gammadelta T cells contribute to the systemic immunoglobulin E response and local B-cell reactivity in allergic eosinophilic airway inflammation

IgG from Dermatophagoides pteronyssinus (Der p)-atopic individuals modulates non-atopic thymic B cell phenotype (alfa-4/beta-7) and cytokine production (IFN-γ, IL-9, and IL-10) with direct membrane interaction

Studies about thymic B cells are scarce in the literature, but it was suggested that they can exert modulatory and regulatory functions on the immune system. Thymic B cells can play some role in regulating the most frequent allergic background worldwide, the atopy induced by the mite Dermatophagoides pteronyssinus (Der p). Here, we aimed to evaluate if the polyclonal IgG repertoire produced by Der p-atopic individuals can influence the homing and cytokine profile of human thymic B derived from non-atopic children aged less than seven days. With this purpose, we produced polyclonal IgG formulations and cultivated human thymocytes in their presence. We also assessed IgG subclasses and the direct interaction of IgG with thymic B cell membranes. Our results could demonstrate that Der p-atopic IgG could not reduce the expression of α4β7 homing molecule as observed in response to the other IgG formulations and could reduce the frequency of IFN-γ- and IL-9-producing thymic B cells compared to the mock condition. Der p-atopic IgG could also induce thymic IL-10-producing B cells compared to control conditions. The IgG derived from Der p-atopic individuals failed to diminish the population of IL-13-producing thymic B cells, unlike the reduction observed with other IgG formulations when compared to the mock condition. All IgG formulations had similar levels of IgG subclasses and directly interacted with thymic B cell membranes. Finally, we performed experiments using peripheral non-atopic B cells where IgG effects were not observed. In conclusion, our observation demonstrates that IgG induced in allergic individuals can modulate non-atopic thymic B cells, potentially generating thymic B cells prone to allergy development, which seems to not occur in mature B cells.

γδ T Cells and Allergic Diseases

Gamma-delta (γδ) T cells play an essential role in allergic diseases and have emerged as a potential treatment target in recent decades. To clarify the effects of γδ T cells on atopic illnesses, we reviewed the literature on the physical roles and functions of various subsets of γδ T cells, including type 1 T helper (Th1)-like, type 2 T helper- (Th2)-like, and type 17 T helper (Th17)-like γδ T cells. Mouse Vγ1 T cells increase interleukin (IL)-4 levels and trigger B cell class switching and immunoglobulin E production. Meanwhile, mouse Vγ4 T cells and human CD8lowVδ1 T cells secrete interferon-γ and exert an anti-allergy effect similar to that of Th1 cells. Moreover, mouse Vγ6 T cells produce IL-17A, while Th17-like γδ T cells enhance neutrophil and eosinophil infiltration in the acute phase of inflammation, but exert anti-inflammatory effects in the chronic phase. Human Vγ9δ2 T cells may exhibit Th1- or Th2-like characteristics in response to certain types of stimulation. In addition, the microbiota can modulate epithelial γδ T cell survival through aryl hydrocarbon receptors; these γδ T cells play crucial roles in the repair of epithelial damage, antibacterial protection, antigen tolerance, and effects of dysbiosis on allergic diseases.

γδ T cells in autoimmune uveitis pathogenesis: A promising therapeutic target

Autoimmune uveitis is a non-infectious, inflammatory intraocular disease that affects the uveal and adjacent tissues. It frequently causes varying degrees of visual loss. Evidence for the strong association between activated γδ T cells and the development of autoimmune uveitis is growing. The innate and adaptive immune response are connected in the early phases by the γδ T cells that contain the γ and δ chains. γδ T cells can identify antigens in a manner that is not constrained by the MHC. When activated by various pathways, γδ T cells can not only secrete pro-inflammatory factors early on (such as IL-17), but they can also promote Th17 cells responses, which ultimately exacerbates autoimmune uveitis. Therefore, we review the mechanisms by which γδ T cells affect autoimmune uveitis in different activation and disease states. Moreover, we also prospect for immunotherapies targeting different γδ T cell-related action pathways, providing a reference for exploring new drug for the treatment of autoimmune uveitis.

Gamma-delta (γδ) T cell-derived cytokines (IL-4, IL-17, IFN-γ and IL-10) and their possible implications for atopic dermatitis development

Atopic dermatitis (AD) is a chronic disease related to skin disorders that affect individuals in their childhood and can persist or start in adulthood. Patients affected by this disease commonly show skin lesions on the body surface (mainly on the upper and lower limbs) and allergic rhinitis or asthma crises. Looking at the disease from a molecular perspective, the major cytokines involved in inflammatory skin diseases, not only AD, include IL-4, IL-17, IFN-γ and IL-10. Although they can produce these cytokines and infiltrate the affected epithelia in patients with AD, γδ T cells are still almost unexplored. In this update, we briefly discuss the involvement of IL-4, IL-17, IFN-γ and IL-10 in the pathophysiology of AD and the possible role of γδ T cells during the inflammatory process.

Tissue-resident immunity in the lung: a first-line defense at the environmental interface

The lung is a vital organ that incessantly faces external environmental challenges. Its homeostasis and unimpeded vital function are ensured by the respiratory epithelium working hand in hand with an intricate fine-tuned tissue-resident immune cell network. Lung tissue-resident immune cells span across the innate and adaptive immunity and protect from infectious agents but can also prove to be pathogenic if dysregulated. Here, we review the innate and adaptive immune cell subtypes comprising lung-resident immunity and discuss their ontogeny and role in distinct respiratory diseases. An improved understanding of the role of lung-resident immunity and how its function is dysregulated under pathological conditions can shed light on the pathogenesis of respiratory diseases.

γδ T Lymphocytes in Asthma: a Complicated Picture

A minor subset (approximately 5%) of peripheral T cells has their TCR build up from γ and δ chains instead of α and β—those are the γδ T lymphocytes. They can be functionally divided into subsets, e.g., Th1-, Th2-, Th9-, Th17-, Tfh-, and Treg-like γδ T cells. They share some specifics of both innate and adaptive immunity, and are capable of rapid response to a range of stimuli, including some viral and bacterial infections. Atopic diseases, including asthma, are one of major health-related problems of modern western societies. Asthma is one of the most common airway diseases, affecting people of all ages and having potential life-threatening consequences. In this paper, we review the current knowledge about the involvement of γδ T cells in the pathogenesis of asthma and its exacerbations. We summarize both the studies performed on human subjects as well as on the murine model of asthma. γδ T cells seem to be involved in the pathogenesis of asthma, different subsets probably perform opposite functions, e.g., symptom-exacerbating Vγ1 and symptom-suppressing Vγ4 in mice model of asthma.

Infiltration pattern of gammadelta T cells and its association with local inflammatory response in the nasal mucosa of patients with allergic rhinitis

BACKGROUND

gammadelta (γδ) T cells play important roles in allergic lower airway inflammation. However, little is known about their infiltration pattern in the nasal mucosa during upper airway inflammation. This study investigated γδ T cell distribution in nasal tissues of allergic rhinitis (AR) patients and the relationship between γδ T cells and other inflammatory cell types.

METHODS

A total of 30 patients with septal deviation were examined, including 22 with and 8 without AR. The localization of γδ T cells and other cells (eosinophils, neutrophils, mast cells, macrophages, B cells, cluster of differentiation [CD]4+ T cells, CD8+ T cells, regulatory T cells [Tregs], interferon [IFN]-γ+ cells, interleukin [IL]17+ cells, and IL10+ cells) was evaluated by histological analysis and immunohistochemistry. T helper cell (Th)1/Th2/Th17 and Treg gene expression was analyzed by quantitative polymerase chain reaction (PCR).

RESULTS

γδ T cells were localized in the epithelium or subepithelial region of nasal mucosa, and their infiltration was higher in AR patients relative to control subjects. The number of γδ T cells was associated with the presence of eosinophils, macrophages, mast cells, B cells, CD8+ T cells, Forkhead box (Fox)p3+ Tregs, IL17+ cells, and IL10+ cells but not of neutrophils or IFN-γ+ cells. The messenger RNA (mRNA) level of a γδ T cell subunit was positively correlated with those of Th1 genes (T-bet and IFN-γ), Th2 cytokine (C-C motif chemokine ligand 18), and Treg genes (Foxp3 and IL10).

CONCLUSION

γδ T cells play multiple roles in mucosal inflammation in AR including immune surveillance and adaptive and innate immune responses.

Characterization of Mouse γδ T Cell Subsets in the Setting of Type-2 Immunity

Accumulating evidence indicates that γδ T cells are a critical component of type-2 immunity. However, the role of these cells in type-2 immune responses seems to be divergent. γδ T cells are heterogeneous lymphocytes that can be further divided into TCR-Vγ/δ definable subsets. Different subsets have distinct and sometimes opposite function during immune responses. In this chapter, we describe the detailed protocol for characterization of γδ T cell subsets in a mouse model of ovalbumin (OVA)/alum-induced type-2 immunity. Our protocol includes identifying γδ T cell subsets by flow cytometry, functionally inactivating individual subsets in vivo, purifying γδ T cell subsets, and using adoptive cell transfer to explore the role of individual subsets in OVA/alum-induced IgE responses.

A Retrospective Analysis of γδ T Cell Expression in Chronic Rhinosinusitis and Its Association with Recurrence of Nasal Polyps

BACKGROUND/AIMS

To examine whether γδ T cell is expressed in the nasal mucosa of chronic rhinosinusitis (CRS) patients and its potential association with recurrence of nasal polyps.

METHODS

Thirty-six patients with CRS with nasal polyps (CRSwNP) and 25 patients with CRS without nasal polyps (CRSsNP) were recruited. Twenty-six patients with other nasal diseases served as controls. The CRSwNP group was divided into the eosinophilic CRSwNP and noneosinophilic CRSwNP groups. The expression of γδ T cells was detected by immunohistochemistry. The expression of each subtype of γδ T cells was detected by using qRT-PCR. All patients underwent nasal endoscopy, and postoperative follow-up lasted over 12 months. CRS patients were evaluated by preoperative VAS scores of symptoms and nasal endoscopy Lund-Kennedy scores.

RESULTS

The expression of γδ T cells in the CRSwNP groups was stronger than in the CRSsNP and the control group (p < 0.05, p < 0.05). The expression of Vγ1+γδ T cells in the eosinophilic CRSwNP group was higher than that in the CRSsNP group and the control group (p < 0.05, p < 0.05). The expression of γδ T cells was associated with high rate of recurrence, tissue eosinophil infiltration, worse symptom score of nasal obstruction, and higher Lund-Kennedy score (all p < 0.05).

CONCLUSIONS

Increased expression of γδ T cells in CRSwNP may be associated with recurrence of nasal polyps.

Lung eosinophil recruitment in response to Aspergillus fumigatus is correlated with fungal cell wall composition and requires γδ T cells

The differential recognition of fungal cell wall polysaccharides that program innate and adaptive immunity to the human opportunistic fungal pathogen Aspergillus fumigatus has been a focus of considerable interest. In a mouse model of fungal conidia aspiration, decreased relative levels of cell wall core carbohydrates β-1,3-glucan to chitin in A. fumigatus isolates and mutant strains were correlated with increased airway eosinophil recruitment. In addition, an increase in fungal surface chitin exposure induced by the β-1,3-glucan synthesis-targeting drug caspofungin was associated with increased murine airway eosinophil recruitment after a single challenge of conidia. The response to increased A. fumigatus chitin was associated with increased transcription of IL-17A after a single aspiration, although this cytokine was not required for eosinophil recruitment. Rather, both RAG1 and γδ T cells were required, suggesting that this subset of innate-like lymphocytes may be an important regulator of potentially detrimental type 2 immune responses to fungal inhalation and infection.

Regulation of IgE Responses by γδ T Cells

Immunoglobulin E (IgE) antibodies play a crucial role in host defense against parasite infections. However, inappropriate IgE responses are also involved in the pathogenesis of allergic diseases. The generation of IgE antibodies is a tightly controlled process regulated by multiple transcription factors, cytokines, and immune cells including γδ T cells. Accumulating evidence demonstrates that γδ T cells play a critical role in regulating IgE responses; however, both IgE-enhancing and IgE-suppressive effects are suggested for these cells in different experimental systems. In this review, we examine the available evidence and discuss the role of γδ T cells in IgE regulation both in the context of antigen-induced immune responses and in the state of partial immunodeficiency.

Genetic variation influences immune responses in sensitive rats following exposure to TiO2 nanoparticles

This study examines the immunological responses in rats following inhalation to titanium dioxide nanoparticles (TiO2 NPs), in naïve rats and in rats with induced allergic airway disease. The responses of two different inbred rat strains were compared: the Dark Aguoti (DA), susceptible to chronic inflammatory disorders, and the Brown Norwegian (BN), susceptible to atopic allergic inflammation. Naïve rats were exposed to an aerosol of TiO2 NPs once daily for 10 days. Another subset of rats was sensitized to the allergen ovalbumin (OVA) in order to induce airway inflammation. These sensitized rats were exposed to TiO2 NPs before and during the allergen challenge. Naïve rats exposed to TiO2 NPs developed an increase of neutrophils and lymphocytes in both rat strains. Airway hyperreactivity and production of inflammatory mediators typical of a T helper 1 type immune response were significantly increased, only in DA rats. Sensitization of the rats induced a prominent OVA-specific-IgE and IgG response in the BN rat while DA rats only showed an increased IgG response. Sensitized rats of both strains developed airway eosinophilia following allergen challenge, which declined upon exposure to TiO2 NPs. The level of neutrophils and lymphocytes increased upon exposure to TiO2 NPs in the airways of DA rats but remained unchanged in the airways of BN rats. In conclusion, the responses to TiO2 NPs were strain-dependent, indicating that genetics play a role in both immune and airway reactivity. DA rats were found to be higher responder compared to BN rats, both when it comes to responses in naïve and sensitized rats. The impact of genetically determined factors influencing the inflammatory reactions pinpoints the complexity of assessing health risks associated with nanoparticle exposures.

Regulatory effect of astragalus polysaccharides on intestinal intraepithelial γδT cells of tumor bearing mice

Astragalus polysaccharides (APS) possess multiple immunomodulatory activities. Due to its high molecular weight, orally administration of APS is not easily absorbed into the blood stream, and how APS exerts its capacity in vivo is still not well elucidated. We assume that enteric mucosal immune response might trigger the immune regulation of APS, and our previous studies demonstrated that APS had regulatory activity on intraepithelial lymphocytes (IELs). Therefore, this study aimed to investigate the functions of APS on intestinal intraepithelial γδT cells, a major subset in IELs and an essential component of maintaining homeostasis and immune regulation in enteric mucosa. Results showed that APS could promote proliferation and function of intestinal intraepithelial γδT cells in vitro, the IFN-γ, FasL and GrB mRNA levels in γδT cells were all significantly increased. Moreover, APS also improved the activity of intestinal intraepithelial γδT cells in vivo, as cytokines production and cytotoxicity of γδT cells were all remarkably improved in tumor-bearing mice treated with APS. In addition, the levels of TNF-α and IFN-γ were significantly increased, whereas the levels of IL-10 and TGF-β were significantly decreased in tumor-bearing mice treated with APS. In conclusion, this study demonstrated that APS could improve proliferation and function of intestinal intraepithelial γδT cells, which might an important pathway for immunomodulation of APS in cancer therapy.

The role of the γ δ T cell in allergic diseases

The predominant distribution of γδ T cells in the mucosal and epithelial tissues makes these unconventional lymphocytes the “guards” to contact external environment (like allergens) and to contribute to immune surveillance, as well as “vanguards” to participate in initiating mucosal inflammation. Therefore, γδ T cells have been considered to bridge the innate and adaptive immunity. The role these cells play in allergy seems to be complicated and meaningful, so it makes sense to review the characteristics and role of γδ T cells in allergic diseases.

Infection with respiratory syncytial virus influences FasL-mediated apoptosis of pulmonary γδ T cells in a murine model of allergen sensitization

BACKGROUND

It has been reported that adoptive transfer of γδ T cells increases the cellular infiltration, especially eosinophils, in the lungs of allergic mice, suggesting that γδ T cells may play a proinflammatory role in allergic airway inflammation. Respiratory syncytial virus (RSV) infection can decrease the number of Th2-type γδ T cells. However, the underlying mechanisms remain unknown.

METHODS

BALB/c mice were inoculated intranasally with RSV before or after sensitization to OVA. The amounts of Th1/Th2 cytokines as well as the levels of specific antibodies were determined by ELISA. The apoptotic death of pulmonary γδ T cells was analyzed by flow cytometry.

RESULTS

Adoptive transfer of γδ T cells increased the production of Th2 cytokines in the lungs and allergy-related antibodies in the serum, further confirming that γδ T cells act as pro-inflammatory cells or a promoter for the development of allergic asthma. RSV infection before sensitization to OVA enhanced apoptotic death of pulmonary γδ T cells. The percentage and absolute number of FasL-expressing γδ T cells in the lungs of allergic mice were elicited significantly by prior RSV infection. Blocking FasL with monoclonal antibody diminished apoptotic death of γδ T cells, suggesting that FasL is important for RSV-induced apoptosis of pulmonary γδ T cells.

CONCLUSIONS

This work provides evidence that RSV infection suppresses the subsequent development of OVA-induced allergic responses partly by enhancing FasL-mediated apoptosis of pulmonary γδ T cells.

γδ T cells and their potential for immunotherapy

Vγ9Vδ2 (also termed Vγ2Vδ2) T cells, a major human peripheral blood γδ T cell subset, recognize microbial (E)-4-hydroxy-3-methylbut-2-enyl diphosphate and endogenous isopentenyl diphosphate in a TCR-dependent manner. The recognition does not require specific accessory cells, antigen uptake, antigen processing, or MHC class I, class II, or class Ib expression. This subset of T cells plays important roles in mediating innate immunity against a wide variety of infections and displays potent and broad cytotoxic activity against human tumor cells. Because γδT cells express both natural killer receptors such as NKG2D and γδ T cell receptors, they are considered to represent a link between innate and adaptive immunity. In addition, activated γδ T cells express a high level of antigen-presenting cell-related molecules and can present peptide antigens derived from destructed cells to αβ T cells. Utilizing these antimicrobial and anti-tumor properties of γδ T cells, preclinical and clinical trials have been conducted to develop novel immunotherapies for infections and malignancies. Here, we review the immunological properties of γδ T cells including the underlying recognition mechanism of nonpeptitde antigens and summarize the results of γδ T cell-based therapies so far performed. Based on the results of the reported trials, γδ T cells appear to be a promising tool for novel immunotherapies against certain types of diseases.

γδ T Lymphocytes Coordinate Eosinophil Influx during Allergic Responses

Tissue eosinophil infiltration, which is a hallmark of allergic and helminthic diseases, is mainly coordinated by T lymphocytes, via the production of eosinophilotactic chemokines. Among T lymphocyte subsets, lymphocytes expressing γδ T cell receptor have been determined as a key factor for eosinophil accumulation via direct and indirect mechanisms. This knowledge is strongly supported by the fact that, in different experimental models of eosinophilic airway inflammation and helminth-induced Th2 lung inflammation, an evident tissue accumulation of γδ T lymphocytes is observed. In addition, the depletion of γδ T lymphocytes is correlated with the impairment of eosinophil accumulation in inflamed tissue. γδ T lymphocytes are non-conventional T lymphocytes, which comprise a minor T lymphocyte subset, mainly distributed in the tissue, and present crucial roles in innate and acquired immune responses. γδ T lymphocytes recognize several danger- and pathogen-associated molecular pattern molecules and stress antigens in a MHC-independent fashion and can provide rapid tissue-specific responses, via the production of a wide range of chemical mediators capable to modulate other cell populations. These mediators include chemoattractant cytokines and chemokines that attract eosinophils into the tissue by either direct recognition (such as IL-5, CCL11/eotaxin), or indirect mechanisms via the modulation of αβ T lymphocytes and macrophages (through the production of interferon-γ, IL-4, and CCL2/Monocyte chemoattractant protein-1, MCP-1, for example). The present review presents an overview of how γδ T lymphocytes coordinate eosinophil accumulation in allergy, by focusing on their role in airway inflammation and by discussing the involvement of cytokines and chemokines in this phenomenon.

CCL25 induces α₄β₇ integrin-dependent migration of IL-17⁺ γδ T lymphocytes during an allergic reaction

Herein, we provide evidence that during allergic inflammation, CCL25 induces the selective migration of IL-17(+) γδ T cells mediated by α(4) β(7) integrin. Intrapleural injection of CCL25 into ovalbumin (OVA)-immunized C57BL/6 mice triggered the accumulation of γδ T lymphocytes expressing CCR9 (CCL25 receptor) and α(4) β(7) integrin in the pleura, but failed to attract αβ T lymphocytes. CCL25 attracted CCR6(+) γδ T cells producing IL-17 (but not IFN-γ or IL-4). OVA challenge triggered increased production of CCL25 followed by the accumulation of CCR9(+) , α(4) β(7) (+) , and CCR6(+) /IL-17(+) γδ T cells into the pleural cavities of OVA-immunized mice, which was inhibited by the in vivo neutralization of CCL25. The in vivo blockade of α(4) β(7) integrin also inhibited the migration of IL-17(+) γδ T lymphocytes (but not of αβ T lymphocytes) into mouse pleura after OVA challenge, suggesting that the CCL25/α(4) β(7) integrin pathway is selective for γδ T cells. In addition, α(4) β(7) integrin blockade impaired the in vitro transmigration of γδ T cells across endothelium (which expresses α(4) β(7) ligands VCAM-1 and MadCAM-1), which was induced by CCL25 and by cell-free pleural washes recovered from OVA-challenged mice. Our results reveal that during an allergic reaction, CCL25 drives IL-17(+) γδ T-cell mobilization to inflamed tissue via α(4) β(7) integrin and modulates IL-17 levels.

γδ T cells augment rejection of skin grafts by enhancing cross-priming of CD8 T cells to skin-derived antigen

Gamma delta T cells (γδ T cells) possess innate-like properties and are proposed to bridge the gap between innate and adaptive immunity. In this study, we explored the role of γδ T cells in cutaneous immunity using a skin transplantation model. Following engraftment of skin expressing cell-associated model antigen (Ag) (ovalbumin) in epithelial keratinocytes, skin-resident γδ T cells enhanced graft rejection. Although the effector function of CD8 T cells was intact in the absence of γδ T cells, cross-priming of CD8 T cell to graft-derived Ag was impaired in the absence of γδ T cells. The reduced graft rejection and graft priming of γδ T-cell-deficient mice was evident in both acutely inflamed and well-healed grafting models. Furthermore, expression of the CD40 activation marker on migrating dendritic cells was lower in TCRδ(-/-) mice compared with wild-type mice, regardless of the presence or absence of inflammation associated with grafting. These results indicate that γδ T cells enhance graft priming and consequently the likelihood of a successful immune outcome in the context of skin graft rejection, suggesting that γδ T cells may be an important component of immunity to epithelial cancers or infection.

Krüppel-like factor 2 regulates trafficking and homeostasis of gammadelta T cells

gammadelta T cells are generated in the thymus and traffic to secondary lymphoid organs and epithelial surfaces, where they regulate immune responses. alphabeta T cells require sphingosine 1-phosphate receptor type 1 (S1P(1)) and CD62L for thymic emigration and circulation through secondary lymphoid organs. Both of these genes are regulated by the transcription factor Krüppel-like factor 2 (KLF2) in conventional alphabeta T cells. It is unclear if gammadelta T cells use similar mechanisms. In this study, we show that thymic gammadelta T cells express S1P(1) and that it is regulated by KLF2. Furthermore, KLF2 and S1P(1)-deficient gammadelta T cells accumulate in the thymus and fail to populate the secondary lymphoid organs or gut, in contrast to the expectation from published work. Interestingly, KLF2 but not S1P(1) deficiency led to the expansion of a usually rare population of CD4(+) promyelocytic leukemia zinc finger(+) "gammadelta NKT" cells. Thus, KLF2 is critically important for the homeostasis and trafficking of gammadelta T cells.

Analysis of gamma delta T cell functions in the mouse

Mouse models of disease and injury have been invaluable in investigations of the functional role of gammadelta T cells. They show that gammadelta T cells engage in immune responses both early and late, that they can function both polyclonally and as peripherally selected clones, and that they can be effector cells and immune regulators. They also suggest that functional development of gammadelta T cells occurs stepwise in thymus and periphery, and that it is governed by gammadelta TCR-signaling and other signals. Finally, they indicate that gammadelta T cell functions often segregate with TCR-defined subsets, in contrast to conventional T cells. From the functional studies in mice and other animal models, gammadelta T cells emerge as a distinct lymphocyte population with a unique and broad functional repertoire, and with important roles in Ab responses, inflammation and tissue repair. They also are revealed as a potentially useful target for immune intervention.

Mouse mast cell protease 4 is the major chymase in murine airways and has a protective role in allergic airway inflammation

It is widely established that mast cells (MCs) have a harmful role in asthma, for example by secreting various proinflammatory substances stored within their secretory granule. However, in this study, we show that one of the substances stored within MC granule, chymase, in fact has a protective role in allergic airway inflammation, indicating that MCs may possess both harmful and protective activities in connection with this type of disease. Wild-type (WT) mice and mice lacking mouse MC protease 4 (mMCP-4), a chymase that is functionally homologous to human chymase, were sensitized and challenged with OVA, followed by the assessment of airway physiology and inflammatory parameters. Our results show that the airway hyperresponsiveness was significantly higher in mMCP-4(-/-) as compared with WT mice. Moreover, the degree of lung tissue inflammation was markedly higher in mice lacking mMCP-4 than in WT controls. Histological analysis revealed that OVA sensitization/challenge resulted in a marked increased in the thickness of the smooth muscle cell (SMC) layer and, notably, that the degree of SMC layer thickening was more pronounced in mMCP-4(-/-) animals than in WT controls, thus indicating that chymase may have an effect on airway SMCs. In support of this, mMCP-4-positive MCs were located in the close vicinity of the SMC layer, mainly in the upper airways, and mMCP-4 was shown to be the major chymase expressed in these MCs. Taken together, our results indicate that chymase present in the upper airways protects against allergic airway responses, possibly by regulating SMCs.

Polysaccharides derived from Yamoa (Funtumia elastica) prime gammadelta T cells in vitro and enhance innate immune responses in vivo

Yamoa (ground bark of Funtumia elastica tree) is marketed and sold as a dietary supplement with anecdotal therapeutic effects in the treatment of asthma and hay fever. We determined that Yamoa and Yamoa-derived polysaccharides affected innate immunity, in part, by priming gammadelta T cells. Gene expression patterns in purified bovine gammadelta T cells and monocytes induced by Yamoa were similar to those induced by ultrapure lipopolysaccharide (uLPS). In the presence of accessory cells, Yamoa had priming effects that were similar to those of LPS on bovine and murine gammadelta T cells, but much more potent than LPS on human gammadelta T cells. The bioactive component of Yamoa was delineated to a complex polysaccharide fraction (Yam-I). Intraperitoneal injection of Yamoa and Yam-I in mice induced rapid increases in peritoneal neutrophils directed by changes in chemokine expression. In support of a unique agonist found in Yam-I, similar peritonitis responses were also observed in TLR4- and MyD88-deficient mice. Therapeutic treatment with Yam-I resulted in decreased bacterial counts in feces from mice with Salmonella enterica serotype typhimurium (ST)-induced enterocolitis. This characterization of the immune stimulatory properties of polysaccharides derived from Yamoa suggests mechanisms for the anecdotal positive effects of its ingestion and that these polysaccharides show potential for application in innate protection from disease.

Chronic inflammation and asthma

Allergic asthma is a complex and chronic inflammatory disorder which is associated with airway hyper-responsiveness and tissue remodelling of the airway structure. Although originally thought to be a Th2-driven inflammatory response to inhaled innocuous allergen, the immune response in asthma is now considered highly heterogeneous. There are now various in vivo systems which have been designed to examine the pathways leading to the development of this chronic immune response and reflect, in part this heterogeneity. Furthermore, the emergence of endogenous immunoregulatory pathways and active pro-resolving mediators hold great potential for future therapeutic intervention. In this review, the key cellular and molecular mediators relating to chronic allergic airway disease are discussed, as well as emerging players in the regulation of chronic allergic inflammation.

The influence of IgE-enhancing and IgE-suppressive gammadelta T cells changes with exposure to inhaled ovalbumin

It has been reported that the IgE response to allergens is influenced by gammadelta T cells. Intrigued by a study showing that airway challenge of mice with OVA induces in the spleen the development of gammadelta T cells that suppress the primary IgE response to i.p.-injected OVA-alum, we investigated the gammadelta T cells involved. We found that the induced IgE suppressors are contained within the Vgamma4(+) subset of gammadelta T cells of the spleen, that they express Vdelta5 and CD8, and that they depend on IFN-gamma for their function. However, we also found that normal nonchallenged mice harbor IgE-enhancing gammadelta T cells, which are contained within the larger Vgamma1(+) subset of the spleen. In cell transfer experiments, airway challenge of the donors was required to induce the IgE suppressors among the Vgamma4(+) cells. Moreover, this challenge simultaneously turned off the IgE enhancers among the Vgamma1(+) cells. Thus, airway allergen challenge differentially affects two distinct subsets of gammadelta T cells with nonoverlapping functional potentials, and the outcome is IgE suppression.

Enhanced development of CD4+ gammadelta T cells in the absence of Itk results in elevated IgE production

The Tec kinase Itk is critical for the development of alphabeta T cells as well as differentiation of CD4(+) T cells into Th2 cells. Itk null mice have defects in the production of Th2 cytokines; however, they paradoxically have significant elevations in serum IgE. Here we show that Itk null mice have increased numbers of gammadelta T cells in the thymus and spleen. This includes elevated numbers of CD4(+) gammadelta T cell, the majority of which carry the Vgamma1.1 and Vdelta6.2/3 gammadelta T-cell receptor with a distinct phenotype. The development of these CD4(+) gammadelta T cells is T cell intrinsic, independent of either major histocompatibility complex class I or class II, and is favored during development in the absence of Itk. Itk null CD4(+) gammadelta T cells secrete significant amounts of Th2 cytokines and can induce the secretion of IgE by wild-type B cells. Our data indicate that Itk plays important role in regulating gammadelta T-cell development and function. In addition, our data indicate that the elevated IgE observed in Itk-deficient mice is due in part to the enhanced development of CD4(+) gammadelta T cells in the absence of Itk.

Tec kinase Itk in gammadeltaT cells is pivotal for controlling IgE production in vivo

In conventional alphabeta T cells, the Tec family tyrosine kinase Itk is required for signaling downstream of the T cell receptor (TCR). Itk also regulates alphabeta T cell development, lineage commitment, and effector function. A well established feature of Itk(-/-) mice is their inability to generate T helper type 2 (Th2) responses that produce IL-4, IL-5, and IL-13; yet these mice have spontaneously elevated levels of serum IgE and increased numbers of germinal center B cells. Here we show that the source of this phenotype is gammadelta T cells, as normal IgE levels are observed in Itk(-/-)Tcrd(-/-) mice. When stimulated through the gammadelta TCR, Itk(-/-) gammadelta T cells produce high levels of Th2 cytokines, but diminished IFNgamma. In addition, activated Itk(-/-) gammadelta T cells up-regulate costimulatory molecules important for B cell help, suggesting that they may directly promote B cell activation and Ig class switching. Furthermore, we find that gammadelta T cells numbers are increased in Itk(-/-) mice, most notably the Vgamma1.1(+)Vdelta6.3(+) subset that represents the dominant population of gammadelta NKT cells. Itk(-/-) gammadelta NKT cells also have increased expression of PLZF, a transcription factor required for alphabeta NKT cells, indicating a common molecular program between alphabeta and gammadelta NKT cell lineages. Together, these data indicate that Itk signaling regulates gammadelta T cell lineage development and effector function and is required to control IgE production in vivo.

The Tec kinases Itk and Rlk regulate conventional versus innate T-cell development

Tec family kinases are important components of antigen receptor signaling pathways in B cells, T cells, and mast cells. In T cells, three members of this family, inducible T-cell kinase (Itk), resting lymphocyte kinase (Rlk), and Tec, are expressed. In the absence of Itk and Rlk, T-cell receptor signaling is impaired, with defects in mitogen-activated protein kinase activation, Ca(2+) mobilization, and actin polymerization. During T-cell development in the thymus, no role has been found for these kinases in the CD4(+) versus CD8(+) T-cell lineage decision; however, several studies indicate that Itk and Rlk contribute to the signaling leading to positive and negative selection. In addition, we and others have recently described an important role for Itk and Rlk in the development of conventional as opposed to innate CD4(+) and CD8(+) T cells. Natural killer T and gammadelta T-cell populations are also altered in Itk- and Rlk/Itk-deficient mice. These findings strongly suggest that the strength of T-cell receptor signaling during development determines whether T cells mature into conventional versus innate lymphocyte lineages. This lineage decision is also influenced by signaling via signaling lymphocytic activation molecule (SLAM) family receptors. Here we discuss these two signaling pathways that each contribute to conventional versus innate T-cell lineage commitment.

Requirement of L-selectin for gammadelta T lymphocyte activation and migration during allergic pleurisy: co-relation with eosinophil accumulation

Intra-thoracic antigenic challenge (ovalbumin, 12.5 microg/cavity) led to increased numbers of gammadelta T lymphocytes in pleural cavities, blood and thoracic lymph nodes in sensitized mice within 48 h. Part of these cells expressed CD62L, which increased on gammadelta T cell surfaces obtained from lymph nodes after ovalbumin (OVA) challenge. Selectin blockade by fucoidan pre-treatment (10 mg/kg, i.v.) impaired in vivo increase in CD25(+) and c-fos(+) gammadelta T cell numbers in lymph nodes, indicating a role for selectins on gammadelta T lymphocyte activation and proliferation. In vivo selectin blockade by fucoidan or alpha-CD62L mAb (200 microg/mice, i.p.) also inhibited OVA-induced gammadelta T cell accumulation in pleural cavities. Confirming the direct effect of CD62L on gammadelta T cell transmigration, the migration of i.v. adoptively-transferred CFSE-labeled gammadelta T lymphocytes into pleural cavities of challenged recipient mice was impaired by fucoidan ex vivo treatment. It is noteworthy that eosinophil influx was also impaired in those mice, indicating that reduced eosinophil migration by CD62L in vivo blockade depended on gammadelta T cell migration via CD62L molecules. Accordingly, pleural gammadelta T lymphocytes from fucoidan-treated mice presented reduced OVA-induced IL-5 and CCL11 production. Supporting these data, the depletion of Vgamma4 T lymphocytes, which are pulmonary gammadelta T cells, decreased OVA-induced eosinophil influx into allergic site. Such results demonstrate that CD62L is crucial for the activation of gammadelta T cells in lymph nodes, for their migration into inflamed tissue and for the modulation of eosinophil influx during allergic response.

Involvement of CC chemokines in gammadelta T lymphocyte trafficking during allergic inflammation: the role of CCL2/CCR2 pathway

In the present study, we show that the intra-thoracic injection of ovalbumin (OVA, 12.5 microg per cavity) into C57BL/10 mice induced a significant increase in gammadelta T lymphocyte numbers in the pleural cavity, blood and thoracic lymph node of challenged mice. Such increase was significant within 12 h, peaked within 48 h and returned to basal counts within 120 h. Levels of CC chemokine ligand (CCL)-2/monocyte chemotactic protein-1, CCL5/regulated upon activation, normal T cell expressed and secreted, CCL3/macrophage inflammatory protein-1 alpha and CCL25/thymus-expressed chemokine were above control values in pleural washes recovered 24 h after OVA challenge (OPW) and were likely produced by pleural macrophages and mesothelial cells. Antigenic challenge also induced an up-regulation in CC chemokine receptor (CCR)-2, CCR5 and CCR9 on gammadelta T cells from pleural cavities, blood and lymph nodes, suggesting that cells found in mice pleural cavity migrate from secondary lymphoid organs into the inflammatory site via blood stream. The in vitro neutralization of CCL2 (but not of CCL3, CCL5 or CCL25) abrogated OPW-induced gammadelta T lymphocyte transmigration. Confirming such results, the in vivo administration of alpha-CCL2 mAb inhibited gammadelta T lymphocyte accumulation in the pleural cavity of challenged mice, whereas the blockade of CCL3, CCL5 or CCL25 showed no effect on gammadelta T cell mobilization. In addition, OVA challenge failed to induce gammadelta T lymphocyte accumulation in the pleural cavity of C57BL/6 CCR2 knockout mice, which also showed decreased numbers of these cells in blood and lymph nodes when compared with wild-type mice. Overall, such results demonstrate that CCR2/CCL2 pathway is crucial for gammadelta T lymphocyte mobilization during the allergic response.

Mechanisms of type I food allergy

The gastrointestinal tract represents the biggest immune organ of the human body and has 3 distinct functions: (1) barrier and defense against potential pathogens, (2) ignorance or tolerance of innocuous agents, and (3) digestion and nutritional uptake of alimentary compounds. Recent studies have indicated that especially structural features of dietary proteins seem to be a precondition for the induction of immediate type immune responses. Crystallographic studies of allergen molecules have been fundamental for epitope studies in a 3-dimensional format using peptides or mimotopes. The identified IgE epitopes were all conformational and responsible for high-affinity interactions with specific IgE. Moreover, numerous studies have indicated that allergens, among them food allergens, preferentially form di-, tri-, or multimers, thus leading to a repetitive display of epitopes. As B-lymphocytes are pattern recognizers, this feature is essential for a memory response, but may also be critical for the very first allergen contact and initiation of the IgE response. Here we review the key candidate cells in the gut, which are capable of recognizing conformation and molecular patterns, but may also be involved in skewing the immune response towards Th2. Animal models have been basic for understanding the molecular principles of food allergy and they will be increasingly indispensable for the definition of novel vaccination strategies. Therefore, the available models are critically analyzed in this review.

What targets have knockouts revealed in asthma?

There have been numerous studies of mice rendered genetically deficient of various genes in the context of allergic inflammatory airway disease. These studies have provided invaluable information about basic immune processes, but have also been considered to be useful in predicting novel pharmacological targets. In this review, the effect of a wide range of individual knockouts (KO) on the development of asthma-like pathologies in mice is compiled and considered. How the results of these studies compare with effects of agents that interfere with the function of each gene product, where known, is also described. Finally, a personal view of the utility of these studies in drug development is presented.

Distribution of leucocyte subsets in bronchial mucosa from dogs with eosinophilic bronchopneumopathy

Immunohistochemistry was used to characterize the distribution of leucocyte subsets in the bronchial mucosa of 11 dogs with idiopathic eosinophilic bronchopneumopathy (EBP). Formalin-fixed tissues from all dogs were included in the study, but frozen tissue from only one dog was available. MHC class II(+) cells were found in moderate numbers in the lamina propria (LP). These cells were morphologically either dendritic-like cells or macrophages, but many macrophages did not express MHC class II. Such molecules were expressed by occasional fibroblasts. L1(+) cells, which formed a relatively small component of the LP inflammatory infiltrate, were morphologically either macrophages or polymorphonuclear cells (probably eosinophils). IgA(+) plasma cells were found in varying numbers in the LP, mostly in association with glandular tissue. IgG(+) plasma cells were less common, and IgM(+) plasma cells were present in low numbers. Many CD3(+) cells were present in the LP. In the single case from which frozen tissue was available, most of the lymphocytes were labelled with CD4 marker, while smaller numbers were CD8(+) T cells. Most of the lymphocytes in this case were positively labelled with T-cell receptor (TCR)-alphabeta marker. TCR-gammadelta(+) cells, although less common, were present in significant numbers throughout the LP. CDlc(+) dendritic cells were numerous in the epithelium and in the LP, immediately beneath the basement membrane. These findings, which were similar to those described in human asthma, are suggestive of a Th2 dominant immune response in canine EBP. As in human asthma, this provides a possible basis for new forms of treatment in canine EBP.

Distribution and leukocyte contacts of γδ T cells in the lung

Pulmonary gammadelta T cells protect the lung and its functions, but little is known about their distribution in this organ and their relationship to other pulmonary cells. We now show that gammadelta and alphabeta T cells are distributed differently in the normal mouse lung. The gammadelta T cells have a bias for nonalveolar locations, with the exception of the airway mucosa. Subsets of gammadelta T cells exhibit further variation in their tissue localization. gammadelta and alphabeta T cells frequently contact other leukocytes, but they favor different cell-types. The gammadelta T cells show an intrinsic preference for F4/80+ and major histocompatibility complex class II+ leukocytes. Leukocytes expressing these markers include macrophages and dendritic cells, known to function as sentinels of airways and lung tissues. The continuous interaction of gammadelta T cells with these sentinels likely is related to their protective role.

A mouse model for in vivo tracking of the major dust mite allergen Der p 2 after inhalation

Inhaled environmental antigens, i.e. allergens, cause allergic symptoms in millions of patients worldwide. As little is known about the fate of an allergen upon inhalation, we addressed this issue for a major dust mite allergen, Der p 2. First, a model for Der p 2-sensitization was established in C57BL/6 J mice, in which sensitized mice mounted a Der p 2-specific IgE-response with eosinophilic lung inflammation after allergen challenge in the airways. In this model, we applied recombinant Der p 2 carrying a novel C-terminal tetrapeptide Sel-tag enabling labelling with the gamma-emitting radionuclide 75Se at a single selenocysteine residue ([75Se]Der p 2). In vivo tracking of intratracheally administered [75Se]Der p 2 using whole-body autoradiography revealed that [75Se]Der p 2-derived radioactivity persisted in the lungs of sensitized mice as long as 48 h. Radioactivity was also detected in kidneys, liver and in enlarged lung-associated lymph nodes. Interestingly, a larger proportion of radioactivity was found in the lungs of sensitized compared with nonsensitized mice 24 h after intratracheal instillation of [75Se]Der p 2. A radioactive protein corresponding to intact Der p 2 could only be detected in the lungs, whereas [75Se]Der p 2-derived radioactivity was recovered in known selenoproteins both in lung and other organs. Hence, using the recently developed Sel-tag method in a mouse model for Der p 2-sensitization, we could track the fate of an inhaled allergen in vivo. Based upon our findings, we conclude that the inflammatory state of the lung influences the rate of metabolism and clearance of Der p 2. Thus, an allergic response to the inhaled allergen may lead to prolonged retention of Der p 2 in the lung.

Allergies and the risk of pancreatic cancer: a meta-analysis with review of epidemiology and biological mechanisms

Previous reports suggest that allergic disorders may protect against various types of cancer, but the association between history of allergy and pancreatic cancer risk has not been well studied. We did a systematic review and meta-analysis of published studies to evaluate the association of any type, and specific types, of allergy and the risk of pancreatic cancer. We did a comprehensive literature search using MEDLINE, PUBMED, and the ISI Web of Science databases to identify potential relevant case-control and cohort studies. Pooled relative risks (RR) and 95% confidence intervals (95% CI) were calculated using the fixed- and random-effects model. Fourteen population-based studies (4 cohort and 10 case-control studies) with a total of 3,040 pancreatic cancer cases fulfilled our inclusion criteria. A history of allergy was associated with a reduced risk of pancreatic cancer (RR, 0.82; 95% CI, 0.68-0.99). The risk reduction was stronger for allergies related to atopy (RR, 0.71; 95% CI, 0.64-0.80), but not for asthma (RR, 1.01; 95% CI, 0.77-1.31). There was no association between allergies related to food or drugs and pancreatic cancer (RR, 1.08; 95% CI, 0.74-1.58). Overall, there was no evidence of publication bias. Allergies, in particular those related to atopy, seem to be associated with a decreased risk of pancreatic cancer. The hyperactive immune system of allergic individuals may, therefore, in some way lead to increased surveillance and protect against pancreatic cancer development.

Analysis of circulating gammadelta T cells in children affected by IgE-associated and non-IgE-associated allergic atopic eczema/dermatitis syndrome

Recent studies have suggested that not only alphabeta(+) T cells, but also the less common gammadelta(+) T cells may play a role as effectors and immunoregolatory cells in the development and perpetuation of allergic inflammation. The objective of this study was to focus on the role of gammadelta(+) T cells in atopic dermatitis (AD), a chronic relapsing inflammatory disease of the skin, often associated with allergic bronchial asthma. The present study employed flow cytometric analysis to compare numbers and phenotypic characteristics of gammadelta(+) T cells in the peripheral blood of children with atopic dermatitis and age-matched healthy controls. The percentage of circulating Vgamma 9Vdelta2(+) T lymphocytes was significantly increased in AD patients with respect to the age-matched controls, with a positive correlation with clinical score severity. The prevalent phenotype in both AD patients and controls was CD45RO(+), with no differences observed in the percentage of Vdelta2(+) CD45RO(+) between these groups. Conversely, memory CD45RO(+) CD62L(+) Vdelta2(+) lymphocytes were significantly lower in AD patients. Furthermore, naive circulating Vdelta2(+) T lymphocytes were significantly lower in AD children than in aged-matched controls. No correlation was observed between circulating Vgamma 9Vdelta2(+) expansion and IgE serum levels. It was concluded that an association exists between the levels of circulating gammadelta(+) T lymphocytes and atopic dermatitis, with a positive correlation with clinical score but no link with IgE serum levels. The pathophysiological role of gammadelta T lymphocytes in atopic dermatitis awaits further investigation.

Increased levels of hypoxia-sensitive proteins in allergic airway inflammation

In this study we investigated the alterations in protein levels that are induced by allergic eosinophilic lung inflammation. Lung tissue eosinophilia and sequestration of inflammatory cells in airspaces were provoked by systemic sensitization with ovalbumin followed by repeated inhalation challenge with aerosolized ovalbumin. Proteome alterations in lung tissue and bronchoalveolar lavage fluid, respectively, were examined by two-dimensional gel electrophoresis followed by identification of proteins by mass spectrometry. Several proteins were markedly increased in inflamed tissue. In particular, several proteins that are known to be associated with hypoxia were elevated, for example, glycolytic enzymes, glucose-regulated protein 78 kD, prolyl-4-hydroxylase, peroxiredoxin 1, and arginase. Out of the identified proteins, Ym2 displayed the clearest increase, present at high levels in animals with lung eosinophilia, while being undetectable in control subjects. Furthermore, the levels of cathepsin S were markedly increased in inflamed tissue. Taken together, this study identifies a number of marker proteins associated with the pathogenesis of allergic lung inflammation and indicates a link between allergic airway inflammation and induction of hypoxia-related gene products.

Different Potentials of γδ T Cell Subsets in Regulating Airway Responsiveness: Vγ1+ Cells, but Not Vγ4+ Cells, Promote Airway Hyperreactivity, Th2 Cytokines, and Airway Inflammation

Allergic airway inflammation and hyperreactivity are modulated by gammadelta T cells, but different experimental parameters can influence the effects observed. For example, in sensitized C57BL/6 and BALB/c mice, transient depletion of all TCR-delta(+) cells just before airway challenge resulted in airway hyperresponsiveness (AHR), but caused hyporesponsiveness when initiated before i.p. sensitization. Vgamma4(+) gammadelta T cells strongly suppressed AHR; their depletion relieved suppression when initiated before challenge, but not before sensitization, and they suppressed AHR when transferred before challenge into sensitized TCR-Vgamma4(-/-)/6(-/-) mice. In contrast, Vgamma1(+) gammadelta T cells enhanced AHR and airway inflammation. In normal mice (C57BL/6 and BALB/c), enhancement of AHR was abrogated only when these cells were depleted before sensitization, but not before challenge, and with regard to airway inflammation, this effect was limited to C57BL/6 mice. However, Vgamma1(+) gammadelta T cells enhanced AHR when transferred before challenge into sensitized B6.TCR-delta(-/-) mice. In this study Vgamma1(+) cells also increased levels of Th2 cytokines in the airways and, to a lesser extent, lung eosinophil numbers. Thus, Vgamma4(+) cells suppress AHR, and Vgamma1(+) cells enhance AHR and airway inflammation under defined experimental conditions. These findings show how gammadelta T cells can be both inhibitors and enhancers of AHR and airway inflammation, and they provide further support for the hypothesis that TCR expression and function cosegregate in gammadelta T cells.

The role of regulatory T cells in allergy

Atopic diseases are characterized by Th2 and IgE responses to common environmental and food antigens. In vivo, IgE production depends on interactions between allergen-specific B lymphocytes and Th2 lymphocytes. IgE levels are extremely low in normal individuals, suggesting that IgE production is under strong regulation. One of the reasons behind the lack of atopy in healthy individuals is the activity of regulatory T cells, which prevent naïve T helper cell precursors from acquiring a differentiated Th2 phenotype. In addition to naturally occurring regulatory T cells, atopy can be prevented by allergen-specific tolerant/regulatory cells induced through mucosal stimulation, and by mechanisms that directly suppress Iepsilon sterile transcript production on activated B lymphocytes. This article reviews the recent progress on thymic-derived as well as peripherally induced regulatory T cells as they relate to atopy. The latter discussion also includes regulatory T cells that arise through immunotherapy.