL-5 (p = 0.001) and IL-13 (p = 0.03) mRNA in sputum compared with non-asthmatic controls. IL-4 mRNA and IFN-gamma mRNA were detectable in the sputum of 44% and 21% of patients, respectively, but not in controls. Sputum IL-10 mRNA levels did not differ significantly between patients and controls. Sputum mRNA expression levels of IL-4, IL-5, and IL-13 were significantly correlated with the percentage of eosinophils and were higher in subjects with allergic asthma than in those with non-allergic asthma (p = 0.03, p = 0.02 and p = 0.0002, respectively); they did not differ between mild asthmatic subjects and those with moderate to severe asthma. In contrast, IFN-gamma mRNA expression was higher in non-allergic than in allergic patients (p = 0.04) and higher in patients with moderate to severe asthma than in those with mild asthma (p<0.01). Sputum IL-5 mRNA levels (but not the other cytokine mRNA levels) were also correlated with exhaled nitric oxide (eNO) and with bronchial hyperreactivity expressed as the histamine concentration resulting in a 20% decrease in forced expiratory volume in 1 second.

CONCLUSION

Real time RT-PCR analysis of mRNA in induced sputum confirms a predominance of Th2 cytokines in both allergic and non-allergic asthma. IL-5 levels reflect eosinophil infiltration as well as eNO levels and hyperreactivity, and levels of the Th1 cytokine IFN-gamma indicate asthma severity. The technique is a promising tool for use in further studies of asthma severity and disease activity.

Airway generation-specific differences in the spatial distribution of immune cells and cytokines in allergen-challenged rhesus monkeys

BACKGROUND

Accumulation of immune cell populations and their cytokine products within tracheobronchial airways contributes to the pathogenesis of allergic asthma. It has been postulated that peripheral regions of the lung play a more significant role than proximal airways with regard to inflammatory events and airflow obstruction.

OBJECTIVE

To determine whether immune cell populations and associated cytokines are uniformly distributed throughout the conducting airway tree in a non-human primate model of allergic asthma.

METHODS

We used a stereologic approach with a stratified sampling scheme to measure the volume density of immune cells within the epithelium and interstitium of trachea and 4-5 intrapulmonary airway generations from house dust mite (HDM) (Dermatophagoides farinae)-challenged adult monkeys. In conjunction with immune cell distribution profiles, mRNA levels for 21 cytokines/chemokines and three chemokine receptors were evaluated at four different airway generations from microdissected lungs.

RESULTS

In HDM-challenged monkeys, the volume of CD1a+ dendritic cells, CD4+ T helper lymphocytes, CD25+ cells, IgE+ cells, eosinophils, and proliferating cells were significantly increased within airways. All five immune cell types accumulated within airways in unique patterns of distribution, suggesting compartmentalized responses with regard to trafficking. Although cytokine mRNA levels were elevated throughout the conducting airway tree of HDM-challenged animals, the distal airways (terminal and respiratory bronchioles) exhibited the most pronounced up-regulation.

CONCLUSION

These findings demonstrate that key effector immune cell populations and cytokines associated with asthma differentially accumulate within distinct regions and compartments of tracheobronchial airways from allergen-challenged primates.

Autologous serum skin test reactivity in patients with non-allergic asthma

BACKGROUND

Inflammatory alterations of respiratory airways have been found in patients with non-allergic asthma, but the triggering event has not been defined. An autoimmune activation of inflammatory cells has been hypothesized.

OBJECTIVE

To evaluate whether histamine-releasing factors are present in sera from non-allergic asthmatics.

METHODS

Twenty-four patients with non-allergic asthma underwent in vivo autologous serum skin test (ASST) and in vitro basophil histamine release assay using autologous basophils as well as basophils from normal donors. Twenty-seven subjects with respiratory allergy and three normal subjects were chosen as control.

RESULTS

ASST was positive in 14/24 non-allergic asthmatics (58%) whereas it was negative in all 30 control subjects (P<0.001). The serum of only one ASST-positive patient out of 12 (8.4%) induced in vitro histamine release from autologous basophils. The serum from another ASST-positive patient induced histamine release from membrane IgE-stripped autologous basophils. Sera from either non-allergic asthmatics or from control subjects did not provoke significant histamine release from basophils from three normal donors.

CONCLUSION

Skin reactivity to autologous serum is common among non-allergic asthmatics, indicating the presence of circulating histamine-releasing factors. However, only in a minority of patients in vitro functional evidence of histamine-releasing autoantibodies (anti-FcepsilonRI or anti-IgE) was obtained. The presence of circulating histamine-releasing factors might contribute to initiation/maintenance of inflammation in respiratory airways of non-allergic asthmatics.

Is occupational asthma to diisocyanates a non-IgE-mediated disease?

BACKGROUND

Exposure to diisocyanates in the workplace is an important cause of occupational asthma. The majority of patients with diisocyanate-induced asthma have no detectable diisocyanate-specific IgE antibodies in serum. There has been much debate as to whether this is due to diisocyanate-induced asthma being mediated by non-IgE mechanisms or whether it is the result of using inappropriate conjugates.

OBJECTIVE

We sought to determine whether RNA message for Cepsilon, IL-4, and other associated inflammatory markers could be detected locally within the bronchial mucosa after diisocyanate challenge.

METHODS

Fiberoptic bronchoscopic bronchial biopsy specimens were obtained at 24 hours after both a control and an active challenge in 5 patients with positive and 7 patients with negative inhalation test responses to diisocyanates. Using both immunohistochemistry and in situ hybridization, we determined mRNA for Cepsilon, IL-4, IL-5, and other associated inflammatory markers.

RESULTS

There was a striking absence of Cepsilon and IL-4 mRNA-positive cells in bronchial biopsy specimens from patients challenged with diisocyanate (Cepsilon median of 0 and interquartile range of 0-1.85; IL-4 median of 0 and interquartile range of 0-0.85). In contrast, there were increased numbers of IL-5-, CD25-, and CD4-positive cells and a trend toward an increase in eosinophils after active challenge with diisocyanate.

CONCLUSION

We found a striking absence of both bronchial Cepsilon and IL-4 RNA message after inhalation challenge with diisocyanates, irrespective of whether the challenge test response was positive or negative. We propose that diisocyanate-induced asthma is a non-IgE-mediated disease, at least in patients in whom specific IgE antibodies to diisocyanates are undetectable.

T-bet polymorphisms are associated with asthma and airway hyperresponsiveness

RATIONALE

T-bet (TBX21 or T-box 21) is a critical regulator of T-helper 1 lineage commitment and IFN-gamma production. Knockout mice lacking T-bet develop airway hyperresponsiveness (AHR) to methacholine, peribronchial eosinophilic and lymphocytic inflammation, and increased type III collagen deposition below the bronchial epithelium basement membrane, reminiscent of both acute and chronic asthma histopathology. Little is known regarding the role of genetic variation surrounding T-bet in the development of human AHR.

OBJECTIVES

To assess the relationship between T-bet polymorphisms and asthma-related phenotypes using family-based association.

METHODS

Single nucleotide polymorphism discovery was performed by resequencing the T-bet genomic locus in 30 individuals (including 22 patients with asthma). Sixteen variants were genotyped in 580 nuclear families ascertained through offspring with asthma from the Childhood Asthma Management Program clinical trial. Haplotype patterns were determined from this genotype data. Family-based tests of association were performed with asthma, AHR, lung function, total serum immunoglobulin E, and blood eosinophil levels.

MAIN RESULTS

We identified 24 variants. Evidence of association was observed between c.-7947 and asthma in white families using both additive (p = 0.02) or dominant models (p = 0.006). c.-7947 and three other variants were also associated with AHR (log-methacholine PC(20), p = 0.02-0.04). Haplotype analysis suggested that an AHR locus is in linkage disequilibrium with variants in the 3'UTR. Evidence of association of AHR with c.-7947, but not with other 3'UTR SNPs, was replicated in an independent cohort of adult males with AHR.

CONCLUSIONS

These data suggest that T-bet variation contributes to airway responsiveness in asthma.

Epistatic effect of TLR4 and IL4 genes on the risk of asthma in females

BACKGROUND

Many studies have demonstrated a connection between asthma and T-cell cytokine genes, such as genes coding for interleukin-4 (IL4) and IL-13, which are involved in the regulation of the TH1/TH2 balance. The toll-like receptor 4 (TLR4), the principal receptor for bacterial endotoxin, has attracted attention as a potential risk factor for asthma. We examined whether the polymorphisms of the TLR4 (A/G at +896) and IL4 (C/T at -590) showed an epistatic effect on the risk of asthma or atopy.

METHODS

Gene polymorphism analyses and skin prick tests were performed on asthmatic and nonasthmatic adult subjects of a Finnish population-based case-control study. The phenotype studied was persistent asthma.

RESULTS

The results showed that genotypes of neither the TLR4 SNP at +896 nor IL4 SNP at -590 were separately found to be associated with asthma. However, the female carriers of allele G (i.e. genotype AG or GG) of TLR4 and allele T (genotype CT or TT) of IL4 had a significantly increased risk for asthma. No association of these genes and atopy was found.

CONCLUSIONS

Our results indicate that in females the TLR4 and IL4 genes show an epistatic effect on the risk of asthma. The low LPS-responsive allele G of TLR4 and high IgE production allele T of IL4 were found to be the predisposing combination. However, there was no epistatic effect on the risk of atopy.

Human airway epithelial cell determinants of survival and functional phenotype for primary human mast cells

Mast cells (MCs) are found in increased numbers at airway mucosal surfaces in asthmatic patients. Because human airway epithelial cells (HAECs) actively participate in airway inflammatory responses and are in direct contact with MCs in the mucosa, we hypothesized that HAEC-MC interactions may contribute to the differentiation and survival of MCs in the airway mucosa. Here, we show that HAECs express mRNA and protein for soluble and membrane-bound stem cell factor, releasing soluble stem cell factor into the cell culture supernatant at a concentration of 5.9 +/- 0.1 ng per 10(6) HAEC. HAECs were able to support MC survival in coculture in the absence of any exogenous cytokines for at least 4 d. Before the initiation of coculture, MCs were uniformly tryptase and chymase (MC(TC)) double positive, but by 2 d of coculture the majority of MCs expressed tryptase (MC(T)) alone. MCs supported in coculture generated low amounts of cysteinyl-leukotrienes (cys-LT) after FcepsilonRI-dependent activation (0.2 +/- 0.1 ng of cys-LT per 10(6) cells) and required priming with IL-4 and IL-3 during coculture to achieve a quantity of cys-LT generation within the range expected for human lung mucosal MC (26.5 +/- 16 ng of cys-LT per 10(6) cells). In these culture conditions, HAECs were able to direct mucosal MC protease phenotype, but T cell-derived Th2 cytokines were required for the expression of a functional airway MC eicosanoid phenotype. Thus, distinct cell types may direct unique aspects of reactive mucosal MC phenotype in the airways.

CD4CD25 regulatory T lymphocytes in allergy and asthma

Allergic asthma is characterized by airway hyper-responsiveness and chronic mucosal inflammation mediated by CD4(+) Th2 lymphocytes. Regulatory CD4(+)CD25(+) T cells are important components of the homeostasis of the immune system, as impaired CD4(+)CD25(+) T cell activity can cause autoimmune diseases and allergy. The mechanism of suppression by CD4(+)CD25(+) T cells remains controversial; different in vivo and in vitro studies raise possible roles for the immunosuppressive cytokines interleukin-10 and transforming growth factor-beta, forkhead transcription factor Foxp3, glucocorticoid-induced tumor necrosis factor receptor, cytotoxic lymphocyte associated antigen-4, 4-1BB costimulator receptor, a CD4-related molecule LAG-3, and neuropilin-1. Current data suggest that Th2 responses to allergens are normally suppressed by CD4(+)CD25(+) T cells. Suppression by CD4(+)CD25(+) T cells is decreased in allergic individuals. Furthermore, CD4(+)CD25(+) T cells play a key role in regulating airway eosinophilic inflammation. The immunomodulatory properties of CD4(+)CD25(+) T cells do extend to Th2 responses, most notably by limiting the development of a proinflammatory CD4(+) Th2 phenotype characterized by reduced cytokine production. An understanding of the roles of CD4(+)CD25(+) T cells in vivo could provide better insight into the design of novel approaches to modulate the chronic airway inflammatory reaction evident in bronchial asthma.

Structure and function of CLCA proteins

CLCA proteins were discovered in bovine trachea and named for a calcium-dependent chloride conductance found in trachea and in other secretory epithelial tissues. At least four closely located gene loci in the mouse and the human code for independent isoforms of CLCA proteins. Full-length CLCA proteins have an unprocessed mass ratio of approximately 100 kDa. Three of the four human loci code for the synthesis of membrane-associated proteins. CLCA proteins affect chloride conductance, epithelial secretion, cell-cell adhesion, apoptosis, cell cycle control, mucus production in asthma, and blood pressure. There is a structural and probable functional divergence between CLCA isoforms containing or not containing beta4-integrin binding domains. Cell cycle control and tumor metastasis are affected by isoforms with the binding domains. These isoforms are expressed prominently in smooth muscle, in some endothelial cells, in the central nervous system, and also in secretory epithelial cells. The isoform with disrupted beta4-integrin binding (hCLCA1, pCLCA1, mCLCA3) alters epithelial mucus secretion and ion transport processes. It is preferentially expressed in secretory epithelial tissues including trachea and small intestine. Chloride conductance is affected by the expression of several CLCA proteins. However, the dependence of the resulting electrical signature on the expression system rather than the CLCA protein suggests that these proteins are not independent Ca2+-dependent chloride channels, but may contribute to the activity of chloride channels formed by, or in conjunction with, other proteins.

Ultrastructure of bronchial biopsies from patients with allergic and non-allergic asthma

Epithelial damage is commonly found in airways of asthma patients. The aim of this study was to investigate epithelial damage in allergic and non-allergic asthma at the ultrastructural level. Bronchial biopsies obtained from patients with allergic asthma (n=11), non-allergic asthma (n=7), and healthy controls (n=5) were studied by transmission electron microscopy. Epithelial damage was found to be extensive in both asthma groups. Both in basal and in columnar cells, relative desmosome length was reduced by 30-40%. In columnar cells, half-desmosomes (i.e., desmosomes of which only one side was present) were frequently noticed. Eosinophils showing piece-meal degranulation were commonly observed in allergic asthma. Degranulating mast cells were more often observed in allergic asthma. Goblet cell hyperplasia was only found in allergic asthma. Lymphocytes were increased in both groups. In both groups, the lamina densa of the basal lamina was thicker than the control by about 40-50%. In allergic asthma the lamina densa was irregular with focal thickening. While there was always a tendency for changes (epithelial damage, desmosomes, degranulating mast cells, basal lamina) to be more extensive in allergic asthma compared to non-allergic asthma, there was no significant difference between the two groups in this respect. Reduced desmosomal contact may be an important factor in the epithelial shedding observed in patients with asthma.

How frequent is altered gene expression among susceptibility genes to human complex disorders?

It is regularly thought that human complex disorder susceptibility genes show differences in gene expression between normal and pathologic tissues. Thus, differences of transcript amounts could be indicative of complex disorder susceptibility loci and, therefore, be used for the discovery or the validation of human susceptibility genes to complex disorders/traits. Whether human complex disorder susceptibility genes effectively display differences in transcript amounts was tested by meta-analysis of the published literature comparing transcript amounts of well-validated human susceptibility genes to complex traits/disorders. A total of 94 gene-disease associations, which were studied in at least three independent studies and showed strong evidence of positive association, were analyzed. For 23 out of these 94 well-validated gene-disease associations, 120 gene expression studies comparing normal and pathologic human tissues were found. For 60 out of these 120 gene expression studies, the difference of level expression between normal and pathologic human tissues was statistically significant. This result was highly significant, as only 6 significant results were expected randomly under the null hypothesis (P < 10(-112)). A large excess of replication studies were also found, which were in agreement with the original report (P = 6 x 10(-4)). However, the overall level of expression change between normal and pathologic human tissues was relatively moderate, because only 36 (60%) and 19 (31.6%) out of the 62 statistically significant gene expression studies reached 2- or 3-fold changes in expression level, respectively. The present meta-analysis confirms statistical differences of expression levels between normal and pathologic human tissues for human susceptibility genes to complex traits/disorders. However, the levels of differences in transcript amounts appear to be relatively weak. These findings rationalize the use of gene expression for the discovery/validation of human susceptibility genes, but the weak differences of expression typically found should be taken into account for the design of such studies.

Discovery of genetic difference between asthmatic children with high IgE level and normal IgE level by whole genome linkage disequilibrium mapping using 763 autosomal STR markers

The genome-wide linkage disequilibrium screen for loci associated with genetic difference between allergic and nonallergic asthma was conducted with 763 autosomal STR markers and included 190 asthmatic children. Evidence for association with differences between the two forms of asthma was observed for 36 STR markers. Marker-to-marker synergetic effect and by simulation resampling tests revealed D5S2011, D6S305, and D9S286 were important loci in allergic asthma while D6S1574, D8S1769, and D19S226 were important in nonallergic asthma. Our results show strong genetic evidence that these markers play an important role in defining allergic and nonallergic asthma and provides important candidates of susceptible genes in these two categories of asthma. This study further shows that asthma is, indeed, a heterogeneous group of underlying diseases and, although with similar clinical phenotypes, may have different clinical severities, outcomes, and need more tailor-made management.

Phenotypes of asthma revisited upon the presence of atopy

Immunological studies claimed that atopic and non-atopic asthma share more similarities than differences. However, these two phenotypes of asthma are considered to be distinguishable upon distinct clinical patterns, which were not systematically assessed before in a large population. We studied characteristics discriminating atopic from non-atopic asthma among 751 asthmatic patients and 80 factors were analysed in univariate and multivariate analysis. Age, age of onset of asthma, female/male ratio were higher in non-atopic (n=200) than in atopic (n=551) asthmatics. Familial asthma, seasonal symptoms, rhinitis, conjunctivitis, allergen-triggered symptoms, improvement in altitude, exercise-induced asthma were associated with atopy. Non-atopic asthmatics displayed lower FEV(1) and FVC. Smoking was more frequent and asthma was more severe in these patients. Younger age, early onset, male sex, rhinitis and smoking were independent factors discriminating atopic from non-atopic asthma. This study establishes in a large population of asthmatics that although similarities exist between atopic and non-atopic asthma, two clinical phenotypes can still distinguish both kinds of asthma.

Determinants of increased exhaled nitric oxide in patients with suspected asthma

Exhaled nitric oxide (FENO) has been proposed as a marker of asthmatic inflammation, but it is unclear whether FENO in clinical use selects patients primarily according to their atopic or asthmatic status. The aim of this study was to investigate the determinants of increased FENO in patients with suspected asthma, by means of multinomial logistic regression analysis. The FENO of 132 patients referred because of symptoms suggestive of asthma were studied, and the explanatory factors tested included atopy according to prick skin tests, clinical asthma according to lung function tests, sputum eosinophilia and bronchial hyperresponsiveness (BHR). Slightly elevated FE(NO) levels were significantly explained only by sputum eosinophilia (OR: 3.7; 95% CI: 1.1-13.1; P=0.04), but for high levels of FE(NO) (> or =3 SD of predicted), clinical asthma (OR: 16.3; 95% CI: 5.4-49.7; P <0.0001) and sputum eosinophilia (OR: 12.0; 95% CI: 4.1-35.0; P >0.0001) were the characteristics with the highest prediction, followed by atopy and BHR. A significant interaction between asthma and atopy was observed relating to the effect on high FENO, but further analyses stratified by atopy showed significant associations between asthma and high FENO both in atopic and nonatopic patients. We conclude that in patients with symptoms suggesting asthma, slightly elevated and high levels of FENO are associated with sputum eosinophilia, whereas asthma is significantly associated only with high levels of FENO, irrespective of atopy. The results suggest that FENO is primarily a marker of airway eosinophilia, and that only high values of FENO may be useful to identify patients with atopic or nonatopic asthma.

Racial Differences in T-Lymphocyte Response to Glucocorticoids

BACKGROUND

Asthma morbidity and mortality is increased in blacks.

OBJECTIVE

The primary objective of this cross-sectional study was to determine if blacks, asthmatic or nonasthmatic, displayed diminished T-lymphocyte response to glucocorticoids in vitro compared to their white counterparts. If differences were noted, this would suggest a racial predisposition to decreased glucocorticoid responsiveness among blacks.

METHODS

Asthmatic (n = 395, 27% blacks) and control (n = 202, 52% blacks) subjects recruited from National Jewish Medical and Research Center and from the surrounding community participated in the study. In vitro glucocorticoid responsiveness was determined by assessing the log-transformed concentration of dexamethasone required to suppress phytohemagglutinin-induced T-lymphocyte proliferation by 50% (log(10) IC(50)). Asthma medication history, atopic status, and spirometric lung function measures corrected for race were collected.

RESULTS

Black and white asthmatic subjects had similar FEV(1) percentage of predicted values and inhaled and oral glucocorticoid requirements. Black asthmatic subjects displayed significantly diminished glucocorticoid responsiveness compared to white asthmatic subjects, as follows: median (first, third quartile) log(10) IC(50) values of 1.00 nmol (0.48, 1.83) vs 0.78 nmol (0.29, 1.45) [p = 0.028]. Similar results were found between black and white control subjects, as follows: median, 1.26 nmol (0.70, 2.14) vs 0.95 nmol (0.55, 1.48) [p = 0.01]. Age, race, and basal T-lymphocyte activity were significantly positively correlated to the log(10) IC(50) values.

CONCLUSION

Our observation that black asthmatic subjects and non-asthmatic control subjects require greater concentrations of glucocorticoid in vitro to suppress T-lymphocyte activation suggests that blacks have a racial predisposition to diminished glucocorticoid responsiveness, which may contribute to their heightened asthma morbidity.

Different IL-5 and IFN-gamma production from peripheral blood T-cell subsets in atopic and nonatopic asthmatic children

Defective Th1 and enhanced Th2-type cytokine responses have been implicated in the development of atopic disease. However, the immunopathology of nonatopic asthma, especially in children, remains unclear, and there have been few studies to compare the cytokine profile in peripheral blood T-cell subsets between atopic and nonatopic asthmatic children. To document whether atopic asthmatic children have a cytokine imbalance and to compare the cytokine profile between atopic and nonatopic asthmatic children, we investigated the interleukin (IL)-5-producing and interferon (IFN)-gamma-producing T-cell subsets from peripheral blood mononuclear cells (PBMC). The percentages of IFN-gamma-producing CD4+ and CD8+ T cells from atopic asthmatic children were decreased, but those in nonatopic asthmatic children were not decreased. In both groups of asthmatic children, the percentages of IFN-gamma-producing CD4+ T cells were inversely correlated with the peripheral blood eosinophils and had a significant correlation with airway responsiveness (PC20). Thus, we found that the mechanism underlying allergic inflammation of nonatopic asthma is not simple a Th1/Th2 cytokine imbalance. Considering the inverse relationship between IFN-gamma-producing CD4+ T cells and eosinophilia or airway hyperresponsiveness, IFN-gamma from CD4+ T cells may play an important role in allergic inflammation and airway hyperresponsiveness in asthmatic children.

Regulatory CD4+CD25+ T lymphocytes in peripheral blood from patients with atopic asthma

The aim of this study was to analyze whether regulatory CD4+CD25+ T lymphocytes exist and function normally in patients with atopic asthma. Our data showed that a significant increase in CD4+CD25+ cell numbers was seen in atopic asthmatics during acute exacerbation, but not in those stable asthmatics, atopic nonasthmatics, and normal subjects. The mean inhibition values of the proliferation response of CD4+CD25- cells by CD4+CD25+ cells from normal controls and asthmatics were almost the same. There was no difference in inhibitory effects on both Th1 and Th2 cytokine production of CD4+CD25- cells by CD4+CD25+ cells in the two groups. These data demonstrated that although CD4+CD25+ cells increase in atopic asthma during exacerbation, these regulatory T cells appear to function normally with regard to suppression of T-cell proliferation as well as Th1-Th2 cytokine production.

Mechanisms of intrinsic asthma

PURPOSE OF REVIEW

The phenomenon of intrinsic or nonatopic asthma continues to raise questions about the possible role of IgE-mediated mechanisms in asthma pathogenesis. With the current availability of anti-IgE therapy for asthma, clarification of this issue has never been more timely and relevant.

RECENT FINDINGS

This article summarizes recent studies for and against the proposition that IgE-mediated mechanisms play a critical role in asthma pathogenesis. These data comprise epidemiological studies and recent molecular studies, suggesting that IgE synthesis may take place in the bronchial mucosa of patients with nonatopic asthma, despite the fact that allergen-specific IgE is not detectable in the periphery by standard skin prick testing.

SUMMARY

At present, available data do not allow a firm conclusion to be made as to whether or not IgE-mediated mechanisms play an obligatory role in asthma pathogenesis. Implications for the future therapy of nonatopic asthma in either case are discussed, as well as some suggestions for further research.

Biology and therapeutic potential of the interleukin-4/interleukin-13 signaling pathway in asthma

The future management of patients with allergic asthma is poised to change in the coming one to two decades. This prediction is based on fundamental new insights into the pathogenesis of disease, gained through the study of both humans and experimental models of asthma. These studies have revealed that allergic asthma is an immune-mediated disease which, despite the redundancy characteristic of all immune responses, may be induced through a single dominant signaling cascade called the interleukin (IL)-4/IL-13 signaling pathway. In addition to the cytokine IL-4, this pathway includes IL-13, the cytokine receptor subunit IL-4 receptor alpha (IL-4Ralpha), Janus-associated tyrosine kinases and the transcription factor, signal transducer and activator of transcription 6. The IL-4 signaling pathway controls the most important cellular developmental (afferent) events that underlie asthma. These include T helper (Th) type 2 cell activation, B cell activation and immunoglobulin (Ig) E secretion, mast cell development, and effector (efferent) events related exclusively to immune effects on the lung such as goblet cell metaplasia and airway hyperresponsiveness. Any of the IL-4 signaling molecules are potentially amenable to pharmacological intervention, but a detailed understanding of the entire pathway is required to appreciate their actual potential for drug development. For example, neutralization strategies that target only IL-4 are unlikely to succeed because they leave IL-13 free to continue the signaling cascade. In contrast, neutralization of IL-4Ralpha may represent a more feasible strategy, as it should prevent signaling by both IL-4 and IL-13. The therapeutic potential of targeting intracytoplasmic tyrosine kinases has already been achieved with the use of small molecules, suggesting that this approach may be realistically adopted for the treatment of asthma. However, well designed asthma clinical trials are warranted to determine with certainty, the efficacy of therapies based on IL-4/IL-13 blockade.

Is there a causative role for tetanus toxoid vaccination in the development of allergy-like symptoms and in the increasing prevalence of atopic diseases?

Allergic diseases are a worldwide health problem. They mainly affect people living in developed countries where an increasing prevalence of allergy symptoms has been recorded in the last 20-30 years. The cause of this increase is still disputed, and, among others, the "hygiene hypothesis" supported the concept that relevant changes in lifestyle could have a relationship with the phenomenon. More recently the recorded parallel increase in autoimmune diseases has suggested to consider the "hygiene hypothesis" as a cause of a more general disregulation of the immune system leading to both allergy and to autoimmunity. Here are reported a series of observations, evidence, and data from the literature leading to a different hypothesis. The key points are: (1) the presence of two subsets of patients having allergy symptoms based on an IgE-mediated mechanism or not; (2) the positive results obtained with the autologous serum skin test in either cutaneous or respiratory affected subjects, mainly in children and adult females; (3) the presence of IgG autoantibodies against the alpha-chain of the high affinity IgE receptor (FcepsilonRIalpha) in non-IgE-mediated urticaria and even in respiratory subjects; (4) the cross-reactivity between epitopes of the tetanus toxoid molecule and the FcepsilonRIalpha detected by means of an alpha-chain affinity purified IgG fraction; (5) the positive skin reactivity obtained using IgG anti-tetanus toxoid preparations in allergic and non-allergic volunteers. The presence of IgG autoantibodies actively generated by the population-based vaccination with tetanus toxoid could induce both mediator release from activated mast cell and Th2 cytokine production early in life. There are epidemiological evidences that tetanus toxoid vaccination could be linked with an increased tendency to have allergy symptoms. The different epidemiological distribution of non-IgE-mediated symptoms, mainly affecting young infants would be in agreement with the present hypothesis. The prevalent mother-to-child relationship in terms of risk for allergy symptoms could be explained with the trans-placenta transfer of IgG. A similar transfer could also take place through the mother milk during breast feeding. It may thus be hypothesized that the increased prevalence of allergic diseases could be caused by the generalized tetanus toxoid immunization procedure, progressively extended to most of the countries worldwide in the last 30-40 years. Both the induction of non-IgE-mediated symptoms caused by the mast cell activation via the anti-FcepsilonRIalpha IgG and the long lasting Th2 inflammation of affected tissues would be the inducing mechanisms. This hypothesis would re-configure part of the allergic diseases as a Th2 phenotypic expression of an autoimmune disease.

Rhinovirus-induced interferon-gamma and airway responsiveness in asthma

The majority of asthma exacerbations are caused by respiratory infections, with rhinovirus (RV) being the most common virus. Recent evidence has suggested that decreased generation of IFN-gamma is associated with more severe colds and delayed elimination of virus. Whether the generation of IFN-gamma also has any relationship to general features of asthma severity has yet to be determined. To evaluate this hypothesis, peripheral blood mononuclear cells from 19 subjects with atopy and asthma were incubated with RV16 for 6 days to determine IFN-gamma and interleukin (IL)-5 production; these responses were then compared with measurements of airflow obstruction and airway responsiveness. RV16-induced IFN-gamma production correlated significantly with the methacholine PD (r = 0.50, p = 0.03), and the ratio of RV16-induced IFN-gamma:IL-5 correlated with % predicted FEV1 (r = 0.53, p = 0.02). In contrast, there were no significant associations between measures of asthma severity and RV-induced IL-5. These findings suggest that a cytokine imbalance with a deficient Th1 response to RV, but not a Th2 response, is associated with measures of asthma severity and support the concept that impaired antiviral responses may be associated with asthma severity.

Airway inflammation and basement membrane tenascin in newly diagnosed atopic and nonatopic asthma

Previous studies have shown both similar and distinct inflammatory changes in atopic and nonatopic asthma. This study was set to investigate the bronchial inflammatory cell infiltrate and subepithelial basement membrane (BM) tenascin deposition in subjects with newly diagnosed asthma and bronchial hyperresponsiveness (BHR). Seventy-nine asthmatic subjects (age 18-60 years) were recruited and 58 were atopic according to skin prick testing. The patients recorded asthma symptoms and peak flow measurements for 14 days. Lung function and BHR were measured by spirometry and histamine challenge. Serum eosinophil cationic protein (ECP) and blood eosinophils were assessed. Fiberoptic bronchoscopy was performed to obtain bronchial biopsies. Serum ECP was higher in the atopic group but eosinophil counts did not differ. There were no differences in inflammatory cells studied (activated eosinophils, T-lymphocytes, mast cells or macrophages) between nonatopic and atopic subjects. BM tenascin layer was significantly thicker in atopic compared with nonatopic subjects (7.6 vs 6.3 microm, P = 0.007). The thickness of tenascin correlated with eosinophil, T-lymphocyte, and macrophage counts, as well as with IL-4-positive cell counts and the correlation was seen only in atopic asthmatics. These findings suggest that inflammatory cells may have a regulatory role in tenascin expression in atopic asthma.

Prostaglandin D2 reinforces Th2 type inflammatory responses of airways to low-dose antigen through bronchial expression of macrophage-derived chemokine

PGD2, a lipid mediator released from mast cells, is known to participate in allergic reactions. However, the mechanism by which PGD2 contributes to such reactions remains unclear. We established a novel experimental model of asthma that permitted direct assessment of the role of PGD2 in airway inflammation. Antigen-sensitized mice were exposed to aerosolized prostaglandin D2 (PGD2) 1 d before challenge with low-dose aerosolized antigen. Not only the numbers of eosinophils, lymphocytes, and macrophages but also the levels of IL-4 and IL-5 in bronchoalveolar lavage fluid were higher in PGD2-pretreated mice than in control mice. The expression of macrophage-derived chemokine (MDC), a chemoattractant for Th2 cells, was greater in PGD2-pretreated mice than in control. Injection of anti-MDC antibody into PGD2-pretreated mice markedly inhibited inflammatory cell infiltration as well as Th2 cyto-kine production after antigen challenge. These results indicate that PGD2 accelerates Th2 type inflammation by induction of MDC. Our results suggest that this mechanism may play a key role in the development of human asthma and that MDC might be a target molecule for therapeutic intervention.

The role of mast cells in asthma

While the role of mast cells in allergic reactions is unequivocal, their precise functions in asthma remain controversial. Mast cells uniquely populate all vascularized organs and tissues, including the upper and lower respiratory tree, even in healthy individuals. Histologic evidence suggests that asthma is accompanied by a mast cell hyperplasia in the inflamed mucosal epithelium and the adjacent smooth muscle. The mechanisms responsible for constitutive mast cell development have been partly elucidated. Moreover, both in vitro studies and in vivo disease models indicate that mast cells have a remarkably flexible program of gene expression, and this program can be drastically altered by the T-cell-derived Th2 cytokines relevant to asthma. Moreover, the role of mast cells in innate immunity is now firmly established, and the capacity for numerous microbial pathogens to initiate their activation in vitro and in vivo suggest mechanisms by which microbes could initiate disease exacerbations.

Allergic and nonallergic forms of atopic diseases

Atopic dermatitis, allergic rhinitis, and asthma are atopic diseases that develop on a complex genetic background, the so-called atopic diathesis. Although they target different organs, in most patients they are characterized by the presence of elevated total serum IgE levels. However, a subgroup of atopic patients exhibits normal IgE levels and mechanisms contributing to the so-called "intrinsic" or "nonallergic form" have been the matter of intensive research work in the last years. Because of the rapid advancements in the research field of atopic diseases, it now becomes possible for the first time to delineate a new disease classification of allergic and nonallergic subtypes of atopic diseases, thereby bringing hope to the clinician for a more specific treatment approach for each subgroup of these patients.

Differential roles for CD4 and CD8 T cells after diisocyanate sensitization: genetic control of TH2-induced lung inflammation

BACKGROUND

Exposure to diisocyanates is a major cause of occupational asthma. We previously developed a novel mouse model of diisocyanate-induced asthma involving epicutaneous sensitization to hexamethylene diisocyanate (HDI) that demonstrates many features of the human disease, including airway eosinophilia and mucus hypersecretion.

OBJECTIVE

To determine what factors are critical for the development of HDI-induced airway inflammation, we investigated the strain distribution of this response and the roles of CD4(+) and CD8(+) T cells.

METHODS

Mice were epicutaneously exposed to HDI and then challenged with HDI, either by means of inhalation to induce airway inflammation or on the ear to induce contact hypersensitivity (CHS). Lymph node cytokine production and serum antibodies were also measured.

RESULTS

Induction of airway eosinophilia was highly dependent on the mouse strain used, with C57BL/6, A/J, CBA, C3H, and C57BL/10 mice all having significantly fewer eosinophils than BALB/c mice. HDI-specific antibodies and lymph node IL-5 and IL-13 production were also diminished in non-BALB/c strains. In contrast, CHS to HDI developed in all strains tested. Studies in mice deficient in either CD4(+) or CD8(+) T cells revealed that CD4(+) T cells were critical for HDI-induced airway eosinophilia, whereas CD8(+) T cells were the major effector cells in CHS.

CONCLUSION

The data suggest that, in contrast to CHS, induction of T(H)2 responses after epicutaneous exposure to diisocyanates is strongly genetically influenced. Furthermore, the lung inflammatory response to inhaled HDI appears to depend primarily on effective generation of these CD4(+) T(H)2 responses, as is the case in atopic asthma.

Transient receptor potential (TRP) channels as potential drug targets in respiratory disease

Calcium-permeable channels have traditionally been thought of as therapeutic targets in excitable cells. For instance, voltage-operated Ca2+ channels in neurones and smooth muscle cells for neurological and cardiovascular diseases although calcium-permeable channels are also functionally important in electrically non-excitable cells. In the lung, calcium channels play a pivotal role in the activation of all the cell types present, whether resident cells such as airway smooth muscle cells and macrophages or migratory cells such as neutrophils or lymphocytes.Previously, research in this area has been hindered by the lack of obvious molecular identity. More recently, the emergence of the transient receptor potential (TRP) cation family has yielded promising candidates which may underpin the different receptor-operated calcium influx pathways. The challenge now, is to ascribe function to the TRP channels expressed in each cell type as a first step in identifying which TRP channels may be potential drug targets for asthma and chronic obstructive pulmonary disease (COPD) (Fig. 1).

Interleukin-4 and interleukin-4 soluble receptor alpha levels in bronchoalveolar lavage from children with asthma

BACKGROUND

In asthma there is increased expression of the Th2-type cytokine interleukin-4 (IL-4). IL-4 is important in immunoglobulin isotype switching to immunoglobulin E and adhesion of eosinophils to endothelium.

OBJECTIVE

We hypothesized that levels of IL-4 in bronchoalveolar lavage (BAL) fluid would be increased in stable, atopic asthmatic children compared with controls and that levels of its physiologic inhibitor IL-4 soluble receptor alpha (IL-4sR alpha) would be correspondingly decreased.

METHODS

One hundred sixteen children attending a children's hospital for elective surgery were recruited. A nonbronchoscopic BAL was performed, and IL-4 and IL-4sR alpha were measured in the BAL supernatants.

RESULTS

There was no significant difference in IL-4 concentrations between atopic asthmatic children, atopic normal controls, and nonatopic normal controls [0.13 pg/mL (0.13 to 0.87) vs 0.13 pg/mL (0.13 to 0.41) vs 0.13 pg/mL (0.13 to 0.5), P = 0.65]. IL-4sR alpha levels were significantly increased in asthmatic patients compared with atopic controls [6.4 pg/mL (5.0 to 25.5) vs 5.0 pg/mL (5.0 to 9.9), P = 0.018], but not when compared with the nonatopic controls [5.2 pg/mL (5.0 to 10.6), P = 0.19].

CONCLUSIONS

Contrary to expectation, IL-4sR alpha levels are increased in BAL from stable asthmatic children compared with nonatopic controls, and we speculate that IL-4sR alpha is released by inflammatory cells in the airways to limit the proinflammatory effects of IL-4.

The role of T lymphocytes in the pathogenesis of asthma

There is considerable evidence to support a role for T cells in asthma, particularly the involvement of T(H)2 cells both in atopic allergic asthma and in nonatopic and occupational asthma. There might also be a minor contribution from T(C)2 CD8+ T cells. Several T(H)2 cytokines have the potential to modulate airway inflammation, particularly IL-13, which induces airway hyperresponsiveness independently of IgE and eosinophilia in animal models. The identification of transcription factors controlling T(H)1 and T(H)2 development further support the T(H)2 hypothesis because GATA3 is overexpressed and T-bet is underexpressed in the asthmatic airway. Specific T cell directed immunotherapy might allow induction, modulation, or both of T-cell responses, and elucidation of the mechanisms of regulatory T cells might allow further optimization of immunotherapy. Recent advances in our understanding of dendritic cell function in directing T-cell responses might uncover further therapeutic targets. The efficacy of cyclosporin A and anti-CD4 treatment in patients with chronic severe asthma argues for continued T-cell involvement, but whether remodeling contributes to pathology inaccessible to anti-inflammatory treatment or T-cell immunotherapy will be an important future question.

Interleukin-10 gene promoter region polymorphism is associated with eosinophil count and circulating immunoglobulin E in adult asthma

BACKGROUND

IL-10 has several functional effects relevant to asthma. It can modulate IgE production and induce apoptosis in eosinophils. Polymorphisms of IL-10 gene have been shown to affect IL-10 production.

OBJECTIVE

To establish whether IL-10 polymorphisms are associated with asthma and phenotype-related characteristics.

METHODS

The frequency of three single base exchange polymorphisms (at positions - 1082, - 819 and - 592) and corresponding haplotypes of the IL-10 gene were analysed in 245 adult asthmatic subjects and 405 controls using PCR and restriction fragment length polymorphism (RFLP). The data were assessed for correlations with the eosinophil count, serum IgE and lung function.

RESULTS

The IL-10 haplotype frequencies were similar in asthmatics and controls. Eosinophil count median was 2.0- to 3.2-fold higher among asthmatics with rare ATA/ATA genotype than in asthmatics with other genotypes. No such difference was seen in the control group. When analysed by IL-10 haplotype carrier state and gender, male asthmatics with ATA haplotype had 2.8-fold higher serum IgE than those without ATA. A converse association was found in male controls with ATA haplotype, who had 1.9-fold lower serum IgE than their ATA-negative counterparts. The high IL-10-producing GCC haplotype was associated with impaired lung function in smoking male controls while in asthmatics no clear effect on lung function was found with any of the haplotypes studied.

CONCLUSION

These results suggest that the eosinophil counts and serum IgE are differently regulated by IL-10 genotype in asthmatic and in normal subjects. However, IL-10 polymorphism is not related to susceptibility in asthma.

TH2 cytokine expression in bronchoalveolar lavage fluid T lymphocytes and bronchial submucosa is a feature of asthma and eosinophilic bronchitis

BACKGROUND

Asthma is characterized by variable airflow obstruction and airway hyperresponsiveness in association with airway inflammation under the influence of T(H)2 cytokines. Eosinophilic bronchitis has similar immunopathology to asthma but without disordered airway physiology. Whether eosinophilic bronchitis is associated with increased expression of T(H)2 cytokines is unknown.

OBJECTIVE

We sought to assess the expression of T(H)2 cytokines in eosinophilic bronchitis.

METHODS

Expression of activation markers and chemokine receptors from blood and bronchoalveolar lavage (BAL) fluid T cells and the T(H)2 cytokine expression from these T cells and bronchial mucosa biopsy specimens were assessed from subjects with eosinophilic bronchitis, subjects with asthma, and healthy control subjects.

RESULTS

The proportion of resting (stimulated) CD4 BAL fluid T cells expressing intracellular IL-4 was significantly higher in the subjects with eosinophilic bronchitis 7.2% (11.4%) and subjects with asthma 5.3% (5.5%) than in healthy control subjects 2.8% (3.9%) (P =.03). The number of IL-4(+) (P <.001) and IL-5(+) (P =.003) cells per square millimeter of bronchial submucosa was significantly higher in the disease groups than in the healthy control subjects. Expression of intracellular IFN-gamma was significantly higher in stimulated blood CD8 T cells from subjects with eosinophilic bronchitis (24%) and asthma (17%) than in the healthy control subjects (5%; P =.003). There were no between-group differences in expression of IFN-gamma in the BAL fluid T cells or in the bronchial submucosa and no differences in expression of activation markers or chemokine receptors.

CONCLUSION

These findings support the concept of asthma as a disease associated with activation of T(H)2 lymphocytes in the airway and provide evidence that these cytokines play a role in the development of airway inflammation in eosinophilic bronchitis but suggest that the release of T(H)2 cytokines is not sufficient for the elaboration of disordered airway physiology in asthma.

Preclinical efficacy and safety of pascolizumab (SB 240683): a humanized anti-interleukin-4 antibody with therapeutic potential in asthma

The type 2 helper T cell (T(H)2) cytokine interleukin (IL)-4 is thought to play a central role in the early stages of asthma. In an effort to develop an antibody treatment for asthma that neutralizes the effects of IL-4, a murine monoclonal antibody, 3B9, was generated with specificity for human IL-4. In vitro studies demonstrated that 3B9 inhibited IL-4-dependent events including IL-5 synthesis, (T(H)2) cell activation and up-regulation of immunoglobulin E expression. 3B9 was then humanized (pascolizumab, SB 240683) to reduce immunogenicity in humans. SB 240683 demonstrated species specificity for both monkey and human IL-4 with no reactivity to mouse, rat, cow, goat or horse IL-4. Pascolizumab inhibited the response of human and monkey T cells to monkey IL-4 and effectively neutralized IL-4 bioactivity when tested against several IL-4-responsive human cell lines. Affinity studies demonstrated rapid IL-4 binding by pascolizumab with a slow dissociation rate. In vivo pharmacokinetic and chronic safety testing in cynomolgus monkeys demonstrated that pascolizumab was well tolerated, and no adverse clinical responses occurred after up to 9 months of treatment. Three monkeys developed an anti-idiotypic response that resulted in rapid pascolizumab clearance. However, in the chronic dosing study the antibody response was transient and not associated with clinical events. In conclusion, pascolizumab is a humanized anti-IL-4 monoclonal antibody that can inhibit upstream and downstream events associated with asthma, including (T(H)2) cell activation and immunoglobulin E production. Clinical trials are under way to test the clinical efficacy of pascolizumab for asthma.

Analysis of induced sputum in adults with asthma: identification of subgroup with isolated sputum neutrophilia and poor response to inhaled corticosteroids

BACKGROUND

The debate as to whether asthma is a single or heterogeneous disease remains unresolved although pathological studies, mostly using fibreoptic bronchoscopy on small numbers of subjects, have emphasised the similarities between different clinical phenotypes.

METHODS

Lower airway inflammation was assessed non-invasively using induced sputum in 34 normal controls and 259 adults with symptomatic asthma receiving treatment at steps 1-3 of the British Thoracic Society (BTS) guidelines. A subgroup of 49 patients treated with as required beta(2) agonists only who met BTS criteria for a step up in treatment were studied before and 2 months after treatment with inhaled budesonide 400 micro g twice daily.

RESULTS

There was considerable heterogeneity in induced sputum cell counts, particularly in non-atopic patients. A subgroup of 60 patients had a distinctive sputum cell profile with a neutrophil count higher than our normal range (>65.3%) and a normal sputum eosinophil count (<1.9%). These patients were older, predominantly female, and were more likely to be non-atopic but otherwise had similar clinical and physiological features to the group as a whole. Among the 49 subjects studied before and after inhaled budesonide, 11 patients had an isolated sputum neutrophilia. Following treatment, these patients showed significantly less improvement in visual analogue symptom scores (-5.5 v -19.4 mm; mean difference 13.9; 95% CI 0.7 to 27.0), forced expiratory volume in 1 second (FEV(1)) (-0.08 v 0.13 l; mean difference 0.21; 95% CI 0.03 to 0.39), and concentration of methacholine provoking a fall in FEV(1) of 20% or more (PC(20)) (0.15 v 1.29 doubling doses; mean difference 1.11; 95% CI 0.13 to 2.15) than the remaining 38 patients.

CONCLUSIONS

These results suggest the presence of a distinct subgroup of patients with mild to moderate asthma who have predominantly neutrophilic airway inflammation and who respond less well to treatment with inhaled corticosteroids.

Key role for mast cells in nonatopic asthma

The mechanisms involved in nonatopic asthma are poorly defined. In particular, the importance of mast cells in the development of nonatopic asthma is not clear. In the mouse, pulmonary hypersensitivity reactions induced by skin sensitization with the low-m.w. compound dinitrofluorobenzene (DNFB) followed by an intra-airway application of the hapten have been featured as a model for nonatopic asthma. In present study, we used this model to examine the role of mast cells in the pathogenesis of nonatopic asthma. First, the effect of DNFB sensitization and intra-airway challenge with dinitrobenzene sulfonic acid (DNS) on mast cell activation was monitored during the early phase of the response in BALB/c mice. Second, mast cell-deficient W/W(v) and Sl/Sl(d) mice and their respective normal (+/+) littermate mice and mast cell-reconstituted W/W(v) mice (bone marrow-derived mast cells-->W/W(v)) were used. Early phase mast cell activation was found, which was maximal 30 min after DNS challenge in DNFB-sensitized BALB/c, +/+ mice but not in mast cell-deficient mice. An acute bronchoconstriction and increase in vascular permeability accompanied the early phase mast cell activation. BALB/c, +/+ and bone marrow-derived mast cell-->W/W(v) mice sensitized with DNFB and DNS-challenged exhibited tracheal hyperreactivity 24 and 48 h after the challenge when compared with vehicle-treated mice. Mucosal exudation and infiltration of neutrophils in bronchoalveolar lavage fluid associated the late phase response. Both mast cell-deficient strains failed to show any features of this hypersensitivity response. Our findings show that mast cells play a key role in the regulation of pulmonary hypersensitivity responses in this murine model for nonatopic asthma.

Allergic vs nonallergic asthma: what makes the difference?

BACKGROUND

The aim of this work was to describe clinical similarities and differences between allergic and nonallergic asthmatics, notably concerning the nasosinusal involvement.

METHODS

A total of 165 asthmatics (122 allergics and 43 nonallergics) and 193 controls (40 allergics and 153 nonallergics), recruited in the frame of EGEA study (Epidemiological study on the Genetics and Environment of Asthma, bronchial hyperresponsiveness and atopy), were included. Asthmatics were included on the basis of positive answer to four standardized items. To establish differences and similarities between allergic and nonallergic asthmatics, general characteristics (age, sex, smoking habits, history of hay fever and allergic dermatitis), history of asthma, severity and nasosinusal involvement were examined. Clinical assessment was based on the answers to a detailed questionnaire, and spirometry.

RESULTS

Greater age, female sex, sinusal polyposis, and FEV1 below 80% of the predicted value increased the risk of displaying a nonallergic type of asthma, whereas history of hay fever, seasonal exacerbation of asthma, and asthma duration lowered this risk. Unexpectedly, we found no difference in terms of rhinitic symptoms between both groups, probably resulting from distinct causes.

CONCLUSION

These results give new insights into the contrasts between clinical features of allergic and nonallergic asthma. The terminology of extrinsic asthma was first introduced by Rackeman in 1947 (1) and referred to the triggering role of allergens in asthma. By symmetry, he described intrinsic asthma as a disease characterized by later onset in life, female predominance, higher degree of severity, and more frequent association to nasosinusal polyposis. As these asthmatics were not improved by conventional treatment, this author considered their disease as caused by a nonallergic, unknown phenomenon. It is now widely admitted that nonallergic asthma can be objectively distinguished from allergic asthma based on negative skin tests to usual aeroallergens. On the other hand, positive skin test shows a tendency to produce IgE antibodies in response to low doses of allergens. "Atopy" and "atopic" are the terms used to describe this clinical trait and predisposition (2). Allergic clinical manifestations of atopy are of various types, for example rhinitis and asthma. Nowadays the terminology of "extrinsic" and "intrinsic" asthma should no longer be used, and should be replaced by the terminology of "allergic" or "nonallergic" asthma (2).

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.

A novel mouse model of diisocyanate-induced asthma showing allergic-type inflammation in the lung after inhaled antigen challenge

BACKGROUND

Exposure to diisocyanates, a group of highly reactive, low-molecular-weight compounds, is a major cause of occupational asthma. In contrast to mouse models of atopic asthma, previous mouse models of diisocyanate-induced asthma have failed to show lung inflammation with characteristics of human disease.

OBJECTIVE

Our goal was to establish a novel mouse model of diisocyanate-induced asthma in which lung inflammation reminiscent of that seen in human asthma is generated after inhaled antigen challenge.

METHODS

BALB/c mice were epicutaneously sensitized to hexamethylene diisocyanate (HDI) and then challenged with an HDI-protein conjugate administered by means of an intranasal droplet.

RESULTS

HDI sensitization resulted in development of contact hypersensitivity and HDI-specific antibody production. Most importantly, however, vigorous inflammatory responses with characteristics of human asthma were generated in the lung after inhaled HDI challenge. Challenge of sensitized, but not unsensitized, mice resulted in airway eosinophilia, mucus hypersecretion, and production of T(H)1-type (IFN-gamma) and T(H)2-type (IL-4, IL-5, and IL-13) cytokines by lung inflammatory cells. Despite the mixed T(H)1/T(H)2 response induced by HDI sensitization, use of cytokine-deficient mice revealed that airway eosinophilia was mediated by T(H)2 cytokines and not by IFN-gamma.

CONCLUSION

We report a novel mouse model of diisocyanate-induced asthma that, in contrast to previous models, demonstrates antigen-induced lung inflammation with characteristics of human disease. This model will allow investigation of the immunopathogenesis of diisocyanate-induced asthma and should provide insight into this common form of occupational disease.

Increased Th1 and Th2 allergen-induced cytokine responses in children with atopic disease

BACKGROUND

Polyclonal cytokine responses following stimulation of T cells with mitogens or superantigens provides information on cytokine production from a wide range of T cells. Alternatively allergen-induced T cell responses can provide information on cytokine production by allergen-reactive T cells. While there is evidence of increased Th2 and reduced Th1 cytokine production following T cell stimulation with non-specific mitogens and superantigens, the evidence that Th1 cytokine production to allergens is decreased in line with a postulated imbalance in Th1/Th2 responses is unclear, with studies finding decreased, no difference or increased IFN-gamma responses to allergens in atopic subjects.

OBJECTIVE

To examine childhood polyclonal and allergen-induced cytokine responses in parallel to evaluate cytokine imbalances in childhood atopic disease.

METHODS

PBMC cytokine responses were examined in response to a polyclonal stimulus, staphylococcal superantigen (SEB), in parallel with two inhalant allergens, house dust mite (HDM) and rye grass pollen (RYE), and an ingested allergen, ovalbumin (OVA), in (a) 35 healthy children (non-atopic) and (b) 36 children with atopic disease (asthma, eczema and/or rhinitis) (atopic).

RESULTS

Atopic children had significantly reduced IFN-gamma and increased IL-4 and IL-5 but not IL13 production to SEB superantigen stimulation when compared with non-atopic children. HDM and RYE allergens stimulated significantly increased IFN-gamma, IL-5 and IL-13, while OVA stimulated significantly increased IFN-gamma production in atopic children.

CONCLUSION

We show that a polyclonal stimulus induces a reduced Th1 (IFN-gamma) and increased Th2 (IL-4 and IL-5) cytokine pattern. In contrast, the allergen-induced cytokine responses in atopic children were associated with both increased Th1 (INF-gamma) and Th2 (IL-5 and IL-13) cytokine production. The increased Th1 response to allergen is likely to reflect prior sensitization and indicates that increases in both Th1 and Th2 cytokine production to allergens exists concomitantly with a decreased Th1 response to a polyclonal stimulus in atopic children.

Regulatory effect of cytokine production in asthma patients by SOOJI CHIM (Koryo Hand Acupuncture Therapy)

Acupuncture has become quite familiar to many Koreans not only for pain, but also for many other health problems, both in acute and chronic conditions. Actually, acupuncture is a therapeutic technique that is part of a larger system of traditional oriental medicine. There are several styles of acupuncture. We investigated the regulatory effects of cytokine production in peripheral blood of asthma patients (AP) by SOOJI CHIM (Koryo Hand Acupuncture Therapy, KHT). Clinical signs of asthma disappeared markedly by KHT. The mean interleukin (IL)-2 and IL-6 plasma levels were lower in the AP group than in the normal group, whereas the mean interferon (IFN)-gamma, IL-4, and tumor necrosis factor (TNF)-alpha levels were higher in the AP group. Plasma IFN-gamma and IL-2 levels derived from T helper (Th)1 cells and IL-4 levels derived from Th2 cells were elevated in the AP group by KHT. Especially, plasma IL-6 levels derived from Th2 cells were elevated significantly in the AP group by KHT. Reduced plasma levels of TNF-alpha were observed in the AP group by KHT. Plasma IgE levels were also measured but there were no significant differences from each other. During the KHT, there were no other adverse effects. These results indicate that KHT has a good asthma treatment effect, and that its action may be due to the regulation of cytokine production.

The pathophysiology of asthma

Asthma is a chronic disorder of the airways that is characterized by reversible airflow obstruction and airway inflammation, persistent airway hyperreactivity, and airway remodeling. The etiology of asthma is complex and multifactorial. Recent advances have demonstrated the importance of genetics in the development of asthma, particularly atopic asthma. Environmental stimuli, particularly early childhood infections, have also been associated with the development of asthma. Most current data seem to suggest that these factors drive the development of a Th-2 lymphocyte-predominant immune response, which has been associated with atopy and IgE-mediated inflammation. The concept of reversible airflow obstruction has also recently been challenged. It is now clear that chronic airway changes occur, which may contribute to progressive airflow obstruction. We discuss the important influence of genetic and environmental factors on the emergence of the asthmatic phenotype. The significance of Th-1 and Th-2 lymphocyte-mediated immunity are discussed, and the inflammatory processes leading to chronic airway inflammation are detailed.

Similar T helper Th2-like cytokine mRNA expression in vernal keratoconjunctivitis regardless of atopic constitution

BACKGROUND

Many patients with vernal keratoconjunctivitis (VKC), a severe chronic allergic eye disease in children, exhibit IgE-sensitization, but about 40% of cases lack this immunologic trait. As a disease factor in VKC, IgE is thus not fully understood. The aim of this study was to investigate whether there are any differences in the conjunctival cytokine messenger (m)RNA pattern related to IgE-sensitization in children suffering from VKC.

METHODS

Tissue samples were obtained from 16 symptomatic VKC subjects with sub-tarsal disease and six control subjects. Expression of mRNA for interleukin (IL)-4, IL-5, IL-13, and interferon (IFN)-gamma was investigated with a semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR) technique. The presence of T cells, IgE+ cells, mast cells, and eosinophils was analyzed with immunohistochemical methods. Allergen-specific IgE antibodies were assessed in serum and with skin prick testing.

RESULTS

Ten out of the 16 VKC subjects showed evidence of IgE-sensitization. No differences were detected for any tissue variable between VKC subjects with and without IgE-sensitization. Statistically significant increases over controls were found for both VKC groups with regard to all cell markers.

CONCLUSIONS

The amount of messenger RNA encoding cytokines and inflammatory cell markers in VKC did not correlate with IgE-sensitization. Tissue changes in all patient samples were characterized by a prevalence of T cells, eosinophils, mast cells and cell-bound IgE molecules. However, the role of cell-bound IgE molecules in VKC patients lacking IgE-sensitization remains to be determined.

Increased interleukin-4 and decreased interferon gamma production in children with asthma: function of atopy or asthma?

Both atopy and asthma are claimed to be associated with a Th-2 cytokine pattern. We sought to determine the contribution of atopy and asthma to the observed Th-2/Th-1 imbalance in these conditions. Of 60 children aged 6-16 years that were included in the study, 13 were nonatopic nonasthmatic, 15 atopic nonasthmatic, 14 nonatopic asthmatic, and 18 atopic asthmatic. Atopic children had positive skin prick tests to grass pollens only. All children were studied after an asymptomatic and drug-free period of at least three months. Total IgE was measured in serum. Peripheral blood mononuclear cells were cultured and stimulated in vitro with phytohemagglutinin and interferongamma (IFN-gamma) and interleukin-4 (IL-4) measured in the supernatants. Total IgE was significantly higher in atopic asthmatics compared to nonatopic asthmatics (p = 0.004), and nonatopic nonasthmatics (p = 0.001), but was not different from atopic nonasthmatics (p >0.05). On the other hand, IL-4 was significantly elevated in atopic asthmatics and in nonatopic asthmatics compared to nonatopic nonasthmatics (p = 0.037 and p = 0.009, respectively). Although atopic asthmatics had lower IFN-gamma values than nonatopic asthmatics, the difference did not reach statistical significance. No correlation was detected between any two parameters. Our results suggest that both atopy and asthma contribute to the increased levels of IL-4 and that, whereas nonatopic asthma is associated with increases in both IL-4 and IFN-gamma release by mononuclear cells, only atopic asthma is characterized by a Th-2 type cytokine dominance.

Mycoplasma pneumoniae-induced activation and cytokine production in rodent mast cells

BACKGROUND

Mycoplasma pneumoniae is a respiratory tract pathogen that has been associated with severe exacerbations in patients with chronic asthma. Murine models of infection have recently been established, with disease manifestations similar to those observed in human subjects. Previous studies have suggested that this organism is capable of producing activation of a wide range of immunologic cell types.

OBJECTIVE

We sought to determine whether M pneumoniae can induce mast cell activation in the rodent mast cell line RBL-2H3.

RESULTS

After 4 hours of coculture, morphologic changes indicative of activation were observed by means of electron microscopy, and M pneumoniae was identified, by means of immunoelectron microscopy, adhering to mast cell membranes. Coculture of rat basophilic leukemia cells with viable M pneumoniae for 4 hours resulted in net release of beta-hexosaminidase and serotonin into the supernatant. Live, but not heat-killed, organisms induced the release of IL-4 protein into the culture supernatant, with a peak at 4 hours. During coculture with M pneumoniae, production of mRNA for IL-4, IL-6, and TNF-alpha was upregulated after 2 hours and had returned to near baseline by 24 hours after infection.

CONCLUSIONS

We conclude that viable M pneumoniae induces activation of mast cells with release of granule contents, as well as cytokine production.