Eosinophil chemoattractants in the middle ear of patients with eosinophilic otitis media

BACKGROUND: Patients with intractable otitis media associated with bronchial asthma have an extensive accumulation of eosinophils in the effusion and mucosa of the middle ear; this condition is called eosinophilic otitis media (EOM). It remained to be determined how eosinophils accumulate in the middle ear. OBJECTIVES: To clarify the pathogenesis of middle ear diseases, we measured the concentration of eosinophil chemoattractants in middle ear effusion (MEE), and carried out immunohistochemical studies of middle ear mucosa specimens to demonstrate the expression of eosinophil chemoattractants. METHODS: Middle ear effusion samples were obtained from 15 EOM patients with bronchial asthma and from six controls for the measurement of eosinophil cationic protein (ECP), IL-5, eotaxin and regulated on activation, normal T expressed and secreted concentrations. Middle ear mucosa samples were also taken from 14 EOM patients and 16 controls for immunohistochemical study. In 10 EOM patients, the numbers of immunoreactive cells as well as apoptotic cells were determined before and after the topical application of triamcinolone acetonide into the middle ear. RESULTS: In EOM, significantly higher ECP and IL-5 concentrations were detected in MEE than in serum, and ECP, IL-5 and eotaxin concentrations in MEE were higher in the EOM patients than in the controls. ECP concentration positively correlated with that of IL-5. Immunohistochemically, the numbers of cells positive for EG2 and ecalectin were significantly higher in the EOM patients than in the controls. After the topical application of triamcinolone acetonide, the numbers of infiltrating cells and immunoreactive cells distinctly decreased, whereas the number of apoptotic cells significantly increased. CONCLUSION: In EOM, locally produced IL-5 may play a crucial role in the accumulation of eosinophils in the middle ear. Chemokines such as ecalectin and eotaxin are also produced in the middle ear, and help activate and enhance the survival of eosinophils to induce the intractable condition in the middle ear. The topical application of triamcinolone acetonide induces the apoptosis of not only eosinophils but also eosinophil chemoattractant-producing cells, thereby improving the middle ear condition.     

Eosinophil accumulation induced by human interleukin-8 in the guinea-pig in vivo.

Interleukin-8 (IL-8) is a neutrophil chemoattractant cytokine. Initially IL-8 appeared to exhibit specificity for neutrophils over other cells of the immune system. However, several recent studies have shown that this mediator can also activate other leucocyte types in vitro. In this study we have used an in vivo model of local [111In]leucocyte accumulation in the guinea-pig and an in vitro assay of leucocyte activation (changes in cytosolic-free Ca2+) to investigate the eosinophil chemoattractant activity of IL-8. The intradermal injection of recombinant human (rh)IL-8 induced a dose-dependent accumulation of intravenously administered [111In]eosinophils into the skin sites over 4 hr. Time-course experiments revealed that this cell infiltration was delayed in onset, occurring between 1 and 2 hr after injection of IL-8. The delay may indicate that IL-8 operates via an indirect mechanism. In contrast, eosinophil accumulation induced by the complement fragment C5a occurred within the first hour following injection. Other human cytokines, IL-1, IL-3, IL-5, tumour necrosis factor (TNF) and granulocyte-macrophage colony-stimulating factor (GM-CSF), were not eosinophil chemoattractants in this in vivo test system. Direct activation of eosinophils by IL-8 was demonstrated in vitro by a transient elevation in cytoplasmic-free Ca2+ levels where it was less potent than either rhC5a or leukotriene B4 (LTB4). Experiments using [111In]neutrophils in vivo indicated that rhIL-8 and rhC5a were similar in potency in inducing local neutrophil infiltration into guinea-pig skin. The demonstration of the eosinophil chemoattractant activity of IL-8 in vivo raises the possibility that this cytokine, or a structurally related molecule, contributes towards eosinophil infiltration in a number of inflammatory conditions such as asthma, helminthic infections and adult respiratory distress syndrome.     

Eotaxin and eotaxin receptor (CCR3) expression in Sephadex particle-induced rat lung inflammation

The beta chemokine eotaxin is a potent eosinophil activator and chemoattractant. We examined immunohistochemically eotaxin protein expression in a range of normal rat tissues and in rat lung during Sephadex particle-induced pulmonary inflammation. The time course of eotaxin expression in lung at various time points after Sephadex administration was related to the appearance of eosinophils in the bronchoalveolar lavage fluid and tissue distribution of eotaxin receptor (CCR3) positive cells. Results showed that eotaxin protein was constitutively expressed by both lung airway epithelial cells and gut epithelial cells in normal tissues in the absence of inflammation. During Sephadex induced pulmonary inflammation, eotaxin expression increased in alveolar macrophages prior to the major increase in eosinophil numbers which reached a peak at 72 h. The pattern of eotaxin pulmonary expression and the location of CCR3 receptor positive cells suggest a chemoattractant gradient resulting in migration firstly into the tissue and subsequently through the airway epithelium into the airways. Treatment of rats with the glucocorticoid dexamethasone or the immunosuppressant cyclosporin A reduced eosinophil entry into lung tissue and airways but had no apparent effect on eotaxin expression in vivo, indicating that both these drugs inhibit eosinophil recruitment either by an eotaxin-independent mechanism, or by targetting factors that synergise with eotaxin, or an event post eotaxin expression.     

Eosinophil infiltration and enhancement of airway reactivity by leukocyte chemotactic factor, formyl-methionyl-leucyl-phenylalanine (fMLP), in guinea pigs.

N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) is a bacterial-derived chemotactic factor for eosinophils and neutrophils. This study is aimed to examine whether or not eosinophil infiltration induced by intra-airway administration of fMLP causes the damage of the bronchial epithelium and results in airway hyperresponsiveness in normal non-sensitized guinea pigs. In normal guinea pigs fMLP administered by aerosol inhalation or intratracheal injection caused significant infiltration of eosinophils in the tracheal mucosa and enhanced bronchial reactivity to inhaled histamine 6 and 24 hours after exposure. Electron microscopic examination showed damage of the alignment of the epithelial cells in the bronchial mucosa in fMLP-treated guinea pigs. PAF antagonists CV3988 and WEB2086 and a 5-lipoxygenase inhibitor (AA-861) did not prevent fMLP induced eosinophil infiltration, which suggests that fMLP caused eosinophil infiltration mainly by its chemotactic activity, not by the release of platelet activating factor (PAF) or leukotrienes in this experimental condition. These results showed that in normal guinea pigs a bacteria-derived chemoattractant of fMLP could reproduce a sequence of eosinophil infiltration and airway hyperresponsiveness, similar to the inflammatory pathophysiology after antigen challenge in sensitized animals. We concluded that eosinophil infiltration induced by either immunological or non-immunological mechanisms can cause airway damage and airway hyperresponsiveness.     

The effects of a soluble factor released by sensitized mononuclear cells incubated with S. haematobium ova on eosinophil migration.

Incubation of sensitized mononuclear cells from patients with schistosomiasis with specific antigen containing a suspension of viable Schistosoma haematobium ova resulted in the release of a soluble factor which was chemotactic for eosinophils. Production of this substance was detectable at 24 h and demonstrated peak chemotactic activity after 2 days in culture. The chemotactic potential was dose-dependent and attracted eosinophils obtained from patients with schistosomiasis or allergic diathesis. Human neutrophil motility was unaffected by this chemoattractant. Preliminary studies demonstrated that the chemotactic factor is a heat-stable substance with peak activity associated with a molecular weight of approximately 42,000. These findings may reflect an in vitro correlate of cell-mediated immunity and may indicate a role played by the lymphocyte in the control of eosinophil function in human biology.     

Hierarchy of eosinophil chemoattractants: role of p38 mitogen-activated protein kinase

Several chemoattractants can regulate the recruitment of eosinophils to sites of inflammation, but the hierarchy among them is unknown. We observed here that eosinophil chemotaxis towards eotaxin or 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) was amplified up to sixfold in the presence of prostaglandin (PG) D2. This effect was only seen in eosinophils, and not in neutrophils or basophils. Pretreatment with the chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) antagonist ramatroban prevented the PGD2 enhancement of eosinophil migrations. In contrast, eotaxin or 5-oxo-ETE inhibited the migration of eosinophils towards PGD2. 5-oxo-ETE enhanced the chemotaxis to eotaxin, while eotaxin had no effect on 5-oxo-ETE-induced migration. 5-oxo-ETE induced the phosphorylation of p38 mitogen-activated protein kinase, and inhibition of p38 mitogen-activated protein kinase by SB-202190 converted the effect of 5-oxo-ETE on the chemotaxis to PGD2 from inhibition to enhancement. The presence of blood or plasma markedly decreased the sensitivity of eosinophils to eotaxin or 5-oxo-ETE, while responses to PGD2 were unaltered. In conclusion, PGD2 might be an initial chemoattractant, since it maintains its potency in the circulation and augments the responsiveness of eosinophils to other chemoattractants. In contrast, eotaxin seems to be an end-point chemoattractant, since it has reduced efficacy in blood and is capable of down-modulating eosinophil responsiveness to other chemoattractants.     

IL-10+IL-4 能提高M2 巨噬细胞表型和嗜酸性粒细胞的迁移

目的:研究论证IL-10 是否能通过诱导IL-4 来提高M2。方法:用C57BL/6J 鼠中的骨髓细胞诱导M-CSF 诱导的骨髓源巨噬细胞,利用小鼠全基因组版本进行转录,进而嗜酸性粒细胞的迁移实验,体内巨噬细胞的转移实验。结果:研究发现在M-CSF 诱导的BMDMs 中通过IL-4、IL-10 及IL-4+IL-10 诱导来分析M2 巨噬细胞,IL-10 通过IL-4 来提高M2a 标志物的表达,此外,IL-4 和IL-10 诱导产生CCL24 时起协同作用。在GM-CSF 诱导的BMDMs 中CCL24 的表达提高。CCL24 是CCR3 的激动剂和嗜酸性粒细胞的趋化因子。在体外,IL-4+IL-10 激活的巨噬细胞产生大量的CCL24,并且能提高嗜酸性粒细胞的迁移。这个过程能被抗CCL24 抗体抑制。IL-4+IL-10 激活的巨噬细胞转移到C57BL/6J 小鼠的腹膜,这能增加嗜酸性粒细胞浸润腹膜腔。结论:IL-4+IL-10 激活的巨噬细胞能增强M2a 巨噬细胞相关基因的表达,提高CCL24 的产生和嗜酸性粒细胞的浸润,导致嗜酸性粒细胞相关疾病的发生。     

Interferon-gamma stimulates the expression of galectin-9 in cultured human endothelial cells

Galectin-9 is a member of the galectin family and has been identified as an eosinophil chemoattractant produced by activated T lymphocytes. Vascular endothelial cells play an important role in the initial step of eosinophil recruitment and activation in immune and inflammatory responses. We have addressed the stimulation of galectin-9 expression in endothelial cells. Galectin-9 was detected in membrane and cytosolic fractions of human umbilical vein endothelial cells stimulated with interferon-gamma (IFN-gamma). IFN-gamma also enhanced the adhesion of human eosinophilic leukemia-1 cells to endothelial monolayers, and it was inhibited by the presence of lactose. Interleukin-4, which induces eotaxin expression, did not affect the expression of galectin-9. The in situ endothelium from patients with inflammatory diseases was found to express galectin-9. IFN-gamma-induced production of galectin-9 by endothelial cells may play an important role in immune responses by regulating interactions between the vascular wall and eosinophils.     

Inhibition of eosinophil chemotaxis by a new antiallergic compound (cetirizine)

The in vivo inhibitory effect of a new antiallergic, anti-H1 drug, cetirizine, on eosinophil attraction at skin sites challenged with various stimuli has been recently suggested. In the present work, we confirmed that this molecule, at therapeutical concentration, has a potent inhibitory action on eosinophil response to different chemoattractant mediators such as platelet-activating factor (PAF acether) and N-formyl methionyl leucyl phenyl alanyl in vitro. Another anti-H1 drug, polaramine, did not show this effect at the same concentration. These findings suggest that cetirizine in addition to its antihistaminic effect could also play a direct inhibitory effect on eosinophil recruitment. Moreover, cetirizine was not toxic for eosinophils and did not induce degranulation, as shown by the absence of peroxidase release. Comparison between cetirizine and a PAF acether antagonist (BN 52021) suggested that cetirizine did not act by a PAF receptor-blocking activity.     

Secretion of 10-kDa and 12-kDa thioredoxin species from blood monocytes and transformed leukocytes

Thioredoxins (TRX) are ubiquitous, small redox-active proteins with multiple functions, including antioxidant, cytoprotective, and chemoattractant activities. In addition to a 12-kDa intracellular form, extracellular 10-kDa and 12-kDa TRX have been defined. The biological activities of the 10-kDa TRX were previously measured as eosinophil cytotoxicity enhancing activity or B-cell stimulatory activity. Cytotrophoblastic cell lines also release a 10-kDa TRX form. To study the biological role of 10-kDa TRX, we established two highly sensitive enzyme-linked immuno-spot assays (ELISPOT), which detect secreted truncated 10-kDa and full-length 12-kDa TRX at the single cell level. TRX secretion was investigated in several cell lines including the T-helper cell hybridoma MP6, the Jurkat T-cell leukemia, the U-937 myelomonocytic leukemia, and the 3B6, EBV-transformed, lymphoblastoid B-cell line. The highest number of secreting cells was found in 3B6 cultures, median = 34 (quartiles, 27-39) per well (10(5) cells). Peripheral blood monocytes isolated from healthy donors secreted significantly more TRX after stimulation with ionomycin, phorbol myristate acetate (PMA), fMLP, and lipopolysaccharide (LPS), compared to unstimulated cells. Oxidative stress induced by thioloxidant diamide also induced the secretion of both truncated and full-length TRX measured in ELISPOT (p = 0.047 and p = 0.031, respectively). The biological activity of the truncated and full-length forms was tested in a cell migration assay. Truncated TRX was devoid of protein disulfide reductase activity, but retained strong chemoattractant activity for human monocytes, in the same range as full-length TRX, as previously reported (Bertini et al., 1999).     

Chemotactic Activity of LTB4 in Man

An improved skin window chamber technique has been developed and used for a quantitative study of the chemotactic effect of leukotriene B4 (LTB4). LTB4 (0.5 microM) was exposed to a skin window on the forearm of eight healthy volunteers, while phosphate buffered saline served as control in a skin window on the other forearm. Skin window exudates and samples of blood draining the skin window areas were collected after 1, 2, 4, 8, and 24 h. The samples were quantitated for the different types of leukocytes as well as the intra- and extracellular concentration of the eosinophilic cationic protein and lactoferrin as markers of eosinophil and neutrophil granulocytes. A significantly increased migration of neutrophil granulocytes into the skin window chamber containing LTB4 was found from the 2nd to the 8th hour after the initial LTB4 exposure. The eosinophils reached a significant peak at the 4th hour. The rise in the actual number of eosinophil cells did not reach significance, whereas measurements of the eosinophilic cationic protein in the cellular fraction of the exudate exhibited a significant increase as a reflection of the number of eosinophils. This highlights the potential clinical value of eosinophilic cationic protein measurements to reveal eosinophilia instead of the traditional eosinophil counts. Extracellular eosinophilic cationic protein and lactoferrin did not change significantly in the LTB4-exposed skin window, implying that LTB4 does not activate the eosinophils and neutrophils to exocytosis of their enzymes. The present in vivo results support the concept of LTB4 being a potent chemoattractant to neutrophil and less so to eosinophil granulocytes in humans, a chemoattractant that recruits the leukocytes but does not seem to activate them.     

Regulatory mechanisms of galectin-9 and eotaxin-3 synthesis in epidermal keratinocytes: possible involvement of galectin-9 in dermal eosinophilia of Th1-polarized skin inflammation

BACKGROUND: Skin eosinophilia is a common feature of allergic skin diseases, but it is unclear how epidermal and dermal eosinophil infiltration is controlled. To investigate regulation of localization of eosinophils in skin, we examined the regulatory mechanisms of expression of eosinophil-specific chemoattractants in dermal fibroblasts and epidermal keratinocytes. METHODS: We analyzed production of eotaxin, eotaxin-2, eotaxin-3 and galectin-9 by dermal fibroblasts and epidermal keratinocytes in response to several stimuli in vitro. RESULTS: Dermal fibroblasts produced eotaxin and eotaxin-3 in response to stimulation by interleukin (IL)-4 and/or tumor necrosis factor-alpha. Similarly, IL-4 stimulated epidermal keratinocytes to secrete eotaxin-3. However, we did not detect eotaxin mRNA expression or protein secretion by keratinocytes stimulated in vitro. Interferon (IFN)-gamma induced galectin-9 expression on dermal fibroblasts. Conversely, expression of galectin-9 on epidermal keratinocytes was dose-dependently inhibited by IFN-gamma. The immunohistochemical assays revealed that dermal fibroblasts (but not epidermal keratinocytes) in the lesional skin of psoriasis vulgaris (a Th1-polarized disease) express significant levels of galectin-9. CONCLUSION: Eotaxin-3 contributes to dermal and epidermal eosinophil infiltration in Th2-polarized skin inflammation in which IL-4 is produced. In contrast, IFN-gamma-dominated inflammation appears to mediate eosinophil extravasation into the dermis and eosinophil adhesion to dermal fibroblasts via galectin-9 in association with decreased chemoattractant activity of epidermal galectin-9. The present results reveal a novel mechanism of dermal eosinophilia in IFN-gamma-mediated skin inflammation, and reflect concerted chemoattractant production involving dermal and/or epidermal eosinophilia during changes in the local cytokine profile.     

Cytokine-regulated accumulation of eosinophils in inflammatory disease

The role of cytokines in the accumulation of eosinophil granulocytes in inflamed tissue has been studied extensively during recent years, and these molecules have been found to participate throughout the whole process of eosinophil recruitment. Haematopoietic cytokines such as IL-3, IL-5 and GM-CSF stimulate the proliferation and differentiation of eosinophils in the bone marrow, and the release of mature eosinophils from the bone marrow into the blood is probably promoted by IL-5. Priming of eosinophils in the blood following, for example, allergen challenge is performed mainly by IL-3, IL-5 and GM-CSF. An important step in the extravasation of eosinophils is their adhesion to the vascular endothelium. Adhesion molecules are upregulated by, e.g. IL-1, IL-4, TNF-alpha and IFN-gamma and the same cytokines may also increase the affinity of adhesion molecules both on eosinophils and endothelial cells. Finally, a number of cytokines have been shown to act as eosinophil chemotactic factors, attracting the cells to the inflammatory focus in the tissue. Some of the most important eosinophil chemoattractant cytokines are IL-5, IL-8, RANTES, eotaxin, eotaxin-2, eotaxin-3, MCP-3, MCP-4 and TNF-alpha. Th2 cells, mast cells and epithelial cells are important sources of proinflammatory cytokines, but in recent years, the eosinophils have also been recognized as cytokine-producing and thereby immunoregulatory cells. The aim of this paper is to review the role of cytokines in the process of eosinophil recruitment in asthma, allergy and ulcerative colitis.     

Comparison of platelet-activating factor-induced chemotaxis of normodense and hypodense eosinophils

Platelet-activating factor (PAF)-induced eosinophil (EOS) migration is an important event in the development of tissue eosinophilia and allergic inflammation. EOSs are heterogeneous cells in that different states of activation have been ascribed to EOSs of varying densities. We therefore studied the ability of PAF to induce hypodense and normodense EOS chemotaxis. Both hypodense and normodense EOSs were isolated in pure form from seven subjects and studied concurrently. Dose-response and time-course experiments indicated no significant differences in PAF-induced hypodense versus normodense EOS chemotactic responses. Hypodense and normodense cells achieved maximal chemotaxis in response to 1 mumol/L of PAF, and maximal chemotaxis was achieved at 2 hours. However, marked differences in PAF-induced EOS chemotactic responses existed between patients. We conclude that PAF is a potent EOS chemoattractant, and despite reported differences in metabolic activity, normodense and hypodense EOSs exhibit similar chemotactic responsiveness to PAF.     

Selective modulation of chemokinesis, degranulation, and apoptosis in eosinophils through the PGD2 receptors CRTH2 and DP.

BACKGROUND: PGD(2) is the major prostanoid released by mast cells during an allergic response. Its role in the allergic response, however, remains unclear. OBJECTIVE: Because the accumulation of eosinophils is a feature of allergic reactions, we investigated the role of PGD(2) in the modulation of eosinophil function. METHODS: Circulating human eosinophils were isolated and challenged with PGD(2). The effects of PGD(2) on various eosinophil functions were then analyzed. RESULTS: PGD(2) binds with high affinity preferentially to 2 receptors, DP and chemoattractant receptor-homologous molecule expressed on T(H)2 cells (CRTH2). We show that both DP and CRTH2 are detectable on circulating eosinophils. We demonstrate that PGD(2) (1-10 nmol/L) induces a rapid change in human eosinophil morphology and an increase in chemokinesis and promotes eosinophil degranulation. These effects are induced by the CRTH2-selective agonist 13-14-dihydro-15-keto-PGD(2) (DK-PGD(2)) but not by the DP-selective agonist BW245C. These results suggest a role for CRTH2 in the modulation of eosinophil movement and in triggering the release of cytotoxic proteins. Finally, we demonstrate that BW245C, but not DK-PGD(2), can delay the onset of apoptosis in cultured eosinophils, presumably through interaction with DP. CONCLUSION: These data support the hypothesis that PGD(2) controls eosinophil functions through 2 pharmacologically distinct receptors with independent functions. Blockade of PGD(2)-mediated effects on human eosinophils may reduce the damage caused by these cells during an allergic response, but inhibition of both receptors may be required.     

A recombinant topoisomerase I used for autoantibody detection in sera from patients with systemic sclerosis.

We reported three additional cases of a newly described syndrome called episodic angioedema with hypereosinophilia. In order to investigate its pathophysiological mechanisms, four parameters were concurrently investigated, including blood eosinophil density, serum chemoattractant activity, serum major basic protein (MBP) levels and the presence of anti-endothelial cell antibodies. Distribution of eosinophils through a metrizamide density gradient showed a preferential sedimentation of blood eosinophils in intermediate layers, clearly different from the hypodense cells (low-density layers) identified in a group of seven patients with idiopathic hypereosinophilic syndrome (HES). In two of the three patients with cyclic angioedema, a chemotactic activity towards eosinophils was detected in the serum (30 +/- 6 and 42 +/- 12 eosinophils per high-power field; P less than 0.05 compared with a control group). Serum MBP levels were at 1524, 619 and 1200 pg/ml. All three patients had circulating anti-endothelial cell antibodies, predominantly of the IgG isotype, in contrast to controls (P less than 0.01) or to patients with HES (P less than 0.01). Specificity of the antibody for endothelial cells was demonstrated in the three patients studied by the absence of binding to various blood cells, including monocytes, lymphocytes, eosinophils and platelets. In one case (patient 2), the levels of anti-endothelial cell antibodies, as well as the serum chemoattractant activity to eosinophils varied according to the successive acute phases of the disease. Although further investigations are needed to clarify the exact pathophysiology of this syndrome, and especially the possible participation of the anti-endothelial cell antibodies in the cutaneous lesions, these data suggest that angioedema observed in this syndrome could result from the combined effects of activated eosinophils and of immunologically induced endothelial lesions.     

Effect of a specific cysteinyl leukotriene-receptor 1-antagonist (montelukast) on the transmigration of eosinophils across human umbilical vein endothelial cells

BACKGROUND: Leukotrienes have been implicated in the selective infiltration of eosinophils into the bronchial mucosa in asthma. OBJECTIVE: We studied whether eosinophil transmigration through cultured human umbilical vein endothelial cells (HUVECs) can be blocked by a specific cysteinyl LT1-receptor-antagonist. METHODS: Unstimulated and stimulated eosinophils from patients with asthma and normal controls were subjected to confluent human umbilical vein endothelial cell (HUVEC) monolayers separating the upper and lower chamber of Transwell culture plates. Unstimulated eosinophils or cells pre-incubated in the presence of the eosinophil activating cytokines GM-CSF or IL-13 were placed in the upper chambers while PAF, a potent chemoattractant factor for eosinophils, was added to the lower chamber. Migration of eosinophils was quantified by a beta-glucuronidase assay. RESULTS: The assumption that eosinophils express CysLT1 (cysteinyl-leukotriene 1)-receptors was based on our demonstration of mRNA-expression for the CysLT-1-receptor by polymerase chain reaction on purified eosinophils. The chemotactic response to PAF was significantly reduced when eosinophils were pre-incubated with montelukast for 15 min. When eosinophils were pre-incubated with GM-CSF and/or IL-13, the migratory response to PAF was also significantly reduced by montelukast. CONCLUSION: From these data we conclude that the specific cysteinyl LT1-receptor antagonist montelukast can inhibit PAF-induced eosinophil transmigration through cultured HUVEC monolayers.