gamma delta T cells, allergen recognition and airway inflammation

Omonijo F, A Ganai N, M. Ibeagha-Awemu E, Mudasir Ahmad S. Immunotherapy in mastitis: state of knowledge, research gaps and way forward

Mastitis is an inflammatory condition that affects dairy cow's mammary glands. Traditional treatment approaches with antibiotics are increasingly leading to challenging scenarios such as antimicrobial resistance. In order to mitigate the unwanted side effects of antibiotics, alternative strategies such as those that harness the host immune system response, also known as immunotherapy, have been implemented. Immunotherapy approaches to treat bovine mastitis aims to enhance the cow's immune response against pathogens by promoting pathogen clearance, and facilitating tissue repair. Various studies have demonstrated the potential of immunotherapy for reducing the incidence, duration and severity of mastitis. Nevertheless, majority of reported therapies are lacking in specificity hampering their broad application to treat mastitis. Meanwhile, advancements in mastitis immunotherapy hold great promise for the dairy industry, with potential to provide effective and sustainable alternatives to traditional antibiotic-based approaches. This review synthesizes immunotherapy strategies, their current understanding and potential future perspectives. The future perspectives should focus on the development of precision immunotherapies tailored to address individual pathogens/group of pathogens, development of combination therapies to address antimicrobial resistance, and the integration of nano- and omics technologies. By addressing research gaps, the field of mastitis immunotherapy can make significant strides in the control, treatment and prevention of mastitis, ultimately benefiting both animal and human health/welfare, and environment health.

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.

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.

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.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

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.

CD8+ T cells in asthma: friend or foe?

While it is well established that CD4(+) T lymphocytes play a crucial role in the initiation, progression and persistence of asthma, the role of CD8(+) T cells is less understood. CD8(+) T cells form functionally similar subsets which exhibit similar cytokine profiles as Th1 and Th2 cells, known as Tc1 and Tc2. Evidence from animal studies suggest that CD8(+) T cells are capable of regulating IgE production through the induction of IL-12 and IL-18 production in dendritic cells, and that CD8(+) T cells may act to moderate Th2 polarisation within the localised lymph nodes during allergic sensitisation. Such findings have led to the suggestion that Th1 polarising, CD8(+) T cell-inducing vaccines would inhibit the development of airway hyperresponsiveness (AHR) and Th2 cell infiltration. Despite these positive findings, the role of CD8(+) T cells within the lung remains poorly understood. While CD8(+) T cells, particularly those expressing the Tc1 phenotype, are capable of moderating inflammation and suppressing AHR, it has been postulated that Tc2 CD8(+) T cells predominate within established asthma and may act to amplify the inappropriate immune response which defines the condition. Within the clinic, the association between CD8(+) T cells and asthma is almost universally defined as injurious, further suggesting a prejudicial role for these cells within the established disease. CD8(+) T cells may be a valuable potential target for therapeutic intervention, either by potentiating their regulatory effects prior to the development of sensitisation, or through suppressing their pro-inflammatory properties within established atopy.

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.

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.

[IgE and respiratory disease]

INTRODUCTION

IgE is known to provide the biological basis for allergy and immediate hypersensitivity. However, recent data provide some evidence that IgE responses are involved in other inflammatory processes apart from allergy, including several respiratory diseases.

STATE OF THE ART

IgE binds to mast cells and basophils but also to other inflammatory cells, which are involved in non-allergic processes. IgE has a role in antigen presentation and is implicated in a number of other immune mechanisms. In the airways, IgE plays an important role in bronchial hyperactivity, even in the absence of an allergen. Epidemiological studies have demonstrated that IgE response is related not only to allergy but also to asthma symptoms, in the presence or absence of atopy, as well as exposure to cigarette smoke. IgE response is altered in several respiratory diseases including extrinsic and intrinsic asthma and allergic bronchopulmonary aspergillosis.

CONCLUSION AND PERSPECTIVES

Since anti-IgE monoclonal antibodies are now available for administration to humans, a better understanding of the IgE response may allow the identification of novel therapeutic targets in the field of respiratory disease.

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.

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.

Human CD1-restricted T cell recognition of lipids from pollens

Plant pollens are an important source of environmental antigens that stimulate allergic responses. In addition to acting as vehicles for foreign protein antigens, they contain lipids that incorporate saturated and unsaturated fatty acids, which are necessary in the reproduction of higher plants. The CD1 family of nonpolymorphic major histocompatibility complex–related molecules is highly conserved in mammals, and has been shown to present microbial and self lipids to T cells. Here, we provide evidence that pollen lipids may be recognized as antigens by human T cells through a CD1-dependent pathway. Among phospholipids extracted from cypress grains, phosphatidyl-choline and phosphatidyl-ethanolamine were able to stimulate the proliferation of T cells from cypress-sensitive subjects. Recognition of phospholipids involved multiple cell types, mostly CD4⁺ T cell receptor for antigen (TCR)αβ⁺, some CD4⁻CD8⁻ TCRγδ⁺, but rarely Vα24i⁺ natural killer–T cells, and required CD1a⁺ and CD1d⁺ antigen presenting cell. The responding T cells secreted both interleukin (IL)-4 and interferon-γ, in some cases IL-10 and transforming growth factor-β, and could provide help for immunoglobulin E (IgE) production. Responses to pollen phospholipids were maximally evident in blood samples obtained from allergic subjects during pollinating season, uniformly absent in Mycobacterium tuberculosis–exposed health care workers, but occasionally seen in nonallergic subjects. Finally, allergic, but not normal subjects, displayed circulating specific IgE and cutaneous weal and flare reactions to phospholipids.

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.

Differential modulation of murine lung inflammation by bradykinin B1 and B2 selective receptor antagonists

The effect of bradykinin receptor antagonists was studied in a mouse (C57Bl/6) model of allergic lung inflammation. Bradykinin B(2) receptor antagonist HOE-140 (D-Arg-[Hyp(3),Thi(5),Dtic(7)-Oic(8)]bradykinin) or bradykinin B(1) receptor antagonist R-954 (Ac-Orn[Oic(2),alphaMePhe(5),betaD-Nal(7)Ile(8)]des-Arg(9)-bradykinin) were given i.p. to ovalbumin sensitized mice 30 min before antigen challenge. After 24 h, bronchoalveolar lavage was performed for cell analysis and the lungs were removed for evaluation of airway hyperreactivity and histopathology. Treatment with HOE-140 caused a significant increase in bronchoalveolar lavage cell number: eosinophils (182%), neutrophils (98%), lymphocytes CD(4)(+) (192%), CD(8)(+) (236%), B220 (840%), Tgammadelta(+) (194%) and NK1.1(+) (246%). Hyperreactivity and mucus secretion were not significantly affected in this group. Treatment with R-954 significantly reduced eosinophil (79%) and neutrophil (83%) but has no effect on lymphocytes number in bronchoalveolar lavage fluid. Airway hyperreactivity and mucus secretion were reduced by this treatment (84% and 35%, respectively). These results show important modulatory effect of bradykinin B(1) and B(2) receptors on allergic lung inflammation.

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

Allergic airway inflammation induced in mice is T-cell dependent and recruitment of eosinophils to airspaces requires both alphabeta and gammadelta T cells. From previous studies it is evident that alphabeta T cells are essential for the allergic T helper type 2 (Th2)-like response, while the mechanistic contribution of gammadelta T cells is still unclear. In this study, we have investigated the role of gammadelta T cells in allergic airway eosinophilia induced by ovalbumin hypersensitivity. By comparing the responsiveness to sensitizing allergen of wild-type mice with that of T-cell receptor gammadelta knockout mice (TCRgammadelta KO) we demonstrated that mice lacking gammadelta T cells are defective in the systemic ovalbumin-specific immunoglobulin E (IgE) response. Furthermore, after aerosol challenge with allergen, gammadelta T-cell deficient mice exhibited a significantly decreased migration of B cells and natural killer cells to airways and reduced levels of allergen-specific IgG and IgA in bronchoalveolar lavage fluid. The role for B cells in the airway inflammation was indicated by the impaired ability of mice lacking functional B cells to evoke an eosinophilic response. The diminished eosinophilia in TCRgammadelta KO mice could not be explained by a defective Th2 activation since these mice displayed a normal IgG response in serum and an unaffected IG2b/IgG1 ratio in airways. Analysis of immunoregulatory cytokines in isolated lung tissue, thoracic lymph nodes and spleen further supported the notion that these mice are able to evoke a sufficient activation of T helper cells and that gammadelta T cells are not required for maintaining the Th2 profile. These results indicate that gammadelta T cells contribute to allergic airway inflammation by pathways separate from classical Th2 immune activation.

CD1--the pathology perspective

CD1 molecules are a family of cell surface-associated glycoproteins now recognized as having a role in antigen presentation. These glycoproteins are distinct from yet have some similarities to classical major histocompatibility complex class I and class II molecules. The role of these molecules has been studied in detail over recent years, with an explosion of interest following the demonstration that they can present nonprotein antigens to certain subpopulations of T cells. The purpose of this paper is to provide an overview of current knowledge of the function of the CD1 family with specific emphasis on the potential role in the pathogenesis of certain diseases. Although much of the current research in this field has inevitably concentrated on mice and humans, this work also has potential significance for veterinary species.

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.

CD8+ T cells have an essential role in pulmonary clearance of nontypeable Haemophilus influenzae following mucosal immunization

A rodent respiratory experimental model has proved useful for investigating the immune mechanisms responsible for clearance of bacteria from the lungs. Immunohistochemical studies in immune and nonimmune rats have identified the cellular kinetics of response to bacterial pulmonary infection for CD8+, CD4+, and gammadelta+ T cells; B cells; and the expression of major histocompatibility complex class II (MHC-II). During the course of bacterial clearance, there was no apparent proliferation or extravasation of lymphocytes, nor was there increased expression of MHC-II in nonimmune animals despite an influx of polymorphonuclear leukocytes, whereas in immunized animals there was an early influx of CD8+ and gammadelta+ T cells, followed by enhanced expression of the MHC-II marker, cellular infiltration by polymorphonuclear leukocytes, and finally an increased number of CD4+ T cells. Depletion of CD8+ T cells confirmed their vital contribution in the preprimed immune response to pulmonary infection by significantly decreasing the animals' ability to clear bacteria following challenge.

Mucosal immunity in the lung and upper airway

The mucosal surfaces of the lungs and upper airways are common sites for infection. Extensive studies of the mechanisms associated with immune responses in the respiratory tract have found that understanding the system is challenging and involves many complex interactions to prevent and eliminate infection. Immune protection against diseases transmitted through the respiratory tract requires an understanding of the important aspects associated with beneficial, detrimental or ineffective immune responses. Two critical aspects of an immune response against a pathogen are that of the inductive stage, either induced by vaccination or primary infection, and the effector stage, the ability to recognise, respond to and eliminate the infection without detriment to the host. An immunisation strategy must not only have a measure of the induced antigen specific response, but this response must also be protective.

Human gammadelta T cells express a higher TCR/CD3 complex density than alphabeta T cells

The aim of our study was to compare CD3 expression on gammadelta T cells and alphabeta T cells in human patients. The antigen density of TCR and CD3 on both subsets was assessed by a quantitative method in eight patients. In parallel, we developed and validated a reliable direct tricolor staining protocol that we tested on samples from hospitalized and healthy individuals (n = 60). Our results demonstrate that human gammadelta T cells constitutively express approximately twofold more of the TCR/CD3 complex than alphabeta T cells. We suggest that this enhanced expression of the TCR/CD3 complex could contribute to the higher reactivity of gammadelta T cells compared to alphabeta T cells. These clinical laboratory results confirm the fundamental data described elsewhere. gammadelta T cells deserve further clinical investigations to understand their precise role in human immunity.

Human gamma/delta T-cell lines derived from airway biopsies

gamma/delta T cells have been postulated to play an important role in the immune response at epithelial boundaries, but have not been well described in human lung tissue. We have identified and characterized gamma/delta T-cell lines from human airway biopsies and compared them with T-cell lines from paired peripheral blood samples. Airway-derived T-cell lines stimulated with tetanus toxoid (TT) contained a greater proportion of gamma/delta T cells compared with T-cell lines stimulated with mitogens, other antigens, or without antigen. TT-stimulated airway T cells expressed different T-cell receptors (TCRs) than did blood- derived T cells, and used predominantly variable region (V)gamma I family genes rather than V gamma II family genes. Airway-derived gamma/delta T cells produced high levels of interferon-gamma and were associated with T helper 1--like cytokine profiles. This study describes the presence and antigen-dependent proliferation of gamma/delta T cells from human airway tissue, and demonstrates differences in lung-derived gamma/delta TCRs compared with gamma/delta T cells derived from peripheral blood. The data suggest that gamma/delta T cells may be functionally enriched in human airways relative to peripheral blood.

Use of transgenic animals to investigate drug hypersensitivity

Hypersensitivity reactions to drugs and environmental agents are often due to exaggerated humoral (Th(2)) or cell mediated (Th(1)) immune responses with typical cytokine profiles. Overexpression of Th(2) cytokines, such as IL-4, IL-5 or IL-13 in mice, enhances an IgE antibody mediated response, while deletion of these cytokines attenuates and/or prevents allergic responses. Conversely, modulation of Th(1) cytokine gene expression may affect cell-mediated immune responses. Therefore, cytokine transgenic mice are used as investigative tools to study potential chemicals and/or drug allergies. In addition to cytokines and chemokines, other factors are important for the development of allergic responses, such as IgE, Fc receptors, vasopressin and several other factors, which can be tested in transgenic mice.

gammadelta T-cell-deficient mice do not differ from normal controls in their induction or expression of type 2 dominant responses to exogenous antigen

The roles that gammadelta T cells play in shaping initial CD4 T cell activation, and sensitivity to development of atopic diseases, remain controversial. Using a genetic knockout model of gammadelta T-cell deficiency, we investigated the role of these cells in initiation of exogenous antigen specific murine cytokine and antibody responses. Given that the most widely distributed and clinically prominent class of allergens are soluble protein antigens, we utilized OVA to examine the role played by gammadelta T cells in shaping the induction and expression of exogenous Ag specific immune responses. Focusing on immunization conditions that stimulate in vivo induction of type 2 dominant immunity, we report that gammadelta deficient and intact C57Bl6 mice exhibit similar OVA-specific responses as indicated by the (i) intensity of initial T-cell activation (ii) the type1 vs. type 2 balance of exogenous Ag specific cytokine synthesis and the (iii) intensity and the relative balance of the resulting IgE vs. IgG(2a) responses in vivo seen in these strains. Taken together, the data are consistent with the hypothesis that gammadelta T cells do not play an essential role in shaping induction of systemic immune responses to soluble exogenous antigen in type 2 dominated responses.

Experimental approaches to analysis of immune dysregulation in human allergic disease

Over the last 40 years, much attention has been directed towards identification of the immunologic, genetic and environmental factors that predispose towards development of allergic disease. An implicit assumption in many such studies is that clinical tolerance reflects from immunologic tolerance. Here we critically review the conceptual background and experimental data arguing for the alternative hypothesis that failure to develop atopic disease reflects the success of type 1 dominated immunity that constitutively impedes development of type 2 responses to environmental antigens, hence, clinical immediate hypersensitivity. We report that endogenous production of type 1 chemokines such as IP-10 by non-atopic individuals may play a substantive role in maintaining this putatively protective type 1 bias in non-atopic subjects. Polyclonal activators (superantigen TSST-1, anti-CD3, PHA) were used to activate distinct intracellular signaling pathways, inducing quantitatively different IFNgamma:IL-4 ratios in primary culture of human PBMC. In parallel, physiologic stimuli such as grass pollen or cat antigen were used to evaluate the impact of IP-10 on CD4 T cell dependant, chloroquine-sensitive cytokine synthesis. IFNgamma responses by non-atopic subjects were markedly increased in the presence of nM concentrations of rhIP-10 while type 2 cytokine synthesis remained unaffected. Optimal rIP-10 concentrations for promoting expression and maintenance of type 1 cytokine synthesis in vitro (0.1 to 10 ng/ml) were at or well below those generally used for chemotaxis (5 to 100 ng/ml). Collectively, our findings suggest a potential role for this T cell focused chemokine in maintaining the default type 1 responses usually caused to environmental antigens in non-atopic subjects. These may play a role in determining the relative susceptibility of individuals to develop atopic disease. Taken together with recent reports of other roles played by chemokines in shaping the nature of immune responses, the data suggest that constitutive, endogenous type 1 chemokine synthesis may play a homeostatic role in inhibiting development of atopic disease.

Are chemokines essential or secondary participants in allergic responses?

OBJECTIVES

This review will provide a concise and critical overview of the rapidly evolving concepts in chemokine biology with a special relevance to allergic responses. The article is intended for clinicians with little or no expertise in chemokine biology.

DATA SOURCES

A detailed literature search was performed through MEDLINE (PubMed). Those reports considered important and relevant to the topic were critically reviewed and their conclusions included.

RESULTS

Chemokines are a group of structurally related small proteins with a common biological activity of inducing directional migration (chemotaxis) of various cell types. Chemokines such as eotaxins and MCP-4 play a key role in selective eosinophil recruitment to sites of inflammation in allergies and asthma. Several other chemokine activities relevant to allergic responses are: activation of basophils and eosinophils to release inflammatory mediators, regulation of IgE responses, and Th1/Th2-type cytokine balance. A number of therapeutic strategies aimed at inhibiting chemokine function are being tested in animal models of allergies and asthma.

CONCLUSIONS

Chemokines have been widely viewed as pathogenic mediators of acute and chronic inflammation and tissue damage in allergies and asthma. On the other hand, recent evidence suggests that endogenous production of certain chemokines might be beneficial to the host in preventing allergic response. Met-RANTES, a modified antagonist of RANTES, and eotaxin receptor (CCR3) antagonists, represent promising novel therapeutic agents potentially useful in atopic disorders. Thus, suppression of chemokines may interrupt the sequence of signals culminating in an allergic response. Whether chemokines are actually essential for an allergic response awaits confirmation with gene knockout animal experiments.

Selective recruitment of T-cell subsets to the udder during staphylococcal and streptococcal mastitis: analysis of lymphocyte subsets and adhesion molecule expression

During bacterial infection of the bovine mammary gland, large numbers of leukocytes migrate into the udder, resulting in the establishment of a host response against the pathogen. Currently, the specific leukocyte populations mediating this immune response are not well defined. In the studies described here, we analyzed blood and milk from healthy cows and cows with naturally occurring mastitis to determine if distinct alphabeta and gammadelta T-lymphocyte subsets were involved in the response of the udder to a mastitis pathogen and if the type of mastitis pathogen influenced the subset composition of these responding leukocytes. Although blood samples from cows with confirmed staphylococcal and streptococcal mastitis were characterized by increased numbers of gammadelta T cells, the most dramatic changes in leukocyte distributions occurred in milk samples from these cows, with a 75% increase in alphabeta T-cell levels and a 100% increase in gammadelta T-cell levels relative to the levels in milk samples from healthy animals. Interestingly, the increase in alphabeta T-cell numbers observed in milk from cows with staphylococcal mastitis was primarily due to increased numbers of CD4(+) T cells, while the increase in alphabeta T-cell numbers observed in cows with streptococcal mastitis was due to a parallel increase in both CD4(+) and CD8(+) T-cell numbers. The increased numbers of gammadelta T cells in milk from cows with staphylococcal and streptococcal mastitis were due to a selective recruitment of a distinct gammadelta T-cell subset (GD3.1(+)), while no change in the numbers of GD197(+) gammadelta T cells was observed. We also analyzed adhesion protein expression on blood and milk leukocytes and found that, in comparison to the situation for healthy cows, L-selectin was down-regulated and CD18 was up-regulated on leukocytes from cows with mastitis. Thus, shedding of L-selectin and up-regulation of CD18 by neutrophils may provide a sensitive indicator of early inflammatory responses during bovine mastitis. Overall, these studies suggest that distinct alphabeta and gammadelta T-cell subsets are involved in the host defense of the udder against mastitis infection and that selective recruitment of these T-cell subsets depends on the infectious agent involved.

Essential Role for Both CD80 and CD86 Costimulation, But Not CD40 Interactions, in Allergen-Induced Th2 Cytokine Production from Asthmatic Bronchial Tissue: Role for αβ, But Not γδ, T Cells

CD80 and CD86 interact with CD28 and deliver costimulatory signals required for T cell activation. We demonstrate that ex vivo allergen stimulation of bronchial biopsy tissue from mild atopic asthmatic, but not atopic nonasthmatic, subjects induced production of IL-5, IL-4, and IL-13. Explants from both study groups did not produce IFN-γ, but secreted the chemokine RANTES without any overt stimulation. In addition to allergen, stimulation of asthmatic explants with mAbs to CD3 and TCR-αβ but not TCR-γδ induced IL-5 secretion. Allergen-induced IL-5 and IL-13 production by the asthmatic tissue was inhibited by anti-CD80 and, to a lesser extent, by anti-CD86 mAbs. In contrast, the production of these cytokines by PBMCs was not affected by mAbs to CD80, was inhibited by anti-CD86, and was strongly attenuated in the presence of both Abs. FACS analysis revealed that stimulated asthmatic bronchial tissue was comprised of CD4+ T cells that expressed surface CD28 (75.3%) but little CTLA-4 (4.0%). Neutralizing mAbs to CD40 ligand had no effect on the cytokine levels produced by asthmatic tissue or PBMCs. Collectively, these findings suggest that allergen-specific αβ T cells are resident in asthmatic bronchial tissue and demonstrate that costimulation by both CD80 and CD86 is essential for allergen-induced cytokine production. In contrast, CD86 appears to be the principal costimulatory molecule required in PBMC responses. Attenuation of type 2 αβ T cell responses in the bronchial mucosa by blocking these costimulatory molecules may be of therapeutic potential in asthma.

Comparison of the effects of fluticasone propionate, aqueous nasal spray and levocabastine on inflammatory cells in nasal lavage and clinical activity during the pollen season in seasonal rhinitics

BACKGROUND

Treatment options for allergic rhinitis include antihistamines, decongestants, anticholinergics, cromolyn sodium and corticosteroids. As the nose is a small organ, comprising less than 1% of total body mass and surface area, it seems logical to confine treatment of rhinitis to the diseased organ.

OBJECTIVE

To evaluate the effects of therapy with intranasal fluticasone propionate (FP), both on subjective symptoms and pathophysiological mechanisms, in rhinitis patients during pollen season when the patients were symptomatic.

METHODS

We used a double-blind, placebo (PLA)-controlled, randomized, double dummy, parallel group study of the effect of 6 weeks treatment. The double-blind comparison was made between the following three treatments: FP aqueous nasal spray, 200 microg taken once daily, levocabastine (LEV) nasal spray, 200 microg taken twice daily and PLA nasal spray. Clinical evaluation and the levels of cells and mediators in nasal washing were performed before and after treatments. Twenty-four patients (11 men and 13 women, aged 17-50 years, mean age 30.1 +/- 8.5) with strictly seasonal allergic rhinitis to Parietaria entered the study. Clinical evaluation and the levels of inflammatory cells (eosinophils and activated eosinophils, i.e. EG2+) and their mediators (tryptase, eosinophil cationic protein, eosinophil protein X and neutrophil myeloperoxidase) in nasal-lavage were performed before and after treatments.

RESULTS

Treatment with FP significantly increased, with respect to placebo, the percentage of days without sneezing (P < 0. 001), nasal blockage (P < 0.001), rhinorrhea (P < 0.001), nasal itching (P < 0.001). Furthermore, treatment with FP showed additional benefits with respect to LEV. The percentage of days without nasal blockage was significantly higher in the FP group that in the placebo group (P = 0.018). The same applied to rhinorrhea (P = 0.009). The percentages of days without sneezing and itching were instead not significantly different between the two groups. As expected, no significant differences were observed in baseline medians of the rhinitis symptom scores as well as in mean values of all mediators and eosinophils in nasal lavages of the various groups under study. After treatment the mean of subjective symptoms as well as all values in nasal lavage level fell significantly only in the FP group, whereas no significant changes were observed either in LEV or PLA groups. Accordingly, significant differences were observed at the end of the treatments between the values of fluticasone group vs LEV and PLA group values. Significant correlations between these values and symptom scores were found, according with literature data suggesting a pathogenetic role for these mediators and eosinophils in rhinitis.

CONCLUSION

FP (200 microg once daily) affords a significant degree of improvement in rhinitis control during pollen season, as measured by subjective and objective parameters, compared with LEV (200 microg twice daily) and PLA. The therapeutic benefits of intranasal FP are reflected in, and may be caused by, the decrease in nasal inflammatory cells.

Mucosal cytokine therapy: marked antiviral and antitumor activity

Mucosal administration of the Th1 stimulatory cytokines interleukin-2 (IL-2), IL-12, IL-15, IL-18, or granulocyte-macrophage colony-stimulating factor (GM-CSF) induced antiviral activity in mice challenged systemically with a lethal dose of encephalomyocarditis virus (EMCV) similar to that observed following parenteral administration. In contrast, mucosal administration of the Th2 stimulatory cytokines IL-4, IL-5, IL-10, or IL-13 did not affect significantly the survival of EMCV-infected animals. Mucosal administration of IL-2 or IL-12 also exerted a marked antitumor activity in mice inoculated intravenously with Friend erythroleukemia cells. Recombinant IL-2 and IL-18, but none of the other recombinant cytokines tested, induced low levels of IFN in vitro. Polyclonal antibodies to both mouse and human interferon-alpha/beta (IFN-alpha/beta) abrogated the antiviral activity of IL-2 in vivo, even though the anti-human IFN-alpha/beta antibody did not neutralize mouse IFN-alpha/beta, and neither antibody bound to IL-2. IL-15 did not exhibit antiviral activity in IFN-alpha/beta R-/- mice, which are deficient in natural killer (NK) cell activity. These results suggest that mucosal Th1 cytokine therapy induces a soluble factor or activates a specific cell population in the lymphoid or epithelial tissue of the oropharyngeal cavity, which potentiates elimination of virus-infected or neoplasic cells systemically.

Shifts in lung lymphocyte profiles correlate with the sequential development of acute allergic and chronic tolerant stages in a murine asthma model

T lymphocytes have a central regulatory role in the pathogenesis of asthma. We delineated the participation of lymphocytes in the acute allergic and chronic tolerant stages of a murine model of asthma by characterizing the various subsets of lymphocytes in bronchoalveolar lavage and lung tissue associated with these responses. Acute (10-day) aerosol challenge of immunized C57BL/6J mice with ovalbumin resulted in airway eosinophilia, histological evidence of peribronchial and perivascular airway inflammation, clusters of B cells and TCRgammadelta cells in lung tissue, increased serum IgE levels, and airway hyperresponsiveness to methacholine. In mice subjected to chronic (6-week) aerosol challenge with ovalbumin, airway inflammation and serum IgE levels were significantly attenuated and airway hyperresponsiveness was absent. The marked increases in lung B and T cell populations seen in the acute stage were also significantly reduced in the chronic stage of this model. Thus, acute ovalbumin challenge resulted in airway sensitization characteristic of asthma, whereas chronic ovalbumin challenge elicited a suppressed or tolerant state. The transition from antigenic sensitization to tolerance was accompanied by shifts in lymphocyte profiles in the lung and bronchoalveolar lavage fluid.

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.