Human eosinophils have prolonged survival, enhanced functional properties, and become hypodense when exposed to human interleukin 3

Distinct role of IL-3 promoter and enhancer region in murine mast cells

Crosslinking of Fcvarepsilon receptor on mast cells induces IL-3 gene expression with the concentration dependent of intracellular calcium, but its regulatory mechanism remains unclear. Here, we found that phorbol 12-myristate 13-acetate (PMA) alone did not induce IL-3 gene expression, but potentiated A23187-induced IL-3 gene expression. Interestingly, the A23187-induced IL-3 promoter activity was suppressed by PMA, but it was enhanced when IL-3 promoter contained enhancer region, a DH site. While IL-3 mRNA expression was increased by A23187 and PMA in a dose-dependent manner, the promoter activity appeared all or none in all doses of A23187 and PMA. IL-3 promoter region between -293 and -150bp was responsible for A23187-induced gene expression and PMA- or cyclosporin A (CsA)-mediated suppression. Taken together, IL-3 gene expression was primarily regulated at the transcriptional level, which was differentially controlled by a restricted promoter and enhancer region.

Interleukin-3 and c-Kit/stem cell factor are required for normal eosinophil responses in mice infected with Strongyloides venezuelensis

To evaluate the potential roles of Interleukin-3 (IL-3) and c-Kit, the tyrosine kinase receptor for stem cell factor (SCF), in eosinophil responses in vivo, we examined eosinophil numbers in uninfected or nematode-infected wild-type mice, IL-3-/- mice, and IL-3-/- mice that also have a marked reduction in SCF/c-Kit signaling (ie, Kit(W)/Kit(W-v), IL-3-/- mice). We found no significant differences in the numbers of eosinophils in the blood, bone marrow or various tissues of IL-3-/- vs IL-3+/+ mice, either at baseline or after the induction of bone marrow, blood or tissue eosinophilia in response to infection with Strongyloides venezuelensis (S.v.) or Nippostrongylus brasiliensis (N.b.). However, in mice with markedly impaired SCF/c-Kit signaling, IL-3 contributed significantly to the increased numbers of eosinophils that were observed in multiple tissues during S.v. infection, but not during infection with N.b.

CD48 is an allergen and IL-3-induced activation molecule on eosinophils

Eosinophils are involved in a variety of allergic, parasitic, malignant, and idiopathic disorders by releasing a variety of factors including specific granule proteins, lipid mediators, and proinflammatory and immunoregulatory cytokines and chemokines. In addition, they interact with various cell types in the inflamed tissue. Yet, the mechanism of eosinophil activation is still poorly understood. Recently, we described the expression and function of the CD2-subfamily of receptors and especially 2B4 on human eosinophils. In this study we focus on CD48, the high-affinity ligand of 2B4. CD48 is a GPI-anchored protein involved in cellular activation, costimulation, and adhesion, but has not been studied on eosinophils. We demonstrate that human eosinophils from atopic asthmatics display enhanced levels of CD48 expression and that IL-3 up-regulates CD48 expression. Furthermore, cross-linking CD48 on human eosinophils triggers release of eosinophil granule proteins. Assessment of CD48 expression in a murine model of experimental asthma revealed that CD48 is induced by allergen challenge and partially regulated by IL-3. Additionally, anti-IL-3 reduces CD48 expression and the degree of airway inflammation. Thus, CD48 is an IL-3-induced activating receptor on eosinophils, likely involved in promoting allergic inflammation.

[Activated eosinophils: techniques to characterize them]

The deleterious role thought to be played by eosinophils in many situations is linked to their ability to secrete various inflammatory substances, mainly toxic proteins and lipid mediators, in body tissue. This ability is a particular feature of activated eosinophils, which have undergone numerous metabolic, functional, and phenotypic changes from their resting state. Characterizing the properties of these activated cells is an essential step in improving our understanding of their contributions to local inflammatory response, as both regulatory and effector cells. Improvements in existing methods as well as the development of new technical approaches have facilitated the ex vivo and in vitro study of activated eosinophils and their contribution to various disease states.

High expression of eosinophil chemoattractant ecalectin/galectin-9 in drug-induced liver injury

BACKGROUND

Ecalectin/galectin-9 (ECL/GL9) is an eosinophil chemoattractant isolated from T lymphocytes. Drug-induced liver injury (DILI), often caused by an allergic mechanism, is occasionally accompanied by eosinophilic infiltration. In this study, we intended to determine whether DILI can induce augmentation of ECL/GL9 expression. Further, we investigated whether this augmentation is associated with tissue eosinophilia.

METHODS

We examined the expression of ECL/GL9 in biopsy specimens of DILI using the immunohistochemical technique. A rabbit anti-ECL/GL9 antibody was produced by immunizing rabbits with synthetic peptide corresponding to a molecular epitope of ECL/GL9. Thereafter, immunohistochemical staining with the use of this antibody was performed on 16 DILI needle biopsy specimens, and on biopsy specimens of chronic viral hepatitis, liver cirrhosis, and normal liver tissues as controls.

RESULTS

In all cases of DILI specimens, but not in control liver specimens, a clear positive staining for ECL/GL9 was observed. Such positive staining was noted on Kupffer cells, fibroblasts, and histiocytes, but not on lymphocytes or hepatocytes. However, the intensity of immunolabeling did not correlate with the extent of eosinophile leukocyte infiltration.

CONCLUSION

High expression of ECL/GL9 is suggested to be a specific finding of DILI. However, tissue eosinophilia in DILI cannot be explained by the augmentation of ECL/GL9 expression.

[Role of eosinophils in allergic inflammation]

Eosinophils are one of the cells that play a critical role in the pathogenesis of allergic diseases. The increase in the number of eosinophils in such diseases is regulated by interleukin-5 (IL-5). The author have prepared recombinant rat IL-5 using a baculovirus expression system and examined its biological activities in rat eosinophils. It was demonstrated that recombinant rat IL-5 prolongs the survival of mature eosinophils and differentiates immature eosinophils into mature eosinophils, suggesting that rat IL-5 is a factor for eosinophilia in rats. Recombinant rat eosinophil-associated ribonuclease (Ear)-1 and Ear-2 were also prepared. Eosinophil granule proteins are thought to cause tissue damage due to their cytotoxic activity, but using recombinant rat Ear-1 and Ear-2, it was found that rat Ear-1 and Ear-2 have strong RNase A activity and bactericidal activity, suggesting that these proteins play critical roles in host defense. Finally, the important role of acetylation of histones was clarified in the differentiation of HL-60 clone 15 cells into eosinophils using the histone deacetylase inhibitors sodium n-butyrate, apicidin, and trichostatin A. These findings would be useful for further investigations of the role of eosinophils in allergic inflammation.

NR4A orphan nuclear receptor family in peripheral blood eosinophils from patients with atopic dermatitis and apoptotic eosinophils in vitro

To identify novel genes related to the clinical signs of atopic dermatitis (AD), differentially expressed genes were sought in peripheral blood eosinophils from both AD patients and healthy volunteers. RNA was prepared from eosinophils, expression of various genes was monitored using the Affymetrix GeneChip, and expression was quantified by real-time RT-PCR. Two genes, Nur77 and NOR1, members of NR4A orphan nuclear receptor family, were expressed at a significantly higher level in AD patients than in healthy volunteers. Expression of another gene in the NR4A receptor family, Nurr1, was also higher in AD patients than in healthy volunteers. When peripheral blood leukocytes from healthy volunteers were fractionated, NOR1 expression was highest in eosinophils, but expression of Nur77 and Nurr1 genes was not eosinophil-specific. Extremely intense apoptosis was induced in both eosinophils and an eosinophil cell line, AML14.3D10, by treatment with antibody (Ab) to both CD30 and Fas. Rapid expression of the genes for the NR4A receptor family was observed with anti-CD30 Ab treatment but not with anti-Fas Ab. The NR4A orphan nuclear receptor family gene expression and the subsequent eosinophil apoptosis were downregulated by the MAPK inhibitor, U0126. These results suggest that the expression of the NR4A receptor family genes through CD30 signaling may regulate eosinophil apoptosis in allergic conditions such as AD.

Expression of interleukins in patients with nasal polyposis

OBJECTIVE

To correlate the levels of interleukins 1beta, 3, 4, and 5 before and after surgery and compare the levels between patients with and without recurrence of nasal polyposis.

STUDY DESIGN AND SETTING

Thirty-nine patients with NP were selected, 13 of them allergic and 26 nonallergic. A control group of 11 individuals was also studied. The concentrations of interleukins were measured by enzyme-linked immunosorbent assay.

RESULTS

There was a higher incidence of NP after the fourth decade of life and among men. The clinical symptoms were similar in both groups of patients with nasal polyposis and characterized by nasal obstruction and anosmia. A significant reduction of all interleukins studied was observed after surgical treatment.

CONCLUSION

Levels of interleukins 1beta, 3, 4, and 5 were significantly reduced after surgery and the levels of interleukins 1beta and 5 were significantly lower in patients without recurrence of nasal polyposis after surgery when compared to those with recurrence.

Absence of interleukin-3 does not affect the severity of local and systemic anaphylaxis but does enhance eosinophil infiltration in a mouse model of allergic peritonitis

Interleukin-3 (IL-3), which is derived from T cells and other sources, can promote the differentiation, proliferation, and migration of mast cells, basophils, and eosinophils. However, little is known about the ability of IL-3 to regulate the function of these cells in IgE-dependent and -independent allergic responses in vivo. Therefore, we sought to investigate the extent to which endogenously produced IL-3 can influence mast cell secretory function, the expression of local and systemic anaphylactic responses, and ragweed-induced eosinophilic peritonitis. We found that peritoneal mast cells from IL-3 deficient (IL-3 -/-) mice released less serotonin following challenge with low doses of anti-IgE antibody or antigen ex vivo than do cells isolated from corresponding wild-type (IL-3 +/+) mice. Both IL-3 -/- and +/+ mice expressed equivalent IgE-dependent passive cutaneous anaphylaxis responses following challenge with specific antigen and exhibited equivalent active systemic anaphylaxis responses to ovalbumin as assessed by changes in body temperature, death rates, total IgE production, and histamine release. In contrast, ragweed allergen immunization and peritoneal allergen challenge resulted in eosinophil recruitment that was greater in IL-3 -/- mice than in IL-3 +/+ mice. Our data demonstrates that IL-3 does not appear to be essential for local or systemic anaphylaxis. However, IL-3 production in vivo was found to enhance the mediator release from freshly isolated peritoneal mast cells stimulated ex vivo, and, unexpectedly, to inhibit the accumulation of eosinophils associated with a ragweed-induced allergic peritonitis model.

Possible mechanism of action of the histone deacetylase inhibitors for the induction of differentiation of HL-60 clone 15 cells into eosinophils

1 We have examined the effect of the histone deacetylase inhibitors apicidin, trichostatin A (TSA) and n-butyrate on the histone acetylation and the differentiation of human eosinophilic leukemia HL-60 clone 15 cells into eosinophils. 2 Viability of the cells incubated with apicidin (100 nm), TSA (30 nm) or n-butyrate (500 microm) did not change significantly, but higher concentrations of apicidin (> or =300 nm) or TSA (> or =100 nm) decreased the viability when examined at day 1. 3 Apicidin (100 nm) as well as n-butyrate (500 microm) induced continuous acetylations of histone H4 and lysine14 residue on histone H3, while TSA (30 nm) induced transient acetylations. 4 After 6 days incubation, eosinophilic cells stained by Luxol-fast-blue were generated by apicidin (100 nm) and n-butyrate (500 microm) but not by TSA (30 nm). Other markers for differentiation into eosinophils such as changes in intracellular structure, and expressions of integrin beta7 and major basic protein, and the inhibition of cell proliferation were also induced by apicidin and n-butyrate but not by TSA. 5 Continuous acetylation of histone H4 achieved by repeated treatment with TSA (30 nm) at an interval of 12 h for more than three times induced such changes when examined on day 6. In addition, the induction was impaired by shortening the period of incubation with apicidin (100 nm) or n-butyrate (500 microm). 6 CCAAT/enhancer binding protein was continuously activated by apicidin (100 nm) and n-butyrate (500 microm), but was transiently activated by TSA (30 nm). 7 These findings suggest that the continuous acetylation of histones H3 and H4 is necessary for the differentiation of HL-60 clone 15 cells into eosinophils.

Extremely rapid and intense induction of apoptosis in human eosinophils by anti-CD30 antibody treatment in vitro

Apoptosis is an important cellular mechanism for controlling cell viability and proliferation. With respect to eosinophils, cytokines prolong their survival, whereas corticosteroids reduce their survival in vitro. CD30, a member of the TNFR family, is expressed on the surface of many cell types, including Hodgkin's lymphoma cells. CD30 is capable of inducing apoptosis after Ab treatment in some cell lines. To determine whether this surface structure is involved in apoptosis of human eosinophils, we examined its expression and the effect of anti-CD30 Ab treatment on the viability of eosinophils. Purified human eosinophils expressed low, but consistently detectable, levels of CD30. Immobilized, but not soluble, forms of anti-CD30 Abs (HRS-4 and Ber-H8) or recombinant mouse CD30 ligand exhibited an extremely rapid and intense survival-reducing effect on the eosinophils in the presence of exogenous IL-5; this effect was both concentration and time dependent. Furthermore, high concentrations of IL-5 could not reverse the reduced survival rates. After treatment with anti-CD30 Ab, gel electrophoresis of DNA extracted from the eosinophils demonstrated changes consistent with apoptosis. The immobilized F(ab')(2) of the anti-CD30 Ab failed to induce eosinophil apoptosis. The addition of anti-CD18 Ab also completely abrogated the induction of eosinophil apoptosis. Further examination using specific signal transduction inhibitors suggested the involvement of p38, mitogen-activated protein kinase kinase 1/2, and specific tyrosine kinase, but not NF-kappaB, in the induction of CD30-mediated eosinophil apoptosis. These data demonstrate that CD30 can modify eosinophil survival by causing an extremely rapid and intense induction of apoptosis through a tightly regulated intracellular signaling pathway.

Interleukin-3 Binding to the Murine βIL-3 and Human βc Receptors Involves Functional Epitopes Formed by Domains 1 and 4 of Different Protein Chains

Interleukin-3 (IL-3) is a cytokine produced by activated T-cells and mast cells that is active on a broad range of hematopoietic cells and in the nervous system and appears to be important in several chronic inflammatory diseases. In this study, alanine substitutions were used to investigate the role of residues of the human beta-common (hbetac) receptor and the murine IL-3-specific (beta(IL-3)) receptor in IL-3 binding. We show that the domain 1 residues, Tyr(15) and Phe(79), of the hbetac receptor are important for high affinity IL-3 binding and receptor activation as shown previously for the related cytokines, interleukin-5 and granulocyte-macrophage colony-stimulating factor, which also signal through this receptor subunit. From the x-ray structure of hbetac, it is clear that the domain 1 residues cooperate with domain 4 residues to form a novel ligand-binding interface involving the two protein chains of the intertwined homodimer receptor. We demonstrate by ultracentrifugation that the beta(IL-3) receptor is also a homodimer. Its high sequence homology with hbetac suggests that their structures are homologous, and we identified an analogous binding interface in beta(IL-3) for direct IL-3 binding to the high affinity binding site in hbetac. Tyr(21) (A-B loop), Phe(85), and Asn(87) (E-F loop) of domain 1; Ile(320) of the interdomain loop; and Tyr(348) (B'-C' loop) and Tyr(401) (F'-G' loop) of domain 4 were shown to have critical individual roles and Arg(84) and Tyr(317) major secondary roles in direct murine IL-3 binding to the beta(IL-3)receptor. Most surprising, none of the key residues for direct IL-3 binding were critical for high affinity binding in the presence of the murine IL-3 alpha receptor, indicating a fundamentally different mechanism of high affinity binding to that used by hbetac.

Differential effect of dexamethasone on cell death and STAT5 activation during in vitro eosinopoiesis

Glucorticoids reduce eosinophilia through a direct effect on eosinophils or indirectly on cells producing cytokines and chemokines. Conflicting data have been previously reported concerning glucocorticoid effects on eosinopoiesis. To elucidate this point, dexamethasone was added during eosinophil differentiation of CD34+ cells. Dexamethasone enhanced proliferation and differentiation through an early effect on immature cells. Dexamethasone inhibited apoptosis during early differentiation, whereas death of mature cells was increased. Signal transducer and activator of transcription 5 (STAT5) is a transcription factor involved in the proliferation, differentiation and survival of haematopoietic cells, which interacts with glucocorticoid receptor. Activation of STAT5 by interleukin-5 was investigated during eosinophil differentiation. Long isoforms of STAT5 were activated during the entire period in the culture as well as in blood eosinophils, while short isoforms were only activated during early differentiation. Short isoforms were less activated in the presence of dexamethasone. This suggests that dexamethasone could act on proliferation, differentiation and apoptosis during eosinophil differentiation through an association of STAT5 with the glucocorticoid receptor.

Inhibition of prostate cancer cell growth by activated eosinophils

BACKGROUND

Host Immune response to prostate cancer primarily involves the CTL and NK effector cells. Recent immunotherapeutic strategies incorporating cytokine genes into the tumor cell and/or dendritic cells have had encouraging results. In this study, we describe the inhibitory activity of a third potential effector cell, the eosinophil, against DU 145 and PC-3 prostate tumor cells growth in vitro.

METHODS

Subconfluent monolayer cultures of DU 145 and PC-3 cells were incubated with peripheral blood eosinophils from allergic or asthmatic individuals and also with eosinophil cultured supernatants. Newly established eosinophil cell lines were also studied. After harvesting, the plates were washed and stained with Hematoxylin/eosin (H/E) then photographed. The combination of monolayer cell growth inhibition and colony formation inhibition assays were used to evaluate eosinophil inhibitory activity. In the colony formation inhibition assay one hundred cells per well in 6-well plates were incubated overnight, after which peripheral blood eosinophils, conditioned media and cytokines, IL-4 and TNF-alpha were added. The plates were harvested after 10 days incubation period. Colonies were stained and counted.

RESULTS

Hypo- and hyperdense peripheral blood eosinophils from allergic and asthmatic individuals as well as eosinophil cell lines established from these subpopulations inhibited both DU 145 and PC-3 cell growth at 58-78% and 10-38%, respectively. IL-5 up-regulated eosinophil cell line activity by 21-24%. The conditioned media which contained the released mediators of activated eosinophils were potent in their actions on both DU 145 and PC-3, inhibiting colony formation by as much as 90-100%.

CONCLUSION

These results clearly demonstrate the inhibitory potential of activated eosinophils and their released "soup" of mediators and therefore support the hypothesis that eosinophils may participate in host response to prostate cancer together with CTLs and NK cells. Furthermore, this study offers insights into possible strategies for enhancing eosinophilic activity in prostate cancer.

Human platelets produce granulocyte-macrophage colony-stimulating factor and delay eosinophil apoptosis

An association between eosinophils and platelets has been described in several diseases, most notably asthma. Although the mechanisms through which platelets influence eosinophil behavior are not well defined, platelets seem to contribute to the selective accumulation of eosinophils at sites of allergic inflammation by virtue of their ability to produce eosinophil chemotactic factors. We report here for the first time that platelets delay apoptosis, thus enhancing eosinophil survival. A marked inhibition of spontaneous apoptosis was observed using eosinophil:platelet ratios of 1:50, 1:25, 1:10, and 1:5. Moreover, promotion of eosinophil apoptosis by either pronase or dexamethasone was also inhibited greatly in the presence of platelets. The antiapoptotic effect mediated by platelets was dependent on the release of soluble products and was significantly inhibited by neutralizing antibodies directed to GM-CSF. Studies performed by flow cytometry, directed to analyze the cellular source of this cytokine, demonstrated that intracytoplasmic GM-CSF is present in resting platelets. Moreover, GM-CSF was found in platelet supernatants, at concentrations able to prevent eosinophil apoptosis. Our findings support a novel mechanism through which platelets may contribute to eosinophil accumulation at allergic inflammatory sites.

The antiallergic drug oxatomide promotes human eosinophil apoptosis and suppresses IL-5-induced eosinophil survival

BACKGROUND

Eosinophils accumulated in sites of allergic inflammation are thought to play a crucial role in the pathogenesis of allergic disorders including asthma, allergic rhinitis, and atopic dermatitis, and tissue eosinophilia is attributable to increased eosinophil survival or decreased eosinophil apoptosis.

OBJECTIVE

Effects of the antiallergic, histamine H1 blocker oxatomide on viability and apoptosis of eosinophils isolated from the peripheral blood of atopic subjects were studied.

METHODS

Eosinophil viability and apoptosis were evaluated by using a colorimetric assay and annexin V-labeling, caspase-3 activity, and DNA fragmentation assay.

RESULTS

The viability of eosinophils increased in the presence of IL-5 (10 ng/mL), confirming that IL-5 prolongs eosinophil survival in vitro. Application of oxatomide at concentrations over 20 micromol/L for 24 hours decreased the IL-5-induced enhancement of eosinophil viability. Double staining of the cells with annexin V and propidium iodide showed that deprivation of IL-5 promoted spontaneous eosinophil apoptosis and that oxatomide facilitated apoptosis and suppressed the prolongation of eosinophil survival stimulated by IL-5. In the absence of IL-5, approximately 71% and 96% of eosinophils after 24 and 48 hours, respectively, underwent spontaneous apoptosis. IL-5 decreased the rate of eosinophil apoptosis to 38% and 52% after 24 and 48 hours, respectively. Oxatomide increased eosinophil apoptosis in a concentration-dependent manner in the presence of IL-5. Furthermore, oxatomide increased caspase-3 activity and DNA fragmentation.

CONCLUSION

We demonstrated that oxatomide possesses a novel therapeutic effect of apoptosis promotion on eosinophils and prevents the antiapoptotic effects of IL-5, suggesting that oxatomide may contribute to resolution of tissue eosinophilia in allergic inflammation.

2. Cytokines and chemokines

Cytokines and chemokines are redundant secreted proteins with growth, differentiation, and activation functions that regulate and determine the nature of immune responses and control immune cell trafficking and the cellular arrangement of immune organs. Which cytokines are produced in response to an immune insult determines initially whether an immune response develops and subsequently whether that response is cytotoxic, humoral, cell-mediated, or allergic. A cascade of responses can be seen in response to cytokines, and often several cytokines are required to synergize to express optimal function. An additional confounding variable in dissecting cytokine function is that each cytokine may have a completely different function, depending on the cellular source, target, and, most important, specific phase of the immune response during which it is presented. Numerous cytokines have both proinflammatory and anti-inflammatory potential; which activity is observed depends on the immune cells present and their state of responsiveness to the cytokine. For this chapter, cytokines are grouped according to those that are mononuclear phagocytic-derived or T-lymphocytic-derived; that mediate cytotoxic (antiviral and anticancer), humoral, cell-mediated, or allergic immunity; and that are immunosuppressive. The biology of chemokines are then reviewed, grouped by family.

Inflammatory cells in asthma: mechanisms and implications for therapy

Recent clinical studies have brought asthma's complex inflammatory processes into clearer focus, and understanding them can help to delineate therapeutic implications. Asthma is a chronic airway inflammatory disease characterized by the infiltration of airway T cells, CD(+) (T helper) cells, mast cells, basophils, macrophages, and eosinophils. The cysteinyl leukotrienes also are important mediators in asthma and modulators of cytokine function, and they have been implicated in the pathophysiology of asthma through multiple mechanisms. Although the role of eosinophils in asthma and their contribution to bronchial hyperresponsiveness are still debated, it is widely accepted that their numbers and activation status are increased. Eosinophils may be targets for various pharmacologic activities of leukotriene receptor antagonists through their ability to downregulate a number of events that may be key to the effector function of these cells.

Differential expression of TRAIL and TRAIL receptors in allergic asthmatics following segmental antigen challenge: evidence for a role of TRAIL in eosinophil survival

Asthma is a chronic lung disease exhibiting airway obstruction, hyperresponsiveness, and inflammation, characterized by the infiltration of eosinophils into the airways and the underlying tissue. Prolonged eosinophilic inflammation depends on the balance between the cell's inherent tendency to undergo apoptosis and the local eosinophil-viability enhancing activity. TRAIL, a member of the TNF family, induces apoptosis in most transformed cells; however, its role in health and disease remains unknown. To test the hypothesis that Ag-induced inflammation is associated with TRAIL/TRAIL-R interactions, we used a segmental Ag challenge (SAC) model in ragweed-allergic asthmatics and nonasthmatic patients and analyzed bronchoalveolar lavage (BAL) material for 2 wk. In asthmatic patients, the level of TRAIL in BAL fluid dramatically increased 24 h after SAC, which significantly correlated with BAL eosinophil counts. Immunohistochemical analysis of bronchial biopsies from asthmatic patients demonstrated that TRAIL staining was increased in epithelial, airway smooth muscle, and vascular smooth muscle cells and throughout the interstitial tissue after SAC. This was confirmed by quantitative immunocytochemical image analysis of BAL eosinophils and alveolar macrophages, which demonstrated that expression levels of TRAIL and DcR2 increased, whereas expression levels of the TRAIL-Rs DR4 and DR5 decreased in asthmatic subjects after SAC. We also determined that TRAIL prolongs eosinophil survival ex vivo. These data provide the first in vivo evidence that TRAIL expression is increased in asthmatics following Ag provocation and suggest that modulation of TRAIL and TRAIL-R interactions may play a crucial role in promoting eosinophil survival in asthma.

Treatment of asthmatic patients with a cysteinyl leukotriene receptor-1 antagonist montelukast (Singulair), decreases the eosinophil survival-enhancing activity produced by peripheral blood mononuclear leukocytes in vitro

BACKGROUND

Montelukast (Singulair, MSD) has been shown to have a beneficial effect on the clinical symptoms of asthma. We aimed to investigate the effect of montelukast treatment on the production of eosinophil survival-enhancing cytokines by peripheral blood mononuclear cells (PBMNC).

METHODS

PBMNC obtained from 15 grass-allergic patients (7 treated with montelukast and 8 with a placebo) were cultured for 72 h. Eosinophils from allergic patients were cultured with MNC supernatants alone or with addition of neutralizing antibodies, and the proportion of living cells was assessed by flow cytometry. In another experiment PBMNC from 6 allergic patients were cultured in vitro in the presence of montelukast or vehicle. Following stimulation the production of GM-CSF in monocytes was assessed.

RESULTS

Eosinophil survival in the MNC supernatants from the placebo-treated patients was significantly (P < 0.05) higher than in supernatants from montelukast-treated patients. GM-CSF was the predominant cytokine responsible for the eosinophil survival-enhancing activity (ESEA). In vitro production of GM-CSF by allergen-stimulated monocytes was significantly suppressed by addition of montelukast.

CONCLUSION

Treatment of patients with montelukast decreased the production of MNC-derived cytokines, particularly GM-CSF. We suggest that cysteinyl leukotriene receptor-1 (CysLT-R1) antagonists may act, at least partially, by diminishing the production of GM-CSF from PBMNCs.

Interleukin-3, but not granulocyte-macrophage colony-stimulating factor and interleukin-5, inhibits apoptosis of human basophils through phosphatidylinositol 3-kinase: requirement of NF-kappaB-dependent and -independent pathways

Basophils are key effector cells of allergic reactions. Although proinflammatory cytokines, such as interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-5, inhibit eosinophil apoptosis in vitro, little is known about basophil apoptosis, and the signalling mechanisms required for basophil survival remain undefined. To address this issue, we used a novel negative-selection system to isolate human basophils to a purity of > 95%, and evaluated apoptosis by morphology using light and transmission electron microscopy, and by annexin-V binding and propidium iodide incorporation using flow cytometry. In this study, we demonstrated that the spontaneous rate of apoptotic basophils was higher than that of eosinophils as, at 24 hr, 57.6 +/- 4.7% of basophils underwent apoptosis compared with 39.5 +/- 3.8% of eosinophils. In addition, basophil cell death was significantly inhibited when cultured with IL-3 for 48 hr (84.6 +/- 4.9% vehicle-treated cells versus 40.9 +/- 3.9% IL-3-treated cells). IL-3 also up-regulated basophil CD69 surface expression. The effects of IL-3 on apoptosis and CD69 surface expression of human basophils were completely blocked by LY294002 (LY), a potent inhibitor of phosphatidylinositol 3-kinase (PI3-K), but only partially inhibited by lactacystin, a proteasome inhibitor that prevents degradation of IkappaB and NF-kappaB translocation. These observations reveal the novel finding that IL-3 prevents basophil apoptosis through the activation of PI3-K, which is only partially NF-kappaB dependent. As basophils are active participants in allergic reactions and IL-3 is one of the abundant proinflammatory cytokines in secretions from allergic tissue, we suggest that IL-3-mediated inhibition of basophil apoptosis may exacerbate the inflammation associated with allergic disorders.

CD40 engagement enhances eosinophil survival through induction of cellular inhibitor of apoptosis protein 2 expression: Possible involvement in allergic inflammation

BACKGROUND

CD40 engagement enhances eosinophil survival, suggesting a role for this receptor in the development of eosinophilia.

OBJECTIVE

We examined whether CD40 enhances eosinophil survival by inducing the expression of antiapoptotic proteins. Three members of the inhibitor of apoptosis protein (IAP) family, namely cellular (c)-IAP1, c-IAP2, and XIAP, and 2 antiapoptotic proteins of the Bcl-2 family, namely Bcl-x(L) and Bfl-1/A1, were investigated.

METHODS

Blood and sputum were obtained from healthy subjects and atopic asthmatic patients. Blood eosinophils were isolated by means of magnetic selection. Expression of CD40, IAPs, and Bcl-2 proteins was investigated by using flow cytometry, immunoblotting, or both. CD40 stimulation was achieved with agonistic antibodies or soluble ligands. Apoptosis was assessed by staining with propidium iodide and FITC-conjugated annexin-V. c-IAP2 expression was inhibited with antisense oligonucleotides.

RESULTS

Freshly isolated eosinophils from healthy and asthmatic patients did not express CD40. Conversely, eosinophils expressed CD40 spontaneously when cultured for 48 hours. At this time point, CD40 stimulation significantly delayed eosinophil apoptosis. Inhibition of eosinophil apoptosis was accompanied by induction of c-IAP2 but not c-IAP1, XIAP, Bcl-x(L), or Bfl-1/A1 expression. Antisense knockdown of c-iap2 abolished CD40-induced enhancement of eosinophil survival. Sputum cells from asthmatic patients, unlike those from healthy subjects, substantially expressed CD40 and c-IAP2. Moreover, a strong correlation was found between the percentage of eosinophils in the sputum from asthmatic patients and the sputum level of CD40 and c-IAP2 expression.

CONCLUSION

The results demonstrate that CD40 engagement enhances eosinophil survival through induction of c-IAP2 expression and suggest a role for this mechanism in allergic inflammation.

Comparison of effects of anti-IL-3, IL-5 and GM-CSF treatments on eosinophilopoiesis and airway eosinophilia induced by allergen

Allergic inflammation is dominated by eosinophils. IL-3, IL-5, and GM-CSF are involved in production and activation of eosinophils. IL-5 has been reported to be crucial for the induction of airway eosinophilia. However, the contribution of IL-3 and GM-CSF to allergic airway inflammation remains to be determined. To address this issue, ovalbumin-sensitized Balb/c mice were repeatedly exposed to allergen via airway route. Animals were pretreated intraperitoneally with neutralising anti-IL-3, anti-IL-5 and/or anti-GM-CSF antibodies. Newly produced inflammatory cells were pulse-labelled with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU), which is incorporated into DNA during the cell mitosis. BAL and bone marrow cells were collected 24 h after the last allergen exposure, and differential cell counts and immunocytochemical detection of BrdU-labelled cells were performed. Anti-IL-5 strongly reduced both BAL and bone marrow eosinophilia, as well as the number of BrdU-positive BAL-granulocytes. In contrast, anti-IL-3 and anti-GM-CSF alone had little and no inhibitory effect on these responses, respectively. Even the combined treatment with anti-IL-3 and anti-GM-CSF showed only a non-significant tendency to attenuate these responses. These data suggest that the efficacy of treatments with anti-IL-3 and anti-GM-CSF is much weaker than that with anti-IL-5. IL-5 may be the preferred target to block eosinophilia in allergic diseases.

Mechanisms of eosinophil recruitment and activation

The role of the eosinophil in the pathophysiology of allergy and asthma has been the focus of intense interest during the last two decades. While the presence of eosinophils in humans with allergy and asthma is well established, the precise role of this cell in humans and in animal models is less clear. However, recent developments in research on many organ systems have provided novel insights into the possible underlying role of the eosinophil in both allergic and nonallergic inflammation. This review examines the pathways associated with eosinophil recruitment and activation and discusses these findings, with reference to clinically defined categories.

Biological activities of ecalectin: a novel eosinophil-activating factor

Ecalectin, produced by Ag-stimulated T lymphocytes, is a potent eosinophil-specific chemoattractant in vitro as well as in vivo and thus is implicated in allergic responses. Ecalectin differs structurally from other known eosinophil chemoattractants (ECAs); ecalectin belongs to the galectin family defined by their affinity for beta-galactosides and by their conserved carbohydrate recognition domains. These characteristic features suggest that ecalectin has unique activities associated with allergic inflammation besides ECA activity. Conversely, ecalectin may mediate ECA activity by binding to a receptor of a known ECA via affinity for the beta-galactosides present on this receptor. In this study, we have tested whether ecalectin mediates ECA activity by binding to a receptor of a known ECA, and we have assessed its effects on eosinophils. Ecalectin did not mediate ECA activity by binding to the IL-5R or to CCR3. Also, the ECA activity of ecalectin was mainly chemokinetic. In addition, ecalectin induced concentration-dependent eosinophil aggregation, a marker for eosinophil activation. Ecalectin induced concentration-dependent superoxide production from eosinophils but did not induce degranulation; usually these two events are coupled in eosinophil activation. Moreover, ecalectin directly prolonged eosinophil survival in vitro and did not trigger eosinophils to secrete cytokines that prolong eosinophil survival. These results demonstrate that ecalectin has several unique effects on eosinophils. Therefore, we conclude that ecalectin is a novel eosinophil-activating factor. Presumably, these effects allow ecalectin to play a distinctive role in allergic inflammation.

Selective phosphodiesterase type 4 inhibitors reduce the prolonged survival of eosinophils stimulated by granulocyte-macrophage colony-stimulating factor

It is well known that bronchial asthma is defined as chronic eosinophilic inflammation of the respiratory tract and that as one of the various types of inflammatory cells, eosinophils induce the airway inflammation of chronic asthma. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to play an important role in the prolongation of the survival of eosinophils. We investigated the inhibitory effect of the selective phosphodiesterase (PDE) 4 inhibitors, 3,4-dipropyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-i]purin-5-one (XT-611) and rolipram, and the nonselective PDE inhibitor theophylline, against GM-CSF-induced prolongation of the survival of eosinophils isolated from patients with bronchial asthma. Eosinophils (10(6) cells/ml) were incubated in the presence of GM-CSF together with or without theophylline, rolipram or XT-611 at 37 degrees C, and the viable cells were assessed up to 4d using Trypan blue dye exclusion. The presence of theophylline (10(-4) M), rolipram (10(-4)-10(-5) M) or XT-611 (10(-4)-10(-5) M) significantly reduced the GM-CSF (10 pg/ml)-induced prolongation of viability of eosinophils. These findings suggest that selective PDE 4 inhibitors, including XT-611, may effectively reduce the activities of inflammatory cells in the airway of bronchial asthma patients.

IL-3 induces B7.2 (CD86) expression and costimulatory activity in human eosinophils

Eosinophils in tissues are often present in intimate contact with T cells in allergic and parasitic diseases. Resting eosinophils do not express MHC class II proteins or costimulatory B7 molecules and fail to induce proliferation of T cells to Ags. IL-5 and GM-CSF induce MHC class II and B7 expression on eosinophils and have been reported in some studies to induce eosinophils to present Ag to T cells. The cytokine IL-3, like IL-5 and GM-CSF, is a survival and activating factor for eosinophils and the IL-3 receptor shares with the IL-5 and GM-CSF receptors a common signal transducing beta-chain. IL-3-treated eosinophils expressed HLA-DR and B7.2, but not B7.1 on their surface and supported T cell proliferation in response to the superantigen toxic shock syndrome toxin 1, as well as the proliferation of HLA-DR-restricted tetanus toxoid (TT) and influenza hemagglutinin-specific T cell clones to antigenic peptides. This was inhibited by anti-B7.2 mAb. In contrast, IL-3-treated eosinophils were unable to present native TT Ag to either resting or TT-specific cloned T cells. In parallel experiments, eosinophils treated with IL-5 or GM-CSF were also found to present superantigen and antigenic peptides, but not native Ag, to T cells. These results suggest that eosinophils are deficient in Ag processing and that this deficiency is not overcome by cytokines that signal via the beta-chain. Nevertheless, our findings suggest that eosinophils activated by IL-3 may contribute to T cell activation in allergic and parasitic diseases by presenting superantigens and peptides to T cells.

IL-3 induces down-regulation of CCR3 protein and mRNA in human eosinophils

Cytokines and chemokines are responsible for the attraction and activation of eosinophils in allergic and inflammatory diseases. Whereas cytokines such as IL-3, IL-5, and GM-CSF activate eosinophils via heterodimeric receptors containing a distinct alpha-chain (binding domain) and a common beta-chain (signaling domain), chemokines such as eotaxin activate eosinophils via seven-transmembrane G(i) protein-coupled CCRs. Recent studies have demonstrated the importance of CCR3 on human eosinophils that undergo receptor recycling after chemokine activation, but the modulation of this receptor by cytokines has not yet been addressed. In this study, we demonstrate that IL-3 induces a dose- and time-dependent down-regulation of CCR3 from the surface of human eosinophils comparable to the CCR3-specific ligand eotaxin, whereas IL-5, GM-CSF, IL-4, IL-10, IL-13, IFN-gamma, and TNF-alpha had no effect. Maximal down-regulation of CCR3 in response to IL-3 was reached at 24 h. Reduction of CCR3 surface protein in response to IL-3 could be prevented by an anti-IL-3 mAb and was neither due to the release of CC chemokines nor to nonspecific binding of IL-3 to CCR3. Moreover, down-regulation was prevented by phenylarsine oxide, a nonspecific inhibitor of receptor internalization. After 24 h, IL-3-induced decrease of CCR3 surface expression correlated with diminished mRNA expression, suggesting a transcriptional regulation mechanism. Since wortmannin partially inhibited IL-3- but not eotaxin-induced CCR3 down-regulation, receptor down-modulation seems to underlie different signaling events. Therefore, these data suggest a novel role for the cytokine IL-3 in the activation process of eosinophils and its predominant chemokine receptor CCR3.

Pathophysiological mechanisms of asthma. Application of cell and molecular biology techniques

Asthma is a common increasing and relapsing disease that is associated with genetic and environmental factors such as respiratory viruses and allergens. It causes significant morbidity and mortality. The changes occurring in the airways consist of a chronic eosinophilic and lymphocytic inflammation, together with epithelial and structural remodeling and proliferation, and altered matrix proteins, which underlie airway wall narrowing and bronchial hyperresponsiveness (BHR). Several inflammatory mediators released from inflammatory cells such as histamine and cysteinyl-leukotrienes induce bronchoconstriction, mucus production, plasma exudation, and BHR. Increased expression of T-helper 2 (Th2)-derived cytokines such as interleukin-4 and 5 (IL-4, 5) have been observed in the airway mucosa, and these may cause IgE production and terminal differentiation of eosinophils. Chemoattractant cytokines (chemokines) such as eotaxin may be responsible for the chemoattraction of eosinophils to the airways. The initiating events are unclear but may be genetically determined and may be linked to the development of a Th2-skewed allergen-specific immunological memory. The use of molecular biology techniques on tissues obtained from asthmatics is increasing our understanding of the pathophysiology of asthma. With the application of functional genomics and the ability to transfer or delete genes, important pathways underlying the cause if asthma will be unraveled. The important outcome of this is that new preventive and curative treatments may ensue.

Interleukin-2 activates human peripheral blood eosinophils

The effect of interleukin (IL)-2 on eosinophil survival and mediator release was investigated in vitro. Human peripheral blood eosinophils were isolated and purified from mildly atopic donors and cultured on albumin-coated wells with different concentrations of IL-2, interferon (IFN)-gamma, and granulocyte-macrophage colony stimulating factor (GM-CSF) and their viability was evaluated after 4 days in culture. Eosinophils were cultured with IL-2 (1000 u/ml), IFN-gamma (1000 u/ml), or GM-CSF (10 ng/ml) for 18 h, or with platelet activating factor (PAF) (10(-6) M) for 20 min, and the release of eosinophil peroxidase (EPO) and IL-6 was measured. Nedocromil sodium (10(-5) M) was added with each of the above cytokines to study the inhibitory effect of this drug on EPO release. A significant increase of EPO release was induced by IL-2, IFN-gamma, and GM-CSF after 18 h in culture. IL-2 as well as IFN-gamma induced a significant IL-6 release from eosinophils. Nedocromil sodium significantly inhibited EPO release from eosinophils induced by IL-2 or PAF. These results show that IL-2 can activate peripheral blood eosinophils to release granule mediators (EPO) and cytokines (IL-6). Taken together with the presence of IL-2 receptors on eosinophils, we conclude that IL-2 is an important mediator in allergic inflammation and a possible target for pharmacological modulation.

Granulocyte macrophage-colony-stimulating factor mRNA is stabilized in airway eosinophils and peripheral blood eosinophils activated by TNF-alpha plus fibronectin

Airway eosinophils show prolonged in vitro survival compared with peripheral blood eosinophils (PBEos). Recent studies have shown that autocrine production and release of GM-CSF is responsible for enhanced survival, but the mechanisms controlling cytokine production remain obscure. We compared GM-CSF mRNA decay in eosinophils from bronchoalveolar lavage (BALEos) after allergen challenge or from PBEos. BALEos showed prolonged survival in vitro (60% at 4 days) and expressed GM-CSF mRNA. The enhanced survival of BALEos was 75% inhibited at 6 days by neutralizing anti-GM-CSF Ab. Based on transfection studies, GM-CSF mRNA was 2.5 times more stable in BALEos than in control PBEos. Treatment of PBEos with fibronectin and TNF-alpha increased their in vitro survival, GM-CSF mRNA expression, and GM-CSF mRNA stability to a comparable level as seen in BALEos. These data suggest that TNF-alpha plus fibronectin may increase eosinophil survival in vivo by controlling GM-CSF production at a posttranscriptional level.

Adenovirus-mediated interleukin 3 beta gene transfer by isolated limb perfusion inhibits growth of limb sarcoma in rats

Cytokine gene transfer using (multiple) intratumoral injections can induce tumor regression in several animal models, but this administration technique limits the use for human gene therapy. In the present studies we describe tumor growth inhibition of established limb sarcomas after a single isolated limb perfusion (ILP) with recombinant adenoviral vectors harboring the rat IL-3 beta gene (IG.Ad.CMV.rIL-3 beta). In contrast, a single intratumoral injection or intravenous administration did not affect tumor growth. Dose-finding studies demonstrated a dose-dependent response with a loss of antitumor effect below 1 x 10(9) IU of IG.Ad.CMV.rIL-3 beta. Perfusions with adenoviral vectors bearing a weaker promoter (MLP promoter) driving the rIL-3 beta gene did not result in antitumor responses, suggesting that the rIL-3 beta-mediated antitumor effect depends on the amount of rIL-3 beta protein expressed by the infected cells. Furthermore, it was shown by direct comparison that ILP with IG.Ad.CMV.rIL-3 beta in the ROS-1 osteosarcoma model is at least as efficient as the established therapy with the combination of TNF-alpha and melphalan. Treatment with IG.Ad.CMV.rIL-3 beta induced a transient dose-dependent leukocytosis accompanied by an increase in peripheral blood levels of histamine. Leukocyte infiltrations were also histopathologically demonstrated in tumors after perfusion. These results demonstrate that ILP with recombinant adenoviral vectors carrying the IL-3 beta transgene inhibits tumor growth in rats and suggest that cytokine gene therapy using this administration technique might be beneficial for clinical cancer treatment.

IL-5 up-regulates cysteinyl leukotriene 1 receptor expression in HL-60 cells differentiated into eosinophils

The cysteinyl leukotrienes, leukotriene (LT) C(4), LTD(4), and LTE(4), are lipid mediators that have been implicated in the pathogenesis of several inflammatory processes, including asthma. The human LTD(4) receptor, CysLT(1)R, was recently cloned and characterized. We had previously shown that HL-60 cells differentiated toward the eosinophilic lineage (HL-60/eos) developed specific functional LTD(4) receptors. The present work was undertaken to study the potential modulation of CysLT(1)R expression in HL-60/eos by IL-5, an important regulator of eosinophil function. Here, we report that IL-5 rapidly up-regulates CysLT(1)R mRNA expression, with consequently enhanced CysLT(1)R protein expression and function in HL-60/eos. CysLT(1)R mRNA expression was augmented 2- to 15-fold following treatment with IL-5 (1-20 ng/ml). The effect was seen after 2 h, was maximal by 4 h, and maintained at 8 h. Although CysLT(1)R mRNA was constitutively expressed in undifferentiated HL-60 cells, its expression was not modulated by IL-5 in the absence of differentiation. Differentiated HL-60/eos cells pretreated with IL-5 (10 ng/ml) for 24 h showed enhanced CysLT(1)R expression on the cell surface, as assessed by flow cytometry using a polyclonal anti-CysLT(1)R Ab. They also showed enhanced responsiveness to LTD(4), but not to LTB(4) or platelet-activating factor, in terms of Ca(2+) mobilization, and augmented the chemotactic response to LTD(4). Our findings suggest a possible mechanism by which IL-5 can modulate eosinophil functions and particularly their responsiveness to LTD(4), and thus contribute to the pathogenesis of asthma and allergic diseases.

Systemic activation of basophils and eosinophils: markers and consequences

Basophils and eosinophils are important effector cells in human allergic diseases; they play a significant role in promoting allergic inflammation through the release of proinflammatory mediators (such as histamine, leukotriene C(4), major basic protein, eosinophil cationic protein, IL-4, and IL-13, among others). Notably, in allergic subjects, these cells exist in higher numbers and in a more activated state compared with nonatopic control subjects. Evidence for the greater activation state includes increased expression of intracellular and surface markers and hyperreleasability of allergy mediators. We have been interested in the phenotypic markers of effector-cell activation for many years. There is considerable overlap among activation markers, and few activation markers have been found that define a unique phenotype that is quantifiable in the assessment of the presence and severity of allergic disease. This review summarizes the existing evidence for systemic activation of human basophils and eosinophils in allergic diseases. The potential mechanisms responsible for functional and morphologic alterations in these effector cells and the specificity and utility of surface markers in the assessment of allergic disease activity or severity are also discussed.

Cytokine profile in minor salivary glands from patients with bronchial asthma

BACKGROUND

T lymphocytes are important components of the bronchial inflammatory cell infiltrate in asthma. Because lymphocytes activated in the respiratory tract recirculate to remote glandular and mucosal sites, we previously studied the histologic features of minor salivary glands (MSGs) in bronchial asthma and found an airway-like inflammation with T-lymphocyte infiltration, the presence of mast cells that were often degranulated, and basement membrane thickening but no eosinophil infiltration.

OBJECTIVE

We sought to investigate the cellular infiltration and cytokine profile in MSGs from untreated asthmatic subjects, steroid-treated asthmatic subjects, and control subjects and to compare these values with those found in bronchial biopsy specimens.

METHODS

The cellular infiltration was studied by using immunohistochemistry. Cytokine messenger (m)RNA expression for IL-4, IL-5, and IFN-gamma was determined by using in situ hybridization and cytokine immunoreactivity with immunohistochemistry.

RESULTS

A significant increase in CD4 and IL-4 mRNA(+) cells was observed in MSGs from asthmatic patients (both untreated and steroid-treated subjects) when compared with control subjects, which correlated with the clinical severity of asthma (FEV(1) and Aas score). In contrast to the bronchi, no IL-5 mRNA expression was observed in MSGs, and no difference was observed for MSG IFN-gamma mRNA between the groups. At the level of MSG protein expression, the 3 cytokines were seen, with a significant increase in IL-4 protein expression in steroid-treated asthmatic subjects compared with untreated asthmatic subjects and control subjects, but there were no differences between the groups in IL-5 and IFN-gamma protein expression.

CONCLUSION

The cytokine mRNA expression pattern observed in the MSGs of asthmatic subjects was different from that found in the bronchi, suggesting a different local immune regulation.

The effect of transendothelial migration on eosinophil function

In bronchial asthma, eosinophils found in the airways have an enhanced inflammatory capacity. We hypothesized that, at least in part, changes in functional phenotype are due to the effect of transendothelial migration. To model in vivo eosinophil trafficking to the lung, we cultured human pulmonary microvascular endothelial cell (HPMEC) monolayers on Transwell filters. The HPMECs were activated with interleukin (IL)-1beta to increase cell expression of intercellular adhesion molecule (ICAM)-1 and, hence, eosinophil transmigration. Peripheral blood eosinophils from allergic patients were added to HPMEC-covered Transwell filters and incubated for 3 h at 37 degrees C. The eosinophils were collected from below (migrated cells) and above (nonmigrated cells) the HPMEC monolayer to determine surface receptor expression, in vitro survival, and oxidative burst. Eosinophils never exposed to HPMECs were used as controls. Eosinophil cell surface expression of CD69, human leukocyte-associated antigen-DR (HLA-DR), and CD54 (ICAM-1) was significantly increased after transendothelial migration through IL-1beta-treated HPMECs compared with control cells (CD69: P<0.0005; HLA-DR and CD54: P<0.05) and nonmigrated eosinophils (CD69 and HLA-DR: P<0.05). Moreover, the percent in vitro survival (48 h) of migrated eosinophils was also significantly greater (P<0.0001 by trypan blue exclusion, P< 0.05 by flow cytometry) than that of control or nonmigrated eosinophils. Prolonged survival of migrated eosinophils was inhibited by addition of anti-granulocyte macrophage colony-stimulating factor (GM-CSF) antibodies (P<0.05) to the 48-h survival culture, suggesting that autocrine production of GM-CSF was, at least partially, responsible for increased eosinophil survival. Although GM-CSF protein was not measurable in survival culture supernates, GM-CSF messenger RNA (mRNA) was expressed in both nonmigrated and migrated eosinophils but not in control cells. Similarly, the eosinophils' oxidative burst induced by platelet-activating factor, formylmethionyl leucylphenylalanine, or phorbol myristate acetate was equally, and significantly, increased in both nonmigrated and migrated eosinophils (P<0.05 versus control). Therefore, whereas exposure of eosinophils to cytokine-activated HPMECs can increase surface receptor expression, in vitro survival, GM-CSF mRNA, and the respiratory burst, transendothelial migration can further potentiate receptor expression and survival in migrated cells. These results suggest that the process of transendothelial migration selectively participates in determining the eventual phenotype of airway eosinophils.

Interleukin-3 and stress

The importance of cytokines as mediators in numerous physiologic and pathologic processes became apparent in the early seventies. In a relatively short period of time the number of characterized and functionally defined interleukins increased rapidly. Concomitantly, the understanding of their role in various important reactions in different systems of the organism in general, and in the interaction between the immune, central nervous and neuroendocrine systems in particular increased. IL-3 is one of the cytokines of great significance for hematopoiesis. In addition, it was shown that interleukin-3 (IL-3) participates in the response of the organism to various types of stress. Surprisingly enough, the reports on its production and activation during or following stress are rather scarce. Therefore, the purpose of this review is to try and compile the information on IL-3 and its role in different types of stress, and also to contribute our own modest experience on the subject.

Expression of CXCR4 in eosinophils: functional analyses and cytokine-mediated regulation

We examined the expression of transcripts of a panel of chemokine receptors in human eosinophils and found intense constitutive expression of CXCR4 mRNA. Although surface CXCR4 protein was hardly detectable in the peripheral blood or freshly isolated eosinophils, surface expression of CXCR4 became gradually apparent during incubation at 37 degrees C. In contrast, the level of CCR3 expression was virtually unchanged during the incubation. Stromal cell-derived factor-1alpha (SDF-1alpha), the natural ligand of CXCR4, elicited an apparent Ca2+ influx in these cells and induced a strong migratory response comparable to that by eotaxin. The surface expression of CXCR4 in eosinophils was up-regulated by IFN-gamma, TNF-alpha, and TGF-beta while it was down-regulated by IL-4 and eosinophil-directed hemopoietins such as IL-5. The CXCR4 expression did not always parallel the apoptotic changes in cytokine-treated eosinophils. In contrast to IL-4 and IFN-gamma, IL-5 potently reduced the level of CXCR4 mRNA. It seems unlikely that CXCR4 is fundamentally involved in the pathogenesis of allergic disorders by inducing the migration of eosinophils toward inflammatory sites, because a Th2-dominant state down-regulates eosinophil CXCR4 expression. However, CXCR4 may affect the size of the mobilizable pool by holding eosinophils at noninflamed tissues. Th2-dominant state may favor the liberation of eosinophils by down-regulating CXCR4 expression. The interplay between CXCR4 and SDF-1alpha in eosinophils potentially plays an important role in the accumulation of these cells at the allergic inflammatory sites.

Induced sputum: validity of fluid-phase IL-5 measurement

BACKGROUND

IL-5 measurement in the fluid phase of induced sputum is considered to be important in the assessment of asthma, but the validity of these measurements is uncertain.

OBJECTIVE

We investigated the validity of sputum IL-5 measurements through a series of spiking experiments and examined the effect of dithiothreitol (DTT) on these measurements.

METHODS

Induced sputum from 26 asthmatic subjects was spiked with IL-5 and processed, and the percentage of recovery was measured by means of immunoassay. In 6 of the 26 samples the effect of adding albumin to the processing fluids was studied. In 3 separate samples radiolabeled IL-5 was added, and the recovery measured by means of gamma counting and immunoassay were compared. In addition, the effect of DTT on the immunoassay was examined.

RESULTS

The mean +/- SD recovery of spiked IL-5 was 26.1% +/- 14.6% measured by means of immunoassay; adding albumin increased the recovery to 47.7% +/- 8.0% (P <.001). The mean recovery measured by means of gamma counting was 84.8% +/- 5.7% (P <.001); adding albumin had no effect on recovery. DTT had no significant effect on IL-5 measurement.

CONCLUSION

The validity of IL-5 measurement by means of current methods is poor. The discrepancy in recovery as measured by gamma counting compared with immunoassay suggests that there is a problem with the recognition of IL-5 epitopes by immunoassay in induced sputum. This cannot be attributed to DTT but may be due to other interfering substances present in sputum, such as sputum proteases, soluble receptors, or autoantibodies.

Cutaneous injection of human subjects with macrophage inflammatory protein-1 alpha induces significant recruitment of neutrophils and monocytes

Macrophage inflammatory protein (MIP-1 alpha), a member of the CC chemokine subfamily, has been shown to attract T cells and monocytes in vitro and to be expressed at sites of inflammation. Although the in vitro activities of MIP-1 alpha have been well documented, the in vivo biological activities of MIP-1 alpha in humans have not been studied. To address this, we challenged human subjects by intradermal injection with up to 1000 pmol of MIP-1 alpha and performed biopsies 2, 10, and 24 h later. Although no acute cutaneous or systemic reactions were noted, endothelial cell activation, as indicated by the expression of E-selectin, was observed. In agreement with its in vitro activity, monocyte, lymphocyte, and, to a lesser degree, eosinophil infiltration was observed, peaking at 10-24 h. Surprisingly, in contrast to its reported lack of in vitro neutrophil-stimulating activity, a rapid infiltration of neutrophils was observed in vivo. This neutrophil infiltration occurred as early as 2 h, preceding the appearance of other cells, and peaked at 10 h. Interestingly, we found that neutrophils in whole blood, but not after isolation, expressed CCR1 on their cell surface. This CCR1 was thought to be functional as assessed by neutrophil CD11b up-regulation following whole-blood MIP-1 alpha stimulation. These studies substantiate the biological effects of MIP-1 alpha on monocytes and lymphocytes and uncover the previously unrecognized activity of MIP-1 alpha to induce neutrophil infiltration and endothelial cell activation, underscoring the need to evaluate chemokines in vivo in humans.

Excretory-secretory product of newly excysted metacercariae of Paragonimus westermani directly induces eosinophil apoptosis

Eosinophils are important effector cells in host defense against parasites. Excretory-secretory product (ESP) produced by helminthic worms plays important roles in the uptake of nutrients, migration in the host tissue, and in immune modulation. However, little is known about the ability of the ESP to directly trigger eosinophil apoptosis. This study investigated whether the ESP of newly excysted metacercariae of Paragonimus westermani could induce apoptosis in human eosinophils. Apoptosis was assayed by staining the cells with FITC-annexin V, and the cells were analyzed by flow cytometry. It was found that the ESP of newly excysted metacercariae of P. westermani induced a direct time- and concentration-dependent increase in the rate of constitutive apoptosis in mature human eosinophils. Eosinophil apoptosis was first apparent 3 hr after treatment with the ESP and continued to increase after 6 hr of incubation with respect to the cells cultured in the absence of the ESP. While only 2.8% of the eosinophils incubated in the medium for 3 hr were apoptotic, 7.6%, 10.9% and 22.6% of the eosinophils treated with 10, 30 and 100 micrograms/ml ESP were apoptotic, respectively. This result suggests that the ESP of newly excysted metacercariae of P. westermani directly induce eosinophil apoptosis, which may be important for the survival of the parasites and the reduction of eosinophilic inflammation in vivo.

The biochemical, molecular, and genomic aspects of leukotriene C4 synthase

Leukotriene C4 (LTC4) synthase is an 18 kD integral membrane enzyme of the 5-lipoxygenase/LTC4 synthase pathway and is positioned as the pivotal and only committed enzyme for the formation of the cysteinyl leukotrienes. Although its function is to conjugate catalytically LTA4 to reduced glutathione, LTC4 synthase is differentiated from other glutathione S-transferase family members by its lack of amino acid homology, substrate specificity, and kinetics. LTC4 synthase (LTC4S) protein is present in the perinuclear membranes of a limited number of hematopoietic cells involved in allergic inflammation, including mast cells, eosinophils, basophils, and macrophages. The cDNA encodes a monomeric protein of 150 amino acids with three hydrophobic domains interspersed with two hydrophilic loops. Site-directed mutagenic studies reveal that the enzyme functions as a homodimer and that arginine-51 in the first hydrophilic loop, and tyrosine-93 in the second hydrophilic loop, are involved in the acid and base catalysis of LTA4 and glutathione, respectively. Homology and secondary structural predictions indicate that LTC4S is a novel member of a new gene superfamily of integral membrane proteins, each with the capacity to participate in leukotriene biosynthesis. The gene for LTC4S is 2.5 kb in length and is localized on chromosome 5q35, distal to that of the genes for cytokines and receptors important in the development and perpetuation of allergic inflammation. Immunohistochemical studies of mucosal biopsies from the bronchi of aspirin-intolerant asthmatics show that LTC4S is overrepresented in individuals with this phenotype, and this finding correlates with overproduction of cysteinyl leukotrienes and lysine-aspirin bronchial hyperreactivity.

The functional basis of granulocyte-macrophage colony stimulating factor, interleukin-3 and interleukin-5 receptor activation, basic and clinical implications

The cytokines granulocyte-macrophage colony stimulating factor, interleukin-3 and interleukin-5 have overlapping activities on cells expressing their receptors. This is explained by their sharing a receptor signal transduction subunit, beta c. This communal signaling subunit is also required for high affinity binding of all three cytokines. Therapeutic approaches attempting to interfere or modulate haemopoietic cells using cytokines or their analogues can in some instances be limited due to functional redundancy amongst cytokines using shared receptor signaling subunits. Therefore, a better approach would be to develop therapeutics against the shared subunit. Studies examining the GM-CSF, IL-3 and IL-5 receptors have identified the key events leading to functional receptor activation. With this knowledge, it is now possible to identify new targets for the development of a new class of antagonist that blocks the biological activity of all the cytokines utilizing beta c. This approach may be extended to other receptor systems such as IL-4 and IL-13 where receptor activation is dependent on a common signaling and binding subunit.