Eosinophil chemotactic factor-L (ECF-L) enhances osteoclast formation by increasing in osteoclast precursors expression of LFA-1 and ICAM-1

ECF-L is a novel autocrine stimulator of osteoclast (OCL) formation that enhances the effects of 1,25-(OH)2D3 and RANK ligand (RANKL) and is increased in inflammatory conditions such as rheumatoid arthritis. ECF-L acts at the later stages of OCL formation and does not increase RANKL expression. Thus, its mechanism of action is unclear. Therefore, RAW 264.7 cells and M-CSF-dependent murine bone marrow macrophage (MDBM) cells were treated with RANKL and/or with recombinant ECF-L expressed as a Fc fusion protein (ECF-L-Fc) to determine their effects on NF-kappaB, AP-1 and JNK activity, and on the expression of the adhesion molecules that have been implicated in OCL formation. These parameters were measured by semiquantitative and PCR and Western blot analysis. In addition, the role of ICAM-1 was further assessed by treating normal mouse marrow cultures with ECF-L-Fc and 10(-10) M 1,25-(OH)2D3 in the presence or absence of a blocking ICAM-1 antibody or treating marrow cultures from ICAM-1 knockout mice with ECF-L and 1,25-(OH)2D3. ECF-L-Fc by itself only modestly increased NF-kappaB binding and JNK activity in RAW 264.7 cells, which was further enhanced by RANKL. In contrast, ECF-L-Fc increased LFA-1alpha and ICAM-1 mRNA levels 1.8-fold in mouse marrow cultures, and anti-ICAM-1 almost completely inhibited OCL formation induced by 10(-10) M 1,25-(OH)2D3 and ECF-L. Furthermore, ECF-L did not increase OCL formation in marrow cultures from ICAM-1 knockout mice. Taken together, these results demonstrate that ECF-L enhances RANKL and 1,25-(OH)2D3-induced OCL formation by increasing adhesive interactions between OCL precursors through increased expression of ICAM-1 and LFA-1.

Toll-like receptor-2-mediated C-C chemokine receptor 3 and eotaxin-driven eosinophil influx induced by Mycobacterium bovis BCG pleurisy

An acute and persistent eosinophil infiltration is observed during Mycobacterium bovis BCG pleural infection in mice. Eosinophil accumulation, lipid body formation, and eotaxin production were significantly reduced in BCG-infected Toll-like receptor-2 (TLR2)-deficient mice compared to wild-type mice. Neutralization of eotaxin or CCR3 drastically inhibited BCG-induced eosinophil accumulation and lipid body formation, indicating that BCG-induced eosinophil recruitment and activation is largely dependent of TLR2-mediated eotaxin generation.

IL-16 activates plasminogen-plasmin system and promotes human eosinophil migration into extracellular matrix via CCR3-chemokine-mediated signaling and by modulating CD4 eosinophil expression

Increased eosinophil counts are a major feature of asthmatic airways. Eosinophil recruitment requires migration through epithelium and tissue extracellular matrix by activation of proteases. We assessed the capacity of IL-16, a CD4(+) cell chemotactic factor, to induce migration of eosinophils through a reconstituted basement membrane and evaluated the proteases, mediators, and receptors involved in this migration. IL-16 added to lower chambers of Invasion Chambers elicited eosinophil migration through Matrigel. This effect was decreased by inhibition of the plasminogen-plasmin system (Abs against urokinase plasminogen activator receptor or plasminogen depletion), but not by anti-matrix metalloproteinase-9 Abs. Abs against CD4 also inhibited IL-16-induced eosinophil migration. At the baseline level, few eosinophils (4.6% positive cells with a mean fluorescence of 0.9) expressed surface membrane CD4, while most permeabilized eosinophils (68% positive cells with a mean fluorescence of 18) express the CD4 Ag. TNF-pretreatment increased surface membrane CD4(+) expression by 6-fold as previously described, and increased IL-16-induced cell migration by 2.2-fold. Incubation of eosinophils with IL-16 also increased surface membrane CD4 expression by 5.4-fold, supporting the role of CD4 as receptor for IL-16. Abs against CCR3, eotaxin, or RANTES blocked IL-16-induced migration. In conclusion, IL-16 promotes eosinophil migration in vitro, by activating the plasminogen-plasmin system and increasing the membrane expression of its receptor. This effect is initiated via CD4 and mediated via the release of CCR3 ligand chemokines. Interestingly, most eosinophils express intracellular CD4. Hence, IL-16 may play an important role in the recruitment of blood eosinophils to the bronchial mucosa of asthmatics.

Antitumor activity of eosinophils activated by IL-5 and eotaxin against hepatocellular carcinoma

We examined the antitumor effects of eosinophils to explore the potential of eosinophils as effector cells in tumor cytotoxicity. We expressed eotaxin in hepatocellular carcinoma cells, MH134, and injected them into either normal or IL-5 TG mice intradermally and monitored cell growth. In normal mice, growth of MH134 cells containing the expression plasmid pCXN2-eotaxin was similar to that of vector-transfected MH134 cells for a period of 2 weeks, suggesting that expression of eotaxin does not change the growth rate of tumor cells. In IL-5 TG mice, however, the growth of eotaxin expressing MH134 cells was significantly suppressed. LPS induced eosinophils to produce TNF-alpha to kill MH134 cells in vitro. Intratumor injection of LPS is effective to kill MH134-pCXN2 and MH134-pCXN2-eotaxin only in normal mice. Administration of anti-CD4 or anti-CD8 antibodies suppressed growth of MH134-pCXN2-eotaxin cells compared with control antibodies, suggesting that T cells may interfere with immunity against MH134. Administration of anti-IL-5Ralpha and anti-asialo GM1 antibodies enhanced growth of MH134-pCXN2-eotaxin cells, suggesting involvement of eosinophils and NK cells in suppression of tumor cell growth. Although we cannot exclude the possibility that NK cells participate in tumor cell killing in vivo, the presence of NK markers such as DX5, asialo GM1, Ly49, and CD94, and NKG2D on large numbers of eosinophils activated by eotaxin suggests that eosinophils function in such suppression of tumor cell growth. Furthermore, we showed that anti-NKG2D antibodies could significantly inhibit the LPS-induced cytotoxicity against MH134 by highly enriched fraction of eosinophils.

Cutting Edge: Serotonin Is a Chemotactic Factor for Eosinophils and Functions Additively with Eotaxin

Elevated levels of serotonin (5-hydroxytryptamine, 5-HT) are observed in the serum of asthmatics. Herein, we demonstrate that 5-HT functions independently as an eosinophil chemoattractant that acts additively with eotaxin. 5-HT2A receptor antagonists (including MDL-100907 and cyproheptadine (CYP)) were found to inhibit 5-HT-induced, but not eotaxin-induced migration. Intravital microscopy studies revealed that eosinophils roll in response to 5-HT in venules under conditions of physiological shear stress, which could be blocked by pretreating eosinophils with CYP. OVA-induced pulmonary eosinophilia in wild-type mice was significantly inhibited using CYP alone and maximally in combination with a CCR3 receptor antagonist. Interestingly, OVA-induced pulmonary eosinophilia in eotaxin-knockout (Eot-/-) mice was inhibited by treatment with the 5-HT2A but not CCR3 receptor antagonist. These results suggest that 5-HT is a potent eosinophil-active chemoattractant that can function additively with eotaxin and a dual CCR3/5-HT2A receptor antagonist may be more effective in blocking allergen-induced eosinophil recruitment.

A new model for studying eosinophil migration across cultured intestinal epithelial monolayers

OBJECTIVE

Eosinophils play an important role in some gastrointestinal inflammatory conditions. Stimulated eosinophils migrate across the vascular endothelial wall and into the intestinal epithelium where by-products such as proteases may contribute to intestinal epithelial damage. Little is known about the epithelial migration of the eosinophils in the gut. The lack of data is attributable in part to the scarcity of human eosinophils for studies. HL-60-differentiated eosinophils present a means to perform studies on eosinophil function and chemotaxis. HL-60 clone 15 can be induced to differentiate into cells closely resembling human eosinophils. The authors describe a novel model for studying eosinophil migration across the intestinal epithelium.

METHODS

Fluorescent-labeled HL-60 eosinophils were incubated for 150 minutes on the basolateral surface of confluent and inverted T-84 monolayers separated by fluoroblock insert membranes. Chemotactic gradients of n-formyl methionyl leucyl phenylalanine (fMLP), eotaxin, and platelet aggregating factor (PAF) were used in variable concentrations. Changes in transepithelial electrical resistance (TEER) were compared with baseline values.

RESULTS

Differentiated HL-60 eosinophils undergo migration in response to fMLP, PAF, and eotaxin. Migration is associated with a drop in TEER.

CONCLUSION

In this model, HL-60-differentiated eosinophils migrate in response to stimulants chemotactic for human eosinophils. The transepithelial migration of eosinophils is associated with epithelial barrier dysfunction, which may contribute to the development of disease.

Chemokines in eosinophil-associated gastrointestinal disorders

Eosinophil-associated gastrointestinal disorders (EGDs) are characterized by a pronounced cellular inflammation. Recent clinical and experimental investigations have implicated a family of molecules known as chemokines in the regulation of leukocyte recruitment in these diseases. The underlying cellular and molecular mechanisms involved in chemokine-mediated cellular infiltration are largely unknown. In this review, we describe the role of CD4+ T cells and eosinophils in the clinical manifestations of EGDs and discuss the current understanding of the role of chemokines in the recruitment of these cells in the expression of diseases.

Variations in eosinophil chemokine responses: an investigation of CCR1 and CCR3 function, expression in atopy, and identification of a functional CCR1 promoter

We previously showed in a small group of donors that eosinophils from a subgroup of individuals responded equipotently to CC chemokine ligand (CCL)11/eotaxin and CCL3/macrophage-inflammatory protein-1alpha in assays of eosinophil shape change (CCL3/macrophage-inflammatory protein-1alpha-highly responsive (MHR) donors). In this study, we investigated the functional role of CCL3 in eosinophil responses in 73 donors. MHR donors, identified by their eosinophil shape change responses, represented approximately 19% of the donor pool. Eosinophils from these donors showed increased eosinophil CCR1 expression and also underwent CCL3-mediated chemotaxis and up-regulation of CD11b. All MHR donors gave a history of atopy-associated diseases. In a further study, we prospectively recruited 110 subjects, subdivided into nonatopics or atopics, and investigated expression of CCR1 and CCR3 on eosinophils, basophils, monocytes, and neutrophils. Eosinophil CCR1 expression was non-normally distributed in atopics, although higher CCR1 expression levels were not predictive of a diagnosis of atopy or atopic disease. We identified the CCR1 promoter and investigated its function. We found a minimal promoter within 177 bp of the transcription start site, and an upstream enhancer region that facilitated expression in leukocyte cell lines. Collectively, these data demonstrate that MHR individuals form an important subgroup that, when associated with a diagnosis of allergic disease, may require tailored therapy to modulate eosinophil recruitment. Identification of a functional CCR1 promoter will facilitate the study of possible genetic determinants underlying this potentially important clinical phenotype.

The role of CCL22 (MDC) for the recruitment of eosinophils during allergic pleurisy in mice

Eosinophils are important inflammatory cells in allergic diseases. In the present study, we have investigated the effects of CCL22 on the recruitment of eosinophils in vivo and in vitro. CCL22 induced a dose- and time-dependent recruitment of eosinophils into the pleural cavity of mice, and this was dependent on the release of platelet-activating factor (PAF) and subsequent generation of CCL11. However, in an allergic pleurisy model, an anti-CCL22 polyclonal antibody given during sensitization or before challenge had no significant effect on eosinophil recruitment. CCL22 did not induce eosinophil chemotaxis in vitro but was able to induce eosinophil degranulation in vitro and in vivo. In conclusion, we show that although exogenously added CCL22 may induce eosinophil migration in vivo via release of PAF and CCL11 (eotaxin), endogenous production of CCL22 does not drive eosinophil migration during allergic inflammation. However, CCL22 may be an important activator of eosinophils once these cells have migrated into tissue.

Selective eosinophil adhesion to fibroblast via IFN-gamma-induced galectin-9

Among galectin family members, galectin-9 was first described as a potent eosinophil chemoattractant derived from Ag-stimulated T cells. In the present study a role of galectin-9 in the interaction between eosinophils and fibroblasts was investigated using a human lung fibroblast cell line, HFL-1. RT-PCR, real-time PCR, and Western blot analyses revealed that both galectin-9 mRNA and protein in HFL-1 cells were up-regulated by IFN-gamma stimulation. On the one hand, IL-4, known as a Th2 cytokine, did not affect the galectin-9 expression in HFL-1 cells. We further confirmed that IFN-gamma up-regulated the expression of galectin-9 in primary human dermal fibroblasts. Flow cytometric analysis revealed that IFN-gamma up-regulated surface galectin-9 expression on HFL-1 cells. Stimulation of HFL-1 cells with IFN-gamma up-regulated adhesion of eosinophils, but not neutrophils, to HFL-1 cells. This adherence of eosinophils to HFL-1 cells was inhibited by both lactose and anti-galectin-9 Ab. These findings demonstrate that IFN-gamma-induced galectin-9 expression in fibroblasts mediates eosinophil adhesion to the cells, suggesting a crucial role of galectin-9 in IFN-gamma-stimulated fibroblasts as a physiological modulator at the inflammatory sites.

Experimental analysis of eosinophil-associated gastrointestinal diseases

Eosinophil infiltration into the gastrointestinal tract occurs in a wide range of diseases. However, the underlying cellular and molecular mechanisms involved in eosinophil migration and the role of eosinophils in disease pathogenesis are largely unknown. Recent studies using experimental models of eosinophil-associated gastrointestinal allergy have revealed differential roles for IL-5 and eotaxin in the modulation of eosinophil accumulation into various regions of the gastrointestinal tract. Furthermore, such studies have revealed a possible role for eosinophils in the pathogenesis of gastrointestinal disorders. The present review describes the clinical manifestations of various eosinophil-associated gastrointestinal disorders and the current understanding of the role of IL-5 and eotaxin in the allergic inflammatory response, and the participation of the eosinophilic granulocyte in the expression of disease.

Eotaxin (CCL11) induces in vivo angiogenic responses by human CCR3+ endothelial cells

Chemokines are attractants and regulators of cell activation. Several CXC family chemokine members induce angiogenesis and promote tumor growth. In contrast, the only CC chemokine, reported to play a direct role in angiogenesis is monocyte-chemotactic protein-1. Here we report that another CC chemokine, eotaxin (also known as CCL11), also induced chemotaxis of human microvascular endothelial cells. CCL11-induced chemotactic responses were comparable with those induced by monocyte-chemotactic protein-1 (CCL2), but lower than those induced by stroma-derived factor-1alpha (CXCL12) and IL-8 (CXCL8). The chemotactic activity was consistent with the expression of CCR3, the receptor for CCL11, on human microvascular endothelial cells and was inhibited by mAbs to either human CCL11 or human CCR3. CCL11 also induced the formation of blood vessels in vivo as assessed by the chick chorioallantoic membrane and Matrigel plug assays. The angiogenic response induced by CCL11 was about one-half of that induced by basic fibroblast factor, and it was accompanied by an inflammatory infiltrate, which consisted predominantly of eosinophils. Because the rat aortic sprouting assay, which is not infiltrated by eosinophils, yielded a positive response to CCL11, this angiogenic response appears to be direct and is not mediated by eosinophil products. This suggests that CCL11 may contribute to angiogenesis in conditions characterized by increased CCL11 production and eosinophil infiltration such as Hodgkin's lymphoma, nasal polyposis, endometriosis, and allergic diathesis.

Eotaxin and asthma

Eotaxin is a small protein that is produced in the lungs of asthmatic patients and is a potent chemoattractant for eosinophils. Eotaxin, a CC chemokine, stimulates the migration of eosinophils from the small blood vessels in the lungs by acting on the CC chemokine receptor CCR3, which is located on the leukocyte cell surface. In the past year, three low molecular weight compounds have been developed that can block this receptor. Such compounds may be developed into orally available drugs aimed at preventing eosinophil recruitment and, hence, the pathogenesis associated with the activation of these cells within the lung tissue.

Eotaxin and RANTES enhance 5-oxo-6,8,11,14-eicosatetraenoic acid-induced eosinophil chemotaxis

BACKGROUND

The 5-lipoxygenase product 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a potent activator of human eosinophils and, among lipid mediators, is the most active chemoattractant for these cells. Studies have demonstrated the importance of 5-lipoxygenase products in allergen-induced pulmonary eosinophilia. Because CC chemokines such as eotaxin and RANTES also play critical roles in this phenomenon, it would seem likely that members of both classes of mediators contribute to this response.

OBJECTIVE

The study was designed to directly compare the effects of 5-oxo-ETE on eosinophils with those of eotaxin and RANTES and to determine whether these chemokines could enhance the chemotactic response to 5-oxo-ETE.

METHODS

Eosinophil chemotaxis was measured with microchemotaxis chambers. CD11b, L-selectin, and actin polymerization were measured by flow cytometry. Calcium mobilization was measured by fluorescence.

RESULTS

5-Oxo-ETE stimulated eosinophil chemotaxis with a potency between those of eotaxin and RANTES and a maximal response about 50% higher than that of eotaxin. Threshold concentrations of eotaxin and RANTES increased the chemotactic potency of 5-oxo-ETE by more than 4-fold. 5-Oxo-ETE and eotaxin were approximately equipotent in mobilizing cytosolic calcium in eosinophils. Eotaxin was more potent in inducing CD11b expression and actin polymerization, but the maximal responses to 5-oxo-ETE were about 50% higher. 5-Oxo-ETE strongly induced L-selectin shedding, whereas eotaxin elicited only a weak and variable response.

CONCLUSION

5-Oxo-ETE is a strong activator of human eosinophils with a chemotactic potency comparable to those of eotaxin and RANTES, both of wwhich enhance 5-oxo-ETE-induced chemotaxis. 5-Oxo-ETE and CC chemokines may combine to induce pulmonary eosinophilia in asthma.

Evidence for a role for IL-5 and eotaxin in activating and recruiting eosinophils in drug-induced cutaneous eruptions

BACKGROUND

Cutaneous drug reactions may be associated with increased numbers of eosinophils in the blood and tissue. However, the factors leading to the generation of eosinophilia have not been fully delineated.

OBJECTIVE

The aim of this study was to investigate the in situ expression of IL-5, eotaxin, RANTES, monocyte chemoattractant protein 3, and IL-8 together with the appearance of eosinophils in acute cutaneous drug reactions.

METHODS

Skin biopsy specimens were obtained from drug-induced maculopapular exanthems (n = 9), from normal skin of control subjects (n = 9), and from the skin of patients with psoriasis (n = 8). The in situ expression of IL-5, eotaxin, RANTES, monocyte chemoattractant protein 3, and IL-8 was analyzed by using immunohistochemistry. Furthermore, the corresponding numbers of eosinophils were determined in the blood and skin sections.

RESULTS

Compared with normal skin and psoriatic skin, a significantly higher number of eosinophils was found both in the blood and tissue of patients with a drug-induced exanthem. In comparison with normal skin, immunoreactivity for IL-5 and all the chemokines was also significantly enhanced in drug-induced exanthem, whereas significant differences in psoriatic were only observed for IL-5 and eotaxin.

CONCLUSION

Our data indicate that IL-5 and eotaxin may particularly contribute to the activation and recruitment of eosinophils and thereby play an important pathogenic part in the development of skin inflammation in drug-induced maculopapular exanthems.

Eosinophils in the human corpus luteum: the role of RANTES and eotaxin in eosinophil attraction into periovulatory structures

We evaluated the presence and number of eosinophils at varying stages in the human corpus luteum from 27 ovaries of women at reproductive age. Eosinophils preferentially accumulated in dilated microvessels of the thecal layer transforming into septa of the corpus luteum. The granulosa layer under luteinization, the thecal layer, and haemorrhages in the former antrum each contained low, moderate and high numbers of extravasated eosinophils respectively. Eosinophils decreased rapidly during the stages of secretion and regression. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) systems were used to investigate the expression and regulation of the eosinophil-attracting chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and eotaxin in granulosa cells obtained from follicular aspirates from women undergoing IVF. Contaminating leukocytes were determined by CD18 mRNA quantification. Granulosa cells expressed RANTES (n = 3; 43 +/- 14 pg/ml, mean +/- SEM). 4ss-phorbol-12-myristate-13-acetate (PMA; 211 +/- 53) and tumour necrosis factor alpha (TNFalpha) (238 +/- 59), but not interleukin (IL)-1 up-regulated RANTES at significant levels. In general, higher basal and stimulated RANTES mRNA and protein were found in cultures with higher CD18 mRNA levels than in those with lower levels. We found only traces of eotaxin mRNA and no eotaxin secretion, even in stimulated granulosa cell cultures, independently of leukocyte levels. Taken together, this is the first study demonstrating the selective presence of eosinophils in human periovulatory structures. RANTES, but not eotaxin, may play an active process in the accumulation of these cells.

A critical role for eotaxin in experimental oral antigen-induced eosinophilic gastrointestinal allergy

Despite marked advances in the understanding of allergic responses, the mechanisms regulating gastrointestinal allergy are not very well understood. We have developed a model of antigen-induced eosinophil-associated gastrointestinal allergy and characterized the role of eotaxin and IL-5. Challenge of allergen-sensitized mice with oral allergen, in the form of enteric-coated beads, resulted in marked allergen-specific IgG(1) and IgE, Th(2)-type (IL-4 and IL-5) cytokine production, and eosinophil accumulation in the blood and small intestine. In the genetic absence of eotaxin, a chemokine constitutively expressed in the gastrointestinal tract, eosinophil recruitment into the small intestine was ablated, and these mice developed enhanced eosinophil accumulation in the blood compared with wild-type mice. Interestingly, in the absence of IL-5, allergen challenge promoted partial eosinophil accumulation into the small intestine and a decline in circulating eosinophil levels. Collectively, these results establish that the accumulation of gastrointestinal eosinophils is antigen induced, can occur independent of IL-5, and provides a molecular mechanism to explain the dichotomy between peripheral blood and tissue eosinophilia. Furthermore, eotaxin is identified as a critical regulator of antigen-induced eosinophilic inflammation in the gastrointestinal tract.

Effect of eotaxin and platelet-activating factor on airway inflammation and hyperresponsiveness in guinea pigs in vivo

Although eotaxin causes selective infiltration of eosinophils into the lung, its role in airway hyperresponsiveness remains unclear. We studied the effects of local administration of eotaxin on airway inflammation and hyperresponsiveness in guinea pigs in vivo. Airway responsiveness to inhaled histamine and differential cell counts in bronchoalveolar lavage fluid (BALF) were evaluated 12 h, 24 h, 3 d, and 7 d after intratracheal instillation of eotaxin. Significant eosinophilia in BALF was observed between 6 h and 7 d after eotaxin administration. Histologically, eosinophil accumulation was observed in the airways but not in the alveoli. In contrast, eotaxin did not affect airway responsiveness between 12 h and 7 d after its administration. We then studied the effects on airway responsiveness of subthreshold doses of interleukin 5, leukotriene D(4) (LTD(4)), and platelet-activating factor (PAF) combined with eotaxin. Neither interleukin 5 nor LTD(4) affected airway responsiveness. After eotaxin treatment, PAF significantly enhanced airway responsiveness without further increases in eosinophil counts. Eotaxin plus PAF significantly increased in eosinophil peroxidase activity in BALF compared with control and with eotaxin alone. These data indicate that eotaxin alone causes eosinophil accumulation in the airways but not hyperresponsiveness, and that additional factors such as PAF are needed to activate eosinophils for the development of airway hyperresponsiveness.

Eotaxin induces degranulation and chemotaxis of eosinophils through the activation of ERK2 and p38 mitogen-activated protein kinases

Eotaxin and other CC chemokines acting via CC chemokine receptor-3 (CCR3) are believed to play an integral role in the development of eosinophilic inflammation in asthma and allergic inflammatory diseases. However, little is known about the intracellular events following agonist binding to CCR3 and the relationship of these events to the functional response of the cell. The objectives of this study were to investigate CCR3-mediated activation of the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase-2 (ERK2), p38, and c-jun N-terminal kinase (JNK) in eosinophils and to assess the requirement for MAP kinases in eotaxin-induced eosinophil cationic protein (ECP) release and chemotaxis. MAP kinase activation was studied in eotaxin-stimulated eosinophils (more than 97% purity) by Western blotting and immune-complex kinase assays. ECP release was measured by radioimmunoassay. Chemotaxis was assessed using Boyden microchambers. Eotaxin (10(-11) to 10(-7) mol/L) induced concentration-dependent phosphorylation of ERK2 and p38. Phosphorylation was detectable after 30 seconds, peaked at about 1 minute, and returned to baseline after 2 to 5 minutes. Phosphorylation of JNK above baseline could not be detected. The kinase activity of ERK2 and p38 paralleled phosphorylation. PD980 59, an inhibitor of the ERK2-activating enzyme MEK (MAP ERK kinase), blocked phosphorylation of ERK2 in a concentration-dependent manner. The functional relevance of ERK2 and p38 was studied using PD98 059 and the p38 inhibitor SB202 190. PD98 059 and SB202 190 both caused inhibition of eotaxin-induced ECP release and chemotaxis. We conclude that eotaxin induces a rapid concentration-dependent activation of ERK2 and p38 in eosinophils and that the activation of these MAP kinases is required for eotaxin-stimulated degranulation and directed locomotion. (Blood. 2000;95:1911-1917)

Identification of a novel eosinophil chemotactic cytokine (ECF-L) as a chitinase family protein

A novel eosinophil chemotactic cytokine (ECF-L) was purified from the culture supernatant of splenocytes of mice by a combination of anion-exchange chromatography, Procion red-agarose affinity chromatography, size exclusion high performance liquid chromatography (HPLC), and reverse phase HPLC. The NH(2)-terminal amino acid sequence was determined by direct protein sequencing. An ECF-L cDNA clone of 1,506 nucleotides was isolated from a cDNA library, and the nucleotide sequence predicted a mature protein of 397 amino acids. A recombinant ECF-L showed a level of eosinophil chemotactic activity comparable with that of natural ECF-L, and the activity was inhibited by a monoclonal antibody to ECF-L. ECF-L also attracted T lymphocytes and bone marrow polymorphonuclear leukocytes in vitro, whereas it caused selective extravasation of eosinophils in vivo. ECF-L mRNA was highly expressed in spleen, bone marrow, lung, and heart. A comprehensive GenBank data base search revealed that ECF-L is a chitinase family protein. ECF-L retains those amino acids highly conserved among chitinase family proteins, but Asp and Glu residues essential for the proton donation in hydrolysis were replaced by Asn and Gln, respectively. Although ECF-L contains a consensus CXC sequence near the NH(2) terminus akin to chemokine family proteins, the rest of ECF-L shows poor homology with chemokines.

Effects of reactive oxygen and nitrogen metabolites on eotaxin-induced eosinophil chemotactic activity in vitro

Peroxynitrite, an oxidant generated by the interaction between superoxide and nitric oxide (NO), has been implicated in the etiology of numerous disease processes. Several studies have shown that peroxynitrite-induced protein nitration may compromise enzyme and protein function. We hypothesized that peroxynitrite may regulate cytokine function during inflammation. To test this hypothesis, the eosinophil chemotactic responses of eotaxin incubated with and without peroxynitrite were evaluated. Peroxynitrite attenuated eotaxin-induced eosinophil chemotactic activity (ECA) in a dose-dependent manner (P < 0.05). The inhibitory effects were not significant on ECA induced by leukotriene B(4) or complement-activated serum incubated with peroxynitrite. The reducing agents deferoxamine and dithiothreitol reversed the ECA inhibition by peroxynitrite, and exogenous L-tyrosine abrogated the inhibition by peroxynitrite. PAPA-NONOate (an NO donor) or a combination of xanthine and xanthine oxidase to generate superoxide did not show an inhibitory effect on ECA induced by eotaxin. In contrast, 3-morpholinosydnonimine, a peroxynitrite generator, caused a concentration-dependent inhibition of ECA by eotaxin. Consistent with its capacity to reduce ECA, peroxynitrite treatment reduced eotaxin binding to eosinophils. Nitrotyrosine was detected in the eotaxin incubated with peroxynitrite. These findings are consistent with nitration of tyrosine by peroxynitrite with subsequent inhibition of eotaxin binding to eosinophils and a reduction in ECA. These data demonstrate that peroxynitrite modulates the eosinophil migration by eotaxin, and suggest that oxidants may play an important role in regulation of eotaxin-induced eosinophil chemotaxis.

Activation of human eosinophil effector functions by CC chemokines

Different kinds of mediators, particularly chemokines, are responsible for the attraction and activation of eosinophils to the site of inflammation. In the last decade, this new family of chemotactic cytokines have become interesting because of their restricted target cell specificity. This article focuses on the activation of eosinophil effector functions in response to different CC chemokines.

Interleukin-5 involvement in ovalbumin-induced eosinophil infiltration in mouse food-allergy model

A number of studies demonstrating the important role of interleukin-5 (IL-5) in eosinophil infiltration were reported. Antigen-induced eosinophil infiltrations to the trachea and skin were inhibited by pretreatment with monoclonal anti-IL-5 antibody. In this study, the role of IL-5 in eosinophil infiltration to the gut by oral challenge in mice is investigated. A marked eosinophil infiltration to the lamina propria was induced by oral challenge with ovalubumin (OVA) in Balb/c mice intraperitoneally sensitized with OVA, and peaked at 6 h after the oral challenge. Intraperitoneal preadministration of monoclonal anti-IL-5 antibody significantly decreased the eosinophil infiltration to the lamina propria. Furthermore, analysis by reverse transcription polymerase chain reaction (RT-PCR) demonstrated that IL-5 mRNA expression was induced in the lamina propria in an antigen-specific manner and the expression peaked at 6 h and declined thereafter. In-situ hybridization (ISH) revealed the presence of IL-5 mRNA positive cells at lesion site. As in bronchial mucosa and skin, IL-5 may play an important role in eosinophil recruitment to the lesion site in IgE mediated gut late phase reaction.

A novel human CC chemokine, eotaxin-3, which is expressed in IL-4-stimulated vascular endothelial cells, exhibits potent activity toward eosinophils

IL-4 has been shown to be involved in the accumulation of leukocytes, especially eosinophils, at sites of inflammation by acting on vascular endothelial cells. To identify novel molecules involved in the IL-4-dependent eosinophil extravasation, cDNA prepared from HUVEC stimulated with IL-4 was subjected to differential display analysis, which revealed a novel CC chemokine designated as eotaxin-3. The human eotaxin-3 gene has been localized to chromosome 7q11.2, unlike most other CC chemokine genes. The predicted mature protein of 71 aa showed 27-42% identity to other human CC chemokines. The recombinant protein induced a transient increase in the cytosolic Ca2+ concentration and in vitro chemotaxis on eosinophils. Furthermore, in cynomolgus monkeys, the accumulation of eosinophils was observed at the sites where the protein was injected. Eotaxin-3 inhibited the binding of 125I-eotaxin, but not 125I-macrophage inflammatory protein-1alpha, to eosinophils and acted on cell lines transfected with CCR-3, suggesting that eotaxin-3 recognized CCR-3. IL-13 as well as IL-4 up-regulated eotaxin-3 mRNA in HUVEC, whereas neither TNF-alpha, IL-1beta, IFN-gamma, nor TNF-alpha plus IFN-gamma did. The expression profile of eotaxin-3 is different from those of eotaxin, RANTES, and monocyte chemoattractant protein-4, which are potent eosinophil-selective chemoattractants and are induced by either TNF-alpha or TNF-alpha plus IFN-gamma. These results suggest that eotaxin-3 may contribute to the eosinophil accumulation in atopic diseases.

Cytokines, chemokines, RANTES, and eotaxin

Over the past several years, a number of cytokines with chemoattractive properties (chemokines) have been identified. These low molecular weight molecules have been shown to be important leukocyte chemical attractants to sites of inflammation and infection. Chemokines act on leukocytes through selective receptors and are now known to function also in leukocyte maturation, trafficking, and homing of these cells. RANTES and eotaxin (among other chemokines) are important chemoattractants for eosinophils. Since eosinophils seem to play a critical role in the production of allergic inflammation, an understanding of the mechanism of action of these chemokines may lead to new therapies for asthma and other allergic processes.

Eotaxin activates T cells to chemotaxis and adhesion only if induced to express CCR3 by IL-2 together with IL-4

The transmigration and adherence of T lymphocytes through microvascular endothelium are essential events for their recruitment into inflammatory sites. In the present study, we investigated the expression of CC chemokine receptor CCR3 on T lymphocytes and the capacities of the CC chemokine eotaxin to induce chemotaxis and adhesion in T lymphocytes. We have observed a novel phenomenon that IL-2 and IL-4 induce the expression of CCR3 on T lymphocytes. We also report that CC chemokine eotaxin is a potent chemoattractant for IL-2- and IL-4-stimulated T lymphocytes, but not for freshly isolated T lymphocytes. Eotaxin attracts T lymphocytes via CCR3, documented by the fact that anti-CCR3 mAb blocks eotaxin-mediated T lymphocyte chemotaxis. In combination with IL-2 and IL-4, eotaxin enhances the expression of adhesion molecules such as ICAM-1 and several integrins (CD29, CD49a, and CD49b) on T lymphocytes and thus promotes adhesion and aggregation of T lymphocytes. The eotaxin-induced T lymphocyte adhesion could be selectively blocked by a specific cAMP-dependent protein kinase inhibitor, H-89, indicating that eotaxin activates T lymphocytes via a special cAMP-signaling pathway. Our new findings all point toward the fact that eotaxin, in association with the Th1-derived cytokine IL-2 and the Th2-derived cytokine IL-4, is an important T lymphocyte activator, stimulating the directional migration, adhesion, accumulation, and recruitment of T lymphocytes, and paralleled the accumulation of eosinophils and basophils during the process of certain types of inflammation such as allergy.

Effect of interleukin-3, interleukin 5 and hyaluronic acid on cultured eosinophils derived from human umbilical cord blood mononuclear cells

BACKGROUND

Several studies have shown that cultured eosinophils can be generated from human umbilical cord blood mononuclear cells (UCMC) in the presence of interleukin (IL)-3 and IL-5 in vitro. Other reports have indicated that cellular adhesion to hyaluronic acid (HA) enhances the proliferation of cultured eosinophils derived from CD34+ cells purified from UCMC. The aim of this study was to obtain large numbers of mature eosinophils from UCMC using IL-3, IL-5 and HA, and to investigate their functions.

METHODS

We examined several combinations of IL-3 and IL-5 and their effect on eosinophil development from UCMC in HA-coated on non-coated flasks. We also examined whether cultured eosinophils degranulated eosinophil-derived neurotoxin (EDN) induced by secretory immunoglobulin A conjugated to sepharose beads (sIgA-beads) and responded to eotaxin.

RESULTS

Culture with HA-coated flasks for 35 days (in the presence of IL-3 and IL-5, with IL-3 omitted after day 14 of culture) caused a 11.2-fold augmentation in the proliferation of UCMC. On day 35 of the culture, 98% of cultured cells were eosinophils judging from May-Grünwald and Giemsa staining and transmission electron micrographs. The EDN content of the cultured eosinophils on day 35 was 156 ng/105 cells. Cultured eosinophils degranulated EDN induced by sIgA-beads and responded to eotaxin by chemotaxis and intracellular Ca2+ mobilization.

CONCLUSION

We found a useful culture system to obtain large numbers of eosinophils derived from UCMC, which may facilitate the investigation of eosinophil function, since there was no significant difference in response to sIgA-beads and eotaxin between cultured and peripheral eosinophils.

Identification of a truncated form of the CC chemokine CK beta-8 demonstrating greatly enhanced biological activity

A new CC chemokine, designated CKbeta-8 or myeloid progenitor inhibitor factor-1, was recently identified in a large scale sequencing effort and was cloned from a human aortic endothelial library. CKbeta-8 cDNA encodes a signal sequence of 21 amino acids, followed by a 99-amino acid predicted mature form. CKbeta-8 was expressed and purified from a baculovirus insect cell expression system, which resulted in the identification of different N-terminal variants of the secreted chemokine. The three major forms (containing amino acids 1-99, 24-99, and 25-99 of the secreted chemokine) showed a large variation in potency. CKbeta-8 activated both monocytes and eosinophils to mobilize intracellular calcium; however, the shortest form of CKbeta-8 (25-99) was >2 orders of magnitude more potent than the longest form. Cross-desensitization experiments in both monocytes and eosinophils suggested that the CCR1 receptor was probably the predominant receptor that mediates this chemokine's physiologic response. However, incomplete desensitization was encountered in both cell systems, suggesting involvement of an additional receptor(s). Interestingly, the short form of CKbeta-8 was the most potent chemotactic chemokine that we have ever evaluated in the monocyte system (EC50 = 54 pM). However, in contrast to its action on monocytes, CKbeta-8 was a very poor chemotactic factor for eosinophils.

Molecular and biological characterization of the murine leukotriene B4 receptor expressed on eosinophils

The movement of leukocytes into tissues is regulated by the local production of chemical mediators collectively referred to as chemoattractants. Although chemoattractants constitute a diverse array of molecules, including proteins, peptides, and lipids, they all appear to signal leukocytes through a related family of seven transmembrane-spanning G protein-coupled receptors. The eosinophil is a potent proinflammatory cell that is attracted into tissues during allergic inflammation, parasitic infection, and certain malignancies. Since the molecular mechanisms controlling eosinophil recruitment are incompletely understood, we performed a degenerate polymerase chain reaction on cDNA isolated from murine eosinophils to identify novel chemoattractant receptors. We report the isolation of a cDNA that encodes a 351-amino acid glycoprotein that is 78% identical to a human gene that has been reported to be a purinoceptor (P2Y7) and a leukotriene B4 (LTB4) receptor (BLTR). Chinese hamster ovary (CHO) cells transfected with this cDNA specifically bound [3H]LTB4 with a dissociation constant of 0.6 +/- 0.1 nM. Furthermore, LTB4 induced a dose-dependent intracellular calcium flux in transfected CHO cells. In contrast, [35S]dATP did not specifically bind to these transfectants. This mRNA was expressed at high levels in interleukin 5-exposed eosinophils, elicited peritoneal macrophages and neutrophils, and to a lesser extent interferon gamma stimulated macrophages. Low levels of expression were detected in the lung, lymph node, and spleen of unchallenged mice. Western blot analysis detected the mBLTR protein in murine eosinophils and alveolar macrophages as well as human eosinophils. In addition, elevated levels of mBLTR mRNA were found in the lungs of mice in a murine model of allergic pulmonary inflammation in a time course consistent with the influx of eosinophils. Our findings indicate that this murine receptor is an LTB4 receptor that is highly expressed on activated leukocytes, including eosinophils, and may play an important role in mediating eosinophil recruitment into inflammatory foci.

Triple role of platelet-activating factor in eosinophil migration across monolayers of lung epithelial cells: eosinophil chemoattractant and priming agent and epithelial cell activator

Infiltration of eosinophils into the lung lumen is a hallmark of allergic asthmatic inflammation. To reach the lung lumen, eosinophils must migrate across the vascular endothelium, through the interstitial matrix, and across the lung epithelium. The regulation of this process is obscure. In this study, we investigated the migration of human eosinophils across confluent monolayers of either human lung H292 epithelial cells or primary human bronchial epithelial cells. Established eosinophil chemoattractants (IL-8, RANTES, platelet-activating factor (PAF), leukotriene B4, and complement fragment 5a (C5a)) or activation of the epithelial cells with IL-1beta induced little eosinophil transmigration (<7% in 2 h). In contrast, addition of PAF in combination with C5a induced extensive (>20%) transepithelial migration of unprimed and IL-5-primed eosinophils. Eosinophil migration assessed in a Boyden chamber assay, i.e., without an epithelial monolayer, was only slightly increased upon addition of PAF and C5a. Preincubation of eosinophils with the PAF receptor antagonist WEB 2086 only inhibited migration of unprimed eosinophils toward PAF and C5a, whereas preincubation of epithelial cells with WEB 2086 abolished migration of both IL-5-primed and unprimed eosinophils. This latter result indicated the presence of PAF receptors on epithelial cells. Indeed, addition of PAF to epithelial cells induced an increase in cytosolic free Ca2+, which was blocked by the PAF receptor antagonists WEB 2086 and TCV-309. Our results show that PAF induces permissive changes in epithelial cells, and that PAF acts as a chemoattractant and priming agent for the eosinophils.

Eotaxin modulates myelopoiesis and mast cell development from embryonic hematopoietic progenitors

Eotaxin is a potent chemoattractant for eosinophils during inflammation and allergic reactions in the adult, but its role in the embryonic development of the hematopoietic system has not been examined. We report here that eotaxin and its receptor, CCR-3, are expressed by embryonic tissues responsible for blood development, such as fetal liver (FL), yolk sac (YS), and peripheral blood. We found that eotaxin acts synergistically with stem cell factor to accelerate the differentiation of embryonic mast cell progenitors, and this response can be suppressed by pertussis toxin, an inhibitor of chemokine-induced signaling through Gialpha protein and chemotaxis. Eotaxin promotes the differentiation of fetal mast cell progenitors into differentiated mast cells as defined by the expression of mast cell specific proteases. Furthermore, in combination with stem cell factor (SCF), it promotes the growth of Mac-1(+) myeloid cells from embryonic progenitors. These studies suggest that eotaxin may be involved in the growth of granulocytic progenitors and the differentiation and/or function of mast cells during embryogenesis and/or pathological conditions that induce high levels of eotaxin, such as allergic responses.

Production of eosinophil chemotactic factor by CD8+ T-cells in Toxocara canis-infected mice

Production of eosinophil chemotactic factor by T-lymphocytes (ECF-L) was examined in Toxocara canis-infected mice. When spleen cells from T. canis-infected mice were cultured in serum-free RPMI1640, ECF-L production was detectable in an antigen-specific manner. The ECF-L production peaked at day 9 post-infection and then decreased. Depletion of Thy 1.2+ cells or CD8+ cells completely abrogated ECF-L production, whereas depletion of CD4+ cells did not, indicating that CD8+ T-cells are involved in the production of ECF-L. When bone marrow eosinophils obtained from T. canis-infected mice were preincubated with ECF-L, their chemotactic reactivity to parasite-derived ECFs was enhanced, whereas that of peritoneal cavity-derived eosinophils was not. Thus, ECF-L seems to be important not only as a chemoattractant but also as an activator of the chemotactic reactivity of naive eosinophils to the parasite-derived ECF in T. canis infection.

Modulation of eosinophil chemotactic activities to leukotriene B4 by n-3 polyunsaturated fatty acids

Eosinophil accumulation induced by leukotriene B4 appears to be involved in the pathogenesis of allergic diseases. We evaluated the effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on chemotaxis to leukotriene B4 in guinea pig peritoneal eosinophils. Guinea pigs that were sensitized to polymyxin B were administered an intraperitoneal injection of polymyxin B (1 mg/animal) alone or combined with DHA (15 or 50 mg/kg, i.p.), EPA (50 or 100 mg/kg, i.p.), or with linoleic acid (LA) (100 mg/kg, i.p.). Forty hours later, eosinophils were obtained from the intraperitoneal lavage fluid and purified. The chemotactic and chemokinetic responses of eosinophils to leukotriene B4 were measured using a 96-well microchemotaxis chamber. DHA significantly decreased the chemotactic and chemokinetic responses of eosinophils in a dose-dependent fashion. A higher dose of EPA also significantly inhibited both of those responses, whereas LA had no effect. Our results suggested a possible mechanism for the improvement of allergic diseases by dietary supplementation with n-3 PUFA.

P-selectin, L-selectin, and alpha 4 integrin have distinct roles in eosinophil tethering and arrest on vascular endothelial cells under physiological flow conditions

The adhesive interactions of eosinophils with purified E-, P-, and L-selectins; vascular cell adhesion molecule-1 molecule; and HUVEC were examined in shear flow. Compared with neutrophils, eosinophils showed markedly less binding to E-selectin, but significantly stronger avidity for P-selectin. Both cell types showed a similar level of tethering and rolling on L-selectin. Eosinophils tethered and arrested abruptly on vascular cell adhesion molecule-1. However, some of the tethers were detached within several seconds; this was prevented by stimulation with eotaxin. Eosinophils also showed immediate arrest on HUVEC stimulated with 100 U/ml TNF-alpha for 6 h. Treatment with L-selectin mAb decreased eosinophil accumulation on the HUVEC by abrogating secondary tethers through interactions between flowing and attached eosinophils. mAb to P-selectin but not to E-selectin strongly inhibited primary tethers and accumulation of eosinophils. mAb to the integrin alpha 4 subunit inhibited arrest, induced rolling or detachment of tethered eosinophils, and resulted in partial reduction of eosinophil accumulation. mAb to the integrin beta 2 subunit had only a slight effect, whereas treatment with mAb to the integrin alpha 4 and beta 2 subunits together abolished rolling interactions as well as arrest, and thus almost totally inhibited eosinophil accumulation. Our data indicate that P-selectin, but not E-selectin, is directly involved in eosinophil tethering on inflammatory endothelium while L-selectin mainly mediates intereosinophil interaction. VLA-4 has a crucial role in eosinophil arrest, and arrest is enhanced by exposure to chemoattractants.

Airway hyperresponsiveness: first eosinophils and then neuropeptides

Airway hyperreactivity to bronchoconstrictor mediators is a main characteristic in the majority of asthmatic patients and correlates well with the severity of the disease. The airways of asthmatic patients are characterized by an inflammatory state resulting in activation of lung tissue cells and attraction and infiltration of leukocytes from the blood. The accumulation of eosinophilic leukocytes is a prominent feature of inflammatory reactions that occurs in allergic asthma. The increase in number of eosinophils is important since it correlates in time with an increase in bronchial hyperresponsiveness. Viral respiratory infections can also induce eosinophilia and airway hyperresponsiveness in humans and animals and can worsen asthmatic reactions. This report reviews current opinions on the relationship between inflammation-induced eosinophil accumulation/activation and the development of airway hyperresponsiveness and the possible role for sensory neuropeptides in this process. Firstly, CC chemokines play an important role in allergic airway inflammation and respiratory viral infections leading to eosinophil recruitment. Secondly, it can be concluded that IL5 is involved in the development in airway hyperresponsiveness. IL5 has profound effects on eosinophils as promoter of growth, differentiation and proliferation, chemoattractant, activator and primer. However, it is conceivable that in animal models for allergic asthma besides IL5 other regulatory mediators may be involved in eosinophil migration and activation in the lung, which in turn will lead to airway hyperresponsiveness. Recent data support the possible role of eotaxin and its eosinophil-specific receptor CCR-3 in eosinophil chemotaxis and activation in allergic asthma. Moreover, it is suggested that the development of airway eosinophilia in vivo involves a two-step mechanism, elicited by eotaxin and IL5. The precise mechanism by which eosinophils induce bronchial hyperresponsiveness is at present unknown. Sensory neuropeptides could be important mediators in this process, since it has been demonstrated that airway nerves are surrounded by and infiltrated with eosinophils after antigen challenge. Sensory neuropeptides could be the final, more downstream, common pathway after eosinophil infiltration and activation in inducing airway hyperresponsiveness due to allergen inhalation or respiratory viral infections. In conclusion, in the process of the development of airway hyperresponsiveness observed during viral infections or in allergic asthma, the IL5/eotaxin-induced infiltration and activation of eosinophils in the airways is evident. Following this step, eosinophil-derived inflammatory mediators will induce the release of sensory neuropeptides (possibly NK2-receptor activating tachykinins) which in turn will lead to airway hyperresponsiveness.

Enhancement of intestinal eosinophilia during Hymenolepis nana infection in mice

The ability of Hymenolepis nana oncosphere extract to induce eosinophil chemotactic response was examined in vitro and in vivo. The extract showed a chemotactic activity specific for eosinophils but not for neutrophils. Partially purified eosinophil chemotactic factors (ECFs) from the oncosphere extract showed apparent molecular mass from 5.5 to 9.6kDa and 30 to 40kDa. These were resistant to heating and proteinase K digestion but sensitive to periodate oxidation. Peritoneal injection of the crude extract or partially purified ECFs to mice resulted in a preferential eosinophil infiltration. The chemotactic activity for eosinophils was not separable from the adhesion molecule expression or oxygen radical-inducing activity by means of chromatography or chemical treatments. Furthermore, histological examination demonstrated a marked tissue eosinophilia around H. nana larvae in the intestinal lamina propria of both humoral and cell-mediated immunodeficiency mice. The present findings suggest that H. nana oncosphere-derived molecules facilitate in vivo the intestinal eosinophilia during the infection.

Human eosinophils express messenger RNA encoding RANTES and store and release biologically active RANTES protein

Eosinophils synthesize and store various cytokines with potential autocrine activity. We hypothesized that eosinophils synthesize and store RANTES, a CC-chemokine with potent eosinophil chemotactic activity. Expression of RANTES mRNA in highly purified eosinophil populations was detected by reverse transcription followed by polymerase chain reaction analysis. In situ hybridization (ISH) with 35S-labeled RANTES-specific riboprobes showed that 6.8-10% of peripheral blood eosinophils obtained from atopic subjects expressed RANTES mRNA, increasing to 25% after incubation (16 h) with interferon (IFN)-gamma, but not ionomycin in vitro. Peripheral blood eosinophils also showed specific immunoreactivity with an anti-RANTES monoclonal antibody, consistent with translation of the mRNA. By enzyme-linked immunosorbent assay, blood eosinophils were shown to contain a median of 7300 pg (range 5200-8800) RANTES per 10(6) cells, of which a mean of 24% was released into culture supernatants after stimulation of the cells with serum-coated particles in vitro. These culture supernatants exhibited eosinophil chemotactic activity which was inhibited (mean 68%) by a specific anti-RANTES antibody. Sequential immunocytochemistry and ISH on biopsies obtained from allergen-induced late-phase cutaneous reactions showed that 55-75% of the infiltrating RANTES mRNA+ cells were EG2+ eosinophils. Allergen, but not diluent challenge, was also associated with a time-dependent increase in the number of cells showing RANTES immunoreactivity. Of these cells, 55% were identified as eosinophils by morphological criteria. Thus, human eosinophils have the capacity to synthesize, store and secrete physiologically relevant quantities of RANTES, and may therefore be an important source of this chemokine in allergic inflammation.

Role of eosinophil-chemotactic C-C chemokines in cutaneous inflammation

In the dermal sites of atopic skin, eosinophil (Eo) granule protein or more rarely intact Eos represent a characteristic histological feature. We addressed the question of whether lesional scales of patients with various eosinophilic skin disorders contain Eo attractant and tried to characterize it biochemically. In scales of a patient with drug reaction, heparin-binding Eo attractants could be identified. High-performance liquid chromatographic analyses together with specific ELISA and Western blot analyses revealed identity with RANTES. No other heparin-binding Eo chemotaxin could be identified. HPLC analysis of pooled lesional scale extracts of patients with atopic dermatitis showed fractions containing only weak heparin-binding Eo-chemotactic activity, which, however, showed RANTES immunoreactivity. In experiments to elucidate the putative cellular origin of Eo-attracting chemokines in human skin we investigated supernatants of atopic skin we investigated supernatants of atopic skin-derived T lymphocytes as well as supernatants of stimulated dermal fibroblasts for Eo-chemotactic factors. Unexpectedly, we did not find any heparin-bound Eo attractants in supernatants of stimulated cultured atopic skin-derived T lymphocyte clones, whereas fibroblasts produced RANTES as well as granulocyte-macrophage colony-stimulating factor. Therefore, fibroblasts are likely source of eosinophil attractant cells, which could contribute to the Eo infiltrate. Selectivity of the infiltrate might come from selective induction of RANTES and/or induction of other as yet unidentified Eo-specific chemokines.

Heterogeneity of eosinophils in chronic eosinophilic pneumonia

It has previously been shown that patients with chronic eosinophilic pneumonia can be divided into 2 groups according to the chemotactic response of their eosinophils to 5 different eosinophil chemotactic factors (ECFs) and laboratory findings. In contrast, eosinophils obtained by bronchoalveolar lavage from both groups responded to all 5 ECFs. The correlation between the two groups and the expression of several antigens (VLA-4, CD69, ICAM-1 and CD11b) on eosinophils. The VLA-4 expression of group 1 eosinophils was higher than that of group 2 eosinophils. More interestingly, eosinophils that migrated towards ECF-PI9 expressed less CD69 than those that migrated towards other STO-2-derived ECF. The heterogeneous response of eosinophils to STO-2-derived ECFs suggests that the population of eosinophils is heterogeneous.

Heterogeneous chemotactic response of eosinophils from patients with atopic dermatitis to eosinophil chemotactic factors

The chemotactic response of eosinophils from 16 patients with atopic dermatitis (AD) to 5 eosinophil chemotactic factors (ECFs) were examined to clarify whether the response is associated with the clinical severity of AD. The factors included ECF-P15, -P16, -P17, -P18 and -P19 and were derived from a T cell line, STO-2. The patients were divided into 2 groups according to the percentage migration of eosinophils produced by the ECFs: a high-responding group (migration > 40%), and a low-responding group (migration < 30%). In a statistical analysis, eosinophils from patients with AD and atopic respiratory diseases (ARD) were found to be high-responding and those from patients with AD alone low-responding (p < 0.01). In a comparison of the chemotactic response of eosinophils from patients with AD alone at remission and at exacerbation, the percentage migrations in response to ECF-P15 and ECF-P16 at exacerbation were significantly higher than that at remission (p < 0.05). It is thus suggested that this type of heterogeneous response of eosinophils to STO-2-derived ECFs could provide a useful tool for evaluation of disease severity in patients with AD.

Chemotactic agonists induce cytokine generation in eosinophils

Recent studies have shown that eosinophils are capable of generating and releasing cytokines, providing a novel biologic aspect of eosinophils for regulating allergic inflammation by an autocrine or paracrine mechanism. Eosinophils synthesize various cytokines; however, the physiologic stimuli that trigger eosinophils to generate cytokines have not been fully elucidated. We examined the effect of chemotactic agonists on eosinophil cytokine generation by employing the determination of IL-8 as the main parameter. Both C5a and FMLP stimulated eosinophils to release IL-8, whereas platelet-activating factor and C-C chemokines did not exert any significant effects. On a molar basis, C5a was two orders of magnitude more potent than FMLP. The generation of IL-8 by chemoattractants was absolutely dependent on the presence of cytochalasin B. Pertussis toxin completely attenuated C5a- and FMLP-induced IL-8 production, indicating the involvement of pertussis toxin-sensitive G-proteins in the signal-transduction process leading to these responses. Experiments of in situ hybridization and PCR amplification revealed that both C5a and FMLP promoted eosinophil IL-8 production through transcriptional gene activation. Pyrrolidine dithiocarbamate completely abrogated chemoattractant-induced IL-8 production, indicating the involvement of NF-kappa B in the cytoplasmic/nuclear signal-transduction process. Furthermore, chemoattractant-induced cytokine production was not limited to IL-8; C5a and FMLP but not platelet-activating factor induced significant secretion of granulocyte-macrophage-CSF from eosinophils. These results indicate that C5a and FMLP stimulate eosinophils to elaborate cytokines, which could be an important mechanism in the regulation of allergic inflammation.

IL-5 accounts for the mouse pleural eosinophil accumulation triggered by antigen but not by LPS

The involvement of interleukin-5 (IL-5) in the pleural eosinophilia induced by LPS or allergen was investigated. The number of pleural eosinophils in actively sensitized mice increased 24 h after the intrathoracic (i.t.) injection of ovalbumin (12 mg/cavity), peaked within 72 h, and persisted significantly increased for at least 120 h. Despite being less intense, the i.t. injection of LPS (250 ng/cavity) also increased the number of pleural eosinophils at 24 h, returning to basal levels within 72 h. Intraperitoneal pretreatment with monoclonal antibody to IL-5 (TRFK-4 and TRFK-5, 500 mg/kg) suppressed the eosinophil accumulation induced by IL-5 (200 units/cavity) or ovalbumin, but had no effect on the LPS-induced eosinophilia. Transfer of the cell-free pleural washing from LPS-treated donor mice to naive recipient animals led to a selective increase in the eosinophil counts. The co-incubation of the pleural washing from LPS-treated animals with monoclonal antibody to IL-5 failed to modify the phenomenon. The results indicate that IL-5 plays an important role in the antigen-induced accumulation of eosinophils in vivo, but not in the eosinophilia triggered by LPS.

Selective regulation of chemotactic lymphokine production by monocytes and macrophage cell line cells

Effects of lipopolysaccharides (LPS) on the production of chemotactic lymphokines for eosinophils and monocytes (ECF and MCF) from antigen- or mitogen-stimulated T cells were examined. Supernatants from monocytes stimulated with various LPS regulated concanavalin A (Con A)- and purified protein derivative (PPD)-induced ECF or MCF production. The regulation varied with LPS used for monocyte stimulation. The supernatant from monocytes stimulated with LPS from Escherichia coli, J-5 strain, selectively potentiated ECF production, whereas that from Salmonella minesota potentiated MCF production. In contrast, supernatant from monocytes stimulated with LPS from Salmonella typhimurium potentiated both ECF and MCF production, whereas that from Vibrio cholerae failed to potentiate production. The supernatants from monocytes stimulated with lipid A of S. typhimurium, S. minesota, and E. coli, however, failed to potentiate ECF and MCF production. The potentiating activity for each lymphokine was recovered from fractions ranging in molecular weight between 10 and 20 kD. Further purification with isoelectric electrophoresis revealed that the potentiating activity for the production of chemotactic lymphokine for eosinophils has a pI value of about 4-5, and that the activity for MCF production is detected in two fractions of pI about 5-6, and 7-8. Macrophage lineage cell line cells, such as THP-1 and U-937, also release similar factors after differential stimulation.

Mechanism of eosinophil infiltration in the patient with subcutaneous angioblastic lymphoid hyperplasia with eosinophilia (Kimura's disease). Mechanism of eosinophil chemotaxis mediated by candida antigen and IL-5

Kimura's disease is a chronic granulomatous disease of unknown etiology. Although eosinophilia is one of the characteristic features in this disease, little is known about the mechanism of eosinophilia. In the present study it was demonstrated that interleukin-5 (IL-5) was produced and released from the site of a granuloma and lymph nodes after stimulation with candida antigen. It was also shown that peripheral blood eosinophils from patients with Kimura's disease contained a large proportion of hypodense eosinophils and that their viability was prolonged. These results strongly suggest that locally produced IL-5 induced by candida antigen contributes to the eosinophilia in this disease.

Chemotactic heterogeneity of eosinophils in Kimura's disease

We evaluated the chemotactic heterogeneity of eosinophils in Kimura's disease. Patients with Kimura's disease were divided into two groups according to their clinical findings: one group had no other symptoms (KD), and another was accompanied with atopic dermatitis (KD + AD). The chemotactic response of eosinophils from two groups to 5 eosinophil chemotactic factors (ECF) derived from STO-2, an established T cell line. Eosinophils from KD were attracted only by ECF-PI5 and PI6 but not by ECF-PI7, PI8 and PI9. On the other hand, eosinophils from KD + AD responded to all 5 ECF. Eosinophils were further fractionated into normodense and hypodense eosinophils, and assessed for their chemotactic response. We thus found that there was little essential difference in their chemotactic responses to STO-2-derived ECF except ECF-PI9, though random migration of hypodense eosinophils was enhanced. The hypothesis that hypodense eosinophils are in the activated form was not always true, especially in the chemotactic response to ECF.