Local Expansion of Allergen-Specific CD30+Th2-Type γδ T Cells in Bronchial Asthma

Double-edged sword: γδ T cells in mucosal homeostasis and disease

The mucosa is a tissue that covers numerous body surfaces, including the respiratory tract, digestive tract, eye, and urogenital tract. Mucosa is in direct contact with pathogens, and γδ T cells perform various roles in the tissue. γδ T cells efficiently defend the mucosa from various pathogens, such as viruses, bacteria, and fungi. In addition, γδ T cells are necessary for the maintenance of homeostasis because they select specific organisms in the microbiota and perform immunoregulatory functions. Furthermore, γδ T cells directly facilitate pregnancy by producing growth factors. However, γδ T cells can also play detrimental roles in mucosal health by amplifying inflammation, thereby worsening allergic responses. Moreover, these cells can act as major players in autoimmune diseases. Despite their robust roles in the mucosa, the application of γδ T cells in clinical practice is lacking because of factors such as gaps between mice and human cells, insufficient knowledge of the target of γδ T cells, and the small population of γδ T cells. However, γδ T cells may be attractive targets for clinical use due to their effector functions and low risk of inducing graft-versus-host disease. Therefore, robust research on γδ T cells is required to understand the crucial features of these cells and apply these knowledges to clinical practices.

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.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.

Phage-display reveals interaction of lipocalin allergen Can f 1 with a peptide resembling the antigen binding region of a human γδT-cell receptor

Although some progress has been achieved in understanding certain aspects of the allergenic mechanism of animal lipocalins, they still remain largely enigmatic. One possibility to unravel this property is to investigate their interaction with components of the immune system. Since these components are highly complex we intended to use a high-throughput technology for this purpose. Therefore, we used phage-display of a random peptide library for panning against the dog allergen Can f 1. By this method we identified a Can f 1 binding peptide corresponding to the antigen-binding site of a putative γδT-cell receptor. Additional biochemical investigations confirmed this interaction.

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.

Gamma/Delta T Cells in the Course of Healthy Human Pregnancy: Cytotoxic Potential and the Tendency of CD8 Expression Make CD56+ γδT Cells a Unique Lymphocyte Subset

To date, pregnancy is an immunological paradox. The semi-allogenic fetus must be accepted by the maternal immune system, while defense against pathogens and immune surveillance cannot be compromised. Gamma/delta T cells are believed to play an important role in this immunological puzzle. In this study, we analyzed peripheral blood CD56+ γδT cells from pregnant women (1^st, 2^nd, and 3^rd trimester) and non-pregnant women by multicolor flow cytometry. Interestingly, γδT cells represent almost half of CD3+/CD56+ cells. Among γδT cells, the CD56+ population expands in the 2^nd and 3^rd trimester. CD56+ γδT cells maintained a predominantly CD4–/CD8– or CD8+ phenotype, while CD56– γδT cells were in similar rates CD4–/CD8– or CD4+ during pregnancy. Investigation of the lysosomal degranulation marker CD107a revealed a preserved elevated rate of potentially cytotoxic CD56+ γδT cells in pregnancy, while their cytotoxic strength was reduced. Furthermore, CD56+ γδT cells continuously showed a higher prevalence of PD-1 expression. CD56+ γδT cells’ rate of PD-1 increased in the 1^st trimester and decreased hereafter back to normal level. We correlated the cytotoxic potential and the expression of the inhibitory immune checkpoint PD-1 and were able to demonstrate that highly cytotoxic cells within this CD56+ γδT population tend to express PD-1, which might allow the inhibition of these cells after binding its ligand in the placenta. These findings should support the understanding of the complex processes, which ensure the maintenance of pregnancy.

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.

Lung-resident γδ T cells and their roles in lung diseases

γδ T cells are greatly enriched in mucosal and epithelial sites, such as the skin, respiratory, digestive and reproductive tracts, and they are defined as tissue-resident immune cells. In these tissues, the characteristics and biological roles of γδ T cells are distinguished from each other. The lungs represent the most challenging immunological dilemma for the host, and they have their own effective immune system. The abundance of γδ T cells, an estimated 8-20% of resident pulmonary lymphocytes in the lung, maintains lung tissue homeostasis. In this review, we summarize the recent research progress regarding lung-resident γδ T cells, including their development, residency and immune characteristics, and discuss the involvement of γδ T cells in infectious diseases of the lung, including bacterial, viral and fungal infections; lung allergic disease; lung inflammation and fibrosis; and lung cancer.

Vitamin D as an adjunctive therapy in asthma. Part 1: A review of potential mechanisms

Vitamin D deficiency (VDD) is highly prevalent worldwide. The classical role for vitamin D is to regulate calcium absorption form the gastrointestinal tract and influence bone health. Recently vitamin D receptors and vitamin D metabolic enzymes have been discovered in numerous sites systemically supporting diverse extra-skeletal roles of vitamin D, for example in asthmatic disease. Further, VDD and asthma share several common risk factors including high latitude, winter season, industrialization, poor diet, obesity, and dark skin pigmentation. Vitamin D has been demonstrated to possess potent immunomodulatory effects, including effects on T cells and B cells as well as increasing production of antimicrobial peptides (e.g. cathelicidin). This immunomodulation may lead to asthma specific clinical benefits in terms of decreased bacterial/viral infections, altered airway smooth muscle-remodeling and -function as well as modulation of response to standard anti-asthma therapy (e.g. glucocorticoids and immunotherapy). Thus, vitamin D and its deficiency have a number of biological effects that are potentially important in altering the course of disease pathogenesis and severity in asthma. The purpose of this first of a two-part review is to review potential mechanisms whereby altering vitamin D status may influence asthmatic disease.

A Novel Prothrombotic Pathway in Systemic Sclerosis Patients: Possible Role of Bisphosphonate-Activated γδ T Cells

Objectives: Infusions of aminobisphonates (ABP) activate Vγ9δ2T cells in vivo and induce an acute inflammatory response in 30% of patients treated for osteoporosis. Following the observation of digital thrombosis in a systemic sclerosis (SSc) patient after treatment with an intravenous ABP, zoledronate (Zol), we evaluated whether patient and control peripheral blood (PB) mononuclear cell (MC, PBMC) acquire a prothrombotic phenotype in response to Zol.

Results: Vγ9δ2T cells of both patients and healthy donors (HD) upregulated the CD69 activation antigen and secreted tumor necrosis factor (TNF)α in response to Zol in vitro. In addition, exposure to either Zol or lipopolysaccharide (LPS), or to both additively, induced expression of the highly procoagulant, tissue factor (TF)-1 on CD14+ monocytes. Importantly, only Zol-induced TF-1 was blocked by a monoclonal antibody to TNFα. Interestingly, we found that SSc, but not HD, Vδ1+ T cells were concurrently activated by Zol to produce interleukin (IL)-4. Addition of plasma from the blood of the SSc patient who developed critical digital ischemia after infusion of Zol, but neither plasma from a second patient with no adverse clinical response to Zol infusion nor of a HD, strongly enhanced Zol-induced monocyte TF-1, which could still be blocked by anti-TNFα.

Conclusion: Aminobisphonates induced secretion of TNFα by Vγ9δ2+ T cells may lead to TNFα-dependent induction of procoagulant TF-1 induction on monocytes. In certain clinical settings, e.g., SSc, TF-1+ monocytes could play a role in triggering clinically relevant thrombosis.

Cytotoxic and regulatory properties of circulating Vδ1+ γδ T cells: a new player on the cell therapy field?

Exploration of cancer immunotherapy strategies that incorporate γδ T cells as primary mediators of antitumor immunity are just beginning to be explored and with a primary focus on the use of manufactured phosphoantigen-stimulated Vγ9Vδ2 T cells. Increasing evidence, however, supports a critical role for Vδ1+ γδ T cells, a minor subset in peripheral blood with distinct innate recognition properties that possess powerful tumoricidal activity. They are activated by a host of ligands including stress-induced self-antigens, glycolipids presented by CD1c/d, and potentially many others that currently remain unidentified. In contrast to Vγ9Vδ2 T cells, tumor-reactive Vδ1+ T cells are not as susceptible to activation-induced cell death and can persist in the circulation for many years, potentially offering durable immunity to some cancers. In addition, specific populations of Vδ1+ T cells can also exhibit immunosuppressive and regulatory properties, a function that can also be exploited for therapeutic purposes. This review explores the biology, function, manufacturing strategies, and potential therapeutic role of Vδ1+ T cells. We also discuss clinical experience with Vδ1+ T cells in the setting of cancer, as well as the potential of and barriers to the development of Vδ1+ T cell-based adoptive cell therapy strategies.

Gamma delta T cells in non-immune patients during primary schistosomal infection

The mevalonate pathway is critical for the survival of Schistosoma. γδ T cells, a small subset of peripheral blood (PB) T cells, recognize low molecular weight phosphorylated antigens in the mevalonate pathway, which drive their expansion to exert protective and immunoregulatory effects. To evaluate their role in schistosomiasis, we measured γδ T cells in the PB of non-immune travelers who contracted Schistosoma hematobium or Schistosoma mansoni in Africa. The maximal level of γδ T-cells following infection was 5.78 ± 2.19% of the total T cells, versus 3.72 ± 3.15% in 16 healthy controls [P = 0.09] with no difference between S. hematobium and S. mansoni in this regard. However, among the nine patients in the cohort who presented with acute schistosomiasis syndrome (AS), the level (3.5 ± 1.9%) was significantly lower than in those who did not (8.6 ± 6.4%, P < 0.05), both before and after therapy. Furthermore, γδ T cells increased significantly in response to praziquantel therapy. In a patient with marked expansion of γδ T cells, most expressed the Vδ2 gene segment, a hallmark of cells responding to cognate antigens in the mevalonate pathways of the parasite or the human host. These results suggest an immunoregulatory role of antigen responsive γδ T cells in the clinical manifestations of early schistosomal infection.

γδT cells suppress inflammation and disease during rhinovirus-induced asthma exacerbations

Most asthma exacerbations are triggered by virus infections, the majority being caused by human rhinoviruses (RV). In mouse models, γδT cells have been previously demonstrated to influence allergen-driven airways hyper-reactivity (AHR) and can have antiviral activity, implicating them as prime candidates in the pathogenesis of asthma exacerbations. To explore this, we have used human and mouse models of experimental RV-induced asthma exacerbations to examine γδT-cell responses and determine their role in the immune response and associated airways disease. In humans, airway γδT-cell numbers were increased in asthmatic vs. healthy control subjects during experimental infection. Airway and blood γδT-cell numbers were associated with increased airways obstruction and AHR. Airway γδT-cell number was also positively correlated with bronchoalveolar lavage (BAL) virus load and BAL eosinophils and lymphocytes during RV infection. Consistent with our observations of RV-induced asthma exacerbations in humans, infection of mice with allergic airways inflammation increased lung γδT-cell number and activation. Inhibiting γδT-cell responses using anti-γδTCR (anti-γδT-cell receptor) antibody treatment in the mouse asthma exacerbation model increased AHR and airway T helper type 2 cell recruitment and eosinophilia, providing evidence that γδT cells are negative regulators of airways inflammation and disease in RV-induced asthma exacerbations.

Gammadelta T cells: innately adaptive immune cells?

T cells employ a cell surface heterodimeric molecule, the T cell receptor (TCR), to recognize specific antigens (Ags) presented by major histocompatibility complex (MHC) molecules and carry out adaptive immune responses. Most T cells possess a TCR with an α and a β chain. However, a TCR constituted by a γ and a δ chain has been described, defining a novel subset of T cells. γδ TCRs specific for a wide variety of ligands, including bacterial phosphoantigens, nonclassical MHC-I molecules and unprocessed proteins, have been found, greatly expanding the horizons of T cell immune recognition. This review aims to provide background in γδ T cell history and function in mouse and man, as well as to provide a critical view of some of the latest developments on this still enigmatic class of immune cells.

The role of vitamin D in asthma

Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways.

Searching for "signal 2": costimulation requirements of γδ T cells

T cell activation requires the integration of signals that arise from various types of receptors. Although TCR triggering is a necessary condition, it is often not sufficient to induce full T-cell activation, as reflected in cell proliferation and cytokine secretion. This has been firmly demonstrated for conventional αβ T cells, for which a large panel of costimulatory receptors has been identified. By contrast, the area remains more obscure for unconventional, innate-like γδ T cells, as the literature has been scarce and at times contradictory. Here we review the current state of the art on the costimulatory requirements of γδ T cell activation. We highlight the roles of members of the immunoglobulin (like CD28 or JAML) or tumour necrosis factor receptor (like CD27) superfamilies of coreceptors, but also of more atypical costimulatory molecules, such as NKG2D or CD46. Finally, we identify various areas where our knowledge is still markedly insufficient, hoping to provoke future research on γδ T cell costimulation.

Pulmonary V gamma 4+ gamma delta T cells have proinflammatory and antiviral effects in viral lung disease

Host defenses, while effecting viral clearance, contribute substantially to inflammation and disease. This double action is a substantial obstacle to the development of safe and effective vaccines against many agents, particularly respiratory syncytial virus (RSV). RSV is a common cold virus and the major cause of infantile bronchiolitis worldwide. The role of alphabeta T cells in RSV-driven immunopathology is well studied, but little is known about the role of "unconventional" T cells. During primary RSV challenge of BALB/c mice, some Vgamma7+ gammadelta T cells were present; however, immunization with a live vaccinia vector expressing RSV F protein substantially enhanced Vgamma4+ gammadelta T cell influx after RSV infection. Harvested early, these cells produced IFN-gamma, TNF, and RANTES after ex vivo stimulation. By contrast, those recruited 5 days after challenge made IL-4, IL-5, and IL-10. Depletion of gammadelta T cells in vivo reduced lung inflammation and disease severity and slightly increased peak viral replication but did not prevent viral clearance. These studies demonstrate a novel role for gammadelta T cells in the development of immunopathology and cellular influx into the lungs after immunization and RSV challenge. Though a minor population, gammadelta T cells have a critical influence on disease and are an attractive interventional target in the alleviation of viral lung disease.

Complementary roles for lipid and protein allergens in triggering innate and adaptive immune systems

BACKGROUND

Recent advances in allergy research mostly focussed on two major headings: improving protein allergen purification, which is aimed towards a better characterization of IgE- and T-cell reactive epitopes, and the potential new role for unconventional innate and regulatory T cells in controlling airway inflammation. These advancements could appear to be in conflict each other, as innate T cells have a poorly-defined antigen specificity that is often directed toward nonprotein substances, such as lipids.

METHOD

To reconcile these contrasting findings, the model of cypress pollinosis as paradigmatic for studying allergic diseases in adults is suggested.

RESULTS

The biochemical characterization of major native protein allergens from undenatured pollen grain demonstrated that the most relevant substance with IgE-binding activity is a glycohydrolase enzyme, which easily denaturizes in stored grains. Moreover, lipids from the pollen membrane are implicated in early pollen grain capture and recognition by CD1(+) dendritic cells (DC) and CD1-restricted T lymphocytes. These T cells display Th0/Th2 functional activity and are also able to produce regulatory cytokines, such as IL-10 and TGF-beta. CD1(+) immature DCs expand in the respiratory mucosa of allergic subjects and are able to process both proteins and lipids.

CONCLUSION

A final scenario may suggest that expansion and functional activation of CD1(+) DCs is a key step for mounting a Th0/Th2-deviated immune response, and that such innate response does not confer long-lasting protective immunity.

Innate immune functions of human gammadelta T cells

gammadelta T cells expressing the Vgamma9Vdelta2 T cell receptor (TCR) account for 1-10% of CD3(+) peripheral blood T lymphocytes. Vgamma9Vdelta2 T cells use their TCR as a pattern recognition receptor to sense the presence of infection through specific recognition of intermediates of the microbial non-mevalonate pathway of isoprenoid biosynthesis. Such phosphoantigens rapidly and selectively activate human gammadelta T cells to produce proinflammatory cytokines, notably interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). In addition, human gammadelta T cells express certain Toll-like receptors (TLR) and directly respond to the corresponding ligands. We have demonstrated expression of TLR3 in Vgamma9Vdelta2 T cells and striking costimulatory effects of the ligand polyinosinic-polycytidylic acid (polyI:C) on TCR-stimulated IFN-gamma production. Gene expression studies by microarray analysis identified additional genes that were up-regulated by combined TCR- and TLR3 stimulation. We discuss these findings in the context of the suspected role of human Vgamma9Vdelta2 T cells as a link between innate and adaptive immune responses.

Recognition of lipids from pollens by CD1-restricted T cells

Allergic rhinitis and asthma should be considered as organ-specific inflammatory diseases in which the genetic background has determined a local overproduction of Th2-type cytokines and an over-expansion of particular APCs and T cells. Among the latter, a potential pathogenetic role could be assumed for natural killer T cells, expressing both invariant (Valpha24/Vbeta11) and classic alphabeta or gammadelta T-cell receptors. Recent studies support this notion and also suggest that surface pollen substances of nonprotein structure, such as lipid components recognized by CD1, could be viewed as one of the foreign materials against which the immune system of the allergic subject can mount a local inflammatory response.

Recognition of pollen-derived phosphatidyl-ethanolamine by human CD1d-restricted gamma delta T cells

BACKGROUND

Evidences from mice and human beings indicate that gammadelta T cells could be relevant in recognition of stress-induced self and/or yet unidentified inhaled foreign antigens. Their specificity differs from classic MHC-restricted alphabeta T cells and involves the immunoglobulin-like structure of the gammadelta T-cell receptor with the recognition of small organic molecules, alkylamines, and self lipid compounds presented by CD1+ dendritic cells.

OBJECTIVE

Because CD1 receptors are mainly devoted to lipid antigen presentation, we sought to determine whether exogenous pollen membrane lipids may act as allergens for CD1-restricted gammadelta T cells.

METHODS

Peripheral blood and nasal mucosa-associated gammadelta T cells were cloned from normal controls and cypress-sensitive subjects and tested for their antigen specificity and CD1-restriction with phospholipids extracted from tree pollen grains, as well with other natural or synthetic compounds. Phospholipid reactivity of cloned gammadelta T cells was measured by mean of proliferative response and cytokine release as well as by testing their helper activity on IgE production in vitro and in vivo.

RESULTS

Cloned gammadelta T lymphocytes from subjects with allergy, but not normal controls, were found to recognize pollen-derived phosphatidyl-ethanolamine (PE) in a CD1d-restricted fashion. Only 16:0/18:2 and 18:2/18:2 PE were stimulatory, whereas no response was recorded for disaturated PE, phosphatidylcholine, neutral lipids, or protein extract. Proliferating clones secreted both T(H)1-type and T(H)2-type cytokines and drove IgE production in vitro and in vivo.

CONCLUSION

CD1d-restricted gammadelta T cells specific for phospholipids can represent a key mucosal regulatory subset for the control of early host reactivity against tree pollens.

CLINICAL IMPLICATIONS

By knowing how lipid allergen constituents interact with mucosal immune system, we can expand our possibilities in diagnostic and therapeutic interventions.

The effects of CD8+gammadelta T cells on late allergic airway responses and airway inflammation in rats

BACKGROUND

Gamma-delta (gammadelta) T cells regulate immune responses to foreign protein at mucosal surfaces. Whether they can modify allergen-induced early (EAR) and late airway responses (LAR) is unknown.

OBJECTIVE

We have tested the hypothesis that the CD8+ subtype of gammadelta T cells decreases allergen-induced LAR and airway eosinophilia in the rat.

METHODS

Brown Norway rats were administered, intraperitoneally, 3.5 x 10(4) lymph node CD8+gammadelta T cells from naive or sensitized rats. The recipients were sensitized to ovalbumin (OVA) in Al(OH)(3) 3 days after cell transfer and challenged with aerosolized OVA 14 days later. Serum IgE was measured before allergen challenge. After challenge, lung resistance was monitored for 8 hours and then bronchoalveolar lavage (BAL) was analyzed for eosinophil major basic protein (MBP), IL-4, IL-5, IL-13, and IFN-gamma messenger RNA-expressing cells.

RESULTS

gammadelta T cells from naive donors significantly decreased LAR in OVA-challenged sensitized rats, whereas MBP(+) eosinophils were decreased by both gammadelta T cells from naive and sensitized donors. EAR and serum IgE levels were unchanged. The expression of IL-4, IL-5, and IL-13 by BAL cells of gammadelta T cell recipients was attenuated compared with OVA-challenged controls. This was accompanied by an increase in the expression of IFN-gamma.

CONCLUSIONS

Our results are consistent with a suppressive role of CD8+gammadelta T cells on allergic airway responses. However, only gammadelta T cells from naive donors inhibit LAR.

The effect of IL-18 on IL-12-induced CD30 expression and IL-4 and IFN-gamma production by allergen and PPD specific T cells

CD30 is expressed on activated T cells that, as has been suggested, preferentially produce IFN-gamma. Interleukin 12 increases antigen-induced CD30 expression on T cells and IFN-gamma production. Synthesis of IFN-gamma can be augmented further by IL-18. The aim of our study was to investigate whether IL-18 affects the IL-12 induced CD30 expression and cytokine production by allergen or PPD specific T cells. Mononuclear cells of healthy or atopic volunteers were stimulated with PPD or allergen, respectively, to obtain specific T cell lines. T cells were restimulated with appropriate antigen and antigen-presenting cells in the presence of IL-12, IL-18 or a combination of these cytokines. After 3 days, expression of CD30 was investigated on CD4 and CD8 T cells and IFN-gamma and IL-4 cytokine production was estimated in the culture supernatants. Flow cytometric analyses showed no effect of IL-18 on CD30 expression during IL-12 co-stimulation. At the same time after the optimal stimulation for CD30 expression, the levels of IFN-gamma were high in PPD-stimulated cell lines but have not been up-regulated by IL-18. IFN-gamma levels were much lower in allergen-stimulated T cells and although they were up-regulated by IL-12 there was no additional or synergistic effect from IL-18. IL-18, however, increased production of IL-4 in allergen-stimulated cell lines. Our studies provide new information about IL-18 activity on human cells and question its exclusive role in Th1 mediated responses.

The ACVD task force on canine atopic dermatitis (IX): the controversy surrounding the route of allergen challenge in canine atopic dermatitis

For decades, the dogma that environmental allergens trigger cutaneous inflammation led to the denomination of canine atopic dermatitis as "allergic inhalant dermatitis". Definitive proof for a respiratory route of allergen challenge is lacking, however. Recent observations suggest, in fact, that skin inflammation could occur because of epidermal allergenic contact. The aim of this paper is to review the evidence published in favor and against the two suspected routes of allergen provocation.

Cytokine profile of bronchoalveolar lavage-derived CD4(+), CD8(+), and gammadelta T cells in people with asthma after segmental allergen challenge

T cell-derived cytokines play an important role in the pathogenesis of allergic asthma, but little is known about the cytokine profile of their different subsets. The aim of the present study was to investigate the cytokine production potential of CD4(+), CD8(+), or gammadelta(+) T cells derived from the bronchoalveolar space of mild atopic asthmatic subjects (n = 11) and nonatopic control subjects (n = 9) before and 24 h after segmental allergen challenge. The cytokine production was determined using the technique of intracellular cytokine detection by flow cytometry. Comparing asthmatic with control subjects we found no difference in the percentage of CD4(+), CD8(+), or gammadelta T cells in the bronchoalveolar lavage fluid before and after allergen challenge. Before allergen challenge the proportion of cells producing the cytokines interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-5, and IL-13 was not different in CD4(+) and CD8(+) cells. The major difference between the groups was an increased percentage of positive-staining cells for the T helper-(Th)2-cytokines IL-5 and IL-13 in the gammadelta T-cell subset. After allergen challenge, all T-cell subsets revealed a decreased proportion of cells producing the Th1-type cytokines IFN-gamma and IL-2. The percentage of IL-4- and IL-5-positive cells did not change in all subsets, and there was a decreased proportion of IL-13- positive cells in the CD4(+) subset. These findings indicate an increased Th2-cytokine profile in gammadelta T cells. After allergen challenge, the dysbalance between Th1 and Th2 cytokines was further accentuated by a reduction in Th1 cytokine-producing T cells.

Role of CD30+ T cells in rheumatoid arthritis: a counter-regulatory paradigm for Th1-driven diseases

CD30 has been proposed to identify Th0/2-type clones. However, the in vivo relevance of this finding is still a matter of debate, as high serum levels of soluble CD30 have been found in both Th1- and Th2- dominated disorders. Among these, rheumatoid arthritis represents a condition where the Th1 predominance is combined with the presence of CD30(+) T-cell activity, particularly in specific stages of the disease. This article discusses the hypothesis that CD30(+) T cells might play a counter-regulatory role at sites of inflammation in Th1-mediated conditions, such as rheumatoid arthritis.

T-helper type 2 cell-directed therapy for asthma

Asthma is a chronic inflammatory disease of the bronchial airways. Current research in humans and animals suggests that T-helper type 2 (Th2) cells and the cytokines they elaborate cause many of the pathophysiologic abnormalities characteristic of the disease. We review the evidence implicating Th2 cells in asthma and discuss the cellular and molecular mechanisms that control Th2 cell differentiation in the respiratory tract. Based on the steps in Th cell development, we discuss how traditional therapies can modulate Th2 cell function. Furthermore, we explore newer immunomodulatory strategies to inhibit Th2 cell effects, including therapies that may block Th2 cell differentiation, neutralize cytokines, and redirect immune responses towards Th1 and away from Th2.

Role of T-helper type 2 cytokines in down-modulation of fas mRNA and receptor on the surface of activated CD4(+) T cells: molecular basis for the persistence of the allergic immune response

The mechanisms responsible for persistence of T lymphocytes at the sites of allergic inflammation are not completely understood. Activated T cells, usually expressing Fas on their surface, undergo activation-induced apoptotic death, thus limiting the dangerous consequences of a persistent immune reaction. We have previously shown that pulmonary T lymphocytes from untreated asthmatic subjects do not express surface Fas receptors nor do they contain Fas mRNA, yet they display normal levels of Fas ligand. This is not an inherited defect and is confined to mucosal T cells. To gain insights into the mechanism responsible for these findings, we performed a set of experiments with both purified Dermatophagoides pteronyssinus allergen and recombinant human cytokines: interleukin 2 (IL-2), IL-4, IL-5, transforming growth factor beta1, interferon gamma, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In vitro exposure of purified CD4(+) lymphocytes to allergen yielded only transient up-regulation of surface Fas but did not influence susceptibility to Fas-mediated cell death. T-helper type 2 cytokines (IL-4, IL-5, and GM-CSF) had a dose-dependent and specific inhibitory effect on Fas mRNA, suggesting a new fundamental biological role in the survival of inflammatory cells during allergen exposure.

Expression of B7 co-stimulatory molecules and CD1a antigen by alveolar macrophages in allergic bronchial asthma

BACKGROUND

Lung allergen recognition that takes place in the airways of asthmatic subjects is still a controversial matter.

OBJECTIVE

We hypothesized that a rapid allergen recognition process requires the presence, at the mucosal surface, of professional APC, such as B7+ alveolar macrophages (AM) and/or CD1+ dendritic cells, which usually have a lower expression in the normal human lung.

METHODS

Studies were performed on bronchoalveolar lavage (BAL) fluid collected from 10 untreated allergic subjects and 10 adult normal volunteers. Further controls consisted of five untreated pulmonary sarcoidosis (PS) and four extrinsic allergic alveolitis (EAA) individuals. To ascertain whether T helper 2-type cytokines or allergen influence B7 and CD1 antigen expression, in vitro studies were carried out using unprimed (naive) cord blood plastic-adherent monocytes.

RESULTS

Cytofluorymetric analysis revealed that AM from asthmatics, unlike those from normal subjects or patients with PS or EAA, overexpressed B7-2, CD1a and, to a lesser extent, B7-1 surface molecules. Immunohistochemical studies confirmed the presence of CD1+ dendritic cells in the BAL fluid from asthmatic subjects. On in vitro cultured naive cord blood monocytes both purified Dermatophagoides pteronyssinus allergen and T-cell cytokines, i.e. IL-4 and granulocyte macrophage colony-stimulating factor, induced surface expression of B7-2 and CD1a receptors, whereas they had no appreciable effect on that of B7-1 membrane molecule.

CONCLUSIONS

Taken together, these findings support the proposal that airways of atopic individuals are equipped with professional APC that synergize with allergen-specific T cells for the recognition of intact allergens. When the recognition process takes place, asthmatic symptoms could develop in genetically susceptible individuals.