Altered phosphorylated signal transducer and activator of transcription profile of CD4+CD161+ T cells in asthma: modulation by allergic status and oral corticosteroids

Immune phenotype changes in IgG4-related disease: CD161 + Treg and Foxp3 + Treg

OBJECTIVE

We aimed to characterize the alterations in the immune phenotypes and explore the potential relevance to pathogenesis in IgG4-RD.

METHODS

Forty-two IgG4-RD patients and thirty-eight healthy controls were recruited in this study. Peripheral immunocompetent cells including T cells, CD4 + T cells, CD8 + T cells, B cells, NK cells CD4 + CD45RA + T cells (naïve T cells), CD4 + CD25 - / + Foxp3 - T cells (Teff), CD4 + CD25hiCD127lowCD161 + T cells (CD161 + Treg), CD4 + CD25hiFoxp3 + T cells (Foxp3 + Treg), CD4 + CD4RA-CXCR5 + PD1 + CCR7low T cells (pTfh), T helper (Th) 1, Th2, and Th17 before and after treatment were immunophenotyped by flow cytometry.

RESULTS

Compared with healthy controls, IgG4-RD patients showed higher proportions of NK (20.1% vs 13.6%, p < 0.01), Th1 (CD4 + IFN-γ + : 17.9% vs 14.2%, p = 0.061; TNF-α: 43.7% vs 36.7%, p < 0.05), Th2 (CD4 + IL-4 + : 2.4% vs 1.3%, p < 0.0001), CD161 + Treg (14.9% vs 11.6%, p < 0.01), pTfh (3.2% vs 2.4%, p < 0.05), and Foxp3 + Treg (8.3% vs 7.0%, p < 0.01) and lower proportions of B lymphocytes (8.4% vs 13.1%, p < 0.001), Teff (91.6% vs 92.6%, p < 0.01), and naïve Th cells (19.9% vs 32.1%, p < 0.01) before treatment. Foxp3 + Treg percentage decreased significantly after treatment (8.6% vs 6.9%, p < 0.05). Both serum C3 (r =  - 0.6374, p < 0.01) and C4 (r =  - 0.6174, p < 0.01) levels were in negative correlation with CD161 + Treg. The eosinophil percentage was positively correlated with Foxp3 + Treg (r = 0.5435, p < 0.05). Serum IgE level was positively correlated with Th2 (r = 0.5545, p < 0.05). There was a positive correlation between CD161 + Treg and pTfh (r = 0.4974, p < 0.05) while a negative correlation between Th2 and B cells (r =  - 0.4925, p < 0.05).

CONCLUSION

Immune phenotypes were altered in IgG4-RD. Treg/Teff balance was shifted toward Treg in IgG4-RD. CD161 + Treg was likely to be involved in the pathogenesis of IgG4-RD. Key Points •Immune phenotypes were altered in B cells, T cells, and NK cells in IgG4-RD. •Treg/Teff balance was shifted toward Treg in IgG4-RD. •CD161+ Treg maybe play a proinflammatory role in IgG4-RD.

The JAK1/2 inhibitor baricitinib suppresses eosinophil effector function and restricts allergen-induced airway eosinophilia

BACKGROUND

Eosinophilic asthma is increasingly recognized as one of the most severe and difficult-to-treat asthma subtypes. The JAK/STAT pathway is the principal signaling mechanism for a variety of cytokines and growth factors involved in asthma. However, the direct effect of JAK inhibitors on eosinophil effector function has not been addressed thus far.

OBJECTIVE

Here we compared the effects of the JAK1/2 inhibitor baricitinib and the JAK3 inhibitor tofacitinib on eosinophil effector function in vitro and in vivo.

METHODS

Differentiation of murine bone marrow-derived eosinophils. Migratory responsiveness, respiratory burst, phagocytosis and apoptosis of human peripheral blood eosinophils were assessed in vitro. In vivo effects were investigated in a mouse model of acute house dust mite-induced airway inflammation in BALB/c mice.

RESULTS

Baricitinib more potently induced apoptosis and inhibited eosinophil chemotaxis and respiratory burst, while baricitinib and tofacitinib similarly affected eosinophil differentiation and phagocytosis. Of the JAK inhibitors, oral application of baricitinib more potently prevented lung eosinophilia in mice following allergen challenge. However, both JAK inhibitors neither affected airway resistance nor compliance.

CONCLUSION

Our data suggest that the JAK1/2 inhibitor baricitinib is even more potent than the JAK3 inhibitor tofacitinib in suppressing eosinophil effector function. Thus, targeting the JAK1/2 pathway represents a promising therapeutic strategy for eosinophilic inflammation as observed in severe eosinophilic asthma.

A phenotypically and functionally distinct human TH2 cell subpopulation is associated with allergic disorders

Allergen-specific type 2 helper T (T_H2) cells play a central role in initiating and orchestrating the allergic and asthmatic inflammatory response pathways. One major factor limiting the use of such atopic disease-causing T cells as both therapeutic targets and clinically useful biomarkers is the lack of an accepted methodology to identify and differentiate these cells from overall nonpathogenic T_H2 cell types. We have described a subset of human memory T_H2 cells confined to atopic individuals that includes all allergen-specific T_H2 cells. These cells are terminally differentiated CD4⁺ T cells (CD27^- and CD45RB^-) characterized by coexpression of CRT_H2, CD49d, and CD161 and exhibit numerous functional attributes distinct from conventional T_H2 cells. Hence, we have denoted these cells with this stable allergic disease-related phenotype as the T_H2A cell subset. Transcriptome analysis further revealed a distinct pathway in the initiation of pathogenic responses to allergen, and elimination of these cells is indicative of clinical responses induced by immunotherapy. Together, these findings identify a human T_H2 cell signature in allergic diseases that could be used for response-monitoring and designing appropriate immunomodulatory strategies.

The Expression of STAT3 and STAT5A Genes in Severe Refractory Asthma

BACKGROUND

Despite being a high burden disorder, the pathogenesis of severe refractory asthma (SRA) is poorly understood. There are some evidences for the involvement of members of the signal transducer and activator of transcription (STAT) family, including STAT3 and STAT5a. Our study aimed to evaluate the gene expression of STAT3 and STAT5a in asthma and SRA to establish if there is an association.

MATERIALS AND METHODS

Using quantitative real-time polymerase chain reactions (qRT-PCR), the transcript levels of STAT3 and STAT5a were evaluated in peripheral blood mononuclear lymphocytes (PBML) isolated from 13 patients with SRA, 14 with mild asthma, and 30 healthy volunteers.

RESULTS

There were no significant differences in STAT3 transcript levels between study groups. There was however a significant difference in STAT5a transcript levels between cases and controls (p-value=0.03). In comparison to healthy controls, the levels of STAT5a were notably lower in patients with mild asthma and significantly least in those with SRA.

CONCLUSION

Our study found no appreciable association between STAT3 gene expression and either mild asthma or SRA. However, the STAT5a down regulation in asthmatics and especially SRA is a notable finding which denotes on association between STAT5a and different level of asthma.

Defective Signaling in the JAK-STAT Pathway Tracks with Chronic Inflammation and Cardiovascular Risk in Aging Humans

Chronic inflammation, a decline in immune responsiveness, and reduced cardiovascular function are all associated with aging, but the relationships among these phenomena remain unclear. Here, we longitudinally profiled a total of 84 signaling conditions in 91 young and older adults and observed an age-related reduction in cytokine responsiveness within four immune cell lineages, most prominently T cells. The phenotype can be partially explained by elevated baseline levels of phosphorylated STAT (pSTAT) proteins and a different response capacity of naive versus memory T cell subsets to interleukin 6 (IL-6), interferon α (IFN-α), and, to a lesser extent, IL-21 and IFN-γ. Baseline pSTAT levels tracked with circulating levels of C-reactive protein (CRP), and we derived a cytokine response score that negatively correlates with measures of cardiovascular disease, specifically diastolic dysfunction and atherosclerotic burden, outperforming CRP. Thus, we identified an immunological link between inflammation, decreased cell responsiveness in the JAK-STAT pathway, and cardiovascular aging. Targeting chronic inflammation may ameliorate this deficiency in cellular responsiveness and improve cardiovascular function.

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

Targeting the JAK-STAT pathway in the treatment of 'Th2-high' severe asthma

Severe asthma is a heterogeneous disease characterized by reversible airway obstruction, chronic inflammation and airway remodeling. Phenotyping and/or endotyping can lead to a more personalized treatment strategy, improving the efficacy of novel drugs. Atopic asthma is associated with high levels of Th2 cells, implicated in a number of inflammatory responses. Differentiation of these cells from naive T cells occurs primarily via the JAK-STAT signaling pathway. Targeting this pathway through inhibition of activating cytokines (IL-4 and IL-13) and their receptors, the JAKs or the STATs, has been shown to have a therapeutic effect on asthma pathology. There are a number of novel drugs currently in development, which target various pathway components; these include both biologics and small molecules at various stages of development.

Activated Phosphorylated STAT1 Levels as a Biologically Relevant Immune Signal in Schizophrenia

OBJECTIVE

Activation of STAT1 is directly downstream of the cytokine receptors that signal from specific proinflammatory cytokines known to be dysregulated in schizophrenia (SZ), such as IFNγ, IL6, IL2 and IL10, as well as hypoxia, viral/bacterial infections and peptide growth factors. If the increased cytokine protein levels repeatedly observed in SZ have biological consequences, then the measurement of pSTAT1 is a logical step forward.

METHODS

Peripheral blood mononuclear cells (PBMCs) from controls (n = 13) and subjects with SZ (n = 22) were extracted using the Ficoll method. Participants with SZ were diagnosed using the SCID, clinical symptomatology was measured using the Positive and Negative Syndrome Scale (PANSS), and cognitive functioning was measured using the MATRICS Consensus Cognitive Battery. Levels of activated STAT1 (Y701), i.e. phosphorylated STAT1 (pSTAT1), were measured by a commercially available ELISA in nuclear extracts from PBMCs.

RESULTS

There was a significant bimodal distribution in the sample, with an SZ subgroup expressing significantly greater levels of activated pSTAT1 than the remainder of the participants. In this subgroup, levels of pSTAT1 were significantly higher than in the control group, as well as significantly higher than in the remainder of the SZ subjects. Furthermore, this subsample of patients manifested significantly poorer cognitive performance on several measures of the MATRICS.

DISCUSSION

pSTAT1 levels may provide a measure of the biological relevance of widely reported elevations in levels of cytokines in SZ over the past several decades. Activation of kinase cascades can be used to partition or disassemble the composite immune signal in patients living with SZ.

The Clinical Relevance of IL-17-Producing CD4+CD161+ Cell and Its Subpopulations in Primary Sjögren's Syndrome

Objective. Th17 cells have been demonstrated to play an important role in the onset and development of primary Sjögren's syndrome (pSS). In this study, we evaluated the expansion and clinical significance of circulating CD4+CD161+ T cell and its “effector” (CD4+CD25−CD161+ T cell) and “regulatory” (CD4+CD25+CD161+ T cell) subpopulations. Methods. Fifty-eight pSS patients and 16 healthy controls (HCs) were recruited in our study. The cell populations and intracellular IL-17 expression were analyzed by flow cytometry. The disease activity was evaluated by the EULAR-SS Disease Activity Index (ESSDAI). Autoantibodies were measured by ELISA or indirect immunofluorescence assay. Results. The CD161+ T cell fractions showed higher proportions of IL-17-producing cells. The frequencies of the overall CD4+CD161+ T cell population and its effector subset were positively correlated with disease activity parameters and more severe disease manifestations. A significant elevation of the CD4+CD25+CD161+ T cell subpopulation was observed in the peripheral blood of pSS patients compared to HCs and this subset showed decreased regulatory functions compared with the CD4+CD25+CD161− population. Conclusion. Circulating CD4+CD161+ T cell populations associated with pSS disease activity and severity. These cells might be involved in the development of pSS and could be potential therapeutic targets in the treatment of pSS.

Wheezing and itching: The requirement for STAT proteins in allergic inflammation

The development of allergic inflammation requires the orchestration of gene expression from the inflamed tissue and from the infiltrating immune cells. Since many of the cytokines that promote allergic inflammation signal through hematopoietin family receptors, the Signal Transducer and Activator of Transcription (STAT) family have obligate roles in pro-allergic cytokine-induced gene regulation in multiple cell types. In this review, we summarize work defining the contribution of each of the STAT family members to the development of allergic inflammation, using data from mouse models of allergic inflammation, studies on patient samples and correlations with single nucleotide polymorphisms in STAT genes.

Role of transcription factors in the pathogenesis of asthma and COPD

Inflammation is a central feature of asthma and chronic obstructive pulmonary disease (COPD). Despite recent advances in the knowledge of the pathogenesis of asthma and COPD, much more research on the molecular mechanisms of asthma and COPD are needed to aid the logical development of new therapies for these common and important diseases, particularly in COPD where no effective treatments currently exist. In the future the role of the activation/repression of different transcription factors and the genetic regulation of their expression in asthma and COPD may be an increasingly important aspect of research, as this may be one of the critical mechanisms regulating the expression of different clinical phenotypes and their responsiveness to therapy, particularly to anti-inflammatory drugs.

Modulation of mTOR effector phosphoproteins in blood basophils from allergic patients

The mammalian target of rapamycin (mTOR) pathway contributes to various immunoinflammatory processes. Yet, its potential involvement in basophil responses in allergy remains unclear. In this pilot study, we quantified two key mTOR effector phosphoproteins, the eukaryotic initiation factor 4E (peIF4E) and S6 ribosomal protein (pS6rp), in blood basophils from nut allergy patients (NA, N = 16) and healthy controls (HC, N = 13). Without stimulation in vitro, basophil peIF4E levels were higher in NA than HC subjects (P = 0.014). Stimulation with nut (offending) but not chicken / rice (non-offending) extract increased basophil peIF4E and pS6rp levels (+32%, P = 0.018, and +98%, P = 0.0026, respectively) in NA but not HC subjects, concomitant with increased surface levels of CD203c and CD63, both known to reflect basophil activation. Pre-treatment with the mTOR inhibitor rapamycin decreased pS6rp and CD203c responses in nut extract-stimulated basophils in NA subjects. Thus, basophil responses to offending allergens are associated with modulation of mTOR effector phosphoproteins.

Immunophenotyping of peripheral eosinophils demonstrates activation in eosinophilic esophagitis

BACKGROUND AND AIM

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder characterized by upper gastrointestinal symptoms and the presence of high numbers of eosinophils in the esophagus. Although eosinophils in the esophagus have been found to be activated in subjects with EoE, detailed studies of intracellular signaling pathways involved in the mechanism of activation of eosinophils in EoE have heretofore been limited. The aim of the study was to assess whether any surface molecules or transcription factors are activated in peripheral eosinophils in subjects with EoE.

METHODS

Eosinophils and CD3+ lymphocytes were identified directly from 50 μL of whole blood of EoE and control subjects. Using Hi-FACS, levels of surface activation markers, including CD66b, and intracellular phosphoepitopes, including phosphorylated forms of signal transducer and activator of transcription (phospho-STAT) 1 and 6, were measured within each cell subset.

RESULTS

Levels of surface CD66b as well as levels of intracellular phospho-STAT1 and phospho-STAT6 in peripheral blood eosinophils were significantly higher for untreated subjects with EoE vs healthy controls (P < 0.05). Levels of phospho-STAT1 and phospho-STAT6 in peripheral blood eosinophils were lower in subjects with EoE on therapy versus untreated subjects with EoE (P < 0.05).

CONCLUSIONS

Levels of phospho-STAT1 and phospho-STAT6, transcription factors involved in inflammatory processes, were both significantly higher in peripheral eosinophils from untreated (ie, newly diagnosed) subjects with EoE versus subjects with EoE on therapy, healthy controls. Blood-based measurements of CD66b and phospho-STAT levels in peripheral eosinophils may be beneficial for identifying EoE.

IL-2 and IL-4 stimulate MEK1 expression and contribute to T cell resistance against suppression by TGF-beta and IL-10 in asthma

The T cell-driven airway inflammation in chronic asthma is uninhibited and sustained. We examined the resistance of T cells from asthmatic patients against suppression by TGF-β, IL-10 and glucocorticoids and explored its signaling mechanism. CD4(+)CD25(-) T cells from allergic asthmatic subjects demonstrated increased TCR-stimulated proliferation as compared with healthy and chronic obstructive pulmonary disease controls. This proliferation was resistant to inhibition by TGF-β, IL-10, and dexamethasone and to anergy induction. CD4 T cells from asthmatic patients, but not chronic obstructive pulmonary disease, allergic rhinitis, and healthy subjects, showed increased expression of MEK1, heightened phosphorylation of ERK1/2, and increased levels of c-Fos. IL-2 and IL-4 stimulated the expression of MEK1 and c-Fos and induced T cell resistance. The inhibition of MEK1 reversed, whereas induced expression of c-Fos and JunB promoted T cell resistance against TGF-β- and IL-10-mediated suppression. We have uncovered an IL-2- and IL-4-driven MEK1 induction mechanism that results in heightened ERK1/2 activation in asthmatic T cells and make them resistant to certain inhibitory mechanisms.

Phosphorylation of signal transducer and activator of transcription 6 (STAT6) and STAT1, but not STAT3, induced by antigen inhalation in bronchial smooth muscles of sensitized mice

The signal transducer and activator of transcription (STAT) family of molecules play a critical role in the signaling of many cytokines. In addition to STAT6, implication of STAT1 and STAT3 in the development of airway hyperresponsiveness (AHR) has also been suggested in allergic bronchial asthma. However, there is little information whether or not antigen challenge really causes the in vivo activation of these STAT molecules in bronchial smooth muscles (BSMs). In the present study, the activations of these STATs were examined in BSMs of mice with allergic bronchial asthma. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin (OA) antigen. Total protein samples of the left main bronchi were prepared at 3 after the last OA challenge, and Western blot analyses for total and tyrosine-phosphorylated STATs molecules were conducted. In addition to the phosphorylation of STAT6, a significant increase in the level of phosphorylated STAT1 was also observed after the antigen exposure. In contrast, no significant increase in the level of phosphorylated STAT3 was observed in this mouse model of allergic bronchial asthma. The antigen exposure did not change the protein expressions of these STATs themselves. These findings suggest that STAT6 and STAT1, but not STAT3, might be crucial signal transducers in the development of BSM hyperresponsiveness, one of the causes of AHR in asthmatics.

Janus kinase-3 dependent inflammatory responses in allergic asthma

Allergic asthma is a chronic inflammatory condition of the lung characterized by reversible airway obstruction, high serum immunoglobulin (Ig) E levels, and chronic airway inflammation. A number of cells including mast cells, T cells, macrophages and dendritic cells play a role in the pathogenesis of the disease. Janus kinase (JAK)-3, a non-receptor protein tyrosine kinase, traditionally known to mediate cytokine signaling, also regulates functional responses of these cells. In this review the role of JAK-3 in regulating various pathogenic processes in allergic asthma is discussed. We propose that targeting JAK-3 is a rationale approach to control the inflammatory responses of multiple cell types responsible for the pathogenesis of allergic asthma.

Activation of signal transducer and activator of transcription factor 1 by interleukins-13 and -4 in cultured human bronchial smooth muscle cells

The family of signal transducer and activator of transcription (STAT) factors play a critical role in the signaling of many cytokines. In addition to the involvement of STAT6 in allergic bronchial asthma, both STAT1 and STAT3 have also been implicated. However, there is little information whether or not the T helper 2 cytokines, which cause several key features of allergic asthma, really induce the activation of STAT1 and/or STAT3 in bronchial smooth muscle (BSM) cells. In the present study, the effects of interleukin-13 (IL-13) and IL-4 on activation of these STAT molecules were examined in cultured human bronchial smooth muscle cells (hBSMCs). After a starvation period, the hBSMCs were treated with 100 ng/ml of IL-13 or IL-4. Total protein samples were prepared at intervals of 1, 3, 6, 12 and 24 hours after the cytokine treatment, and Western blot analyses for total and tyrosine-phosphorylated STATs molecules were conducted. As a result, ut was found that both IL-13 and IL-4 caused a significant increase in the levels of phosphorylated STAT1. Examination of the time-course revealed a peak of STAT1 phosphorylation at 1 hr after cytokine application. In contrast, neither IL-13 nor IL-4 induced phosphorylation of STAT3. Neither of these cytokines changed the protein expression of the STATs themselves. These findings suggest that STAT1, but not STAT3, might also be one of the crucial signal transducers in the development of BSM hyper-responsiveness, which is one of the causes of AHR in asthmatics.

Antigen exposure causes activations of signal transducer and activator of transcription 6 (STAT6) and STAT1, but not STAT3, in lungs of sensitized mice

The signal transducer and activator of transcription (STAT) family of molecules play a critical role in the signaling of many cytokines. In addition to STAT6, implication of STAT1 and STAT3 in the pathogenesis of allergic airway diseases has also been suggested. However, there is little information whether or not antigen challenge to sensitized animals causes the in vivo activation of STAT1 and/or STAT3 in the airways. In the present study, the activations of these STAT molecules were monitored in lungs of mice with allergic bronchial asthma. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin (OA) antigen. Total protein samples of lungs were prepared at ∼1-24 h after the last OA challenge, and western blot analyses for total and tyrosine-phosphorylated STATs (pSTATs) molecules were conducted. In addition to the phosphorylation of STAT6, STAT1 was also phosphorylated in lungs after the inhalation of OA antigen. Both the phosphorylation of STAT6 and STAT1 occurred at the early stage after the antigen exposure. In contrast, no significant increase in the level of pSTAT3 was observed in this mouse model of allergic bronchial asthma. In conclusion, the current findings suggest that STAT6 and STAT1, but not STAT3, might be crucial signal transducers in the pathogenesis of allergic bronchial asthma.

Selective deregulation in chemokine signaling pathways of CD4+CD25(hi)CD127(lo)/(-) regulatory T cells in human allergic asthma

BACKGROUND

CD4+CD25(hi)CD127(lo)/(-) regulatory T cells have been suggested to be critical regulators of inflammatory processes in allergic asthma. Recent studies reported a selective decrease in the frequency of regulatory T cells in the bronchoalveolar lavage fluid of allergic asthmatic (AA) subjects, prompting the possibility of defective recruitment of these cells to the airway in response to chemokines produced during asthmatic inflammation.

OBJECTIVES

This study aimed to characterize the chemotactic profile of circulating regulatory T cells in AA subjects in response to chemokines abundantly produced in airway inflammation, such as CCL1, CCL17, and CCL22.

METHODS

The study was performed in a cohort of 26 AA, 16 healthy control, and 16 non-AA subjects. We used chemotaxis assays to evaluate cell migration, flow cytometry to examine chemokine receptor expression, and phospho-ELISA to study consequent signaling pathways in regulatory T cells.

RESULTS

Regulatory T cells, but not CD4+CD25(-)T cells, from AA subjects showed decreased chemotactic responses, specifically to CCL1, in comparison with their healthy control and non-AA counterparts. Decreased CCL1-mediated chemotaxis in AA regulatory T cells was associated with decreased phosphorylation of protein kinase B (AKT), a protein involved in chemokine intracellular signaling. Furthermore, the decreased chemotactic response to CCL1 in AA regulatory T cells significantly correlated with asthma severity and decreased pulmonary function in AA subjects.

CONCLUSIONS

These results provide the first evidence of dysfunction in the chemokine signaling pathway in AA regulatory T cells.

New insights into mechanisms of immunoregulation in 2007

Substantial progress in understanding the mechanisms of immune regulation in allergic diseases and asthma has been made during the last year. In asthma, rhinitis, and atopic dermatitis the immune system is activated by allergens, autoantigens, and components of superimposed infectious agents. Immune regulation in the lymphatic organs and in the tissue has an important role in the control and suppression of allergic disease in all stages of the inflammatory process, such as cell migration to tissues, cells gaining an inflammatory and tissue-destructive phenotype in the tissues, and their interaction with resident tissue cells to augment the inflammation. After the discovery of regulatory T cells, the importance of their unique suppressive capacity was strongly emphasized for the suppression of effector T-cell responses. However, it seems that all 3 subsets of effector T(H)1, T(H)2, and T(H)17 cells, as well as regulatory T cells, regulate each other at the level of transcription, major cytokines, and surface molecules. This review highlights key advances in immune regulation that were published in the Journal of Allergy and Clinical Immunology.

Increased cytotoxicity of CD4+ invariant NKT cells against CD4+CD25hiCD127lo/- regulatory T cells in allergic asthma

CD4+CD25(hi)CD127(lo/-) regulatory T cells (Treg) have been implicated in the resolution of asthma-associated inflammation while the opposite role of CD4+ invariant NKT (iNKT) cells has been the subject of recent investigations. Studies here focused on mechanisms of interaction between CD4+ iNKT cells and Treg to further explore their roles in allergic asthma (AA). Flow cytometry analysis revealed a significant increase in the expression of the natural cytotoxicity receptors NKp30 and NKp46 by CD4+ iNKT cells in AA subjects compared to healthy controls (HC) and non-allergic asthmatics (NA). Subsequent intracellular staining showed that CD4+ iNKT cells also expressed higher levels of granzyme B and perforin in AA than HC. In in vitro killing assays, AA CD4+ iNKT cells selectively killed autologous Treg, but not CD4+CD25- T cells, more potently than HC and NA counterparts. This increased cytotoxicity positively correlated with asthma severity and granzyme B/perforin expression of CD4+ iNKT cells. Furthermore, it could be abrogated by either inhibition of the granzyme B-/perforin-dependent cell death pathway or oral corticosteroid administration. Altogether, these findings suggest that increased cytotoxicity of CD4+ iNKT cells against Treg might contribute to dysfunctional cellular interactions in AA.

Mechanisms in allergic airway inflammation - lessons from studies in the mouse

Asthma is a chronic inflammatory disease of the airways, involving recurrent episodes of airway obstruction and wheezing. A common pathological feature in asthma is the presence of a characteristic allergic airway inflammatory response involving extensive leukocyte infiltration, mucus overproduction and airway hyper-reactivity. The pathogenesis of allergic airway inflammation is complex, involving multiple cell types such as T helper 2 cells, regulatory T cells, eosinophils, dendritic cells, mast cells, and parenchymal cells of the lung. The cellular response in allergic airway inflammation is controlled by a broad range of bioactive mediators, including IgE, cytokines and chemokines. The asthmatic allergic inflammatory response has been a particular focus of efforts to develop novel therapeutic agents. Animal models are widely used to investigate inflammatory mechanisms. Although these models are not perfect replicas of clinical asthma, such studies have led to the development of numerous novel therapeutic agents, of which some have already been successful in clinical trials.

Profound functional and signaling changes in viable inflammatory neutrophils homing to cystic fibrosis airways

Blood neutrophils recruited to cystic fibrosis (CF) airways are believed to be rapidly killed by resident bacteria and to passively release elastase and other toxic by-products that promote disease progression. By single-cell analysis, we demonstrate that profound functional and signaling changes readily occur within viable neutrophils recruited to CF airways, compared with their blood counterparts. Airway neutrophils have undergone conventional activation, as shown by decreased intracellular glutathione, increased lipid raft assembly, surface mobilization of CD11b+ and CD66b+ granules, and increased levels of the cytoskeleton-associated phospho-Syk kinase. Unexpectedly, they also mobilize to the surface CD63+ elastase-rich granules, usually confined intracellularly, and lose surface expression of CD16 and CD14, both key receptors in phagocytosis. Furthermore, they express CD80, major histocompatibility complex type II, and the prostaglandin D2 receptor CD294, all normally associated with other lineages, which reflects functional reprogramming. This notion is reinforced by their decreased total phosphotyrosine levels, mirroring a postactivated stage, and increased levels of the phospho-S6 ribosomal protein, a key anabolic switch. Thus, we identified a subset of neutrophils within CF airways with a viable but dysfunctional phenotype. This subset provides a possible therapeutic target and indicates a need to revisit current paradigms of CF airway disease.