Granzyme K: a novel mediator in acute airway inflammation.

BACKGROUND: Granzymes are a subfamily of serine proteases involved in the pathogenesis of many inflammatory disorders. In contrast with granzyme A and B, the role of granzyme K (GrK) in human lung diseases is unknown. Therefore, the release and expression of GrK in allergic asthma, chronic obstructive pulmonary disease (COPD) and bronchopneumonia were investigated. METHODS: Soluble GrK was quantified using an enzyme linked immunosorbent assay in the bronchoalveolar lavage fluid of patients with allergic asthma (before and after segmental allergen challenge), and in patients with mild COPD, pneumonia and in healthy controls. The molecular form of GrK was analysed by western blot. Flow cytometry was performed to determine the cellular expression of GrK. RESULTS: Compared with healthy controls, there were normal levels of soluble GrK in the bronchoalveolar lavage fluid of patients with COPD, and patients with allergic asthma before allergen challenge. In contrast, soluble GrK was strongly increased in the bronchoalveolar lavage fluid of patients with acute bronchopneumonia. In patients with allergic asthma, there was a significant increase in soluble GrK as well as in GrK expressing CD8(+) T cells in the bronchoalveolar lavage fluid 24 h and 72 h after allergen challenge. After allergen challenge, soluble GrK correlated with the percentage of GrK expressing CD8(+) T cells. Finally, it was shown that the endobronchial release of the CCR5 ligand CCL3 might be a mechanism for the recruitment of GrK(+)CD8(+) T cells after allergen challenge. CONCLUSION: These data provide the first evidence that expression of GrK is upregulated in acute airway inflammation, both in infectious and non-infectious diseases.

Interleukin-13 acts as an apoptotic effector on lung epithelial cells and induces pro-fibrotic gene expression in lung fibroblasts.

BACKGROUND: IL-13 promotes acute allergic asthma and is discussed to play a role in late asthmatic features such as fibrotic processes and airway remodelling. The contributions of IL-13-mediated mechanisms to subepithelial events related to fibrosis are not yet settled. OBJECTIVE: We investigated the impact of IL-13 on lung epithelial cells as apoptotic effector and on lung fibroblasts as inducer of pro-fibrotic gene expression. METHODS: Using the two lung epithelial cell lines A549 and BEAS-2B as well as primary lung epithelial cells, we investigated the capability of IL-13 to induce apoptosis by both flow-cytometry and ELISA. The ability of IL-13 to increase the expression of pro-fibrotic genes and to exert influence on the expression of its own receptor was investigated by real-time quantitative PCR measurement of mRNAs encoding collagen I, collagen III, basic fibroblast growth factor (bFGF), alpha-smooth muscle actin (alpha-SMA) and the IL-13 receptor alpha1 (IL-13Ralpha1) chain in human primary lung fibroblasts. The specificity of IL-13-mediated cellular responses was confirmed by means of an inhibitory monoclonal antibody directed to the IL-13 receptor. RESULTS: IL-13 induces apoptosis in lung epithelial cell lines as well as in primary lung epithelial cells. Furthermore, IL-13 increases the expression of mRNA for alpha-SMA and collagen III, but not for bFGF in human primary lung fibroblasts. The susceptibility of lung fibroblasts to IL-13-induced up-regulation of pro-fibrotic genes is associated with the regulation of IL-13 receptor expression. IL-13-dependent fibrosis-associated effects could be inhibited by antibody-mediated blockade of the IL-13Ralpha1 subunit. CONCLUSION: Our findings indicate a function of IL-13 as a mediator in fibrotic processes leading to loss of functional airway tissue in asthma. They also highlight the therapeutic potential of specifically targeting the interaction between IL-13 and its receptor.

P2 purinergic receptors of human eosinophils: characterization and coupling to oxygen radical production.

Extracellular nucleotides elicit multiple responses in eosinophils but no information on expression of purinergic receptors in these cells is available so far. In the present study we show that human eosinophils express the following P2Y and P2X subtypes: P2Y(1), P2Y(2), P2Y(4), P2Y(6), P2Y(11), and P2X(1), P2X(4), P2X(7), whose stimulation results in intracellular Ca(2+) increase and production of large amounts of reactive oxygen intermediates. These events are stimulated or inhibited, respectively, by P2 receptor agonists or antagonists.

Differential modulation of interleukin-4 and interleukin-13 secretion from human peripheral blood mononuclear cells.

Interleukin-4 (IL-4) and IL-13 which have been implicated in the pathogenesis of atopic reactions elicit many of the same biologic responses. Therefore, time- and stimulus-dependent differences in the regulation of IL-4 and IL-13 production could be of relevance to their biological effects. In this study we tested the hypothesis that stimulation of peripheral blood mononuclear cells (PBMCs) with different inducers of cell activation would result in a differential expression of IL-4 and IL-13. For this purpose, PBMCs of nonatopic volunteers were incubated with phytohaemagglutinin (PHA), phorbolester (PMA), calcium ionophore A23187, or IL-3. The effect of these stimuli on IL-4 and IL-13 production were analysed by enzyme-linked immunoassay (ELISA) in supernatants of cultured PBMCs. Incubation of PBMCs with A23167 and PHA induced both a dose- and time-dependent increase in IL-4 and IL-13 release. A23187 induced concentrations of IL-4 were higher than those of IL-13 whereas IL-4 release following stimulation with PHA was considerably higher for IL-13 compared to IL-4. In contrast, there was a selective increase in IL-13 but not IL-4 concentrations following stimulation of PBMCs with PMA and IL-3 in vitro. In conclusion in this study evidence is provided that IL-4 and IL-13 production are regulated differently which might explain their functional redundancy.

Leukocyte infiltration and secretion of cytokines in pleural drainage fluid after thoracic surgery: impaired cytokine response in malignancy and postoperative complications.

STUDY OBJECTIVE: To assess the postoperative course of pleural leukocyte counts and cytokine concentrations in patients with malignant and nonmalignant lung disease who underwent thoracic surgery. PATIENTS AND INTERVENTIONS: A total of 21 patients undergoing thoracic surgery were included in the study. Twelve patients had a malignant disease, and 9 had a nonmalignant disease. Six patients underwent video-assisted thoracoscopy and 15 underwent thoracotomy. Pleural drainage fluid from the chest tubes was collected postoperatively at Oh, 3h, 6h, 12h, 24h, 48h, 72h, and 96 h. The same schedule, as well as one additional preoperative sample, was applied for blood collections. RESULTS: A trend toward lower concentrations of tumor necrosis factor-alpha (TNF-alpha), granulocytemacrophage colony-stimulating factor, and interleukin-10 was observed in patients with malignant disease compared to those without malignancy. These differences achieved significance for TNF-alpha in the drainage fluid of those patients with nonmalignant disease who had undergone formal thoracotomy. Patients with malignant disease showed significantly lower macrophage fractions in drainage fluid and lymphocyte fractions in serum. All patients with complications had malignant disease and showed the lowest cytokine concentrations, as well as the lowest fractions of both macrophages in drainage fluid and lymphocytes in serum. CONCLUSION: The data suggest that malignancy may lead to impairment of the wound-healing process via modification of the inflammatory cell infiltrate and locally released cytokines.

CD8+ T cell activation and differentiation in allergic asthma and the impact of cytomegalovirus serological status.

Allergic asthma is a chronic inflammatory T helper 2 (Th2)-associated disease. There is evidence that the atopic milieu affects the development of CD8(+) T cells in patients. We therefore analysed activation and differentiation states of CD8(+) T cells in asymptomatic patients regarding the cytomegalovirus serological status. Memory CD8(+) T cells (CCR5(high)CD3(+)CD8(+)), memory/effector cells (CD27(+)CD28(-)CD3(+)CD8(+)), effector cells (CD27(-)CD28(-)CD3(+)CD8(+)) and activated CD8(+) T cells (CD11b(+)CD3(+)CD8(+)) were identified by flow cytometry in peripheral blood of 19 (seven cytomegalovirus (CMV)(+)/12 CMV(-)) patients with allergic asthma (AA) and 21 (seven CMV(+)/14 CMV(-)) healthy controls (HC). Effector and activated CD8(+) T cells were significantly elevated in CMV(+) HC compared to CMV(-) HC. There was a non-significant trend for reduced percentages of effector CD8(+) T cells in CMV(+) AA (median: 10.4%, range: 4.4-33.8%) compared to CMV(+) HC (median: 23.1%, range: 10.7-54.1%; P = 0.128) and in CMV(-) AA (median: 4.1%, range: 0.6-13.4%) compared to CMV(-) HC (median: 5.7%, range: 0.2-17.0%; P = 0.085). Activated CD8(+) T cells were reduced significantly in CMV(+) AA (median: 17.0%, range: 6.0-29.4%) compared to CMV(+) HC (median: 40.4%, range: 18.9-67.0%; P = 0.004) and showed a non-significant trend in CMV(-) AA (median: 15.0%, range: 2.9-24.0%) compared to CMV(-) HC (median: 20.2%, range: 5.8-71.0%; P = 0.060). Activated CD8(+) T cells are significantly reduced in CMV(+) patients with allergic asthma. Furthermore, a trend for an impaired terminal CD8(+) T cell differentiation is observed in CMV(+) and CMV(-) patients with asthma.

Airway dendritic cell phenotypes in inflammatory diseases of the human lung.

Airway dendritic cells (DCs) are key regulators of pulmonary immune responses. However, information is limited regarding the characteristics of airway DCs in human lung diseases. Plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) were analysed using four-colour flow cytometry in bronchoalveolar lavage fluid (BALF) from nonsmoking controls and patients with sarcoidosis, idiopathic pulmonary fibrosis (IPF) and pneumonia (in the presence or absence of immunosuppression). Compared with controls, immunocompetent patients with pneumonia displayed strongly enhanced pDC counts in BALF. In contrast, pDC counts in BALF from immunocompromised patients with pneumonia were even lower than in controls. This discrepancy was not explained by a different chemotactic milieu in the airways; all patients with pneumonia were characterised by strongly increased concentrations of the pDC-attracting chemokine, CXC chemokine ligand 10, in BALF. Patients with IPF were characterised by normal percentages of DC subtypes. However, the mDCs of patients with IPF were not as mature (CD83-positive) as those of controls. Patients with sarcoidosis displayed a unique increase in CD1a-negative mDCs in the airways. In addition, there was altered expression of costimulatory molecules (increased CD80 and decreased CD86 expression) on mDCs in patients with sarcoidosis. These data suggest that inflammatory diseases of the human lung are associated with a differential phenotype and recruitment of airway dendritic cells.

Decrease of cytotoxic T cells in allergic asthma correlates with total serum immunglobulin E.

BACKGROUND: Allergic asthma has been linked to an increase in T-helper type 2-like cytokines and T cells, but there is growing evidence for a role of lymphocyte-mediated cytotoxic mechanisms in the pathogenesis of asthma. Therefore, we investigated the cytotoxic potential of different lymphocyte subpopulations in patients with allergic asthma. METHODS: Granzyme A, B, K, and perforin expression in peripheral blood lymphocytes was analyzed using flow cytometry. Soluble granzymes were measured in serum using specific enzyme-linked immunosorbent assays. RESULTS: Asthmatics had significantly decreased percentages of granzyme and perforin-positive CD4 T cells compared with non-atopic controls. In patients with asthma, the granzyme B and perforin-positive subset of CD8(+) T cells and natural killer T cells, which represent more differentiated cell populations, were significantly reduced, while this was not observed in the less differentiated granzyme K(+) subsets. In addition, the serum concentrations of granzyme B were significantly reduced in patients with asthma, while granzyme K concentrations were not different. Interestingly, there was a negative correlation between granzyme A, B and perforin expression in T cell subsets as well as serum granzyme B concentrations and total serum immunglobulin E. In CD3-negative natural killer cells, no differences in granzyme or perforin expression between patients with asthma and controls were detected. CONCLUSION: In allergic asthma, cytotoxic T lymphocyte subsets of a more differentiated phenotype are significantly decreased and this is correlated to serum immunglobulin E levels.

Increase in killer-specific secretory protein of 37 kDa in bronchoalveolar lavage fluid of allergen-challenged patients with atopic asthma.

BACKGROUND: Atopic asthma is linked to a T-helper type 2 dominated pathogenesis, but there is increasing evidence of Th1/Tc1-mediated processes in the aetiopathology of asthma. Killer-specific secretory protein of 37 kDa (Ksp37) is expressed in cytotoxic lymphocytes, selectively in the effector subsets of CD8+- and CD4+ T lymphocytes and in CD16+/CD56dim natural killer cells and gamma/delta T cells. This effector cell-specific expression of Ksp37 and its coexpression with perforin suggest that Ksp37 might be involved in processes mediated by cytotoxic cells. OBJECTIVE: We hypothesize that Ksp37 could indicate the involvement of cytotoxic lymphocytes in the pathogenesis of atopic asthma, and investigated Ksp37 concentration in bronchoalveolar lavage fluid (BALF) collected 10 min, 18, 42 or 162 h after segmental allergen provocation and in serum of patients with atopic asthma (n=25). METHODS: Ksp37 concentrations in BALF and serum were detected by ELISA. Flow cytometric analysis was used to assess numbers and cell subsets in BALF. RESULTS: Ksp37 increased significantly in BALF 10 min, 18 and 42 h, but not 162 h after allergen challenge compared with saline-challenged controls, while Ksp37 serum levels did not change significantly at all time-points. In addition, the increase in Ksp37 concentrations in BALF correlated with the corresponding numbers of lymphocytes. CONCLUSIONS: We conclude that Ksp37 level increased in BALF 10 min, 18 and 42 h after allergen challenge but not in peripheral blood. Our findings suggest that segmental allergen challenge in asthma is associated with an increase in Ksp37 concentrations in BALF and an influx of potentially cytotoxic T lymphocytes into the lungs.

Chemokine-receptor expression on T cells in lung compartments of challenged asthmatic patients.

BACKGROUND: The interaction of chemokines with their receptors strongly influences the migration of leucocytes. OBJECTIVE: In order to assess the contribution of these molecules to the local recruitment of T cells in bronchial asthma, we analysed the expression of 14 chemokine receptors on lung-derived T cells. METHODS: Chemokine-receptor expression by T cells derived from the peripheral blood, the bronchoalveolar lavage fluid and the bronchial mucosa was analysed by flow cytometry and immunohistochemistry. Expression profiles in healthy and mildly asthmatic individuals were compared, the latter prior and after segmental allergen provocation. RESULTS: Compared with peripheral blood, alveolar T cells expressed significantly more CCR2, CCR5, CCR6, CXCR3 and CCR4. However, no differences were observed between healthy controls and unchallenged asthmatics. In patients developing significant inflammatory responses following specific allergen challenge, a marked increase in the percentage of CCR4+ and CCR7+, and reduced numbers of CXCR3-bearing alveolar T cells were detected. Following specific allergen challenge, chemokine-receptor expression profiles of T cells from the alveolar space and the mucosa or the submucosa were similar, excluding a particular subcompartmentalization of the chemokine/chemokine-receptor system. CONCLUSION: The expression of certain chemokine receptors by lung T cells suggests a contribution to the physiological recruitment of T cells to the lungs, both in healthy controls and unchallenged mild asthmatics. However, strong allergen-induced airway responses were associated with a specific chemokine-receptor profile, suggesting the involvement of certain chemokine receptors in the pathogenesis of allergic bronchial inflammation.

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.

Endothelin receptors in the cornea, iris and ciliary processes. Evidence from binding, secondary messenger and PCR studies.

Endothelin (ET)-1 (10 nanoM) is about six times more effective than ET-3 in contracting the isolated iris sphincter muscle; the ET-1-induced contraction is insensitive to indomethacin treatment. The effect of ET-2 is intermediatory between ET-1 and ET-3 in contracting the muscle. The relative potency of the ETs to stimulate inositol phosphates (InsPs) in the iris-ciliary processes is ET-1 > ET-2 > ET-3, with ET-1 about six times more potent then ET-3; these effects are also insensitive to indomethacin. Studies utilizing the polymerase chain reaction (PCR) show that ETB receptors are present. Although no evidence could be found for the occurrence of ETA receptors, their presence cannot be excluded. These results suggest that the stimulation of InsPs and contraction of the iris sphincter muscle by ET is mediated by ETB receptors and that products generated via activation of phospholipase A2 are not directly involved in the observed responses. However, another type of ET receptor is indicated by the finding that ET-1 reduced the forskolin-elevated cAMP levels in the iris-ciliary epithelium. Autoradiographic results show that specific [125I]ET-1 binding sites are associated with the iris, ciliary processes and the corneal endothelium. As in the iris-ciliary process tissues, ET-1 is the most effective of the three ETs stimulating InsPs in the cornea, although statistically the differences were insignificant. Moreover, ET-1 was found to have not effect on the forskolin-elevated cAMP levels in the cornea. Whether these results reflect true differences between the ET receptors in the iris-ciliary processes and corneal endothelium remains to be established.

Adherence of neutrophils to human peritoneal mesothelial cells: role of intercellular adhesion molecule-1.

Peritonitis is accompanied by a massive influx of polymorphonuclear leukocytes (PMN) into the peritoneal cavity, little is known, however, about the process of neutrophil transmigration across the peritoneal membrane. The study presented here, therefore, investigates the adherence of human PMN to human peritoneal mesothelial cell monolayers and examines the importance of intercellular adhesion molecule-1 (ICAM-1) in the process. Human peritoneal mesothelial cells (HPMC) constitutively expressed ICAM-1 protein and mRNA. Stimulation with IL-1 beta or TNF alpha resulted in time- and dose-dependent upregulation of ICAM-1 mRNA transcript and increased cell-surface immunoreactive protein expression. Peak surface expression of ICAM-1 occurred between 12 and 24 h after cytokine stimulation when the level of expression was increased by on average threefold above control. The adherence of PMN to HPMC after stimulation with either IL-1 beta or TNF alpha was both dose- and time-dependent. Peaks of PMN binding to HPMC occurred at 2 and 12 h after stimulation. After 12 h, the number of PMN binding to HPMC increased from 71.3 +/- 12.5 in control cells to 180 +/- 36.5 and 125 +/- 23.6 (x 10(3) PMN), after IL-1 beta (100 pg/mL) and TNF alpha (1000 pg/mL), respectively (z = 2.52 and 2.38, N = 6, P < 0.02 versus control for both). The roles of HPMC ICAM-1 and the PMN counter receptor LFA-1 (CD11a/CD18) in the adherence of PMN to HPMC were confirmed by using anti-CAM Fab2' fragments, and anti-integrin antibodies, all of which significantly reduced the adherence of PMN to both control and cytokine-treated HPMC. These data suggest that ICAM-1 expression by HPMC may be one mechanism by which neutrophils adhere to the mesothelium during their transmigration into the inflamed peritoneal cavity.

Effects of TGF-beta on eosinophil chemotaxis.

Transforming growth factor-beta (TGF-beta), which can decrease the effects of interleukin (IL)-3, IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) on eosinophil viability, has been shown to be chemotactic for neutrophils. However, there is little information on its effects on eosinophil chemotaxis. Because TGF-beta has recently been found in increased concentrations in asthmatic sputum, we investigated whether TGF-beta could influence eosinophil migration and eosinophil viability. Purified eosinophils from normal donors were incubated with increasing concentrations of TGF-beta. Chemotaxis was measured with a modified Boyden chamber technique. In addition, eosinophils were incubated for 96 h with either IL-3, IL-5 or GM-CSF (1 ng/ml) together with increasing concentrations of TGF-beta. Eosinophil viability was then determined with propidium jodide and flow cytometry. Eosinophil chemotaxis was significantly increased in the presence of TGF-beta in concentrations between 10(-9) and 10(-4) microg/ml. The optimal concentration of TGF-beta in this assay was between 10(-9) and 10(-8) microg/ml. The chemotactic effect of TGF-beta diminished when higher as well as lower concentrations (between 10[-12] and 10[-3] microg/ml) were employed. In contrast, inhibition of eosinophil survival induced by IL-3, IL-5 and GM-CSF reached its maximum at concentrations of TGF-beta between 10(-4) and 10(-3) microg/ml. From these data we conclude that TGF-beta in low concentrations can induce eosinophil chemotaxis whereas higher concentrations reduce eosinophil survival mediated by IL-3, IL-5 and GM-CSF.

[Immunopathogenesis of allergic bronchial asthma. Detection of activated CD25-CD4 lymphocytes and release of cytokines in the bronchoalveolar space following segmental allergen challenge]. / Immunpathogenese des allergischen Asthma bronchiale. Nachweis aktivierter CD25-CD4-Lymphozyten und Freisetzung von Zytokinen im Bronchoalveolarraum nach segmentaler Allergenprovokation.

The aim of this study was to investigate the fundamental processes underlying the inflammatory response to allergen in mild non-symptomatic asthmatics, using a new model entailing endobronchial segmental provocation. Ten asymptomatic asthmatic volunteers (8 male, 2 female; mean age 28.2 [24-41] years) were challenged employing the segmental allergen provocation technique. 250 PNU in 5 ml 0.9% NaCl solution of either birch (n = 8) or grass (n = 2) pollen were instilled into one segment. As control, only the solvent was instilled into a segment of the contralateral lung. Bronchoalveolar lavage (BAL) with 100 ml prewarmed saline was performed 10 min and 18 h after allergen provocation. The cellular distribution and activation state in BAL fluid and peripheral blood was analysed by immunofluorescence and flow cytometry. The concentration of various cytokines was determined in the BAL fluid using ELISA and bioassays. In blood, segmental allergen provocation led to an increase both in numbers of neutrophils (3833 cells/microliters vs 6830 cells/microliters; P < 0.005) and activated IL-2R expressing (CD25+) CD4+ T cells (3.6% vs 4.8% of all CD4+ lymphocytes; P < 0.05). No change was observed in eosinophils and other leukocytes and lymphocyte subsets. In contrast, a significant 30-fold increase in eosinophils (0.39 x 10(6) vs 11.5 x 10(6) cells/100 ml; P < 0.01) and a twofold increase in CD25+ CD4+ T cells (P < 0.05) were found in BAL samples 18 h after segmental allergen challenge, when compared to the control segment. Analysis of the cytokine profile revealed significantly increased levels of several cytokines. Allergen challenge of extrinsic asthmatic subjects causes differentiation of activated CD25+ CD4+ lymphocytes which may contribute to the pathogenesis of the asthmatic inflammation through the release of various cytokines.

[Cell biology and function of eosinophilic granulocytes in immunologic inflammation]. / Zellbiologie und Funktion des eosinophilen Granulozyten im Rahmen der immunologischen Entzündung.

In recent years, increasing evidence has accumulated to suggest that the eosinophil represents a potent cytotoxic effector cell which plays a key role in the pathogenesis of pulmonary diseases as well as other human disorders. Beside contributing to antiparasitic host defense, eosinophils can prove detrimental to a number of host organs and tissues via release of their preformed basic proteins as well as de novo generated lipid mediators or oxygen radicals. Eosinophil effector functions are stimulated by certain lipid mediators and cytokines released by other cells in the course of active disease. In addition to their effector functions, eosinophils may have other functions in immune responses. Synthesis and expression of class II proteins of the major histocompatibility complex (MHC) may enable eosinophils to serve as antigen-presenting cells, i.e. to the antigens that appear at mucosal surfaces. In addition to collaborative interactions with lymphocytes, CD4-expressing eosinophils may elaborate cytokines that can effect cells within their tissue milieu. In conclusion, the evolving understanding of eosinophils indicates that eosinophils may not only serve as end-stage effector cells but also interact cooperatively with other cellular tissue elements in related diseases.

Pulmonary immune cells in health and disease: the eosinophil leucocyte (Part I).

Increasing evidence has accumulated to suggest that eosinophils play a key role in the pathogenesis of asthma and other pulmonary diseases by damaging infiltrated bronchial tissue and lung parenchyma. The first part of this review on eosinophils describes the cellular characteristics and properties of the cell, which help in understanding its role in disease. The article focuses on origin, maturation and differentiation of the eosinophil, its morphological and phenotypical properties, as well as its preformed and newly generated mediators of inflammation. The cause and putative significance of eosinophil heterogeneity in respect to function and density will also be discussed. In addition, the naturally occurring mediators through which eosinophils are activated and communicate with other inflammatory cells are outlined. The first part closes with new aspects of eosinophil recruitment from the circulation into perivascular tissue, including nonselective and putative selective adhesion mechanisms and chemotaxis.

Inhibition of HLA-DR expression on activated human blood eosinophils by transforming growth factor-beta1.

Peripheral blood, bronchoalveolar lavage and sputum eosinophils of patients with asthma but not peripheral blood eosinophils from normal controls have been shown to express human leucocyte antigen (HLA)-DR on their cell surface. Cytokines implicated in the activation of eosinophils, such as interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF), can up-regulate HLA-DR expression. However, little is known about antagonistic factors that might down-regulate HLA-DR expression on eosinophils. In this study we investigated whether transforming growth factor-beta (TGF-beta), which has been shown to reduce survival of activated eosinophils, can also modulate HLA-DR expression on eosinophils. For this purpose, isolated peripheral blood eosinophils were stimulated with IL-3 and GM-CSF for 24 h and HLA-DR expression was measured by flow cytometry. We found that while isolated eosinophils expressed low levels of surface HLA-DR, incubation with GM-CSF and IL-3 increased HLA-DR expression on eosinophils. TGF-beta alone did not change HLA-DR expression on isolated eosinophils. However, co-incubation of eosinophils with TGF-beta and either GM-CSF or IL-3 significantly decreased HLA-DR expression compared to eosinophils incubated with either GM-CSF or IL-3 alone and this was not reversed by addition of IL-5. This effect of TGF-beta on IL-3-induced HLA-DR expression was attenuated dose-dependently in the presence of monoclonal anti-TGF-beta antibodies. Our results suggest that TGF-beta can reduce cytokine-induced HLA-DR expression on eosinophils and could thus influence eosinophil activation.