New concepts of cytokines in asthma: is the Th2/Th1 paradigm out the window?

Neonatal airway immune profiles and asthma and allergy endpoints in childhood

BACKGROUND

The immune system plays a key role in the pathogenesis of asthma and allergy, but the role of the airway cytokine and chemokine composition in vivo in early life prior to symptom development has not been described previously. Here, we aimed to examine whether the neonatal airway immune composition associates with development of allergy and asthma in childhood.

METHODS

We measured unstimulated levels of 20 immune mediators related to the Type 1, Type 2, Type 17, or regulatory immune pathways in the airway mucosal lining fluid of 620 one-month-old healthy neonates from the COPSAC₂₀₁₀ birth cohort. Allergy and asthma were diagnosed at our research clinic by predefined algorithms and objective assessments at age 6 years. Principal component analyses were used to describe the airway cytokine and chemokine composition.

RESULTS

A neonatal airway immune profile particularly characterized by enhanced IL-1β and reduced CCL26 was significantly associated with later development of elevated specific IgE to inhaled allergens, a positive skin prick test, and allergic rhinitis, but not with food sensitization. Conversely, reduced Type 17 immune-associated markers, including IL-1β and CXCL8, showed trend of association with development of early asthma endpoints.

CONCLUSIONS

Development of early asthma endpoints and inhalant allergy during the first 6 years of life seems associated with distinctly perturbed airway immune profiles in neonatal life, which is suggestive of an early origin and different pathogenesis of childhood asthma and allergy. These exploratory findings suggest pre- and perinatal life as an important window of opportunity for prevention of asthma and inhalant allergy.

Crosstalk between cytokine profile, redox, and iron status in β-Thalassemia: relation to frequency/duration of blood transfusion

β-Thalassemia, a blood disease instigated by mutations in β-globin genes or their regulatory regions. Infectious complications, immune abnormalities and iron overload related organ damage are the chief causes of morbidity and mortality. The role of inflammatory cytokines in the pathophysiology of β-thalassemia is still indistinct, so the present study aimed to evaluate immune-inflammatory and redox status in β-thalassemia and their relation to iron status, frequency/duration of blood transfusion. Seventy β-Thalassemia patients (35 β-thalassemia major; 35 β-thalassemia intermedia) and twenty age and sex-matched healthy controls were included. Interleukin4 (IL4), Interleukin10 (IL10), Interleukin 8 (IL8), and Interleukin 13 (IL13) levels were immunoassayed in addition to iron, hematological and redox status assessment. Significantly increased iron, ferritin, IL8, IL13 levels (p value ˂0.001), meanwhile, decreased IL10 level, total anti-oxidant (TAC) and iron binding capacities were observed in β-thalassemia major compared with β-thalassemia intermedia and control groups (p value ˂0.001) . IL4 level was decreased in patients group compared to control. Positive correlation was found between malondialdehyde (MDA), IL8, IL13 and iron load, transfusion frequency/duration, total leucocyte count and lymphocyte (%). Meanwhile, negative correlation was found with IL4, IL10, and TAC. Multiple blood transfusions increased iron stores which may critically impair the immune-regulatory balance with disturbed redox status and cytokine profile.

Diagnostic Value of Serum Baseline Tryptase Levels in Childhood Asthma and Its Correlation with Disease Severity

BACKGROUND

The aim of this study was to explore whether serum baseline tryptase (sBT) levels might be a useful marker not only for the accurate diagnosis of childhood asthma, but also for the prediction of disease severity.

METHODS

A total of 114 asthmatic children were enrolled in this study, 36 of whom had mild intermittent asthma, 38 had mild persistent asthma, and 40 had moderate to severe persistent asthma. Additionally, 34 age-matched healthy children were enrolled as controls. The sBT levels of these populations were measured using a fluoroenzymeimmunoassay kit. The diagnostic performance of sBT levels and their correlation with asthma severity were systematically investigated using receiver operating characteristic (ROC) analysis and correlation analysis.

RESULTS

Children with mild and moderate to severe persistent asthma had significantly increased sBT levels as compared to those with mild intermittent asthma and healthy controls. ROC analysis further demonstrated that sBT levels not only appear to be highly sensitive and specific for distinguishing asthmatic children from healthy controls, but also show good accuracy for the differentiation of various asthmatic subgroups. Correlation analysis revealed that in all asthmatic subgroups sBT levels were significantly correlated with a variety of key markers that reflect the disease severity of asthma, including childhood asthma control test scores, serum IgE and interleukin-13 levels, blood eosinophil counts, and pulmonary test parameters.

CONCLUSIONS

sBT levels may have a potential use in supporting a diagnosis of asthma in children and as a predictor of disease severity.

Siblings Promote a Type 1/Type 17-oriented immune response in the airways of asymptomatic neonates

BACKGROUND

Siblings have been shown to reduce the risk of childhood asthma and allergy, but the mechanism driving this association is unknown. The objective was to study whether siblings affect the airway immune response in healthy neonates, which could represent an underlying immune modulatory pathway.

METHODS

We measured 20 immune mediators related to the Type 1, Type 2, Type 17, or regulatory immune pathways in the airway mucosa of 571 one-month-old asymptomatic neonates from the Copenhagen Prospective Studies on Asthma in Childhood2010 birth cohort (COPSAC2010 ). The association between airway mediator levels and presence of siblings was investigated using conventional statistics and principle component analysis (PCA).

RESULTS

Neonates with siblings had an upregulated level of airway immune mediators, with predominance of Type 1- and Type 17-related mediators. This was supported by the PCA showing a highly significant difference between children with vs without siblings: P < 10(-10) , which persisted after adjustment for potential confounders including pathogenic airway bacteria and viruses: P < 0.0001. The immune priming effect was inversely associated with time since last childbirth: P = 0.0015.

CONCLUSIONS

Siblings mediate a Type 1/Type 17-related immune-stimulatory effect in the airways of asymptomatic neonates, also after adjustment for pathogenic bacteria and viruses, indicating that siblings exert a transferable early immune modulatory effect. These findings may represent an in utero immune priming effect of the fetal immune system caused by previous pregnancies as the effect was attenuated with time since last childbirth, or it could relate to the presence of unidentified microbes, but further studies are needed to confirm our findings.

Picornavirus-Induced Airway Mucosa Immune Profile in Asymptomatic Neonates

BACKGROUND

Bacterial airway colonization is known to alter the airway mucosa immune response in neonates whereas the impact of viruses is unknown. The objective was therefore to examine the effect of respiratory viruses on the immune signature in the airways of asymptomatic neonates.

METHODS

Nasal aspirates from 571 asymptomatic 1-month-old neonates from the Copenhagen Prospective Studies on Asthma in Childhood 2010 birth cohort were investigated for respiratory viruses. Simultaneously, unstimulated airway mucosal lining fluid was obtained and quantified for levels of 20 immune mediators related to type 1, type 2, type 17, and regulatory immune paths. The association between immune mediator levels and viruses was tested by conventional statistics and partial least square discriminant analysis.

RESULTS

Picornaviruses were detected in 58 neonates (10.2%) and other viruses in 10 (1.8%). A general up-regulation of immune mediators was found in the neonates with picornavirus (P < .0001; partial least square discriminant analysis). The association was pronounced for type 1- and type 2-related markers and was unaffected by comprehensive confounder adjustment. Detection of picornavirus and bacteria was associated with an additive general up-regulating effect.

CONCLUSIONS

Asymptomatic presence of picornavirus in the neonatal airway is a potent activator of the topical immune response. This is relevant to understanding the immune potentiating effect of early life exposure to viruses.

Gpr97 Is Dispensable for Inflammation in OVA-Induced Asthmatic Mice

BACKGROUND

Asthma is a complex inflammatory disorder involving the activation and invasion of various immune cells. GPR97 is highly expressed in some immunocytes, including mast cells and eosinophils, which play critical roles in asthma development. However, the role of Gpr97 in regulating airway inflammation in asthma has rarely been reported. In this study, we investigated the potential role of Gpr97 in the development of allergic asthma in mice.

METHODS

Relevant airway asthmatic mouse models were constructed with both wild-type and Gpr97-/- mice sensitized to 250 μg ovalbumin (OVA). The levels of interleukin IL-4, IL-6 and IFN-γ, which are involved in OVA-induced asthma, in the bronchoalveolar lavage fluid (BALF) and the IgE level in the serum were examined by enzyme-linked immunosorbent assay (ELISA). The invasion of mast cells and eosinophils into lung tissues was assessed by immunohistochemical and eosinophil peroxidase activity assays, respectively. Goblet cell hyperplasia and mucus production were morphologically evaluated with periodic acid-Schiff (PAS) staining.

RESULTS

In our study, no obvious alteration in the inflammatory response or airway remodeling was found in the Gpr97-deficient mice with OVA-induced asthma. Neither the secretion of cytokines, including IL-4, IL-6 and IFN-γ, nor inflammatory cell recruitment was altered in the Gpr97-deficient mice. Moreover, Gpr97 deficiency did not affect airway remodeling or mucus production in the asthma mouse model.

CONCLUSION

Our findings imply that Gpr97 might not be required for the development of airway inflammation in OVA-induced allergic asthma in mice.

Pathogenic bacteria colonizing the airways in asymptomatic neonates stimulates topical inflammatory mediator release

RATIONALE

Bacterial colonization of neonatal airways with the pathogenic bacterial species, Moraxella catarrhalis, Streptococcus pneumoniae, and Haemophilus influenzae, is associated with later development of childhood asthma.

OBJECTIVES

To study a possible association between colonization with pathogenic bacterial strains and the immune signature of the upper airways in healthy neonates.

METHODS

A total of 20 cytokines and chemokines were quantified in vivo in the airway mucosal lining fluid of 662 neonates from the Copenhagen Prospective Study of Asthma in Childhood 2010 birth cohort. Colonization of the hypopharynx with M. catarrhalis, S. pneumoniae, H. influenzae, and Staphylococcus aureus was assessed simultaneously. The association between immune signatures and bacterial colonization or noncolonized controls was analyzed using conventional statistical methods supplemented by a multivariate approach for pattern identification.

MEASUREMENTS AND MAIN RESULTS

Colonization with M. catarrhalis and H. influenzae induced a mixed T helper cell (Th) type 1/Th2/Th17 response with high levels of IL-1β (M. catarrhalis, P = 2.2 × 10(-12); H. influenzae, P = 7.1 × 10(-10)), TNF-α (M. catarrhalis, P = 1.5 × 10(-9); H. influenzae, P = 5.9 × 10(-7)), and macrophage inflammatory protein-1β (M. catarrhalis, P = 1.6 × 10(-11); H. influenzae, P = 2.7 × 10(-7)). S. aureus colonization demonstrated a Th17-promoting profile with elevated IL-17 levels (P = 1.6 × 10(-24)). S. pneumoniae colonization was not significantly associated with any of the mediators.

CONCLUSIONS

M. catarrhalis and H. influenzae colonization of the airways of asymptomatic neonates is associated with an inflammatory immune response of the airway mucosa, which may result in chronic inflammation.

Immunological markers in allergic rhinitis patients treated with date palm immunotherapy

OBJECTIVE

Allergic rhinitis (AR) is regulated by the local production and release of several cytokines. Allergen specific immunotherapy (IT) has been widely used for many years as a specific treatment of allergic diseases. This study aimed to investigate the changes in clinical and immunological markers before and after Phoenix dactylifera IT in AR patients.

MATERIALS AND METHODS

Total symptom score and levels of total immunoglobulin E (IgE), albumin, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-4, and IL-13 were measured in the serum and nasal samples of thirty non-atopic healthy controls and thirty patients with allergic rhinitis before and after 15 months of IT.

RESULTS

We found significantly higher concentrations of serum TNF-α and nasal TNF-α and IL-13, and significantly lower concentration of nasal IL-10, in allergic patients than in non-allergic. Moreover, serum and nasal IL-10 increased significantly after IT. However, there was neither a significant reduction in total IgE nor a significant increase in IFN-γ at the end of IT.

CONCLUSIONS

Our data show a clinical improvement associated with a decline in some inflammation parameters after IT. Moreover, date palm IT induced a significant increase in serum and nasal IL-10 levels.

IL-13 dampens human airway epithelial innate immunity through induction of IL-1 receptor-associated kinase M

BACKGROUND

Impaired airway mucosal immunity can contribute to increased respiratory tract infections in asthmatic patients, but the involved molecular mechanisms have not been fully clarified. Airway epithelial cells serve as the first line of respiratory mucosal defense to eliminate inhaled pathogens through various mechanisms, including Toll-like receptor (TLR) pathways. Our previous studies suggest that impaired TLR2 function in T(H)2 cytokine-exposed airways might decrease immune responses to pathogens and subsequently exacerbate allergic inflammation. IL-1 receptor-associated kinase M (IRAK-M) negatively regulates TLR signaling. However, IRAK-M expression in airway epithelium from asthmatic patients and its functions under a T(H)2 cytokine milieu remain unclear.

OBJECTIVES

We sought to evaluate the role of IRAK-M in IL-13-inhibited TLR2 signaling in human airway epithelial cells.

METHODS

We examined IRAK-M protein expression in epithelia from asthmatic patients versus that in normal airway epithelia. Moreover, IRAK-M regulation and function in modulating innate immunity (eg, TLR2 signaling) were investigated in cultured human airway epithelial cells with or without IL-13 stimulation.

RESULTS

IRAK-M protein levels were increased in asthmatic airway epithelium. Furthermore, in primary human airway epithelial cells, IL-13 consistently upregulated IRAK-M expression, largely through activation of phosphoinositide 3-kinase pathway. Specifically, phosphoinositide 3-kinase activation led to c-Jun binding to human IRAK-M gene promoter and IRAK-M upregulation. Functionally, IL-13-induced IRAK-M suppressed airway epithelial TLR2 signaling activation (eg, TLR2 and human β-defensin 2), partly through inhibiting activation of nuclear factor κB.

CONCLUSIONS

Our data indicate that epithelial IRAK-M overexpression in T(H)2 cytokine-exposed airways inhibits TLR2 signaling, providing a novel mechanism for the increased susceptibility of infections in asthmatic patients.

Gene-environment interaction in childhood asthma

The importance of early life environmental influences on the etiology of asthma is implied by the observed geographic and temporal variation in the prevalence of the disease among children. There is evidence pointing to the role of exposure to allergen, various aspects of diet and hygiene-related factors in the etiology of asthma. There is also evidence that heritable factors influence the impact of hygiene-related exposures on the risk of having asthma. A number of important gene-environment interactions have been identified. These interactions point to the biology of environmental exposures as the involved genetic variation is suggestive of certain underlying mechanisms. Polymorphisms within genes coding for the toll-like receptor-lipopolysaccharide (TLR-LPS) signalling pathway may underlie variations in effects of hygiene-related exposures, including specifically endotoxin, on the risk of developing allergic sensitization and allergic disease. This review presents recent findings illustrating the role of gene-environment interactions in childhood asthma susceptibility.

Post-allergen challenge inhibition of poly(ADP-ribose) polymerase harbors therapeutic potential for treatment of allergic airway inflammation

BACKGROUND

Identifying therapeutic drugs that block the release or effects of T-helper type 2 (Th2) cytokines after allergen exposure is an important goal for the treatment of allergic inflammatory diseases including asthma. We recently showed, using a murine model of allergic airway inflammation, that poly(ADP-ribose) polymerase (PARP) plays an important role in the pathogenesis of asthma-related lung inflammation. PARP inhibition, by single injection of a novel inhibitor, thieno[2,3-c]isoquinolin-5-one (TIQ-A), before ovalbumin (OVA) challenge, prevented airway eosinophilia in C57BL/6 mice with concomitant suppression of Th2 cytokine production and mucus secretion.

OBJECTIVE

To evaluate the efficacy of the drug when it is given after OVA challenge for its possible therapeutic potential.

METHODS

This study was conducted using a murine model of allergic airway inflammation.

RESULTS

A single injection of TIQ-A (6 mg/kg) one or 6 h post-allergen challenge conferred similar reduction in OVA challenge-induced eosinophilia. More significantly, post-allergen challenge administration of the drug exerted even better suppression on the production of IL-4, IL-5, IL-13, and IgE and prevented airway hyperresponsiveness to inhaled-methacholine. The significant decrease in IL-13 was accompanied by a complete absence of airways mucus production indicating a potential protection against allergen-induced airway remodelling.

CONCLUSION

The coincidence of the inflammation trigger and the time of drug administration appear to be important for the drug's more pronounced protection. The observed time window for efficacy, 1 or 6 h after allergen challenge may be of great clinical interest. These findings may provide a novel therapeutic strategy for the treatment of allergic airway inflammation, including asthma.

Exhaled nitric oxide for monitoring childhood asthma inflammation compared to sputum analysis, serum interleukins and pulmonary function

The level of fractional exhaled nitric oxide (FENO) is significantly elevated in uncontrolled asthma and decreases after anti-inflammatory therapy. The aim of this prospective study was to analyze the behavior of FENO in the follow-up and management of the inflammation in asthmatic pediatric patients treated with inhaled corticosteroids (ICS), compared to sputum cellularity, serum interleukins (IL), and pulmonary function. Twenty-six clinically stable asthmatic children aged from 6 to 18 years, previously treated or not with ICS were included. Following an international consensus (GINA), the patients were submitted to standard treatment with inhaled fluticasone for 3 months according to the severity of the disease. During this period, each patient underwent three assessments at intervals of approximately 6 weeks. Each evaluation consisted of the measurement of FENO, determination of serum interleukins IL-5, IL-10, IL-13, and interferon gamma (INF-gamma), spirometry and cytological analysis of spontaneous or induced sputum. A significant reduction in mean FENO and IL-5, without concomitant changes in FEV1, was observed along the study. There was no significant correlation between FeNO and FEV1 in the three assessments. A significant correlation between FeNO and IL-5 levels was only observed in the third assessment (r = 0.499, P = 0.025). In most patients, serum IL-10, IL-13, and INF-gamma concentrations were undetectable throughout the study. Sputum samples were obtained spontaneously in 11 occasions and in 56 by induction with 3% hypertonic saline solution (success rate: 50.8%), with 39 (69.9%) of them adequate for analysis. Only two of the 26 patients produced adequate samples in the three consecutive evaluations, which impaired the determination of a potential association between sputum cellularity and FeNO levels throughout the study. In conclusion, among the parameters of this study, it was difficult to perform and to interpret the serial analysis of spontaneous or induced sputum. Serum interleukins, which remained at very low or undetectable levels in most patients, were not found to be useful for therapeutic monitoring, except for IL-5 that seems to present some correlation with levels of FeNO exhaled. Monitoring of the mean FEV1 indicated no significant variations during the treatment, demonstrating that functional stability or the absence of obstruction may not reflect the adequate management of asthma. Serial measurement of FeNO seemed to best reflect the progressive anti-inflammatory action of ICS in asthma.

Gene-environment interactions in asthma

The underlying pathogenesis of asthma, one of the most common chronic diseases of childhood, is not fully understood. There is a well-documented heritable component to this disease and environmental factors associated with a Westernised lifestyle have also been implicated; recent studies suggest gene-environment interactions are important in the development of this disease. In the absence of a previous review in children, the present report presents the accumulating evidence for gene-environment interactions in asthma pathogenesis. Studies of these interactions in different populations have yielded both expected and unexpected results. This is a new and rapidly developing field where there are currently many more questions than answers.

T-helper type 2 polarization among asthmatics during and following pregnancy

BACKGROUND

Asthma is the most common medical condition during pregnancy. While increased production of T helper cytokines has been reported to occur in both asthma and pregnancy, the effect of T-helper type 2 (Th2) polarization on asthma symptoms during pregnancy has not been well-characterized.

OBJECTIVE

We hypothesized that systemic Th2 cytokine and chemokine polarization occurs among asthmatics to a greater extent during their pregnancy, and is associated with more severe asthma and increased Th2 polarization in the newborn.

METHODS

Fifty-six pregnant asthmatics were recruited from prenatal clinics affiliated with New York Presbyterian Hospital. Systemic production of interleukin-4, interferon-gamma, eotaxin and IP10 were measured by intracytoplasmic staining or ELISA at recruitment, peripartum and post-partum, and in the cord blood. The frequency of asthma symptoms was measured by questionnaires and compared with Th biomarkers.

RESULTS

The chemokine ratio (IP10/eotaxin) declined over the course of pregnancy (from 3.3 +/- 1.3 to 1.4 +/- 0.2, P = 0.016), but IP10 and eotaxin increased post-partum. The decrease in the chemokine ratio was associated with more frequent asthma symptoms. A non-significant trend towards decreased interferon-gamma and increased interleukin-4 production was detected. Cord blood eotaxin levels correlated with maternal levels (r = 0.35, P = 0.03). Other peripartum biomarkers were not associated with Th2 polarization nor with subsequent respiratory symptoms in the newborn.

CONCLUSION

IP10/eotaxin declined over the course of pregnancy and was associated with worse asthma symptoms. Alterations of Th1/Th2 chemokine balance during pregnancy may identify women prone to more severe asthma during pregnancy.

Poly(ADP-ribose) polymerase-1 inhibition prevents eosinophil recruitment by modulating Th2 cytokines in a murine model of allergic airway inflammation: a potential specific effect on IL-5

We recently used a murine model of allergic airway inflammation to show that poly(ADP-ribose) polymerase-1 (PARP-1) plays an important role in the pathogenesis of asthma-related lung inflammation. In this study, we show that PARP-1 inhibition, by a novel inhibitor (TIQ-A) or by gene deletion, prevented eosinophilic infiltration into the airways of OVA-challenged mice. Such impairment of eosinophil recruitment appeared to take place after IgE production. OVA challenge of wild-type mice resulted in a significant increase in IL-4, IL-5, IL-10, IL-13, and GM-CSF secretions. Although IL-4 production was moderately affected in OVA-challenged PARP-1(-/-) mice, the production of IL-5, IL-10, IL-13, and GM-CSF was completely inhibited in ex vivo OVA-challenged lung cells derived from these animals. A single TIQ-A injection before OVA challenge in wild-type mice mimicked the latter effects. The marked effect PARP-1 inhibition exerted on mucus production corroborated the effects observed on the Th2 response. Although PARP-1 inhibition by gene knockout increased the production of the Th1 cytokines IL-2 and IL-12, the inhibition by TIQ-A exerted no effect on these two cytokines. The failure of lung cells derived from OVA-challenged PARP-1(-/-) mice to synthesize GM-CSF, a key cytokine in eosinophil recruitment, was reestablished by replenishment of IL-5. Furthermore, intranasal administration of IL-5 restored the impairment of eosinophil recruitment and mucus production in OVA-challenged PARP-1(-/-) mice. The replenishment of either IL-4 or IgE, however, did not result in such phenotype reversals. Altogether, these results suggest that PARP-1 plays a critical role in eosinophil recruitment by specifically regulating the cascade leading to IL-5 production.

Paediatric basis of adult lung disease

Most lung disease throughout life is programmed in utero or early post-natal life. Factors in the fetal environment such as maternal smoking and diet can lead to reduced lung function, immunological modification or symptoms from birth. There are clear genetic components documented for cystic fibrosis, alpha1 anti-trypsin deficiency and asthma. In early life, the outcomes for those predisposed to asthma or allergy appear to be dependent on the relative timing of exposure to infective agents, allergens or helminths. Abnormal airway structure is present in both transient and persistent wheezers. New drugs and environmental manipulations will need to be developed with an understanding of the mechanisms associated with this early programming.

Does paternal antigen-induced secretion of interleukin-10 by T regulatory cells mediate the birth order effect?

Childhood allergy constitutes a significant burden of disease in the Western world. The prevalence of this condition is highest in first born children, an as yet unresolved phenomenon called the "birth order effect". The hygiene hypothesis attempted to explain this differential risk by stating that less exposure to microbial agents at an early age of first born children would result in reduced activation of the immune system and subsequent polarization towards a Th2 phenotype. However, no conclusive evidence for or against the hygiene hypothesis has been found so far. Another, not necessarily conflicting, theory states that the birth order effect is already established during prenatal life and that the fetal-maternal interaction changes during successive pregnancies. Combining this theory with research on preeclampsia, another disease originating in pregnancy and also related to birth order, could suggest clues about the mechanisms underlying the birth order effect. Recent research on preeclampsia showed that preeclamptic women have higher levels of pro-inflammatory IL-6 and lower paternal antigen-induced secretion of IL-10 compared to normal pregnant women, indicating a lower number or lower functional activity of T regulatory (Treg) cells. These Treg cells play an important role in maintaining tolerance to fetal antigens in pregnancy and they are found in high numbers at the maternal-fetal interface. We hypothesize that nulliparous women have a lower activity of Treg cells specific to paternal antigens compared to parous women, either in peripheral blood or in the decidua (maternal part of the fetal-maternal interface). If this hypothesis is true, this would mean that the allergen suppressor mechanism of Treg cells is sub-optimal in first born children. This would explain at least a part of the mechanism of the birth order effect and would give us directions for developing preventive measures to prevent possibly 30% of future childhood allergies.

Chemokines and their receptors in the pathogenesis of allergic asthma: progress and perspective

PURPOSE OF REVIEW

The importance of chemokines and their receptors to development and maintenance of allergic asthma is reflected in the burgeoning amount of literature currently devoted to this topic. Based on a series of selected references published during the last year, this review now summarizes recent advances and discusses the likely implications of these findings.

RECENT FINDINGS

Of particular interest are reports describing novel interactions between chemokines and both eosinophils and mast cells, including a role for CXCL5 (epithelial cell-derived neutrophil-activating peptide-78) and intracellular CCR3. New insights into TH2-cell dominance are presented in reports dealing with a range of chemokines, including CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CCL5 (RANTES), CXCL9 (Mig), and CXCL10 (IP-10). The increasing importance of structural cell participation is emphasized by reports focusing on the eotaxin family (CCL11, CCL24, and CCL26), as well as CCL17 (TARC), CCL22 (MDC), CXCL9 (Mig), and CX3CL1 (Fractalkine). A developing role for nonreceptor regulatory mechanisms is also emphasized by seminal work relating to metalloproteinases, as well as reports focusing on proteoglycans and beta-Arrestin-2. Finally, significant progress in the field of asthma heritability is featured in reports relating to both known and novel genes, including those encoding CCR5 and DPP-10.

SUMMARY

The critical influence of chemokine biology on the outcome of allergic asthma continues to be highlighted in recent reports describing novel mechanisms by which eosinophils are recruited into the lung and local TH2-cell dominance is maintained. Also of considerable interest is the increasing emphasis currently being realized for structural cell participation, nonreceptor regulatory mechanisms, and the influence of susceptibility genes.

Th2 response of human peripheral monocytes involves isoform-specific induction of monoamine oxidase-A

Monocyte/macrophage function is critically regulated by specific cytokines and growth factors that they are exposed to at inflammatory sites. IL-4 and IL-13 are multifunctional cytokines generated mainly by Th2 lymphocytes that have important biological activities in allergy and inflammation. The Th2 response of human peripheral monocytes is characterized by complex alterations in the gene expression pattern, which involves dominant expression of CD23 cell surface Ag and lipid-peroxidizing 15-lipoxygenase-1 (15-LOX1). In this study, we report that the classical Th2 cytokines IL-4 and IL-13 strongly up-regulate expression of monoamine oxidase A (MAO-A) with no induction of the closely related isozyme, MAO-B. Real-time PCR indicated a >2000-fold up-regulation of the MAO-A transcripts, and immunohistochemistry revealed coexpression of the enzyme with 15-LOX1 in a major subpopulation of monocytes. MAO-A was also induced in lung carcinoma A549 cells by IL-4 in parallel with 15-LOX1. In promyelomonocytic U937 cells, which neither express 15-LOX1 nor MAO-A in response to IL-4 stimulation, expression of MAO-A was up-regulated following transfection with 15-LOX1. This is the first report indicating expression of MAO-A in human monocytes. Its isoform-specific up-regulation in response to Th2 cytokines suggests involvement of the enzyme in modulation of innate and/or acquired immune system.