Activation of CD4+ T cells, increased TH2-type cytokine mRNA expression, and eosinophil recruitment in bronchoalveolar lavage after allergen inhalation challenge in patients with atopic asthma

Mast cell-T cell interactions

In addition to being a major effector cell in the elicitation of allergic inflammation, mast cells have been found to be activated in various T cell-mediated inflammatory processes and to reside in close physical proximity to T cells. Such observations and the wide spectrum of mediators produced and secreted by mast cells have led investigators to propose a functional relationship between these 2 cell populations. Indeed, mast cell activation has been reported to induce T-cell migration either directly by the release of chemotactic factors, such as lymphotactin or IL-16, or indirectly by the induction of adhesion molecule expression on endothelial cells. Mast cells are also able to present antigens to T cells, resulting in their activation in either an MHC class I- or class II-restricted and costimulatory molecule-dependent fashion. Adhesion molecule-dependent intercellular contact or MHC class II cognate interactions between T cells and mast cells result in the release of both granule-associated mediators and cytokines from the latter. Also, T cell-derived mediators, such as beta-chemokines, directly induce mast cell degranulation. On the other hand, mast cell-derived cytokines, such as IL-4, have been found to polarize T cells to preferentially differentiate into the T(H2) subset. Thus T cell-mast cell interactions are bidirectional, fulfilling regulatory and/or modulatory roles affecting various aspects of the immune response.

The late, but not early, asthmatic response is dependent on IL-5 and correlates with eosinophil infiltration

Early-phase reactions (EPRs) and late-phase reactions (LPRs) are characteristic features of bronchial asthma, although the pathogenetic mechanisms responsible for each of the responses are not fully defined. A murine model of EPRs and LPRs was developed to investigate the role of IL-5 and eosinophils in development of both responses. After initial intraperitoneal sensitization and airway challenge to ovalbumin (OVA), mice were provoked by additional exposure to OVA. An EPR, characterized by a transient increase in airway responsiveness, was observed 5-30 minutes after antigen provocation. This response was followed by an LPR that reached its maximum at 6 hours after challenge and was characterized by increased airway responsiveness and significant lung eosinophilia. The EPR was blocked by cromoglycate and albuterol, whereas the LPR was abolished by cromoglycate and hydrocortisone. Before provocation with allergen, administration of anti-IL-5 antibody prevented the influx of eosinophils into the lung tissue and abolished the LPR but not EPR. These results suggest that IL-5 and eosinophils are essential for development of the LPR, but not EPR, in this model.

Asthma: an inflammatory mediator soup

Reversible or partially reversible airway obstruction, inflammation, and bronchial hyperresponsiveness to various stimuli are the defining characteristics of asthma. Airway obstruction in asthma is a complex event that is due to bronchospasm, inflammation, and mucus formation. Inflammation has assumed a more central role in the pathogenesis of the disease, as it contributes not only to airflow obstruction, but also to bronchial hyperresponsiveness. The inciting trigger, or inhaled allergen, in asthma induces the activation of mast cells and macrophages with the subsequent release of several proinflammatory mediators, including leukotrienes, chemotactic factors, and cytokines. Antigen processed by macrophages is presented to undifferentiated T helper cells, inducing differentiation to the Th2 phenotype, with the subsequent release of IL-4 and IL-5, causing IgE synthesis and eosinophil infiltration, respectively. Macrophage-derived cytokines, such as IL-1, TNF-alpha, and IFN-gamma, activate endothelial cells, upregulating the expression of adhesion molecules such as ICAM-1 and VCAM-1, which permit egression of leukocytes from the vasculature to the airway mucosa. Several inflammatory cells, such as eosinophils, mast cells, and macrophages, not only cause airway damage, but also synthesize cytokines that perpetuate the inflammatory process. This complex interplay of inflammatory cells and mediators causes the classic histopathophysiologic features in the airways of both symptomatic and asymptomatic individuals with asthma, emphasizing the importance of early recognition and antiinflammatory treatment.

Interleukin 5 release into asthmatic airways 4 and 24 hours after endobronchial allergen challenge: its relationship with eosinophil recruitment

Interleukin 5 (IL-5), a cytokine with a range of activities on eosinophils, has been implicated in the allergic asthmatic reaction. We have investigated the kinetics of release of this cytokine into asthmatic airways as well as its relationship to eosinophil recruitment following allergen challenge. Twelve asthmatic patients underwent endobronchial allergen challenge and bronchoalveolar lavage (BAL) fluid was obtained either 4 h (n=6) or 24 h (n=6) after challenge. Four hours after challenge, levels of IL-5 were significantly increased in BAL fluid (10-fold concentration obtained from the allergen-challenge site compared with the saline control (median 2.67 pg/ml, range 1.0-7.4 pg/ml vs 1.0 pg/ml <1.0-2.4 pg/ml, P<0.05). At 24 h levels of IL-5 increased further at the allergen site but not at the saline control lavage (31.1 pg/ml, range 3.6-59. 0 pg/ml vs 1.5 pg/ml, range <1.5-4.9 pg/ml, respectively P<0.02). At 4h there was almost a three fold increase in IL-5 level, whereas at 24 h IL-5 levels were 20-fold greater. Differential cell counts showed that eosinophil numbers obtained 4 and 24 h after allergen challenge were 7 and 32 times higher than numbers after saline challenge. The parallel increase of eosinophil numbers and IL-5 concentrations in BAL fluid suggests that this cytokine may contribute to the eosinophil recruitment observed into asthmatic airways after allergen challenge.

Flow cytometric detection of antigen-specific cytokine responses in lung T cells in a murine model of pulmonary inflammation

Multiparameter flow cytometry was used to examine the cytokine responses of antigen-specific T lymphocytes isolated from the lungs of antigen-sensitized mice which developed pulmonary inflammation after aerosol challenge with ovalbumin (OA) (OA/OA). Lung T cells were stimulated in vitro with OA and anti-CD28 monoclonal antibody (mAb) in the presence of the secretion inhibitor, brefeldin A. T cell subsets were examined for intracellular cytokine expression using fluorochrome-labeled cell-surface specific and anti-cytokine antibodies. Antigen-specific responses resulted in significant numbers of CD4+ lung cells expressing cytoplasmic interleukin (IL)-2 (6%), IL-4 (1.5%), IL-5 (4%), and tumor necrosis factor (TNF)-alpha (11%), but not interferon (IFN)-gamma. Dual cytokine analyses demonstrated antigen-specific responses resulted in CD4+ T cells being positive for IL-2 and IL-4 or IL-2 and IL-5. TNF-alpha was the only antigen-specific cytokine response detected in CD8+ lung T cells after in vitro activation with OA. Cytokines in the supernatants of cultures activated with OA and anti-CD28 were measured by ELISA and the results confirmed the antigen-specific responses measured by flow cytometry. Polyclonal activation of lung T cells from OA/OA mice with 12-myristate 13-acetate (PMA), ionomycin, anti-CD3 mAb, and anti-CD28 mAb resulted in higher percentages of IL-2+ (43%) and IL-5+ (7%) CD4 cells when compared to CD4+ T cells from non-OA sensitized, challenged mice. CD8+ cells from OA/OA mice demonstrated intracellular staining for IL-2 (26%), TNF-alpha (55%), and IFN-gamma (37%), but not IL-4 or IL-5, after polyclonal activation. There is less agreement between intracellular cytokine staining of CD4+ T cells and cytokines released into the culture medium after polyclonal activation. Dual cytokine analyses of polyclonal-activated CD4+ cells demonstrated co-expression of IFN-gamma with IL-2, IL-4, or IL-5. T cells co-expressing IL-2 with IL-4 or IL-5 were also detected. These results demonstrate the utility of multiparameter flow cytometry to directly measure antigen-specific cytokine responses in subsets of T lymphocytes isolated from inflammatory sites.

Immunologic basis of antigen-induced airway hyperresponsiveness

The incidence, morbidity, and mortality of asthma has increased worldwide over the last two decades. Asthma is a complex inflammatory disease of the lung characterized by variable airflow obstruction, airway hyperresponsiveness (AHR), and airway inflammation. The inflammatory response in the asthmatic lung is characterized by infiltration of the airway wall with mast cells, lymphocytes, and eosinophils. Although asthma is multifactorial in origin, the inflammatory process in the most common form of the disease (extrinsic asthma) is believed to be a result of inappropriate immune responses to common aero-allergens in genetically susceptible individuals. As such, it has been hypothesized that CD4+ T cells that produce a Th2 pattern of cytokines play a pivotal role in the pathogenesis of this disease. Through the release of cytokines such as IL-4, IL-13, and IL-5, these cells orchestrate the recruitment and activation of the primary effector cells of the allergic response, the mast cell and the eosinophil. Activation of these cells results in the release of a plethora of inflammatory mediators that individually or in concert induce changes in airway wall geometry and produce the symptoms of the disease. The aim of this review is to discuss our current understanding of the pathophysiologic mechanisms by which Th2 cytokines induce airway disease, and the factors that predispose to the generation of these pathogenic cells in response to inhalation of ubiquitous aero-allergens. Elucidation of the exact immunological basis for allergic asthma may yield immunotherapeutic strategies to reverse the development of pathogenic Th2-mediated immune responses and reduce the morbidity and mortality associated with this disease.

Cyclic AMP suppresses interleukin-5 synthesis by human helper T cells via the downregulation of the calcium mobilization pathway

1. To delineate the mechanism by which cyclic AMP (cAMP) suppresses interleukin (IL)-5 synthesis, the effects of prostaglandin (PG) E2, forskolin, dibutyryl (db)-cAMP and the Ca2+ ionophore, ionomycin on cytokine synthesis, proliferation and CD25 expression of human T cells were investigated. Further studies were performed by measurement of the intracellular concentrations of cyclic AMP ([cAMP]i) and Ca2+ ([Ca2+]i) and by electrophoretic mobility shift analysis (EMSA). 2. PGE2, forskolin and db-cAMP suppressed IL-5 production by human T cell line following T cell receptor (TCR)-stimulation. PGE2 suppressed TCR-induced messenger RNA (mRNA) expression of IL-2, IL-4 and IL-5, as well as proliferation and CD25 expression. 3. Cyclic AMP-mediated suppression of cytokine synthesis, proliferation and CD25 expression in human T cells were attenuated by ionomycin. 4. [cAMP]i was increased by PGE2 and forskolin. PGE2 suppressed the TCR-induced biphasic increase in [Ca2+]i. EMSA revealed that four specific protein-DNA binding complexes related to NF-AT were detected at the IL-5 promoter sequence located from -119 to -90 relative to the transcription initiation site. The slowest migrating complex induced by TCR stimulation was enhanced by PGE2 and further upregulated by ionomycin. Another binding which did not compete with cold AP-1 oligonucleotides, was constitutively present and was unaffected by PGE2 but enhanced by ionomycin. 5. The suppressive effect of cyclic AMP on human IL-5 synthesis is mediated by interference with intracellular Ca2+ mobilization but distinct from the NF-AT-related pathway.

An Adoptive Transfer Model of Allergic Lung Inflammation in Mice Is Mediated by CD4+CD62LlowCD25+ T Cells

Animal models of allergic lung inflammation have provided important insight into the cellular and biochemical factors involved in the pathogenesis of human asthma. Herein, we describe an adoptive transfer model of OVA-specific eosinophilic lung inflammation in the mouse that is used to characterize the cells involved in mediating the pulmonary inflammatory response. We report that freshly isolated spleen cells from OVA-sensitized mice are unable to prime naive recipient mice to respond to a subsequent OVA aerosol challenge. Subjecting the spleen cells to short term restimulation with Ag in vitro, however, renders the cells competent to transfer activity. The magnitude and the kinetics of the eosinophilic pulmonary inflammation in the adoptive transfer recipients are nearly identical with those generated by a more conventional active sensitization/challenge protocol, with the notable exception of differential production of plasma IgE in the two models. Extensive negative and positive selection of splenocyte subtypes indicates that the transfer of Ag-primed CD4+ T cells is both necessary and sufficient to establish full responsiveness in the recipient mice. Additional phenotypic characterization of the transfer-reactive CD4+ T cells indicates that they are found within the CD62LlowCD25+ subset and secrete high levels of IL-5 in response to Ag stimulation. Limiting dilution analysis-derived minimal frequency estimates indicate that approximately 1 in 8500 of the sensitized, cultured spleen cells produces IL-5 in response to OVA stimulation in vitro, suggesting that eosinophilic lung inflammation can be induced in naive mice by the transfer of &lt;1200 Ag-specific CD4+ T cells.

Increased levels of IL-5 positive peripheral blood eosinophils and lymphocytes in mild asthmatics after allergen inhalation provocation

BACKGROUND

In allergic inflammation eosinophils and TH2-like lymphocytes are supposed to be the major effector cells and considered to contribute as cellular source of the key cytokine interleukin (IL)-5.

OBJECTIVE

The purpose of this study was to enable detection of IL-5 containing leucocytes and to investigate whether the number of these cells in the blood circulation differed between healthy and asthmatics before and after allergen provocation.

METHODS

The distribution of intracellular IL-5 in human peripheral blood eosinophils (PBE) and lymphocytes (PBL) has been investigated using fixation and cell membrane permeabilization with octyl-glucopyranoside, the FOG-method, and flow cytometry. The intracellular staining was performed on leucocytes without any prior purification and in vitro stimulation. The specificity of IL-5 binding to intracellular compartment of both PBE and PBL was confirmed by complete inhibition with human recombinant IL-5.

RESULTS

Preformed intracellular IL-5 was detected in the main population of PBE (> 70%) in both healthy individuals and asymptomatic patients. Moreover, preformed intracellular IL-5 was also detected in 4.8% and 2.4% of PBL from healthy individuals and asymptomatic patients, respectively. There was a correlation between the absolute number of PBE and IL-5 positive PBE. In patients with pollen-related asthma, the number of IL-5 positive PBE and PBL increased significantly 24 h after an allergen inhalation provocation (P < 0.05). In the healthy control group no differences regarding IL-5 positive PBE and PBL were obtained pre- and post-allergen challenge.

CONCLUSIONS

In patients with mild allergic asthma, but not in healthy individuals, allergen provocation induces an increased absolute number of IL-5 positive PBE and PBL. The reason for the relatively high number of IL-5 positive PBL is unclear, but a plausible explanation might be that other lymphocyte subsets besides CD4+ TH2 can produce IL-5. However, enumeration of IL-5 positive leucocytes may be used as an activity marker and also be a useful tool in monitoring the inflammation in asthma.

Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production

Interleukin (IL)-13 is a pleiotropic cytokine produced in large quantities by activated CD4(+) Th2 lymphocytes. To define further its potential in vivo effector functions, the Clara cell 10-kDa protein promoter was used to express IL-13 selectively in the lung, and the phenotype of the resulting transgenic mice was characterized. In contrast to transgene-negative littermates, the lungs of transgene-positive mice contained an inflammatory response around small and large airways and in the surrounding parenchyma. It was mononuclear in nature and contained significant numbers of eosinophils and enlarged and occasionally multinucleated macrophages. Airway epithelial cell hypertrophy, mucus cell metaplasia, the hyperproduction of neutral and acidic mucus, the deposition of Charcot-Leyden-like crystals, and subepithelial airway fibrosis were also prominently noted. Eotaxin protein and mRNA were also present in large quantities in the lungs of the transgene-positive, but not the transgene-negative, mice. IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-5 were not similarly detected. Physiological evaluations revealed significant increases in baseline airways resistance and airways hyperresponsiveness (AHR) to methacholine in transgene-positive animals. Thus, the targeted pulmonary expression of IL-13 causes a mononuclear and eosinophilic inflammatory response, mucus cell metaplasia, the deposition of Charcot-Leyden-like crystals, airway fibrosis, eotaxin production, airways obstruction, and nonspecific AHR. IL-13 may play an important role in the pathogenesis of similar responses in asthma or other Th2-polarized tissue responses.

Synergistic effects of interleukin-4 or interleukin-13 and tumor necrosis factor-alpha on eosinophil activation in vitro

Increased concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-4, and IL-13 have been measured in bronchoalveolar lavage fluid (BALF) of patients with asthma following allergen provocation. In addition, these cytokines have also been reported to activate eosinophils in vitro. Although cytokine interactions have been postulated in the activation of eosinophils, the combined effects of cytokines on eosinophil activation remain poorly understood. Because activation of eosinophils has been regarded as a crucial event in the pathogenesis of asthmatic inflammation, we tested the hypothesis that IL-4 and IL-13 could enhance the effects of TNF-alpha on eosinophil activation. For this purpose, eosinophils from normal donors were purified and cultured in the presence of IL-4 or IL-13 and TNF-alpha. Eosinophil survival and surface expression of CD69 were assessed by flow cytometry. There was a concentration- and time-dependent upregulation in CD69 expression as well as eosinophil survival when eosinophils were incubated with IL-13, IL-4, or TNF-alpha. However, eosinophil viability and CD69 expression increased synergistically when eosinophils were incubated with IL-13 or IL-4 in the presence of TNF-alpha. This synergistic effect of IL-4 and IL-13 on CD69 expression was not limited to TNF-alpha but was also observed with IL-5. Our study provides evidence that IL-4 can activate eosinophils in a similar fashion as does IL-13. Furthermore, this study shows that the addition of IL-4 or IL-13 to TNF-alpha or IL-5 has synergistic effects on eosinophil activation, suggesting that the combined effects of different cytokines present in BALF following allergen provocation can enhance eosinophil activation in vitro.

Effects of cyclosporin A and dinactin on T-cell proliferation, interleukin-5 production, and murine pulmonary inflammation

We compared the effects of cyclosporin A (CSA) and a macrotetrolide antibiotic, dinactin, on human T-cell proliferation and cytokine production induced by stimulation of the T-cell receptor alone (monoclonal antibody [mAb] directed against CD3) or in combination with costimulatory signals (mAbs directed against CD3 and CD28). These agents were also examined in a murine model of interleukin (IL)-5-mediated pulmonary inflammation. Dinactin inhibited T-cell proliferation induced by IL-2, by mAb to CD3, and by mAbs to CD3 plus alpha-CD28 with identical dose-response curves (IC50 = 10-20 ng/ml). Dinactin inhibited cytokine production with IC50 values of 10 ng/ml for IL-4 and IL-5 and 30 or 60 ng/ml for interferon-gamma or IL-2, respectively. Unlike CSA, exogenous IL-2 did not alter the dinactin-mediated effects on T cells, and nuclear run-on and steady-state messenger RNA (mRNA) analysis showed that dinactin inhibited cytokine production through a post-transcriptional mechanism. CSA selectively blocked T-cell receptor-induced T-cell proliferation and cytokine production (IC50 = 10 ng/ml). Under costimulatory conditions, IL-5 synthesis was only minimally inhibited by high concentrations of CSA, and at CSA concentrations of less than 125 ng/ml, IL-5 was significantly increased above control values. Dinactin and CSA reduced pulmonary eosinophilia when administered within 1 d of airway antigen challenge. Of the cytokine mRNAs examined in the lungs of CSA-pretreated, antigen-challenged mice, IL-5 mRNA levels were the least reduced, paralleling the resistance of IL-5 to CSA observed in vitro and suggesting a role for CD28 in the in vivo induction of IL-5.

Enhancement of human IL-4 activity by soluble IL-4 receptors in vitro

The recombinant form of the extracellular domain of the IL-4 receptor (sIL-4R) is a potential candidate to neutralize IL-4; however, murine sIL-4R displayed both antagonistic and agonistic activity in vivo. Here we show that human recombinant sIL-4R induced the formation of complexed IL-4 in supernatants of activated T cells in a dose-dependent manner as measured by newly developed enzyme-linked immunosorbent assays. These IL-4/sIL-4R complexes liberated free IL-4 even after prolonged culturing. In contrast, in the absence of exogenously added sIL-4R, free IL-4 was rapidly consumed or proteolytically degraded in cultures of activated T cells. Thus, no IL-4 bioactivity could be determined in supernatants of T cells activated in the presence of IL-4 for 6 days. In contrast, the same cultures carried out in the presence of sIL-4R showed marked IL-4 bioactivity. While low concentrations of sIL-4R enhanced IL-4-driven inhibiton of IFN-gamma production by activated T cells, higher concentrations neutralized IL-4. Together, human sIL-4R, besides its activity as an antagonist to IL-4, also possesses protective and agonistic functions for IL-4, which may be relevant for clinical studies aiming to neutralize IL-4 in vivo.

IL-4 and IL-5 mRNA expression in induced sputum of asthmatic subjects: comparison with bronchial wash

BACKGROUND

The local production of TH2 -type cytokines is thought to orchestrate the ongoing eosinophilic inflammation and contribute to the pathophysiologic features of allergic asthma. Previous studies investigating cytokine expression in asthmatic individuals have used invasive fiberoptic bronchoscopy techniques. To date, there have been no reports of cytokine mRNA expression in induced sputum as a means of quantifying local inflammatory events.

OBJECTIVES

We examined whether IL-4, IL-5, and IFN-gamma mRNA expression could be detected in cells from induced sputum in subjects with mild asthma and normal control subjects. In addition, we compared the profile of inflammatory cells and cytokine mRNA in sputum and bronchial wash fluid.

METHODS

Cells positive for IL-4, IL-5, and IFN-gamma mRNA were determined by using in situ hybridization on cytospun aliquots of sputum induced by successive inhalations of hypertonic saline. Inflammatory cells were quantified by using immunologic cell surface markers and immunocytochemistry.

RESULTS

IL-4 and IL-5 mRNA were detected in the sputum of all asthmatic subjects, and the number of cells expressing these cytokines was significantly higher than that found in control subjects. Colocalization studies showed CD3-positive T cells were the major sources of IL-4 and IL-5 mRNA.

CONCLUSIONS

This study demonstrates that induced sputum can be used to detect mRNA for TH2 -type cytokines in bronchial asthma and that the increase in IL-4 and IL-5 mRNA expression is similar to that seen with more invasive techniques. The qualitative differences in inflammatory cell numbers between sputum induction and bronchial wash are consistent with their sampling of different airway compartments.

A murine model of IgE-mediated cow's milk hypersensitivity

BACKGROUND

Cow's milk allergy (CMA) is one of the leading causes of food allergy in children. Understanding the mechanisms involved in the development of CMA has been hampered by the lack of suitable animal models.

OBJECTIVE

We sought to develop a mouse model of IgE-mediated cow's milk hypersensitivity (CMH) that mimics the clinical features of immediate CMA in humans.

METHODS

Three-week-old C3H/HeJ mice were sensitized by intragastric administration of cow's milk (CM) plus cholera toxin and boosted 5 times at weekly intervals.

RESULTS

CM-specific IgE antibody levels were significantly increased at 3 weeks and peaked at 6 weeks after the initial feeding. Intragastric challenge with CM at week 6 elicited systemic anaphylaxis accompanied by vascular leakage, significantly increased plasma histamine, and increased intestinal permeability to casein. Histologic examination of intestinal tissue revealed marked vascular congestion, edema, and sloughing of enterocytes. The role of IgE in mediating CMH was confirmed by abrogation of passive cutaneous anaphylaxis reactions by heat inactivation of immune sera. Development of IgE-mediated CMH in this model is likely to be TH2 cell mediated because in vitro stimulation of spleen cells from mice allergic to CM induced significant increases in the levels of IL-4 and IL-5, but not IFN-gamma.

CONCLUSION

This model should provide a useful tool for evaluating the immunopathogenic mechanisms involved in CMA and for exploring new therapeutic approaches.

The late asthmatic response is associated with baseline allergen-specific proliferative responsiveness of peripheral T lymphocytes in vitro and serum interleukin-5

BACKGROUND

Increasing insights into the mechanism underlying the allergen-induced late asthmatic response (LAR) have been gained with implication of activated eosinophils and CD4+ T lymphocytes. However, the patient characteristics that indicate the individual capacity to develop a LAR are not well-defined.

METHODS

In 22 subjects with mild to moderate house dust mite-allergic asthma, we investigated the relationship between the LAR and two other models of late-phase allergic inflammation, i.e. the allergen-specific proliferative response of peripheral blood T lymphocytes in vitro and the late cutaneous response. Non-specific bronchial responsiveness (PC20histamine), lung function (FEV1), peripheral blood eosinophil count, early phase allergic skin sensitivity, and levels of total and specific immunoglobulin E (IgE) were determined prior to bronchial allergen challenge. Serum levels of interleukin-5 (IL-5) were measured before and at several time points after allergen inhalation.

RESULTS

A significant correlation was found between the magnitude of the LAR and the allergen-specific proliferative response of peripheral T lymphocytes (r = 0.44, P = 0.04) but not the late cutaneous response. Stepwise-multiple linear regression of the magnitude of the LAR on the parameters analysed at baseline, resulted in a model combining PC20 histamine, early phase allergic skin sensitivity, and the allergen-specific proliferative response of peripheral T lymphocytes (R2 = 0.84, P<0.001). No contribution of the late cutaneous response to the prediction of the LAR was found. Serum levels of IL-5 increased significantly at 6 h (P = 0.01) and 24 h (P = 0.003) after bronchial allergen challenge and correlated with the allergen-specific proliferative response of peripheral T lymphocytes in vitro (rho = 0.48, P = 0.02).

CONCLUSIONS

The findings in this study point to a role of TH2-lymphocyte responses in the development of the allergen-induced LAR. In allergic asthmatic patients, allergen-specific responsiveness of peripheral T-lymphocytes in vitro may serve as a model to determine the individual capacity to develop a LAR after allergen inhalation.

TRFK-5 reverses established airway eosinophilia but not established hyperresponsiveness in a murine model of chronic asthma

We studied the effects of an anti-interleukin (IL)-5 monoclonal antibody (TRFK-5) or dexamethasone (DEX) to reverse already established airway hyperresponsiveness (AHR) and tissue eosinophilia in a Schistosoma mansoni antigen-sensitized and airway-challenged mouse model of chronic asthma. In this model at 4 d after antigen challenge there is dramatic bronchoalveolar lavage fluid (BAL) eosinophilia, AHR to intravenous methacholine (MCh), and histologic evidence of peribronchial eosinophilic infiltration and mucoid cell hyperplasia. These changes persist for up to 2 wk after antigen challenge. Treatment with DEX from Days 4 through 10 significantly reduced established airway eosinophilia compared with animals sham-treated with saline from Days 4 -10 (120 +/- 29 eosinophils/microl BAL for DEX-treated mice versus 382 +/- 60 eosinophils/microl BAL for sham-treated animals, p < 0.01). DEX-treated mice also had dramatically reduced mucoid cell hyperplasia, and airway responsiveness returned to normal. In contrast, TRFK-5 given during the same time period reduced airway eosinophilia (86 +/- 32 eosinophils/microl BAL versus 382 +/- 60 eosinophils/microl BAL, p < 0.01) but did not reduce goblet cell hyperplasia or reverse already established AHR. Treatment with DEX but not TRFK-5 also inhibited interferon gamma (IFN-gamma) content of BAL fluid (0.49 +/- 0.09 ng/ml BAL fluid for DEX versus 1.50 +/- 0.24 ng/ml BAL fluid and 1.36 +/- 0.13 ng/ml BAL fluid for TRFK-5 and sham-treated mice, respectively, both p < 0.001 versus DEX). Thus, treatment with DEX reduces established eosinophilic airway inflammation and AHR in S. mansoni-sensitized and airway-challenged mice but treatment with TRFK-5 reversed established eosinophilia without ameliorating established AHR. Together, these data suggest that once airway inflammation develops, neutralizing the effects of IL-5 or reducing eosinophilia alone may not result in inhibiting established AHR in atopic asthma.

The effects of regular inhaled formoterol, budesonide, and placebo on mucosal inflammation and clinical indices in mild asthma

The present study was designed to observe the effects of 8 wk of treatment with formoterol (Foradil) 24 microgram, budesonide 400 microgram, and matched placebo inhaled twice a day on inflammatory indices in the bronchial mucosa of 64 patients with mild atopic asthma. Biopsies were obtained at the start and 1 wk before stopping a 9-wk period of treatment, and inflammatory cell numbers were assessed in the submucosa and epithelium by immunohistochemistry. Regular formoterol significantly reduced the number of submucosal mast cells, with a similar trend for eosinophils but not activated T cells. A subgroup analysis conducted in biopsies with >= 10 eosinophils per mm2 revealed a significant reduction in eosinophil numbers when compared with both pretreatment baseline (p < 0.01) and changes after placebo (p < 0.01). Parallel, but less pronounced, effects were observed on mast cell but not on CD25(+) T cell numbers. There was no effect of any of the three treatments on BAL levels of mast cell or eosinophil mediators. We conclude that regular treatment with inhaled formoterol reduces rather than increases inflammatory cells in the mucosa of asthmatic patients. It is possible that these cellular effects of formoterol may contribute to the therapeutic efficacy of this drug when used regularly in the treatment

Cytokine dysregulation associated with exam stress in healthy medical students

The mechanisms of stress-related immune alterations have not been fully elucidated. Cell-mediated immune responses as well as antibody and certain cytokines are reported as being suppressed during times of high stress. However, the role of suppression vs dysregulation has not been established in human stress models. The effect of exam stress on regulatory cytokines in 16 healthy medical students was assessed by measuring type-1 (IFN-gamma) and type-2 (IL-10) cytokines from 72-h PHA/PMA-stimulated PBMC 4 weeks before and 48 h after exams. Results demonstrated decreased IFN-gamma accompanied by increased IL-10 during exam stress that resulted in a decreased IFN-gamma:IL-10 ratio. There was a significant correlation between the cytokine response to PHA/PMA and number and subjective adjustment to daily hassles. Additionally, students who reported greater levels of loneliness also reported greater numbers of and poorer subjective adjustment to hassles. The differences were consistent in both males and females but did not correlate with AM cortisol levels. Additionally, when individuals were grouped into high vs low preexam hassle levels, the type-1/type-2 shift in the IFN-gamma:IL-10 ratio occurred in the low hassles group only. These data suggest that psychologically stressful situations shift type-1/type-2 cytokine balance toward type-2 and result in an immune dysregulation rather than overall immunosuppression. This may partially explain the increased incidence of type-2-mediated conditions such as increased viral infections, latent viral expression, allergic/asthmatic reactions, and autoimmunity reported during periods of high stress.

Role of nerve growth factor in a mouse model of allergic airway inflammation and asthma

The role of nerve growth factor (NGF), a potent mediator acting in the development and differentiation of both neuronal and immune cells, was examined in a mouse model of allergic asthma. NGF-positive cells were detected in the inflammatory infiltrate of the lung and enhanced levels of NGF were detected in serum and broncho-alveolar lavage fluids. Mononuclear cells in inflamed airway mucosa as well as broncho-alveolar macrophages were identified as one source of NGF production. Splenic mononuclear cells from allergen-sensitized mice produced NGF in response to allergen. They responded to exogenously added NGF with a dose-dependent increase in IL-4 and IL-5 production and augmented IgE and IgG1 synthesis. In contrast, IFN-gamma and IgG2alpha levels remained unaffected. The effects were NGF specific, since they could be blocked by an anti-NGF-antibody. Nasal application of anti-NGF to allergen-sensitized mice significantly reduced IL-4 and prevented development of airway hyperreactivity. These results show that allergic airway inflammation is accompanied by enhanced local NGF production that acts as an amplifier for Th2 effector functions and plays an important role in the development of airway hyperreactivity. Therefore it is suggested that NGF may serve as a link between the immune and nerve system.

IL-5 Production by NK Cells Contributes to Eosinophil Infiltration in a Mouse Model of Allergic Inflammation

IL-5 production in vivo plays a unique role in the production, activation, and localization of eosinophils in a variety of allergic conditions. The current paradigm suggests that allergen-specific Th2 cells are the main source for the IL-5 production. The experiments outlined in this work, however, suggest that in vivo production of IL-5 by NK cells can separately influence eosinophil-associated inflammatory responses. Specifically, a mouse model of allergic inflammation was used in which C57BL/6 mice were immunized and challenged with a short ragweed Ag extract, known to induce a selective eosinophilia within the peritoneal cavity. Peritoneal lavage fluids from these mice also contained increased numbers of T cells and NK cells, as well as significantly elevated levels of IL-4, IL-5, and IFN-γ. Flow-cytometric analysis of cytokine-producing cells in peritoneal lavage fluid revealed increased numbers of IL-5-producing cells in both T cell and NK cell populations following allergen exposure. Depletion of NK cells by treatment with NK1.1 Abs selectively reduced the number of infiltrating eosinophils by more than 50%. Moreover, the inhibition of the infiltration of eosinophils was accompanied by a complete loss of IL-5-producing NK cells and significantly reduced levels of peritoneal lavage fluid IL-5, whereas the number of IL-5-producing T cells was not affected. Thus, the results presented in this study provide clear evidence for a novel immunoregulatory function of NK cells in vivo, promoting allergen-induced eosinophilic inflammatory responses by the production of IL-5.

IL-5 and IL-5 receptor in asthma

Eosinophils, along with mast cells are key cells involved in the innate immune response against parasitic infection whereas the adaptive immune response is largely dependent on lymphocytes. In chronic parasitic disease and in chronic allergic disease, IL-5 is predominantly a T cell derived cytokine which is particularly important for the terminal differentiation, activation and survival of committed eosinophil precursors. The human IL-5 gene is located on chromosome 5 in a gene cluster that contains the evolutionary related IL-4 family of cytokine genes. The human IL-5 receptor complex is a heterodimer consisting of a unique alpha subunit (predominantly expressed on eosinophils) and a beta subunit which is shared between the receptors for IL-3 & GM-CSF (more widely expressed). The alpha subunit is required for ligand-specific binding whereas association with the beta subunit results in increased binding affinity. The alternative splicing of the alpha IL-5R gene which contains 14 exons can yield several alpha-IL-5R isoforms including a membrane-anchored isoform (alpha IL-5Rm) and a soluble isoform (alpha IL-5Rs). Cytokines such as IL-5 produce specific and non-specific cellular responses through specific cell membrane receptor mediated activation of intracellular signal transduction pathways which, to a large part, regulate gene expression. The major intracellular signal transduction mechanism is activation of non-receptor associated tyrosine kinases including JAK and MAP kinases which can then transduce signals via a novel family of transcriptional factors named signal transducers and activators of transcription (STATS). JAK2, STAT1, and STAT5 appear to be particularly important in IL-5 mediated eosinophil responses. Asthma is characterized by episodic airways obstruction, increased bronchial responsiveness, and airway inflammation. Several studies have shown an association between the number of activated T cells and eosinophils in the airways and abnormalities in FEV1, airway reactivity and clinical severity in asthma. It has now been well documented that IL-5 is highly expressed in the bronchial mucosa of atopic and intrinsic asthmatics and that the increased IL-5 mRNA present in airway tissues is predominantly T cell derived. Immunocytochemical staining of bronchial biopsy sections has confirmed that IL-5 mRNA transcripts are translated into protein in asthmatic subjects. Furthermore, the number of activated CD4 + T cells and IL-5 mRNA positive cells are increased in asthmatic airways following antigen challenge and studies that have examined IL-5 expression in asthmatic subjects before and after steroids have shown significantly decreased expression following oral corticosteroid treatment in steroid-sensitive asthma but not in steroid resistant and chronic severe steroid dependent asthma. The link between T cell derived IL-5 and eosinophil activation in asthmatic airways is further strengthened by the demonstration that there is an increased number of alpha IL-5R mRNA positive cells in the bronchial biopsies of atopic and non-atopic asthmatic subjects and that the eosinophil is the predominant site of this increased alpha IL-5R mRNA expression. We have also shown that the subset of activated eosinophils that expressed mRNA for membrane bound alpha IL-5r inversely correlated with FEV1, whereas the subset of activated eosinophils that expressed mRNA for soluble alpha IL-5r directly correlated with FEV1. Hence, not only does this data suggest that the presence of eosinophils expressing alpha IL-5R mRNA contribute towards the pathogenesis of bronchial asthma, but also that the eosinophil phenotype with respect to alpha IL-5R isoform expression is of central importance. Finally, there are several animal, and more recently in vitro lung explant, models of allergen induced eosinophilia, late airway responses (LARS), and bronchial hyperresponsiveness (BHR)--all of which support a link between IL-5 and airway eosinophilia and bronc

Interleukin-4 and interleukin-5 as targets for the inhibition of eosinophilic inflammation and allergic airways hyperreactivity

Clinical and experimental investigations suggest that allergen-specific CD4+ T-cells, IgE and the cytokines IL-4 and IL-5 play central roles in initiating and sustaining an asthmatic response by regulating the recruitment and/or activation of airways mast cells and eosinophils. IL-5 plays a unique role in eosinophil development and activation and has been strongly implicated in the aetiology of asthma. The present paper summarizes our recent investigations on the role of these cytokines using cytokine knockout mice and a mouse aeroallergen model. Investigations in IL-5-/-mice indicate that this cytokine is critical for regulating aeroallergen-induced eosinophilia, the onset of lung damage and airways hyperreactivity during allergic airways inflammation. While IL-4 and allergen-specific IgE play important roles in the regulation of allergic disease, recent investigations in IL-4-/- mice suggest that allergic airways inflammation can occur via pathways which operate independently of these molecules. Activation of these IL-4 independent pathways are also intimately associated with CD4+ T-cells, IL-5 signal transduction and eosinophilic inflammation. Such IL-5 regulated pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell mediated processes. The central role of IL-5 in both components of allergic disease highlights the requirements for highly specific therapeutic agents which inhibit the production or action of this cytokine.

Allergen-induced proliferation and interleukin-5 production by bronchoalveolar lavage and blood T cells after segmental allergen challenge

In order to detect and characterize allergen-specific T cells in the airways of atopic asthmatics, we measured proliferation and cytokine production by bronchoalveolar lavage (BAL) T cells isolated from Dermatophagoides pteronyssinus (Der p)-sensitive asthmatics and nonatopic control subjects, and compared the results with those generated using peripheral blood (PB) T cells. BAL and PB mononuclear cells were collected 24 h after segmental allergen challenge by fibreoptic bronchoscopy and venepuncture, respectively. T cells purified from BAL and PB were stimulated with autologous, irradiated antigen-presenting cells and D. pteronyssinus extract or a control, nonallergen antigen (M. tuberculosis purified protein derivative [PPD]). IL-5 and IFN-gamma concentrations were measured in culture supernatants by ELISA, and T-cell proliferation by 3H-thymidine uptake. D. pteronyssinus-induced proliferation of T cells derived from both BAL and PB was elevated in asthmatics when compared with control subjects (p < 0.05), whereas PPD-induced proliferation was equivalent in both compartments. In the asthmatics, D. pteronyssinus-induced proliferative responses of equivalent numbers of BAL and PB T cells obtained after allergen challenge were statistically equivalent. Nevertheless, BAL T cells stimulated with D. pteronyssinus produced significantly greater amounts of IL-5 than did PB T cells (p < 0.05). Allergen-induced proliferation and IL-5 production by BAL T cells in the asthmatics after segmental allergen challenge correlated with the percentages of eosinophils in the BAL fluid (p < 0.01). Further, BAL T cells from asthmatic patients produced significantly higher amounts of IL-5 than did the same number of cells from nonatopic control subjects (p < 0.05). We conclude that, in D. pteronyssinus-sensitive asthmatics, allergen-specific T cells can be detected in the bronchial lumen after allergen challenge and that allergen-induced proliferation and IL-5 production by these cells correlates with local eosinophil influx. Although bronchial luminal T cells show an equivalent proliferative response to allergen stimulation as compared with PB T cells, they do produce more IL-5, consistent with the hypothesis that local differentiation or priming of these cells within the bronchial mucosal environment results in upregulation of allergen-induced IL-5 secretion.

A Novel T Cell-Regulated Mechanism Modulating Allergen-Induced Airways Hyperreactivity in BALB/c Mice Independently of IL-4 and IL-5

The immunoregulatory functions of IL-4 and IL-5 have identified these cytokines as primary targets for the resolution of airways inflammation and bronchial hyperreactivity in asthma. However, the individual contribution of each of these cytokines and of IL-5-regulated eosinophilia to the induction of airways hyperreactivity in mouse models of asthma remains highly controversial. In this investigation, we have used IL-4- and IL-5-deficient mice of the same genetic background in combination with inhibitory mAbs to these cytokines to identify unequivocally the contribution of these factors to the induction of airways hyperreactivity. Sensitization and aeroallergen challenge of wild-type mice with OVA induced pathological changes to the respiratory epithelium, airways eosinophilia, and hyperreactivity to β-methacholine. Inhibition of the actions of IL-4 and/or IL-5 did not abolish airways hyperreactivity, and in the case of IL-4-deficient mice pretreated with anti-IL-5 mAb, airways hyperreactivity persisted in the absence of pronounced airways inflammation. Airways hyperreactivity was abolished only by anti-CD4+ mAb treatment. However, aeroallergen challenge of IL-5−/− mice showed that morphologic changes to the airways were critically linked to IL-5 and eosinophilia. This investigation demonstrates the existence in BALB/c mice of a novel CD4+ T cell pathway for modulating airways hyperreactivity. These findings may provide an explanation for the dissociation of airways eosinophilia from the development of airways hyperreactivity observed in some cases of asthma and in animal models of this disease.

Evidence that cyclosporin A and dexamethasone inhibit allergic airway eosinophilic inflammation via suppression of interleukin-5 synthesis by T cells

1. We have recently demonstrated that airway eosinophilic inflammation can be transferred to unprimed mice by infusing interleukin (IL)-5-producing T cell clones. Using that murine model, we performed this study to delineate the mechanism of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation. 2. The ovalbumin-reactive murine T cell clones, FJ17, produced IL-2, IL-4 and IL-5 upon stimulation with relevant antigen. In FJ17-transferred mice, messenger RNA (mRNA) of IL-2 and IL-5 expressed in the lungs, the number of eosinophils in bronchoalveolar lavage fluid (BALF) was increased and the bronchial responsiveness to acetylcholine was enhanced after antigen provocation. 3. Cyclosporin A (10, 100 ng ml(-1)) and dexamethasone (10, 100 ng ml(-1) suppressed the production of IL-5 as well as IL-2 and IL-4 by FJ17 in vitro. 4. Subcutaneously administered cyclosporin A (30 mg kg(-1)) and dexamethasone (10 mg kg(-1)) inhibited antigen-induced mRNA expression of IL-2 and IL-5, increase of BALF eosinophils and bronchial hyperresponsiveness of FJ17-transferred mice in vivo. The number of BALF eosinophils was correlated with the bronchial responsiveness to acetylcholine (r=0.672). 5. The results clearly indicated that the suppression of IL-5 synthesis by T cells is involved in the effects of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation.

Bronchial allergen challenge with isolated major allergens of Dermatophagoides pteronyssinus: the role of patient characteristics in the early asthmatic response

BACKGROUND

The use of allergen extracts will hamper studies into quantitative aspects of allergic responses because the precise amount of relevant allergen for each patient is unknown.

OBJECTIVE

We applied isolated IgE-binding components (major allergens) in the technique of bronchial allergen challenge to determine the role of patient characteristics in the early asthmatic response (EAR).

METHODS

In 30 patients with mild-to-moderate asthma, the EAR was investigated after inhalation of an isolated major allergen of Dermatophagoides pteronyssinus (i.e., Der p 1 [n = 16] or Der p 2 [n = 14]). The degree of early-phase bronchial responsiveness to allergen (the cumulated dose of allergen causing a 20% fall in FEV1 [PD20allergen]) was related to the degree of nonspecific bronchial responsiveness (the concentration of histamine causing a 20% fall in FEV1 [PC20histamine]) and the level of specific IgE or allergen thresholds as found in skin tests and basophil histamine release assays.

RESULTS

Twenty-seven patients with an immediate response during allergen and histamine challenges (deltaFEV1, > or = 20%) were analyzed. In these patients, a strong correlation was found between PD20allergen and PC20histamine (r = 0.81, p < 0.001). Weak correlations were found between PD20allergen and the level of specific IgE (r = -0.36, p = 0.07) or allergen thresholds as found in skin tests (skin prick test, r = 0.36 and p = 0.07; intracutaneous test, r = 0.49 and p = 0.01) or basophil histamine release assays (r = 0.37, p = 0.08). Moreover, no significant contribution of these indices of IgE-mediated hypersensitivity to the prediction of PD20allergen by multilinear regression models with PC20histamine was found.

CONCLUSION

In asthmatic patients allergic to house dust mites the degree of nonspecific bronchial hyperresponsiveness is the main determinant of early-phase bronchial responsiveness to allergen. In these patients the degree of allergic sensitivity does not contribute to the prediction of the EAR after allergen inhalation.

Expression of interferon-gamma, interleukin-4 and interleukin-5 mRNA in the nasal mucosal membrane of rats with allergic rhinitis

The production of immunoglobulin E (IgE) antibody is largely dependent on the ratio between interleukin-4 (IL-4) (a T helper 2 (Th2)-type cytokine) and interferon-gamma (IFN-gamma) (a T helper 1 (Th1)-type cytokine). Interleukin-5 (IL-5) (also a Th2-type cytokine) is an important eosinophil differentiation factor and also co-stimulates B-cell growth and differentiation. The present study was designed to evaluate and compare the expression of IFN-gamma, IL-4 and IL-5 mRNA in the nasal mucosal membrane of sensitized Brown-Norway (BN) rats. Fourteen BN rats were divided into two groups: non-sensitized (control) and sensitized. The sensitized group was injected with ovalbumin (OA) intraperitoneally on three consecutive days. Twenty-one days later, rats were exposed to 1% OA aerosol. Twenty-four hours after exposure to aerosol, nasal mucosa was extracted from both groups and reverse transcriptase-polymerase chain reaction (RT-PCR) was performed. The densities of the bands of IL-4, IL-5 and IFN-gamma mRNA were expressed as percentages against beta-actin mRNA. Our results showed that the mean values for IL-4 and IL-5 mRNA were increased significantly in sensitized rats compared with control rats. In contrast, the mean value for IFN-gamma mRNA was significantly lower in sensitized rats compared with those of the control group. Our data therefore suggest that sensitization of rat nasal mucous membranes results in the predominant expression of Th2-type cytokines.

Transfer of allergic airway responses with serum and lymphocytes from rats sensitized to dust mite

House dust mite (HDM) antigen is one of the most common allergens associated with extrinsic asthma. In a model of allergic lung disease, Brown Norway (BN) rats sensitized to HDM with alum and Bordetella pertussis adjuvants produce high levels of IgE antibody and experience bronchoconstriction, increased airway hyperresponsiveness (AHR) to acetylcholine (ACh), and pulmonary inflammation after antigen challenge. The purpose of this study was to determine whether these asthmatic symptoms could be transferred from sensitized animals to naive recipients via humoral or cellular factors. Syngeneic recipient rats were injected (intraperitoneally with 4 x 10(7) cells (precultured overnight with either HDM or bovine serum albumin [BSA]) from lymph nodes of sensitized or control rats, respectively. Other groups received a tail-vein injection of serum from either HDM-sensitized or control rats. Antigen challenge in rats injected with sensitized cells caused increases in pulmonary inflammation and in AHR, but no changes in immediate bronchoconstriction as compared with control recipients. Antigen challenge in serum recipients resulted in immediate bronchoconstriction but had no effect on AHR or on pulmonary inflammation. These data show that immune-mediated lung inflammation and AHR are promoted by antigen-specific lymphocytes, whereas immediate allergic responses are caused by serum factors.

Interleukin-5 mRNA stability in human T cells is regulated differently than interleukin-2, interleukin-3, interleukin-4, granulocyte/macrophage colony-stimulating factor, and interferon-gamma

Interleukin-5 (IL-5) transcriptional activation and mRNA stability were investigated in a human TH0 T-cell clone (SP-B21) and in nonclonal CD4 TH2 cells, differentiated in vitro from peripheral blood T cells. Cells were stimulated with alpha-CD3 monoclonal antibody (mAb) with and without alpha-CD28 mAb. Comparison to other cytokine genes revealed aspects of mRNA regulation unique to IL-5. The half-life (t1/2) of IL-5 mRNA, determined by addition of actinomycin D (ActinoD) or cyclosporin A (CSA) was longer (by >= 2 h) than that of IL-2, IL-3, IL-4, interferon-gamma, or granulocyte/macrophage colony-stimulating factor. With the exception of IL-5, t1/2 values were significantly shorter with CSA as the transcriptional inhibitor than with ActinoD. The t1/2 value of IL-5 mRNA, but not the other cytokine transcripts, determined with either ActinoD or CSA, was longer than predicted from the kinetics of steady-state mRNA decline. Co-stimulation of both cell types with alpha-CD28 mAb increased the stability of cytokine transcripts weakly, and IL-5 remained the most stable transcript. Thus, the degradation pathway that targets IL-5 is distinct from the other cytokine transcripts measured and involves proteins whose transcription is blocked by ActinoD and CSA. From examination of the levels of transcription initiation (nuclear run-on assay) and steady-state mRNA attained in cultures stimulated in the presence of the protein synthesis inhibitor, cycloheximide, only IL-5 transcription initiation had an absolute dependency on new protein synthesis.

Peripheral blood manifestations of T(H)2 lymphocyte activation in stable atopic asthma and during exercise-induced bronchospasm

BACKGROUND

Recently, TH2 lymphocyte activation has been shown to play a key role in initiating and propagating the inflammatory response in asthmatic airways. This is manifest through increased numbers of "activated" CD25-(IL-2R)-bearing T-helper cells and can be seen through the IL-5 driven recruitment of eosinophils and IL-4-mediated B-cell expression of CD23 (low affinity IgE receptor) and ultimately IgE production.

OBJECTIVE

To gain a better understanding of the role of immune cells in asthma by describing the peripheral blood immune cell phenotypes in mild atopic asthma.

METHODS

We enrolled 13 patients with mild atopic asthma and a group of seven nonatopic, nonasthmatic controls. Objective measures of lung function were obtained. The peripheral blood was analyzed by flow cytometry for specific cellular markers at rest and during the development of exercise induced bronchospasm.

RESULTS

At rest the number of CD23-bearing B cells (169/mL versus 117/mL; P = .05) and the number of CD25-bearing T cells (355/mL versus 237/mL; P = .03) were increased in the asthma group. There was a linear relationship between these two lymphocyte subsets and the maximum voluntary ventilation at rest (r = 0.56, P = .01 and r = 0.57, P = .01). With the development of exercise-induced bronchospasm there was a significantly greater increase in CD23-positive B cells (96.7/mL versus 59.7/mL; P = .05) and CD25-positive T cells (111.8/mL versus 45.1; P = .01) in the asthma group.

CONCLUSIONS

These data indicate that TH2 lymphocyte activation is manifested by increased numbers of CD23-bearing B cells and CD25-bearing T cells in the peripheral blood of patients with stable mild atopic asthma. Further, these immune cell subsets correlate with markers of resting lung function and increase in the peripheral blood early after the development of exercise-induced bronchospasm.

Effects of peptide therapy on ex vivo T-cell responses

BACKGROUND

Peptide therapy targets T cells directly with short peptides containing multiple T-cell receptor epitopes. Murine studies suggest T-cell anergy as the mechanism of action; however, changes in T-cell cytokine profiles may be more relevant in human beings.

OBJECTIVE

We sought to study the effects of peptide therapy on ex vivo antigen-specific T-cell responses.

METHODS

Antigen-specific T-cell lines were generated from subjects enrolled in a double-blind, placebo controlled, two-dose study of the ALLERVAX CAT therapeutic, containing Fel d 1 peptides (ImmuLogic Pharmaceutical Corp., Waltham, Mass.) (n = 7, 8, and 7, respectively, for groups receiving placebo, 75 microg, or 750 microg). Each subject had three lines propagated before and after receiving peptide therapy; antigens used were cat hair extract, Fel d 1 peptides, and tetanus toxoid (negative control). Proliferative responses and cytokine generation from each line were assessed after two restimulations with antigen and autologous antigen-presenting cells.

RESULTS

The Fel d 1 peptide lines showed a dose-dependent decrease of IL-4 production (p = 0.02 and 0.025, respectively, for the 750 microg group vs both the 75 microg and placebo groups). IL-4 production from the cat hair allergen extract lines and interferon-gamma production from both the Fel d 1 peptide lines and cat hair allergen extract lines showed no statistically significant changes. The control tetanus toxoid lines showed no changes in cytokine production; there were no significant changes in proliferation with any of the antigens in any of the treatment groups. In the clinical arm of the trial, only the 750 microg dose of peptides produced a significant response.

CONCLUSIONS

Peptide therapy induces a significant, dose-dependent decrease in peptide-stimulated IL-4 production, consistent with either a shift in T-cell phenotype or peptide-specific T-cell tolerance.

CTLA4Ig inhibits airway eosinophilia and hyperresponsiveness by regulating the development of Th1/Th2 subsets in a murine model of asthma

Complete T-cell activation requires two distinct signals, one delivered via the T-cell receptor, and the second "co-stimulatory" signal through CD28/B7 ligation. Previous studies showed that the blockade of CD28/B7 ligation alters differentiation of Th1/Th2 lymphocyte subsets in vitro and in vivo. The present study was designed to determine the effect of a CD28/B7 antagonist (CTLA4Ig) on Th1/Th2 development in Schistosoma mansoni-sensitized and airway-challenged mice. Treatment of mice with CTLA4Ig beginning 1 wk after sensitization abolished airway responsiveness to intravenous methacholine determined 96 h following antigen challenge. We also found a significant reduction in bronchoalveolar lavage (BAL) eosinophilia, and reduced peribronchial eosinophilic infiltration and mucoid-cell hyperplasia. Furthermore, CTLA4Ig treatment significantly decreased interleukin (IL)-4 and IL-5 content in BAL fluid in vivo, and the production of IL-5 by lung lymphocytes stimulated with soluble egg antigen (SEA) in vitro. In contrast, the content of interferon-gamma in BAL fluid and supernatant from SEA-stimulated lung lymphocytes from CTLA4Ig-treated mice was increased significantly compared with untreated animals. Thus, CTLA4Ig inhibits eosinophilic airway inflammation and airway hyperresponsiveness in S. mansoni-sensitized and airway-challenged mice, most likely due to attenuated secretion of Th2-type cytokines and increased secretion of Th1-type cytokines.

Biological and molecular characteristics of interleukin-5 and its receptor

Interleukin-5 (IL5) is a T cell-derived cytokine involved in the pathogenesis of atopic diseases. It specifically controls the production, the activation and the localization of Eosinophils. The Eosinophils are the major cause of tissue damage resulting in the symptoms of asthma and related allergic disorders. T cells purified from bronchoalveolar lavage and peripheral blood of asthmatics secrete elevated amount of IL5. Therefore IL5 emerges to be an attractive target for the generation of new anti-allergic drugs. Agents which inhibit either the production or the activity of IL5 could be expected to ameliorate the pathological effects of the allergic response. A better understanding of the biology of IL5 and the regulation of its expression is, however, a prerequisite for the development of new therapeutic agents. This review covers the major biological, molecular and structural aspects of IL5 research since the identification of this cytokine ten years ago.

The concept of type-1 and type-2 helper T cells and their cytokines in humans

In both mice and humans, functionally distinct helper T (Th)-cell subsets, known as Th1 and Th2 cells, are characterized by the patterns of cytokines they produce. These two polarized forms of the specific cellular immune response provide a useful model for explaining not only the different types of protection, but also the pathogenic mechanisms of several immunopathological disorders. The development of polarized Th1 or Th2 responses depends on either environmental factors, including dose of antigen, nature of immunogen and cytokines (IL-12 and interferons or IL-4) at the time of antigen presentation, or other undefined factors in the individual genetic background, mainly at level of the so-called "natural immunity". Th1-dominated responses are potentially effective in eradicating infectious agents, including those hidden within the host cells. When the Th1 response is poorly effective or exhaustively prolonged, it may result in host damage. In contrast, Th2 responses are apparently insufficient to protect against the majority of infectious agents, but can provide some protection against parasites. Th2 cells are able to make unpleasant the life of parasites in the host and tend to limit potentially harmful Th1-mediated responses. Thus, Th2 cells may be regarded as a part of down regulatory (or suppressor) mechanism for exaggerated and/ or inappropriate Th1 responses. The Th1/Th2 paradigm applied to the study of chronic inflammatory disorders or autoimmune diseases allowed to understand that a number of diseases are mediated by Th1 cells, the two clearest examples being multiple sclerosis and thyroid autoimmunity. In other disorders, Th1/Th2 polarization is less prominent, or rather Th2 responses tend to predominate, such as in systemic lupus erythematosus, progressive systemic sclerosis or allergic diseases. It is of note that in experimental models in animals, a number of diseases can be prevented by switching immune responses from Th1 to Th2 or from Th2 to Th1. Moreover, the Th1/Th2 concept suggests that modulation of the relative contribution of Th1- or Th2-type cytokines makes possible to regulate the balance between protection and immunopathology, as well as the development and/or the severity of some immunologic disorders.

Interferon-gamma inhibits the growth of human bronchial epithelial cells independently of transforming growth factor-beta-1 and nitric oxide (NO)

It has been emphasized that epithelial injury is closely correlated with airway hyperresponsiveness, which is one of the important pathophysiological characteristics of bronchial asthma. Growth of epithelial cells is important in the mucosal repair processes and is believed to be regulated by growth factors produced by inflammatory and immune effector cells as well as epithelial cells themselves. We studied the role of T cell-derived lymphokines IFN gamma and IL-4 on the proliferation of human bronchial epithelial cell line BEAS-2B. IFN gamma, but not IL-4, showed a dose-dependent growth inhibitory activity in vitro. Its activity was via its specific receptors on the cells, was augmented by TNF alpha, and was independent of the activity of endogenous TGF beta and nitric oxide. These results suggested that Th-1 T cells-derived lymphokine IFN gamma might be involved in the repair processes after mucosal injury found in bronchial asthma.

Induction of Pulmonary Allergic Responses by Antigen-Specific Th2 Cells

The development of pulmonary allergic responses was examined in mice following pulmonary transfer of Ag (conalbumin)-specific Th2 cells. The levels of serum-specific IgE, cellular infiltrates, airway mucus goblet cells, and airway responsiveness were analyzed and compared with those in Ag-sensitized and -challenged mice. Pulmonary transfer of the conalbumin-specific Th2 clone (D10) induced, in an Ag-specific manner, high levels of the Th2 cytokines IL-4 and IL-5 in the bronchoalveolar lavage fluids and mucosal eosinophils, concomitant with an increase in airway responsiveness. The D10 cell-induced responses were seen in the absence of serum specific IgE. In the presence of Ag, the transferred D10 cells not only remained in the lungs, but also increased in number 72 h post-cell transfer. Although significantly higher levels of IL-4 and IL-5 in the bronchoalveolar lavage fluids were found in D10-transferred mice, the levels of pulmonary eosinophilia, mucus goblet cells, and airway responsiveness were significantly lower than those in Ag-sensitized and -challenged mice. These results demonstrate that although Ag-specific activation of Th2 cells at mucosal sites is able to mediate the recruitment of eosinophils and the subsequent induction of airway hyper-responsiveness, the more severe pulmonary allergic responses were observed only in mice sensitized and challenged with Ag.

Involvement of intercellular adhesion molecule-1 in the antigen-induced infiltration of eosinophils and lymphocytes into the airways in a murine model of pulmonary inflammation

We investigated the effects of in vivo intraperitoneal treatment with the rat monoclonal antibody (mAb), YN1.7.4 (YN1) against intercellular adhesion molecule-1 (ICAM-1) on the ovalbumin (OA)-inhalation-induced infiltration of leukocytes into the airways of OA-sensitized mice. YN1 (100 to 400 microg) given over a period of 72 h dose-dependently reduced the influx of lymphocytes and eosinophils into the bronchial lumen by > 60% and > or = 70%, respectively, when compared with saline or purified rat IgG-treated controls. Alveolar macrophages (AM) in the bronchoalveolar lavage fluid (BALF) were also decreased by > 50%. Lung tissue inflammation as determined by histopathologic examination was reduced. The number of neutrophils in the blood of OA-sensitized mice 3 days after challenge was significantly increased by treatment with YN1. However, at 24 h and 72 h after OA-challenge, the numbers of eosinophils and mononuclear cells in the bone marrow were reduced by YN1 treatment. Additionally, at 72 h after OA-challenge, the numbers of bone-marrow neutrophils were depressed. BALF levels of interleukin-5 (IL-5) and of IgA were lower for YN1-treated mice than for controls. With increasing doses of YN1, the levels of anti-ICAM-1 mAb in the plasma were proportionally increased. To correlate these results with YN1 treatment, blood and BALF T cells and BALF eosinophils were examined with flow cytometry. Blood T cells from YN1-treated mice were unable to bind phycoerythrin (PE)-labeled anti-ICAM- mAb ex vivo. These results implied that ICAM-1 on these cells was bound (occupied) by YN1 administered in vivo. Dose-related decreases were observed in the percentage and mean channel fluorescence (MCF) values of ICAM-1+ BALF T cells and eosinophils. The percentages of CD11a+ or CD49d+ eosinophils were also suppressed. Our data suggest that ICAM-1 is an important molecule involved in the recruitment of leukocytes into the airways of sensitized mice after pulmonary challenge.

Glucocorticoids: mechanisms of action and anti-inflammatory potential in asthma

GLUCOCORTICOIDS are potent inhibitors of inflammatory processes and are widely used in the treatment of asthma. The anti-inflammatory effects are mediated either by direct binding of the glucocorticoid/glucocorticoid receptor complex to glucocorticoid responsive elements in the promoter region of genes, or by an interaction of this complex with other transcription factors, in particular activating protein-1 or nuclear factor-kappaB. Glucocorticoids inhibit many inflammation-associated molecules such as cytokines, chemokines, arachidonic acid metabolites, and adhesion molecules. In contrast, anti-inflammatory mediators often are up-regulated by glucocorticoids. In vivo studies have shown that treatment of asthmatic patients with inhaled glucocorticoids inhibits the bronchial inflammation and simultaneously improves their lung function. In this review, our current knowledge of the mechanism of action of glucocorticoids and their anti-inflammatory potential in asthma is described. Since bronchial epithelial cells may be important targets for glucocorticoid therapy in asthma, the effects of glucocorticoids on epithelial expressed inflammatory genes will be emphasized.

Cellular and molecular mechanisms of IL-5 synthesis in atopic diseases: a study with allergen-specific human helper T cells

BACKGROUND

Cytokines produced by helper T cells are intimately involved in chronic allergic diseases associated with eosinophilic inflammation.

OBJECTIVE

We investigated the production of IL-5, a potent growth factor and chemotactic factor for eosinophils, by CD4+ T lymphocytes in patients with asthma.

METHODS

Allergen-specific T cell clones and T cell hybridomas were established from the peripheral blood lymphocytes of patients with asthma, and the responses to various stimuli were determined.

RESULTS

After nonspecific stimulation, IL-5 production by CD4+ T cells from both atopic and nonatopic subjects with asthma was significantly enhanced compared with that by cells from healthy controls. Peripheral blood mononuclear cells from atopic asthma patients both proliferated and produced IL-5 after incubation with mite allergen, suggesting that mite-specific helper T cells were involved in the eosinophilic inflammation of atopic asthma. A human IL-5 promoter/enhancer luciferase gene construct transfected into IL-5-producing T cell clones was clearly transcribed after stimulation, indicating that the 515 base pair IL-5 gene segment upstream of the coding region was sufficient to respond to activating signals in human helper T cells. The same gene segment was not transcribed in IL-5-nonproducing T cell clones, suggesting that human T cell IL-5 synthesis is regulated at the transcriptional level. Experiments with T cell hybridomas confirmed these findings and suggested that a unique transcription factor may be essential for human IL-5 gene transcription.

CONCLUSION

Enhanced IL-5 production by helper T cells seems to cause the eosinophilic inflammation of both atopic and nonatopic asthma. Elucidation of IL-5-specific regulatory mechanisms may facilitate the development of novel treatments for allergic diseases associated with eosinophilic inflammation.

The cytokine and histological response in islet xenograft rejection is dependent upon species combination

BACKGROUND

Islet xenografts have clinical potential, may avoid hyperacute rejection, and therefore are a good place to examine the cellular xenograft immune response. The aim of this study was to examine the cellular, humoral, and cytokine response in islet xenograft rejection and to determine the difference in the immune response with a different donor species.

METHODS

Two islet xenograft models (DA rat islets to B6AF1 mouse and canine islets to B6AF1 mouse) and a mouse syngeneic control model were examined histologically and by a semiquantitative polymerase chain reaction method.

RESULTS

There was significant up-regulation of all intragraft cytokines tested (interleukin [IL]-2, IL-4, IL-5, IL-10, and interferon-gamma) in both xenograft models compared with the controls. However, the dog islet grafts had higher levels of IL-4 and IL-5 gene expression than the rat islet grafts, which, conversely, had higher levels of interferon-gamma gene expression. These differences correlated with the histological and anti-donor antibody production differences between the two models. The dog to mouse model had an intense eosinophilic infiltrate and an early up-regulation of anti-donor antibody, whereas there was little eosinophilic infiltrate and a delayed anti-donor antibody up-regulation in the rat to mouse model.

CONCLUSIONS

The mouse used different mechanisms to reject the rat and canine islets, suggesting that the immune response in islet xenograft rejection may be dependent on the species combination. It may not be possible to characterize the cellular xenograft rejection response in a bipolar manner as has been the case with humoral rejection response. Caution therefore needs to be taken before extrapolating the cellular immune responses seen in animal models to the clinical setting.

Animal models of asthma: role of chemokines

In studies of disease processes, increasing knowledge leads to an increased awareness of the complexity of the underlying mechanisms. The intense research activity in the chemokine field has made this acutely manifest. Numerous chemokines have been discovered through the use of (1) bioassay of in vitro cell culture supernatants and in vivo exudates from animal models of inflammation and (2) molecular biology techniques. Any one chemokine can often be produced by a number of different cell types and exert its effects on different target cells. This has been interpreted by some as implying a high degree of redundancy. Although this is understandable, in disease processes parallel and sequential mechanisms are possible, and potentially important therapeutic targets have emerged. There is compelling evidence from animal and clinical studies that eosinophils are important effector cells in asthma, but this relationship is as yet unproven in the human disease. Two possible targets to prevent eosinophil recruitment to the lung are IL-5 and its receptor, which are important in several aspects of eosinophil biology, and eotaxin and its receptor, CCR3. The eotaxin receptor is particularly attractive as a target as it is expressed in high numbers on eosinophils, but not other leukocytes, and appears to be the major detector of the eosinophil for eotaxin and other chemokines such as MCP-4. Eotaxin and CCR3 knockout mice are being developed, and animal models will continue to be invaluable when antagonists are available. In the shape of receptor antagonists, the chemokine field may yet provide the final proof of concept for the long-established eosinophil theory of asthma in humans.

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.

Airway eosinophils, T cells, Th2-type cytokine mRNA, and hyperreactivity in response to aerosol challenge of allergic mice with previously established pulmonary inflammation

Asthma is characterized by acute episodes of nonspecific airway hyperreactivity and chronic pulmonary inflammation exacerbated by stimuli including allergen exposure. In order to reproduce the physiologic and immunologic responses that occur in asthmatic patients, we have characterized a model of antigen-induced inflammation in which allergic mice (B6D2F1) that had been challenged once with aerosolized ovalbumin and had developed a pulmonary cellular infiltrate were rechallenged 1 wk later. Pulmonary inflammation in rechallenged mice was substantially greater than that in single-challenged mice. Eosinophils and activated-memory T cells (CD44+, CD45RBlo) in bronchoalveolar lavage (BAL) fluid accumulated to higher levels and with faster kinetics in response to the second challenge than in response to the first challenge. Eosinophils in lung tissue also accumulated to higher levels but with similar kinetics in response to the second challenge than in response to the first challenge. Similarly, interleukin (IL)-4 and IL-5 steady-state mRNA levels in lung tissue increased after the second challenge and were higher than those measured after a single challenge. Furthermore, treatment of mice with an anti-IL-5 monoclonal antibody 2 h prior to rechallenge inhibited antigen induced eosinophil accumulation in the lungs. In mice challenged twice, peak in vivo bronchoconstrictor responsiveness to acetylcholine was increased following the second challenge compared with that observed following the initial challenge. In contrast, ex vivo tracheal smooth muscle contractile responsiveness to acetylcholine was not altered. Although mucus accumulation and epithelial damage in pulmonary tissue were evident in mice challenged twice, these parameters were slightly reduced compared with those seen at similar times in mice challenged once. Therefore, although these mice exhibit only slight bronchial epithelial damage, the presence of significant inflammation and airway hyperreactivity to acetylcholine as well as slightly increased baseline reactivity demonstrate important similarities with the pathophysiology of asthma.

The effect of segmental bronchoprovocation with allergen on airway lymphocyte function

We hypothesized that allergen-induced airway eosinophilia is linked to activation or recruitment of T cells in the airway and generation of interleukin-5 (IL-5). To evaluate this hypothesis, we performed bronchoscopy with segmental antigen bronchoprovocation in 12 atopic subjects. Bronchoalveolar lavage (BAL) was done 5 min and 48 h after challenge with saline or antigen. Airway cells were isolated and then stimulated ex vivo with a T-cell mitogen, phytohemagglutinin (PHA), and cytokine release was determined. Cells retrieved from the saline-challenged segment secreted principally interferon-gamma (IFN-gamma) and IL-2. In contrast, cells obtained 48 h after allergen challenge secreted high levels of IL-5 and small but increased amounts of IL-4, IL-10, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Although CD4+ T cells were a major source of IL-5, there were no significant changes in the relative proportion of CD4+ cells in response to bronchoprovocation. Additionally, ex vivo secretion of IL-5 by airway cells correlated closely with amounts of IL-5 and eosinophils present in the bronchoalveolar lavage fluid (BALF). These observations suggest that following exposure to allergen, airway T cells are functionally but not phenotypically different from resident airway T cells, and that T cells within the airway contribute to eosinophilic airway inflammation through the secretion of IL-5.