Allergen-induced interleukin-9 production in vitro: correlation with atopy in human adults and comparison with interleukin-5 and interleukin-13

Integrated Analysis of Cytokine Profiles in Malaria Patients Discloses Selective Upregulation of TGF-β1, β3, and IL-9 in Mild Clinical Presentation

The proper control of Plasmodium infection requires a finely balanced immune response. Here, we evaluated the implication of TGF-β1 and TGF-β3 in this process using novel monoclonal antibodies to measure their plasma concentrations in comparison with other cytokines and the expression of FOXP3 mRNA. Plasma cytokine levels were measured in 80 patients with severe anaemic malaria and 186 with a mild presentation using ELISA, and rtPCR was used to measure FOXP3 mRNA expression. While no mature TGF-β isoforms were detected in the plasma, the latent TGF-β1 and TGF-β3 were strongly upregulated in patients with mild malaria and nearly undetected in patients with severe disease. Similar selective upregulation in mild patients was observed for IL-9 and FOXP3 mRNA, while IL-7, IL-10, IL-17, and IL-27, although higher in mild cases, were also detected in severe disease. In contrast, a clearly skewed trend of severe cases towards higher pro-inflammatory (IL-6, IL-13, TNF-α) and Th1 (IFN-γ) responses was observed, which was associated with a higher level of parasitaemia as well as lower IgG and higher IgM responses. Together, these results suggest that the stimulation of regulatory T cells through TGF-β1/TGF-β3 and IL-9 is paramount to an effective and balanced protective immunity in natural human malaria infection.

Allergic airway recall responses require IL-9 from resident memory CD4+ T cells

Asthma is a chronic inflammatory lung disease with intermittent flares predominately mediated through memory T cells. Yet, the identity of long-term memory cells that mediate allergic recall responses is not well defined. In this report, using a mouse model of chronic allergen exposure followed by an allergen-free rest period, we characterized a subpopulation of CD4+ T cells that secreted IL-9 as an obligate effector cytokine. IL-9-secreting cells had a resident memory T cell phenotype, and blocking IL-9 during a recall challenge or deleting IL-9 from T cells significantly diminished airway inflammation and airway hyperreactivity. T cells secreted IL-9 in an allergen recall-specific manner, and secretion was amplified by IL-33. Using scRNA-seq and scATAC-seq, we defined the cellular identity of a distinct population of T cells with a proallergic cytokine pattern. Thus, in a recall model of allergic airway inflammation, IL-9 secretion from a multicytokine-producing CD4+ T cell population was required for an allergen recall response.

IL-9 blockade attenuates inflammation in a murine model of mechanical ventilation-induced lung injury by inhibiting the NLRP3 inflammasome pathway

OBJECTIVES

Ventilation-induced lung injury (VILI) causes a huge economic and social burden, and its prevention and treatment have gained increasing attention in recent years. IL-9 is an important inflammatory factor, but its potential role in VILI remains unclear. This study intended to explore whether blocking IL-9 could alleviate VILI and explore its underlying mechanism.

METHODS

Lung injury was induced by mechanical ventilation (MV) in C57BL/6 mice. Changes in inflammatory factors and NLRP3-related proteins were assessed using quantitative reverse transcription-polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay. Subsequently, Nlrp3^-/- mice were used to further elucidate the underlying mechanism.

RESULTS

The percentage of Th9 cells in the peripheral blood, bronchoalveolar lavage fluid (BALF), and lung tissues of MV mice was increased compared to those of control mice. Treatment with anti-IL-9 mAb significantly alleviated the changes in lung histopathology, wet/dry lung proportion, total protein content, and neutrophil content in BALF induced by VILI. Additionally, administering anti-IL-9 mAb significantly downregulated the expression levels of inflammatory factors in BALF and lung tissues of mice with VILI. In addition, administering anti-IL-9 mAb inhibited NLRP3 inflammasome activation, as evidenced by the observed downregulation of NLRP3, ASC, cleaved caspase-1, and GSDMD-N. Additionally, NLRP3-deficient mice had lower lung injury induced by VILI than wild-type mice. Furthermore, the anti-IL-9 mAb only partially inhibited VILI in Nlrp3^-/- mice.

CONCLUSIONS

In MV mice, the anti-IL-9 mAb alleviated lung injury and reduced the secretion and expression of inflammatory factors partly by inhibiting the NLRP3 inflammasome pathway.

IRF4 transcriptionally activate HOTAIRM1, which in turn regulates IRF4 expression, thereby affecting Th9 cell differentiation and involved in allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is an inflammatory reaction caused by irritation of nasal mucosa by external allergens, which seriously affects the life of patients. Here, we aimed to investigate the effect and mechanism of long non-coding RNA HOX antisense intergenic RNA myeloid 1 (lncRNA HOTAIRM1) on AR development.

METHODS

The nasal mucosa samples were collected from AR patients and AR model mice (induced by ovalbumin). T helper type 9 (Th9) cells were examined by flow cytometry. Fluorescence in situ hybridization was conducted to examine the localization of HOTAIRM1 in CD4⁺ T cells. Dual-luciferase reporter assay or RNA immunoprecipitation was conducted to examine the bond between HOTAIRM1 and miR-148a-3p, miR-148a-3p, and interferon regulatory factor 4 (IRF4). Chromatin Immunoprecipitation assay was conducted to detect the interaction between IRF4 and HOTAIRM1 promoter.

RESULTS

HOTAIRM1, interleukin-9 (IL-9), and IRF4 were highly expressed in the AR model. The ratio of Th9 cells was increased in AR mice and overexpressing HOTAIRM1 further promoted Th9 cell differentiation, while the effect was reversed after overexpression of miR-148a-3p. Besides, in vivo experiments showed that interfering with HOTAIRM1 reduced the number of sneezing and rubbing movements, reduced immunoglobulin E (IgE) and IL-9 levels, as well as Th9 cells. HOTAIRM1 was expressed in the cytoplasm and the interactions between HOTAIRM1 and miR-148a-3p, miR-148a-3p and IRF4, were confirmed. Furthermore, IRF4 bound to the HOTAIRM1 promoter and promoted its transcriptional activation.

CONCLUSION

HOTAIRM1 was highly expressed in the AR model. Besides, IRF4 activated HOTAIRM1 transcription, and HOTAIRM1, in turn, up-regulated IRF4 expression through competitively binding to miR-148a-3p with IRF4, thereby affecting Th9 cell differentiation and participating in the occurrence and development of AR. Our results suggested that interference with HOTAIRM1 might become a treatment for AR.

T-Cell Differentiation to T Helper 9 Phenotype is Elevated by Extremely Low-Frequency Electromagnetic Fields Via Induction of IL-2 Signaling

Owing to the development of information technology and the electronics industry, and the increase in the use of electronic products, an increasing number of people are exposed to electromagnetic fields (EMFs) in daily life. There has been concern about the effects of EMFs on the human body. Th9 cells, which are characterized by the generation of interleukin-(IL-9), are a recently defined subset of T helper (Th) cells. In this study, we investigated the effect of extremely low-frequency (60 Hz) EMFs, such as those generated by household power sources, at 0.8 mT intensity on CD4⁺ T cells. The exposure of CD4⁺ T cells to such EMFs under Th9-polarizing conditions increased IL-9 secretion and gene expression of transcription factors that are important for Th9 development. The expression of GATA3 increased in the early stage, and the phosphorylation of STAT5 and STAT6, which regulate the expression of GATA3, increased. In addition, EMFs increased the expression of IL-2 by the T cells. In conclusion, the differentiation of CD4⁺ T cells to the Th9 phenotype was increased by exposure to extremely low-frequency EMFs, and this appeared to be dependent on the IL-2 signaling pathway. Furthermore, co-cultures of EMF-exposed Th9 cells and mast cells showed an increased expression of mast cell proteases, FcεR1α, and mast cell-derived inflammatory cytokines compared with co-cultures of non-EMF-exposed Th9 cells and mast cells. Our results suggest that EMFs enhance the differentiation of CD4⁺ T cells to the Th9 phenotype, resulting in mast cell activation and inflammation. Bioelectromagnetics. 2019;40:588-601. © 2019 Bioelectromagnetics Society.

Th9 Cells in Allergic Disease

PURPOSES OF REVIEW

Th9 cells are recognized as a novel subset of effector T helper cells that preferentially produce IL-9. Here, we provide a current update on the reports related to the function of Th9 cells in allergic inflammatory diseases.

RECENT FINDINGS

The effector Th9 cells differentiating from naïve T helper cells have recently been identified. Because of accumulating findings of Th9 cells in many inflammatory diseases, including allergic diseases, diverse functions of Th9 cells in regulating immune responses have been suggested. Related reports indicate multiple sources of IL-9 besides Th9 cells and their association with the pathogenesis of allergic rhinitis, asthma, atopic dermatitis, contact dermatitis, and food allergy. More recently, elements of the epigenetic landscape involving in the regulation of IL-9 by Th9 cells have been identified to be the potential target for allergic inflammation. This review provides the most recent information about Th9 cells and their contribution in airway allergic disease, skin, and food allergy.

Stimulation of histamine H4 receptors increases the production of IL-9 in Th9 polarized cells

BACKGROUND AND PURPOSE

Th9 cells represent a recently defined subset of CD4⁺ T-helper cells, characterized by a high production of IL-9. They are found at increased frequency in lesions of atopic dermatitis, where IL-9 is also elevated. As histamine is up-regulated in lesions of inflammatory skin diseases, we investigated the expression profile of histamine receptors and their functional role on Th9 cells.

EXPERIMENTAL APPROACH

Naïve CD4⁺ T-cells were purified from human peripheral blood mononuclear cells, using magnetic beads and further differentiated into Th9 cells. During differentiation, cells were additionally stimulated with histamine receptor agonists or left untreated. Histamine receptor expression as well as IL-9 production was measured.

KEY RESULTS

As proof of a successful differentiation, IL-9 production was measured at mRNA and protein level. Expression of mRNA for histamine H₁ , H₂ and H₄ receptors were up-regulated in differentiated Th9 cells compared to Th0 cells, while no mRNA for the H₃ receptor was detectable. Stimulation of Th9 cells with histamine significantly up-regulated expression of mRNA and protein for IL-9 . Experiments with specific histamine receptor agonists and antagonists revealed that this up-regulation was mediated by H₄ receptors.

CONCLUSIONS AND IMPLICATIONS

In summary, our study demonstrates a functional role for histamine H₄ receptors on Th9 cells, which might amplify the pro-inflammatory potency of these cells. Together with earlier studies on Th2 and Th17 cells, this study underlines the promising approach for the use of H₄ receptor antagonists in inflammatory and allergic diseases such as atopic dermatitis.

LINKED ARTICLES

This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

Th1/Th17 polarization persists following whole-cell pertussis vaccination despite repeated acellular boosters

In the mid-1990s, whole-cell pertussis (wP) vaccines were associated with local and systemic adverse events that prompted their replacement with acellular pertussis (aP) vaccines in many high-income countries. In the past decade, rates of pertussis disease have increased in children receiving only aP vaccines. We compared the immune responses to aP boosters in individuals who received their initial doses with either wP or aP vaccines using activation-induced marker (AIM) assays. Specifically, we examined pertussis-specific memory CD4+ T cell responses ex vivo, highlighting a type 2/Th2 versus type 1/Th1 and Th17 differential polarization as a function of childhood vaccination. Remarkably, after a contemporary aP booster, cells from donors originally primed with aP were (a) associated with increased IL-4, IL-5, IL-13, IL-9, and TGF-β and decreased IFN-γ and IL-17 production, (b) defective in their ex vivo capacity to expand memory cells, and (c) less capable of proliferating in vitro. These differences appeared to be T cell specific, since equivalent increases of antibody titers and plasmablasts after aP boost were seen in both groups. In conclusion, our data suggest that there are long-lasting effects and differences in polarization and proliferation of T cell responses in adults originally vaccinated with aP compared with those that initially received wP, despite repeated acellular boosters.

Reduction of respiratory infections in asthma patients supplemented with vitamin D is related to increased serum IL-10 and IFNγ levels and cathelicidin expression

BACKGROUND

Vitamin D is a molecule that modulates the immune response and shows anti-inflammatory effects that are beneficial for the control of chronic diseases such as asthma. The trial aim was to explore the effect of vitamin D supplementation on the colonization of pathogenic bacteria in the upper respiratory tract of allergic asthmatic patients.

METHODS

This study was conducted in 86 patients between 18 and 50 years of age who were randomly divided into two groups. Both groups received the treatment recommended by the Global Initiative for Asthma (GINA). One group also received calcitriol (1,25-(OH)₂D₃), and the other group received a placebo. At baseline and 6 months, skin prick tests were conducted, pharyngeal bacterial cultures were performed, and cathelicidin LL-37 was measured in sputum. Serum levels of IgE, eosinophils, IL-5, IL-9, IL-10, IL-13, and IFNγ were quantified at the beginning and the end of the study.

RESULTS

Serum levels of IL-10 and IFNγ increased significantly in the group of patients with vitamin D supplementation, while IL-5, IL-9, and IL-13 decreased significantly. At the end of the trial, IgE and eosinophil levels significantly decreased but allergen sensitivity did not show any changes from baseline. Respiratory infections were drastically reduced, and this decrease was related to the number of patients who had high serum levels of IL-10 and IFNγ and expressed LL-37 in their sputum.

CONCLUSION

Treatment of asthma patients with vitamin D reduced respiratory infections, and this effect was related to the increase of cathelicidin LL-37.

Th9 Cells: New Member of T Helper Cell Family

T Helper cells (CD4+ T cells) constitute one of the key arms of adaptive immune responses. Differentiation of naïve CD4+ T cells into multiple subsets ensure a proper protection against multitude of pathogens in immunosufficient individual. After differentiation, T helper cells secrete specific cytokines that are critical to provide immunity against various pathogens. The recently discovered Th9 cells secrete the pleiotropic cytokine, IL-9. Although IL-9 was cloned more than 25 years ago and characterized as a Th2 cell-specific cytokine, not many studies were carried out to define the function of IL-9. This cytokine has been demonstrated to act on multiple cell types as a growth factor. After the discovery of Th9 cells as an abundant source of IL-9, renewed focus has been generated. In this chapter, I discuss the biology and development of IL-9-secreting Th9 cells. Furthermore, I highlight the role of Th9 cells and IL-9 in health and diseases.

Allergic Inflammation and Atopic Disease: Role of Th9 Cells

IL-9-producing T helper cells (Th9) have recently emerged as an important T cell subset contributing to the pathogenicity of allergic diseases. Here, we describe the role of Th9 cells in allergic inflammation and provide detailed protocols to characterize IL-9-producing T cells and analyze OVA-specific IL-9 production in allergic lung diseases using a mouse model of OVA-induced chronic allergic lung inflammation.

Human Vδ2 T cells are a major source of interleukin-9

Vδ2Vγ9 T cells are the dominant γδ T-cell subset in human peripheral blood. Vδ2 T cells recognize pyrophosphate molecules derived from microbes or tumor cells; hence, they play a role in antimicrobial and antitumor immunity. TGF-β, together with IL-15, induces a regulatory phenotype in Vδ2 T cells, characterized by forkhead box protein P3 (FoxP3) expression and suppressive activity on CD4 T-cell activation. We performed a genome-wide transcriptome analysis and found that the same conditions (TGF-β plus IL-15) strongly enhanced the expression of additional genes in Vδ2 T cells, including IKAROS family zinc finger 4 (IKZF4; Eos), integrin subunit alpha E (ITGAE; CD103/αEβ7), and IL9 This up-regulation was associated with potent IL-9 production as revealed by flow cytometry and multiplex analysis of cell culture supernatants. In contrast to CD4 and CD8 αβ T cells, γδ T cells did not require IL-4 for induction of intracellular IL-9 expression. Upon antigen restimulation of Vδ2 T cells expanded in vitro in the presence of TGF-β and IL-15, IL-9 was the most abundant among 16 analyzed cytokines and chemokines. IL-9 is a pleiotropic cytokine involved in various (patho)physiological conditions, including allergy and tumor defense, where it can promote antitumor immunity. Given the conspicuous sensitivity of many different tumors to Vδ2 T-cell-mediated killing, the conditions defined here for strong induction of IL-9 might be relevant for the development of Vδ2 T-cell-based immunotherapy.

Relationship between cytokine expression patterns and clinical outcomes: two population-based birth cohorts

BACKGROUND

Models that incorporate patterns of multiple cytokine responses to allergens, rather than individual cytokine production, may better predict sensitization and asthma.

OBJECTIVE

To characterize the patterns of peripheral blood mononuclear cells' (PBMCs) cytokine responses to house dust mite (HDM) allergens among children from two population-based birth cohorts using machine learning techniques.

METHODS

PBMCs collected at 8 years of age from the UK Manchester Asthma and Allergy Study (n = 268) and at 14 years of age from the Australian Raine Study (n = 1374) were cultured with HDM extract (10 μg/ml). Cytokine expression (IL-13, IL-5, IFN-γ, and IL10) was measured in the supernatant. Cytokine patterns were identified using a Gaussian mixture model clustering, and classification stability was assessed by bootstrapping.

RESULTS

A six-class model indicated complex latent structure of cytokine expression. Based on the characteristics of each class, we designated them as follows: 'Nonresponders' (n = 905, 55%); 'IL-10 responders' (n = 49, 3%); 'IFN-γ and IL-13 medium responders' (n = 56, 3.4%); 'IL-13 medium responders' (n = 351, 21.4%); 'IL-5 and IL-13 medium responders' (n = 77, 4.7%); and 'IL-13 and IL-5 high responders' (n = 204, 12.4%). 'IL-13 and IL-5 high responders' were at much higher risk of HDM sensitization and asthma compared to all other classes, with 88% of children assigned to this class being sensitized and 28.5% having asthma.

CONCLUSION

Using model-based clustering, we identified several distinct patterns of cytokine response to HDM and observed interplay between cytokine expression level, cytokine patterns (especially IL-13 and IL-5), and clinical outcomes. 'IL-13 and IL-5 high responders' class was strongly associated with HDM sensitization. However, among HDM-sensitized children, one-third showed no PBMC response to HDM, and the majority of HDM-sensitized children did not have asthma or wheeze. Our findings suggest that positive HDM 'allergy tests' and asthma are associated with a broad range of immunophenotypes, which may have important implications for the use of cytokine-targeted treatment approaches.

Interleukin-9 and interleukin-17C in chronic rhinosinusitis

BACKGROUND

Interleukin (IL)-9 and IL-17C have been known to play a role in allergic inflammation, yet, their roles in chronic rhinosinusitis (CRS) are not well defined. IL-9 induces changes in epithelial cell gene expression leading to goblet cell metaplasia, whereas IL-17C is functionally distinct in that its expression can be induced by bacterial challenge and inflammatory stimuli. This study aimed to compare levels of IL-9 and IL-17C in CRS with nasal polyps (CRSwNP) and without nasal polyps (CRSsNP) as well as atopy.

METHODS

Nasal polyp or sinus mucosal specimens from CRSwNP (n = 36), CRSsNP (n = 9), and control (n = 9) groups were collected and processed. Patient atopy status was determined by history of skin-prick test and pulmonary function test. Immunohistochemistry was carried out using anti-human IL-9 and IL-17C antibodies. Positively-stained cells were enumerated under high-power (×400) magnification in 5 consecutive fields.

RESULTS

The level of expression of IL-9 was higher in CRSwNP than CRSsNP and control. Similar findings were demonstrated in IL-17C with higher expression in CRSwNP than CRSsNP and control. Both the averages of positively-stained cells expressing IL-9 and IL-17C were higher in CRS with asthma and allergy compared to control. This suggested that IL-9 and IL-17C were both involved in the pathogenesis of CRS, allergy, and asthma.

CONCLUSION

Inflammatory cell expression of IL-9 and IL-17C were increased in CRS, particularly with allergy and asthma. These interleukins may contribute to the pathogenesis of CRSwNP as well as atopy and may serve as therapeutic targets for disease management.

The development and in vivo function of T helper 9 cells

The specialized cytokine secretion profiles of T helper (TH) cells are the basis for a focused and efficient immune response. On the twentieth anniversary of the first descriptions of the cytokine signals that promote the differentiation of interleukin-9 (IL-9)-secreting T cells, this Review focuses on the extracellular signals and the transcription factors that promote the development of what we now term TH9 cells, which are characterized by the production of this cytokine. We summarize our current understanding of the contribution of TH9 cells to both effective immunity and immunopathological disease, and we propose that TH9 cells could be targeted for the treatment of allergic and autoimmune disease.

Expression and Regulation of Interleukin-9 in Chronic Rhinosinusitis

Background

The pathogenesis of human chronic rhinosinusitis (CRS) remains controversial. Recent evidence has suggested that interleukin (IL)-9 is vital in eliciting inflammatory response, stimulating cell proliferation and preventing apoptosis, through binding to the IL-9 receptor (IL-9R). However, little is known about the roles of both molecules in the etiology of CRS. Therefore, this study aimed to assess IL-9 and IL-9R expression and determine their rolesin the pathophysiology of CRS.

Methods

Immunohistochemistry was used to assess IL-9 and IL-9R immunolabeling. In addition, Western blotting and real-time polymerase chain reaction (PCR) were used for IL-9 and IL-9R protein and mRNA level quantitation, respectively, in CRS and control subjects. Furthermore, the effects of various stimulators at different concentrations and time on IL-9 were evaluated using nasal explant cultures.

Results

IL-9 and IL-9R were overexpressed in CRS, especially in CRS with nasal polyps. Interestingly, IL-9 expression was closely related to that of IL-9R. In addition, IL-9 mRNA levels were increased by treatment with IL-4, IL-17A, IL-1beta, and the IL-4 and transforming growth factor (TGF) beta1 combination, but suppressed by interferon gamma and IL-27.

Conclusion

IL-9 and IL-9R were overexpressed in CRS at both protein and mRNA levels. In addition, IL-4, IL-17A, IL-1beta, and the IL-4 and TGF-beta1 combination contributed to increased IL-9 levels. Our findings indicate that IL-9 may play a proinflammatory role after IL-9R binding to induce mucosal epithelial cell growth, gland epithelial cell proliferation, and inflammatory cell infiltration in CRS. Future studies are required to further define the role of IL-9 in CRS etiology.

TH9 cells that express the transcription factor PU.1 drive T cell-mediated colitis via IL-9 receptor signaling in intestinal epithelial cells

The molecular checkpoints that drive inflammatory bowel diseases are incompletely understood. Here we found more T cells expressing the transcription factor PU.1 and interleukin 9 (IL-9) in patients with ulcerative colitis. In an animal model, citrine reporter mice had more IL-9-expressing mucosal T cells in experimental oxazolone-induced colitis. IL-9 deficiency suppressed acute and chronic colitis. Mice with PU.1 deficiency in T cells were protected from colitis, whereas treatment with antibody to IL-9 suppressed colitis. Functionally, IL-9 impaired intestinal barrier function and prevented mucosal wound healing in vivo. Thus, our findings suggest that the TH9 subset of helper T cells serves an important role in driving ulcerative colitis by regulating intestinal epithelial cells and that TH9 cells represent a likely target for the treatment of chronic intestinal inflammation.

Effect of vitamin D on T-helper type 9 polarized human memory cells in chronic persistent asthma

BACKGROUND

Vitamin D suppresses inflammation and vitamin D deficiency is linked to the severity of asthma symptoms. T-helper type 9 (TH9) cells are important in the pathogenesis, yet the effects of vitamin D on this subset of inflammatory T-helper cells from patients with chronic asthma is unknown.

OBJECTIVE

To determine the effects of vitamin D and dexamethasone on TH9 memory cells from adults with chronic persistent asthma and on a recall response to dust mite allergen.

METHODS

T-helper memory cells were cultured with cytokines that drive TH9 polarization with vitamin D and/or dexamethasone. Peripheral blood mononuclear cells (PBMCs) from patients with radioallergosorbent test results for house dust mite were stimulated with allergen in the presence or absence of vitamin D. Intracellular cytokines, transcription factors, and identification of cell surface phenotypic markers were determined by flow cytometry.

RESULTS

Vitamin D decreased interleukin (IL)-9, IL-5, and IL-8 but increased IL-13(+) cells in TH9 cultures. Transcription factors PU.1 and interferon regulatory factor 4 were downregulated by vitamin D but not GATA3 and c-MAF. When PBMCs from patients with positive radioallergosorbent test results were stimulated with dust mite allergen, vitamin D decreased IL-9, IL-5, and IL-13 in T-helper cells (CD4(+)). TH9 cells present in a recall response were classically TH2 (CD294(+)), and polarization by transforming growth factor-β and IL-4 altered that phenotype.

CONCLUSION

Vitamin D decreased inflammatory cytokine profiles in TH9 memory cells and CD4(+) cells stimulated with dust mite allergen. Vitamin D is additive with dexamethasone in decreasing inflammatory cytokine production from T-cell subsets implicated in asthma.

Th9 cells: differentiation and disease

CD4(+) T-helper cells regulate immunity and inflammation through the acquisition of potential to secrete specific cytokines. The acquisition of cytokine-secreting potential, in a process termed T-helper cell differentiation, is a response to multiple environmental signals including the cytokine milieu. The most recently defined subset of T-helper cells are termed Th9 and are identified by the potent production of interleukin-9 (IL-9). Given the pleiotropic functions of IL-9, Th9 cells might be involved in pathogen immunity and immune-mediated disease. In this review, I focus on recent developments in understanding the signals that promote Th9 differentiation, the transcription factors that regulate IL-9 expression, and finally the potential roles for Th9 cells in immunity in vivo.

HSP: Bystander Antigen in Atopic Diseases?

Over the last years insight in the complex interactions between innate and adaptive immunity in the regulation of an inflammatory response has increased enormously. This has revived the interest in stress proteins; proteins that are expressed during cell stress. As these proteins can attract and trigger an immunological response they can act as important mediators in this interaction. In this respect, of special interest are proteins that may act as modulators of both innate and adaptive immunity. Heat shock proteins (HSPs) are stress proteins that have these, and more, characteristics. More than two decades of studies on HSPs has revealed that they are part of intrinsic, “natural” mechanisms that steer inflammation. This has provoked comprehensive explorations of the role of HSPs in various human inflammatory diseases. Most studies have focused on classical autoimmune diseases. This has led to the development of clinical studies with HSPs that have shown promise in Phase II/III clinical trials. Remarkably, only very little is yet known of the role of HSPs in atopic diseases. In allergic disease a number of studies have investigated the possibility that allergen-specific regulatory T cell (Treg) function is defective in individuals with allergic diseases. This raises the question whether methods can be identified to improve the Treg repertoire. Studies from other inflammatory diseases have suggested HSPs may have such a beneficial effect on the T cell repertoire. Based on the immune mechanisms of atopic diseases, in this review we will argue that, as in other human inflammatory conditions, understanding immunity to HSPs is likely also relevant for atopic diseases. Specifically, we will discuss why certain HSPs such as HSP60 connect the immune response to environmental antigens with regulation of the inflammatory response. Thus they provide a molecular link that may eventually even help to better understand the immune pathological basis of the hygiene hypothesis.

Th9: a new player in asthma pathogenesis?

CD4(+) T helper (Th) cells act as important regulators of the mammalian adaptive immune response. CD4(+) Th cells were originally characterized as either Th1 or Th2 types, based on the cytokines they produce. Over the past two decades, however, we have attained a much more detailed understanding of CD4(+) T-cell differentiation, functions, and gene expression profiles, which led to the identification of additional types, such as the Th17 and induced regulatory T cells. Recently, researchers have characterized yet another novel and distinct population that exists among these immune-modulatory cells. The 'Th9' cells were first identified as a Th2 subpopulation that produced exceptionally large quantities of the Th2-specific cytokine interleukin 9. However, experimental analysis revealed that Th9 cells had divergent regulatory capabilities and were critically involved in different immune processes. In particular, we now know that Th9 acts as a major contributor to the onset and progression of allergies, especially asthma. Here, we will review the heterogeneity and biology of CD4(+) Th cells and summarize the characteristics known to date of interleukin 9 and Th9 cells to build a framework for better understanding of their roles in disease processes, especially in allergy-induced asthma.

Importance of cytokines in murine allergic airway disease and human asthma

Asthma is a common, disabling inflammatory respiratory disease that has increased in frequency and severity in developed nations. We review studies of murine allergic airway disease (MAAD) and human asthma that evaluate the importance of Th2 cytokines, Th2 response-promoting cytokines, IL-17, and proinflammatory and anti-inflammatory cytokines in MAAD and human asthma. We discuss murine studies that directly stimulate airways with specific cytokines or delete, inactivate, neutralize, or block specific cytokines or their receptors, as well as controversial issues including the roles of IL-5, IL-17, and IL-13Ralpha2 in MAAD and IL-4Ralpha expression by specific cell types. Studies of human asthmatic cytokine gene and protein expression, linkage of cytokine polymorphisms to asthma, cytokine responses to allergen stimulation, and clinical responses to cytokine antagonists are discussed as well. Results of these analyses establish the importance of specific cytokines in MAAD and human asthma and have therapeutic implications.

Th9 and allergic disease

Helper CD4(+) T-cell subsets have improved our understanding of adaptive immunity in humans and in animal models of disease. These include T helper type 1 (Th1), Th2 and the interleukin-17 (IL-17) -producing population 'Th17'. Th2 cells have been described as orchestrating the immune response in allergic disease based on studies with patient samples and animal models. The cytokine IL-9 has largely been regarded as a Th2 cytokine that makes multifocal contributions to allergic disease. Recent data suggest that under certain conditions relevant to chronic disease (IL-4 and transforming growth factor-beta), a distinct population of IL-9-producing 'Th9' helper T cells can exist. The contribution of Th9 cells in allergic disease is currently unknown, and this review will propose a model for how these cells may regulate chronic allergic inflammation.

T(H)2 cytokines modulate the IL-9R expression on human neutrophils

Interleukin (IL)-9 is associated with key pathological features of asthma such as airway hyperresponsiveness, bronchoconstriction and mucus production. Inflammatory responses mediated by IL-9 rely on the expression of the IL-9R which has been reported on lung epithelial cells, T lymphocytes and recently on airway granulocyte infiltrates. In this study, we assessed the regulatory and constitutive cell surface expression of the IL-9Ralpha in unfractionated and purified human neutrophils from atopic asthmatics, atopic non-asthmatics and healthy normal controls. We demonstrate that T(H)2 cytokines (IL-4 or IL-13) and granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulated mRNA and cell surface expression levels of the IL-9Ralpha in primary human and HL-60 differentiated neutrophils. Pharmacological inhibition of NF-kappaB did not affect T(H)2-mediated IL-9Ralpha expression in human neutrophils although IFN-gamma and IL-10 down-regulated IL-9Ralpha expression when co-incubated with IL-4, IL-13 or GM-CSF. Collectively, our results reveal a regulatory function for IFN-gamma and IL-10 on modulating the inducible IL-9Ralpha expression levels on peripheral blood neutrophils by T(H)2 cytokines.

In vitro allergen challenge of peripheral blood induces differential gene expression in mononuclear cells of asthmatic patients: inhibition of cytosolic phospholipase A2alpha overcomes the asthma-associated response

BACKGROUND

Existing treatments for asthma are not effective in all patients and disease exacerbations are common, highlighting the need for increased understanding of disease mechanisms and novel treatment strategies. The leukotriene pathway including the enzyme responsible for arachidonic acid release from cellular phospholipids, cPLA(2)alpha, is a major contributor to asthmatic responses and an attractive target in asthma therapies.

OBJECTIVE

The study reported here investigates (a) the differential effects of in vitro exposure of peripheral blood mononuclear cells (PBMCs) to allergen between asthma and healthy subjects, and (b) the contribution of cPLA(2)alpha to these differences in gene expression.

METHODS

In vitro responses of asthma (N=26) and healthy (N=11) subject PBMC samples to allergen stimulation in the presence and absence of cPLA(2)alpha inhibition or 5-lipoxygenase inhibition were compared at the gene expression level using oligonucleotide arrays and at the protein level using ELISA.

RESULTS

Subject samples within both asthma and healthy groups showed allergen-dependent cytokine production and allergen-dependent gene expression changes, although transcriptional profiling identified 153 genes that were modulated significantly differently by allergen between asthma and healthy subjects. Among these were genes previously associated with asthma, but the majority (about 80%) have not previously been associated with asthma.

CONCLUSIONS

Transcriptional profiling elucidated novel gene expression differences between the asthmatic and healthy subject samples. Although 5-lipoxygenase inhibition did not significantly affect allergen-modulated gene expression, the inhibition of cPLA(2)alpha activity affected many of the allergen-dependent, asthma-associated gene expression changes.

The role of T cells in the enhancement of respiratory syncytial virus infection severity during adult reinfection of neonatally sensitized mice

Respiratory syncytial virus (RSV) is the major cause of infantile bronchiolitis and hospitalization. Severe RSV disease is associated with the development of wheezing in later life. In a mouse model of the delayed effects of RSV, the age at primary infection determines responses to reinfection in adulthood. During primary RSV infection, neonatal BALB/c mice developed only mild disease and recruited CD8 cells that were defective in gamma interferon production. Secondary reinfection of neonatally primed mice caused enhanced inflammation and profuse lung T-cell recruitment. CD4 cell depletion during secondary RSV challenge attenuated disease (measured by weight loss); depletion of CD8 cells also markedly attenuated disease severity but enhanced lung eosinophilia, and depletion of both CD4 and CD8 cells together completely abrogated weight loss. Depletion of CD8 (but not CD4) cells during primary neonatal infection was protective against weight loss during adult challenge. Therefore, T cells, in particular CD8 T cells, play a central role in the outcome of neonatal infection by enhancing disease during secondary challenge. These findings demonstrate a crucial role for T cells in the regulation of immune responses after neonatal infection.

Immunoreactivity profile of peripheral blood mononuclear cells from patients with ragweed-induced allergic rhinitis

BACKGROUND

Seasonal rhinitis is manifested by a series of nasal symptoms in response to exposure to seasonal allergens including ragweed pollen. Understanding its immunological mechanisms may help to better manage the disease.

OBJECTIVE

We sought to determine comprehensively ragweed-induced cytokine and chemokine production by peripheral blood mononuclear cells from normal individuals and patients with seasonal rhinitis sensitized to ragweed pollen, and to assess its regulation by exogenous IL-10.

METHODS

Cells were cultured in the presence or absence of a purified ragweed pollen extract with or without exogenous IL-10. Cytokines and chemokines were measured in the supernatant. Gene expression was evaluated using real-time quantitative reverse transcription PCR.

RESULTS

Ragweed stimulation significantly increased the production of the Th2-associated cytokines IL-5, IL-9 and IL-13, the chemokines CCL17 and CCL22 and the regulatory cytokine IL-10 in allergic patients, whereas transforming growth factor-beta (TGF-beta) production was increased only in normal individuals. No difference was detected between groups in the production of the Th1 cytokine IFN-gamma or the Th1-affiliated chemokines CXCL10 and CXCL11. Exogenous IL-10 significantly suppressed spontaneous and induced production of both Th1- and Th2-associated cytokines and chemokines.

CONCLUSION

Our work demonstrated that locally manifested allergic rhinitis is underlined by a systemic Th2 immune response specific to allergens. The molecular pathogenesis of allergic rhinitis may be linked to a compromised allergen-specific immune regulation, e.g., reduced spontaneous and allergen-induced TGF-beta production in patients compared with healthy controls. Our data also show that IL-10 inhibits both the effector and directional mechanisms of allergen-specific immune response, further supporting its potential therapeutic benefit in preventing and treating allergic diseases.

IL-9 production by peripheral blood mononuclear cells of atopic asthmatics

BACKGROUND

IL-9 might play a critical role in pathogenesis and development of atopic asthma, but there are few reports on allergen-specific IL-9 production by peripheral blood mononuclear cells (PBMCs) obtained from adult asthmatics.

METHODS

PBMCs were obtained from adult atopic asthmatics and incubated with Dermatophagoides farinae(Der f) extract for the designated time periods. The resulting supernatants were assayed for IL-9 by specific sandwich ELISA.

RESULTS

IL-9 production was detectable on day 2 and reached maximum on day 6 after stimulation of PBMCs with Der f extract. IL-9 production in response to Der f extract increased in a dose-dependent manner. CD2- or CD4-bearing cell depletion completely abolished IL-9 production by PBMCs, while CD8-bearing cell depletion did not affect it.

CONCLUSION

CD4+ lymphocytes are the principal source of IL-9 produced by PBMCs of adult atopic asthmatics.

IL-9 promotes anti-Mycobacterium leprae cytotoxicity: involvement of IFNgamma

Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it has been characterized both in human and murine systems. It is a pleiotropic cytokine with multiple functions on cells of the lymphoid, myeloid and mast cell lineages, as well as on lung epithelial cells. Other activities described for IL-9 support its contribution to asthma and its important role in helminthic infections, where a Th2 response can be protective and IL-9 enhances resistance or is responsible for elimination of the nematode. Nevertheless, until recently there were no studies on its role in bacterial infections in man. We have demonstrated that cytokines can modulate the specific cytotoxicity generation in peripheral blood mononuclear cells from leprosy patients and normal controls. In the present report we studied the effect of IL-9 in this experimental model. Our results indicate that IL-9 can counteract the negative effect mediated by IL-4 on the generation of M. leprae-induced cytotoxic T lymphocytes. Moreover, it can increase this lytic activity in controls and enhance the stimulatory effect of IL-2 or IL-6 in cells from leprosy patients and controls. IL-9 is also able to revert the inhibitory effect of IL-10 and IL-13 on the M. leprae-induced cytotoxic activity. Although the exact mechanism of action of IL-9 remains to be determined, interferon gamma seems to be required for the effect of IL-9 in this experimental model. These data suggest that IL-9 may have an atypical Th2 behaviour and play a role in the modulation of the immune response to mycobacterial infections.