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

Activated T cells and eosinophilia in bronchoalveolar lavages from subjects with asthma correlated with disease severity

Activated T-lymphocytes may regulate the eosinophilic inflammation of bronchial asthma. In the present study, we investigated T cell activation and eosinophilia in blood and bronchoalveolar lavage (BAL) in 17 patients with asthma not receiving steroid treatment. Compared to normal individuals, BAL from patients with asthma contained significantly increased numbers of both lymphocytes and eosinophils (EOSs). The lymphocytosis consisted of increased numbers of both CD4+ and CD8+ T cells, and these T cell populations expressed elevated levels of T cell activation markers (interleukin-2 receptor [CD25], HLA-DR, and very late activation antigen 1). Close correlation was found between numbers of BAL CD4+ IL-2R+ T cells and numbers of EOSs. Moreover, the numbers of activated T cells and EOSs were related to the severity of asthma as measured by impairment of FEV1 and increased methacholine bronchial responsiveness. We demonstrate in both blood and BAL a close correlation between T cell activation, eosinophilia, and severity of asthma, suggesting that recruitment and activation of lymphocytes and EOSs are fundamental to the pathogenesis of bronchial asthma.

Eosinophil hematopoietins antagonize the programmed cell death of eosinophils. Cytokine and glucocorticoid effects on eosinophils maintained by endothelial cell-conditioned medium

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was established as the constitutive and elicited human umbilical vein endothelial cell-derived eosinophil viability-sustaining factor. Stimulation of endothelium cell monolayers with IL-1 alpha (5 U/ml) increased the 48-h elaboration of GM-CSF from a mean of 3.2 to a mean of 8.2 pM (P less than 0.05). Dexamethasone (100 nM) decreased the constitutive GM-CSF elaboration by 49% (P less than 0.001) but did not diminish production by IL-1 alpha-stimulated endothelium. However, eosinophil viability decreased by 21% in dexamethasone-pretreated IL-1 alpha-stimulated endothelial cell-conditioned medium (P less than 0.05), which suggested viability antagonism by glucocorticoids. After 24 h of culture, eosinophil viability for replicate cells in enriched medium alone or with 1 pM GM-CSF decreased from means of 43 and 75% to means of 21 and 54%, respectively, when dexamethasone was included (P less than 0.05). However, 10 pM GM-CSF, IL-3, or IL-5 protected the cells against dexamethasone and against endonuclease-specific DNA fragmentation. In this model system of eosinophil-tissue interactions, dexamethasone prevents the endothelial cells from inducing a pathobiologic phenotypic change in the eosinophil by suppression of GM-CSF elaboration to concentrations that are not cytoprotective. Cytokine priming by GM-CSF, IL-3, or IL-5 may account for the differential responsiveness of select eosinophilic disorders to glucocorticoids.

Endobronchial allergen challenge in asthma. Demonstration of cellular source of granulocyte macrophage colony-stimulating factor by in situ hybridization

Airway inflammation is thought to play an important role in the pathogenesis of asthma. We have used in situ hybridization and an immunoassay to determine whether granulocyte macrophage colony-stimulating factor (GM-CSF) (a cytokine capable of eosinophil activation) is present in the airway of asthmatics (n = 6) who have 37.0 +/- 15.1% airway eosinophilia after endobronchial allergen challenge. Levels of immunoreactive GM-CSF (less than 4 pg/ml pre-allergen versus 180.5 +/- 46.9 pg/ml post-allergen) increased significantly 24 h after endobronchial allergen stimulation. The cellular source of bronchoalveolar lavage (BAL) GM-CSF, as determined by in situ hybridization and immunoperoxidase staining, was derived predominantly from UCHL-1 positive BAL lymphocytes, as well as from a smaller population of alveolar macrophages. Before local endobronchial allergen challenge, less than 1% of lymphocytes and alveolar macrophages recovered by BAL expressed GM-CSF mRNA, whereas after allergen stimulation 92.6 +/- 3.4% of lymphocytes and 17.5 +/- 22.7% of alveolar macrophages expressed GM-CSF mRNA. This study provides evidence that in an experimental model of allergen-induced asthma, activation of the immune and inflammatory response (BAL lymphocyte and alveolar macrophage production of GM-CSF) is temporally associated with an inflammatory cell influx of eosinophils into the airway.

Effects of IL-5, granulocyte/macrophage colony-stimulating factor (GM-CSF) and IL-3 on the survival of human blood eosinophils in vitro

The mechanisms that could affect the lifespan of eosinophils after they have left the bone marrow, and their capacity to respond to activation factors were studied by examining the effects of IL-5, GM-CSF and IL-3 on purified human blood eosinophils in culture. All three cytokines prolonged the lifespan of the majority of blood eosinophils. This effect was dose-dependent: IL-5 greater than GM-CSF greater than IL-3. Light density eosinophils from most patients had a longer lifespan in culture than did normal density eosinophils, with or without the three cytokines. Eosinophil death in the absence of these cytokines occurred by apoptosis. Eosinophils from two patients did not survive when cultured with IL-5, although they survived in the presence of IL-3 or GM-CSF. IL-5, GM-CSF and IL-3 induced the expression of the activation epitope on the eosinophil ribonucleases recognized by monoclonal antibody EG2. We conclude that small amounts of IL-5, GM-CSF and IL-3 prevented programmed cell death in human blood eosinophils and induced the expression of the activation forms of eosinophil ribonucleases. We suggest that differences in the capacity of normal and light density eosinophils to survive in culture, and in the ability of eosinophils from some patients to respond to IL-5 could account for variations in the severity of disease seen in patients with persistent eosinophilia.

Promotion of eosinophil survival by human bronchial epithelial cells and its modulation by steroids

Accumulation of eosinophils in the bronchial tissue occurs in a variety of inflammatory disorders of the human airway. We asked whether airway epithelial cells released factors that could influence eosinophil survival and thus contribute to accumulation of these cells in the tissues. Using conditioned medium (CM) generated from cultured human bronchial epithelial cells (HBEC), we examined the in vitro survival of eosinophils isolated from human peripheral blood. When cultured in control medium, more than 90% of the eosinophils were dead by day 4. In contrast, culture in HBEC-CM resulted in dose-dependent survival at day 6 of 69 +/- 9.4%, 40.5 +/- 5.9%, and 25 +/- 2% viability with 2, 0.5, and 0.1% HBEC-CM, respectively (n = 4). Granulocyte/macrophage colony-stimulating factor (GM-CSF) was detected in the HBEC-CM by enzyme-linked immunosorbent assay at levels of 22 to 48 pg/ml. Furthermore, preincubation of the HBEC-CM with a neutralizing monoclonal antibody to human GM-CSF completely inhibited this increased survival of eosinophils. Because corticosteroids are potent eosinopenic agents, we also examined the effects of the synthetic steroid budesonide on this system. Budesonide inhibited both spontaneous and interleukin-1 (IL-1)-induced GM-CSF production by cultured HBEC. In addition, preincubation of eosinophils with budesonide caused marked abrogation of the survival induced subsequently with either HBEC-CM or recombinant human GM-CSF. In summary, HBEC can support eosinophil survival via the elaboration of GM-CSF and thus may contribute to the local control of inflammatory cell accumulation. Steroids may modulate this process both by inhibiting cytokine production from HBEC and by a direct effect on eosinophils, preventing their response to cytokines.

Eosinophils altered phenotypically and primed by culture with granulocyte/macrophage colony-stimulating factor and 3T3 fibroblasts generate leukotriene C4 in response to FMLP

Normodense eosinophils failed to generate leukotriene C4 (LTC4) in response to incremental concentrations of FMLP but did produce LTC4 when stimulated with calcium ionophore A23187. Normodense eosinophils, maintained in culture with 10(-11) M granulocyte/macrophage colony-stimulating factor (GM-CSF) in the presence of 3T3 fibroblasts, became responsive to transmembrane stimulation with FMLP by day 4 with a maximal effect by day 7. After 7 d of culture, hypodense eosinophils stimulated with 2 x 10(-7) M FMLP generated 26 ng LTC4/10(6) cells, and LTC4 biosynthesis was blocked by N-tertbutoxy-carbonyl-L-methionyl-L-leucyl-L-phenylalanine (N-t-BOC-MLP). Neither calcium ionophore stimulation of LTC4 from endogenous arachidonic acid nor substrate-initiated production of LTC4 from incorporated LTA4 changed when eosinophils were cocultured with GM-CSF and 3T3 fibroblasts. Furthermore, when incubated with 10(-6) M FMLP, normodense eosinophils generated no net superoxide measured by the reduction of cytochrome c, whereas replicate eosinophils cultured for 7 d with 10(-11) M GM-CSF and 3T3 fibroblasts reduced a net of 17 nmol of cytochrome c/10(6) cells. These studies suggest that primed and phenotypically altered eosinophils present at an extravascular site may exert pathobiologic effects by responding to soluble ligands in the tissues.

Human eosinophils are more toxic than neutrophils in antibody-independent killing

Eosinophils (EOSs) are implicated in damaging host tissues in diseases such as asthma and eosinophilic gastroenteritis. In the present study, we assessed the cytotoxicity of human EOSs from peripheral blood of patients with eosinophilia and from peritoneal fluid of patients undergoing continuous peritoneal dialysis and compared them to normal neutrophils. Cytotoxicity was measured by the release of 51chromium from cultured tumor cells and chicken erythrocytes. Both EOSs and neutrophils were separated on discontinuous Percoll gradients with greater than 95% purity. The granulocytes were activated by preincubation in an ice bath with phorbol myristate acetate and washed before incubation with the target cells. The EOSs lysed significantly more tumor cells (K562, Raji, and CEM lines) in an 18-hour assay than did neutrophils, and no significant difference was found between the peritoneal and blood EOSs. The EOSs were also much more efficient than neutrophils in lysing chicken erythrocytes when they were activated by granulocyte-macrophage colony-stimulating factor instead of phorbol myristate acetate. Cytolysis by EOSs is mediated by both oxidative and nonoxidative mechanisms, as indicated by experiments with cells from patients with chronic granulomatous disease. Thus, EOSs are much more cytotoxic than neutrophils and potentially much more damaging to patients with eosinophilia.

Shape changes, exocytosis, and cytosolic free calcium changes in stimulated human eosinophils

Essentially pure preparations of normal density eosinophils obtained from patients with hypereosinophilic syndrome (HES) were stimulated with complement factor 5a (C5a), platelet-activating factor (PAF), FMLP and neutrophil-activating peptide (NAP-1/IL-8). Three responses were studied, the transient rise in cytosolic free calcium concentration ([Ca2+]i) (derived from indo-1 fluorescence), shape changes (measured by laser turbidimetry), and exocytosis of eosinophil peroxidase (EPO) (assessed by H2O2/luminol-dependent chemiluminescence). Responses were obtained with all four agonists, but C5a and PAF were by far more potent than FMLP and NAP-1/IL-8, which induced only minor effects. Pretreatment of the cells with pertussis toxin attenuated [Ca2+]i changes, EPO release and, to a lesser extent, shape changes, indicating that GTP-binding proteins of Gi-type are involved in receptor-dependent signal transduction processes leading to these responses. A clear dissociation was observed in the control of the shape change response and EPO exocytosis. The shape change was not affected by Ca2+ depletion or treatment with the protein kinase inhibitor staurosporine, but exocytosis was prevented by Ca2+ depletion and markedly enhanced by staurosporine. The activation of the contractile system, leading to shape changes and motility, thus appears to be independent of the classical signal transduction pathway involving phospholipase C, a [Ca2+]i rise and protein kinase C activation. Exocytosis is, as expected, Ca2+ dependent and appears to be under a negative control involving protein phosphorylations.

Characteristics of an anti-eosinophil monoclonal antibody that recognizes granulocytes from patients with blood eosinophilia but not from subjects without eosinophilia

To investigate cell surface antigens of activated human eosinophils using monoclonal antibodies, we established a murine anti-human eosinophil monoclonal antibody AE500 by immunizing with blood eosinophils from patients with idiopathic hypereosinophilic syndrome (HES) and characterized the reactivity to a variety of human leucocytes by a fluorescence-activated cell sorter. AE500 reacted with blood eosinophils and neutrophils in nine out of 11 patients with marked eosinophilia (greater than or equal to 2500/microliters) (seven with idiopathic eosinophilia including HES and two with asthma), but not with those in asthmatic patients with mild eosinophilia (n = 10) or in healthy subjects (n = 8). AE500 did not react with blood lymphocytes, monocytes or platelets. AE500 did not react with human myeloid or lymphoid cell lines, including eosinophilic leukemia cell lines EOL-1 and EOL-3. The reactivity of AE500 to blood eosinophils and neutrophils in patients with marked eosinophilia changed in relation to blood eosinophil counts and prednisolone therapy. In addition, the reactivity of AE500 to blood eosinophils was increased in three out of four AE500-positive eosinophils by the incubation of the cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) at 37 degrees C for 30 min, but not with interleukin 3 or interleukin-5. These results suggest that the anti-eosinophil antibody AE500 detects a cell surface antigen expressed on blood granulocytes in a hypereosinophilic state. This anti-eosinophil antibody would be useful for analysing the mechanism of eosinophilia.

Human eosinophils from hypereosinophilic patients spontaneously express the p55 but not the p75 interleukin 2 receptor subunit

The expression of interleukin 2 receptor (IL2R) on eosinophils was investigated in patients with hypereosinophilia. Hypodense activated eosinophils have been described in various diseases such as parasitic or allergic diseases, hypereosinophilic syndrome (HES) associated in some cases to myeloproliferative markers, and more recently described in patients undergoing recombinant IL2 treatment. The presence of p55 alpha chain of IL2R (CD25) on purified eosinophils collected from blood of hypereosinophilic patients was detected by flow cytometry. In 10 out of 19 cases, more than 10% of eosinophils were CD25+. Cross-linking studies on enriched eosinophils showed one 64-75-kDa band, consisting of IL2 (15 kDa) cross-linked to the IL2R p55 subunit. In Northern blot analysis the two messenger mRNA (3.5 and 1.5 kb) encoding the IL2R p55 subunit were identified after hybridization with a CD25 cDNA probe. In contrast, the presence of the IL2R p75 subunit was not detected. These data provide preliminary evidence for the expression of a low-affinity receptor for IL2 on in vivo activated eosinophils and raise the question of the role played by this cytokine in eosinophil differentiation and activation.

Airway eosinophils from actively sensitized guinea pigs exhibit enhanced superoxide anion release in response to antigen challenge

Antigen challenge of actively sensitized guinea pigs produces airway eosinophilia, airway hyperreactivity, and late-phase bronchoconstriction. The recruited eosinophils are thought to be important cells in the development of the airway hyperreactivity and the late-phase bronchoconstriction. However, the functional abilities of these eosinophils have not been determined in response to antigen challenge. The purpose of this study was to describe the characteristics of superoxide anion release from airway eosinophils obtained 24 h after ovalbumin challenge of actively sensitized guinea pigs. Eosinophils were collected by bronchoalveolar lavage. The total bronchoalveolar lavage eosinophil count was 17- to 27-fold greater in sensitized, ovalbumin-challenged guinea pigs (9.30 +/- 0.11 x 10(6)/guinea pig) than in unsensitized guinea pigs (0.35 +/- 0.07 x 10(6)/guinea pig) or sensitized, saline-challenged guinea pigs (0.56 x 10(6)/guinea pig; n = 2). The increase in eosinophils was due to increased lavage leukocyte count and increased eosinophil differential. Eosinophils were isolated on a Percoll-plasma discontinuous gradient. Two populations of eosinophils were collected, one at the 1.093 g/ml gradient step and one at the 1.107 g/ml gradient step. Unstimulated or phorbol myristate acetate (PMA)-stimulated superoxide anion release was measured by the reduction of ferricytochrome c. Unstimulated superoxide anion release from both eosinophil populations of challenged guinea pigs (4.50 +/- 2.37 and 4.07 +/- 1.48 nmol from 1.093 and 1.107 g/ml eosinophils, respectively) was 6- to 7-fold greater than superoxide anion release from eosinophils of control guinea pigs (0.74 +/- 0.43 and 0.56 +/- 025 nmol from 1.093 and 1.107 g/ml eosinophils, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

State of the art; the hypereosinophilic syndromes

Many disease states such as parasitic infestations, malignancies, collagen vascular diseases, and allergies are associated with eosinophilia. The diagnosis of idiopathic hypereosinophilic syndrome (HES) requires a persistent elevation in the total eosinophil count (greater than 1500/mm3) for over 6 months, associated organ damage and no detectable underlying cause. This review provides an updated summary of the cytokine cascade that controls eosinophil production and delineates our current understanding of the clinical features of hypereosinophilic states. We also examine the central role of T-lymphocyte activation in eosinophilia, and have attempted to integrate current treatment strategies for HES with the physiology of eosinophilopoiesis.

Messenger RNA expression of the cytokine gene cluster, interleukin 3 (IL-3), IL-4, IL-5, and granulocyte/macrophage colony-stimulating factor, in allergen-induced late-phase cutaneous reactions in atopic subjects

Cryostat sections from skin biopsies from 24-h allergen-induced late-phase cutaneous reactions (LPR) in 14 human atopic subjects were hybridized with 35S-labeled RNA probes for a number of cytokines. mRNA was detected for interleukin 3 (IL-3) (8/14), IL-4 (10/14), IL-5 (11/14), and granulocyte/macrophage colony-stimulating factor (GM-CSF) (13/14). Only 5 of 14 gave hybridization signals for IL-2, and 0 of 14 for interferon gamma. Biopsies from diluent controls gave only occasional weak signals. These results suggest that cells infiltrating the site of the 24-h LPR transcribe mRNA for the IL-3, IL-4, IL-5, and GM-CSF gene cluster and support the hypothesis that atopy is associated with preferential activation of cells having a similar cytokine profile to the murine T helper type 2 subset.

The effect of interleukin 3 upon IgE-dependent and IgE-independent basophil degranulation and leukotriene generation

Recent investigations have shown that the hematopoietic growth factor interleukin 3 (IL 3) enhances histamine release of mature human basophils. Furthermore, basophils exposed to IL 3 generate large amounts of leukotriene C4 in response to C5a, a basophil agonist which by itself is unable to promote lipid mediator formation. Also IL 3 renders the cells responsive to factors which do not otherwise induce basophil mediator release. Here we show in more detail how IL 3 affects the release of preformed and newly synthesized inflammatory mediators by basophils in response to antigen, anti-IgE, N-formyl-methionyl-leucyl-phenylalanine (FMLP) and C5a. In cells triggered by maximally effective concentrations of these agonists, IL 3 enhances histamine release, although it more profoundly affects leukotriene generation, in particular in response to stimuli which by themselves are inefficient or poor inducers of lipid mediator formation. This change in the mediator-release reaction occurs at low IL 3 concentrations, over the same concentration range of IL 3 of 0.01-1.0 U/ml regardless of which triggering agent is used as a second signal. Pretreatment of basophils with IL 3 results in a left shift of the dose-response curves for mediator release of both IgE-dependent and IgE-independent agonists by approximately one order of magnitude. IL 3 affects only the extent and not the time course of IgE-independent peptide-induced basophil degranulation. By contrast, histamine and leukotrienes are released more rapidly in response to IgE-dependent stimulation after IL 3 priming. IL 3 also shortens the lag time and increases the rate of leukotriene generation in basophils triggered by FMLP. The priming process induced by IL 3 does not require extracellular calcium. Basophils exposed to IL 3 release significant amount of mediators in response to C5a, even in EDTA buffers without addition of Ca2+/Mg2+, indicating that in the presence of IL 3 the Ca2(+)-dependent mediator release induced by C5a becomes partially Ca2+ independent. Thus, we find that IL 3 strongly affects the mediator profile, the amounts of mediators released, the dose-response curves and the kinetic of the release reaction in basophils stimulated with diverse agonists. The data further support the hypothesis that IL 3 plays an important role in inflammatory processes, in particular in hypersensitivity reactions.

Mature eosinophils stimulated to develop in human cord blood mononuclear cell cultures supplemented with recombinant human interleukin-5. Part I. Piecemeal degranulation of specific granules and distribution of Charcot-Leyden crystal protein

Human cord blood mononuclear cells were cultured for 35 days in media containing recombinant human interleukin 5 (rhIL-5) supplemented with a fraction of the culture supernatant of phytohemagglutinin (PHA)-stimulated human T lymphocytes from which interleukin 2 (IL-2) was eliminated. Cultured cells were studied by electron microscopy and an immunogold procedure to detect subcellular site(s) of Charcot-Leyden crystal (CLC) protein. The majority of cells (greater than 70%) developing in this system were mature eosinophils, with descending frequency of other cells, including macrophages, mature basophils, eosinophilic myelocytes, and mature neutrophils. Mature eosinophils were characterized by increased numbers of primary granules, small granules, tubulovesicular structures, and decreased secondary granules. These eosinophils showed extensive piecemeal degranulation (PMD) characterized by partially empty and empty secondary granule chambers in the cytoplasm. Small, smooth vesicles were evident within empty granule chambers as well as adjacent to them. Eosinophils formed close associations with phagocytic macrophages that contained both standard-shaped and irregularly shaped CLC within phagolysosomes. Subcellular sites of CLC protein were demonstrated by immunogold in eosinophils and macrophages arising in these cultures. Charcot-Leyden crystal protein was present in the nuclear matrix and extraorganellar cytoplasm of eosinophils. Primary granules and some cytoplasmic vesicles were labeled for CLC protein, but full and empty secondary granules and the extensive network of tubulovesicles were not. Charcot-Leyden crystals were absent from eosinophils, nor were they present in the extracellular space. Charcot-Leyden crystals were absent from eosinophils, nor were they present in the extracellular space. Charcot-Leyden crystals within phagosomes of macrophages were labeled by the immunogold procedure for CLC protein. These results demonstrate that rhIL-5-supplemented, PHA-stimulated, T-cell-conditioned media induced the development of mature human eosinophils from cord blood cells. These eosinophils underwent PMD of secondary granule contents. Immunogold analysis showed eosinophil CLC protein in the cytoplasm, nucleus, and primary granules of eosinophils. Macrophages also were present in these cultures. They contained CLC protein-containing crystals in their phagosomes, suggesting active sequestration of eosinophil CLC protein by macrophages in vitro.

Hematopoietic colony-stimulating factors

In summary, hematopoietic growth factors have been discovered, biochemically characterized, cloned, produced by recombinant DNA technology, and put into clinical use in a period of 25 years. We are approaching a greater understanding of the cellular anatomy and molecular mechanisms that regulate production of the CSFs, the ways in which the CSFs interact with their cell surface receptors and trigger their biological effects, the nature of these receptors themselves and their mechanisms of signal transduction, and the effects of the CSFs in vitro and in vivo on hematopoietic progenitor cells and mature leukocytes. However, many questions remain. What is the mechanism that couples growth-factor binding to the triggering of cellular proliferation? How do multi-CSF and GM-CSF cross-compete at the level of the cell-surface receptor, and yet show no primary amino acid sequence homology? What are the mechanisms that regulate the tissue expression profile of multi-CSF compared to the genetically similar growth factor GM-CSF? And, what are the optimal dosages, schedules of administration, and combinations of CSFs optimal for each of several conditions of marrow failure? These are but a few of the questions that continue to occupy much current research interest.

Why clinicians should be interested in interleukin-3

Interleukin-3 (IL-3), a product of activated immune cells has recently been cloned and introduced in preclinical and clinical trials. The biological target-cell spectrum of IL-3 is broad and includes progenitor cells of various hematopoietic lineages as well as multiple stages of stem cell differentiation. IL-3 also induces growth of most primitive hemopoietic progenitors (CFU-blast). Synergistic effects on growth of myeloid cells (i.e. macrophages, eosinophils and blood basophils) are obtained by sequential use of IL-3 and later-acting myelopoietic cytokines. In addition, IL-3 supports terminal maturation, prolongs survival and enhances the functional properties of myeloid cells through high-affinity binding sites. In vivo administration of IL-3 is followed by an increase in peripheral white blood cell counts as well as by an increase in the number of circulating progenitor cells giving rise to mature hemopoietic cells in response to more lineage-restricted growth factors. IL-3 also regulates growth of leukemic cells and primes them to become more sensitive to cell cycle specific cytotoxic drugs. IL-3 apparently represents a novel and unique hemopoietic growth factor. Its clinical use should offer new strategies in the treatment of cytopenia, leukemic disease and in stem cell transplantation.

Transcriptional regulation of interleukin 3 gene expression in T lymphocytes

Interleukin 3 (IL-3 or multi-colony-stimulating factor) plays an important role in the hematopoietic response to inflammatory stimuli through its action on both immature and mature blood cells. Like other lymphokines, IL-3 is produced in response to activation of the T-cell receptor and protein kinase C pathways. By using nuclear run-on assays of quiescent and stimulated T-cell lines, we demonstrate that IL-3 gene expression is controlled, at least in part, at the level of transcription. Functional reporter gene analysis was used to delineate two regions of the IL-3 5' flanking sequence responsible for transcriptional stimulation. DNA binding proteins that potentially mediate these responses were then recognized by mobility-shift and DNase footprinting assays. One region responsible for transcriptional enhancement was localized to the sequence GATGAATAAT, the cognate site of a transcription factor, here termed NF-IL3-A. A second region of functional activity and protein binding was localized to a single transcription factor AP-1 site. In addition three functionally inhibitory regions were identified. These results, along with the further characterization of NF-IL3-A, will contribute to the understanding of IL-3 gene regulation in stimulated T cells.

Hypodense eosinophils and interleukin 5 activity in the blood of patients with the eosinophilia-myalgia syndrome

The recent recognition of the eosinophilia-myalgia syndrome (EMS) associated with the ingestion of L-tryptophan prompted an analysis of the peripheral blood eosinophil phenotypes and of the serum eosinophil hematopoietins in this disorder. Five patients with an illness characterized by the abrupt onset of aching skeletal muscles, edema, thickening and induration of the skin, and marked blood eosinophilia associated with L-tryptophan ingestion provided eosinophils, serum, or both, for evaluation. Gradient sedimentation density analysis of the peripheral blood eosinophils from four of these patients revealed that 43 +/- 13% (mean +/- SEM) of the cells had converted to the abnormal (hypodense) sedimenting phenotype. When normodense eosinophils from the reference donors were cultured for 3 days in medium supplemented with increasing concentrations of serum from the patients with EMS, their viability increased in a dose-dependent manner to 45%, which was significantly augmented over the effect of normal serum. This eosinophil viability-sustaining activity was inhibited by 76 +/- 7% (mean +/- SEM; n = 3) by the addition of anti-interleukin 5 (IL-5) but not by neutralizing antibodies monospecific for either granulocyte/macrophage colony-stimulating factor (GM-CSF) or IL-3. IL-5, an eosinophilopoietic factor, converts normodense peripheral blood eosinophils in vitro to a hypodense sedimenting form with extended viability and augmented biologic responses to activating stimuli. Thus, the presence of IL-5 in the sera of patients with EMS may contribute to the development and maintenance of the eosinophilia and may regulate the conversion of the peripheral blood eosinophils to the hypodense phenotype with augmented pathobiologic potential.

The inflammatory response in asthma exacerbation: changes in circulating eosinophils, basophils and their progenitors

Circulating eosinophils, basophils and eosinophil/basophil (Eo/B) progenitors were examined in 12 patients at the time of an exacerbation of asthma accompanied by sputum eosinophilia and after resolution of the exacerbation with inhaled corticosteroid treatment. Differential counts were performed and peripheral blood non-adherent mononuclear cells were cultured for 14 days in methyl-cellulose to determine the number of Eo/B and granulocyte-macrophage (GM) colonies without knowledge of the clinical conditions or findings. With resolution of the asthma exacerbation on beclomethasone therapy, there were significant falls in circulating eosinophils, basophils and Eo/B colonies whereas GM colonies were unchanged. To elucidate whether the observed changes could be due to systemic absorption or local action of inhaled corticosteroid, seven subjects with allergic rhinitis and no current evidence of lower airway inflammation (no symptoms of asthma and normal methacholine airway responsiveness) received 14 days' treatment with the same dose of inhaled beclomethasone or of placebo in a double-blind randomized cross-over study. No significant changes in airway function or in circulating cell counts were observed. The results suggest reduced production of eosinophils and basophils after the resolution of an exacerbation of asthma. This effect may be due to reduced levels of airway-derived eosinophil-basophil growth and differentiation factors.

A new method for measuring eosinophil activating factors, based on the increased expression of CR3 alpha chain (CD11b) on the surface of activated eosinophils

The observation that activation of eosinophils in vitro with PAF increases the surface expression of the alpha chain of the complement receptor CR3 (CD11b) has been extended to other eosinophil activating factors. CD11b may be detected on activated eosinophils by reaction with mouse monoclonal anti-human CD11b IgG, following the addition of urease-conjugated sheep anti-mouse IgG. CD11b levels were increased on eosinophils after incubation with (a) recombinant colony stimulating factors, IL-3, GM-CSF and IL-5, at concentrations of 100 U/ml, or (b) with eosinophil activating factors, recombinant TNF alpha (1000 U/ml), EAF purified from mononuclear cell supernatants and PAF (10(-6) M). CD11b levels were not affected by IL-1 alpha, IL-2 or IFN-gamma. Unstimulated neutrophils had higher levels of CD11b than unstimulated eosinophils, but neutrophil CD11b was unaffected by IL-3, GM-CSF and IL-5 and was only slightly affected by TNF, EAF and PAF. Polyclonal rabbit antibodies to IL-3 and TNF neutralised their CD11b enhancing activities. The PAF antagonists WEB 2086 and WEB 2170 neutralised the CD11b enhancing activity of PAF. We conclude that measurement of CD11b expression on eosinophils is a convenient method for the assay of eosinophil activating activity.

Interleukin 5 activity in sera from patients with eosinophilia

Sera from 10 patients with eosinophilia contained eosinophil colony stimulating factor (Eo-CSF) activity. Using anti murine (m) interleukin-5 (IL-5) antibody, we demonstrated that this activity was mainly derived from IL-5. Administration of prednisolone to patients decreased both Eo-CSF activity in sera and the number of eosinophils in blood. These results extend our recent study demonstrating that T cells from eosinophilic patients produce IL-5 with IL-2 stimulation and may support the speculation that IL-5 is an important factor which induces eosinophilia.

Alteration in density of eosinophils in the cerebrospinal fluid of mice infected with Angiostrongylus cantonensis

The density of eosinophils in the cerebrospinal fluid (CSF) and blood of male ddY mice infected with Angiostrongylus cantonensis was examined on days 14, 20 and 27 post-infection (p.i.) with discontinuous Percoll gradient centrifugation. Normal blood eosinophils had a density of between 1.070 and 1.080 g ml-1. No significant changes in density in blood eosinophils were noted during the course of the observations. CSF eosinophils began to become hypodense (defined as density less than 1.070 g ml-1) on day 20 p.i., and 88% of eosinophils were hypodense on day 27. Our results suggest therefore that eosinophils probably become hypodense in the CSF and brain tissues, but not in the blood.

Preparation of large numbers of highly purified normodense human eosinophils from leukapheresis

Methods have been developed for the preparation of large numbers of virtually pure, normodense eosinophils from the peripheral blood of normal human volunteers by means of leukapheresis. The purification depends on the sequential removal of mononuclear cells using a one-step discontinuous density gradient, lysis of erythrocytes, enrichment of eosinophils by centrifugation through discontinuous Percoll gradients and, finally, passive selection of the eosinophils by removal of the remaining polymorphonuclear neutrophils with a monoclonal antibody to CD16. The purity of the isolated eosinophils was consistently in excess of 95%. Recovery into the normodense eosinophil fraction ranged between 10 and 87% (average 31.6 +/- 4.2) and recovery during the monoclonal antibody step averaged 80.3 +/- 8.6%. These methods have made it possible, for the first time, to isolate 2-20 x 10(7) virtually pure normodense eosinophils from the peripheral blood of a single donor for further biochemical or pharmacological experimentation.

A morphometric study of normodense and hypodense human eosinophils that are derived in vivo and in vitro

Hypodense eosinophils were obtained from two patients with the idiopathic hyperosinophilic syndrome (IHES), and hypodense eosinophils were derived by culturing normodense human eosinophils from control donors in the presence of endothelial cells alone, granulocyte/macrophage-colony-stimulating factor (GM-CSF) alone, or GM-CSF and fibroblasts. These eosinophils were examined ultrastructurally and stereologically for alterations in the volume density (Vv) of their electron-dense granules, the Vv of their lucent granules, the Vv of their lipid droplets, the numerical density of their granules with respect to cytoplasm (Nv), and the plasma membrane surface area-to-cell volume ratio (Sv) that might account for their decreased sedimentation density. The hypodense eosinophils that were obtained from the two patients with IHES exhibited a one-third reduction in granule Vv relative to normodense eosinophils from control donors, primarily because of a decrease in granule size. The culture-derived hypodense eosinophils exhibited 10% to 16% decreases in their granule Vv, significant increases in their lucent granules, and a approximately 7.5% decrease in their Sv. Calculation of the cell volume from cross-sectional area measurements showed that the eosinophils that had been cocultured with fibroblasts in the presence of GM-CSF increased their volume by approximately 15%. The eosinophils that had been cocultured with endothelial cells exocytosed some of their granules. In conclusion, a composite of factors including cell swelling, a decrease in the volume of the cytoplasm occupied by granules, and an increase in granule lucency contributes to the hypodense phenotype in vitro, but only cell swelling and hypogranulation are seen in cells from patients with IHES. The latter could reflect the response of 'primed' hypodense eosinophils in vivo to pertinent tissue ligands.

The effects of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 on the secretory capacity of human blood eosinophils

The effects of recombinant human GM-CSF and interleukin-3 (IL-3) on human blood eosinophil survival, activation, and secretion were studied. Purified normal density eosinophils from patients with the idiopathic hypereosinophilic syndrome (HES) survived in culture for 7 days (50% viable) in the presence of 50 nM GM-CSF or 50 nM IL-3. Neutrophils did not survive after 4 days. No eosinophils survived in the absence of GM-CSF or IL-3. In two out of five patients studied, the cultured eosinophils became elongated with numerous processes. In all five patients the cells became adherent, but there were no morphological signs of degranulation. Both GM-CSF and IL-3 activated eosinophils, transforming the storage form of eosinophil cationic protein (ECP) into the secreted form. The proportion of activated cells increased from less than 20% to over 50% after 4 days in culture. However, GM-CSF and IL-3 did not induce secretion on their own. On the other hand, when GM-CSF/IL-3-activated eosinophils were exposed to known secretory stimuli, there was a six-fold increase in the amount of ECP released when the cells were stimulated with sepharose coated with C3b, and a two-fold increase when they were stimulated with sepharose-activated whole autologous serum. Eosinophils from patients taking steroids were unable to secrete their granule contents, even though they became activated by GM-CSF and IL-3. A novel finding was that sepharose-activated whole serum was an extremely potent secretory signal for ECP, releasing up to 50% of the total ECP content. These studies showed that GM-CSF and IL-3 prime eosinophil effector function by initiating granule solubilization which is the first step in the secretory event, without affecting the subsequent extracellular release of granule proteins.

Antigen challenge induces pulmonary airway eosinophil accumulation and airway hyperreactivity in sensitized guinea-pigs: the effect of anti-asthma drugs

1. Guinea-pigs were sensitized with 3 injections of ovalbumin (OA) (1 or 10 micrograms per animal) using Al(OH)3 and pertussis vaccine as adjuvants at two week intervals. 2. Sensitized guinea-pigs were challenged with an aerosol of OA (0.1%) over a one hour period and both airway reactivity and cellular content of bronchoalveolar lavage (BAL) fluid were assessed at intervals for up to 7 days. 3. Guinea-pigs sensitized with 1 microgram of ovalbumin responded to an aerosol of OA with increased pulmonary airway eosinophilia, which was evident 1 day after challenge and was present for up to 7 days. Airway hyperreactivity was not detectable in these animals. 4. Guinea-pigs sensitized with 10 micrograms of ovalbumin responded to an aerosol of OA with increased pulmonary airway neutrophilia and eosinophilia and with increased airway reactivity which was maximal between 8 and 24 h after exposure to OA. 5. Depletion of circulating platelets or neutrophils, by use of selective antisera, did not alter either the magnitude of eosinophilia or the intensity of airway reactivity in sensitized guinea-pigs (10 micrograms) exposed to an aerosol of OA. 6. Pretreatment of sensitized guinea-pigs (10 micrograms) for 6 days with AH 21-132, aminophylline, dexamethasone or ketotifen inhibited pulmonary airway eosinophilia, but did not diminish airway hyperreactivity. Neither eosinophil accumulation nor development of airway hyperreactivity was influenced by treatment with mepyramine or salbutamol over a 6 day period before OA inhalation. 7. Although eosinophilia may occur in association with increased airway reactivity in this animal model, there is no evidence of a causal relationship.

Human fibroblasts maintain the viability and augment the functional response of human neutrophils in culture

When human neutrophils were co-cultured for 72 h with nontransformed human fibroblasts, 69 +/- 3% (n = 13) survived, as compared with survival levels of 2 +/- 1% (n = 15) and 26 +/- 6% (n = 7), respectively, for neutrophils cultured for the same time period in enriched medium alone or supplemented with 10 pM recombinant human granulocyte/macrophage colony-stimulating factor (rh GM-CSF). Conditioned medium from the human fibroblast cultures enhanced neutrophil survival in a dose-dependent fashion to the same level achieved with neutrophil/fibroblast co-cultures, and its soluble viability-sustaining activity was not inhibited by preincubation with neutralizing antiserum against rh GM-CSF. As compared with freshly isolated replicate samples, neutrophils co-cultured with human fibroblasts for 72 h exhibited augmented FMLP-stimulated superoxide production without spontaneous superoxide generation. This striking extension of survival and associated priming for a ligand response by neutrophils co-cultured with human fibroblasts suggests that fibroblasts may contribute to the proinflammatory properties of neutrophils in tissues.

Cytokines and bronchial hyperreactivity

Cytokines and interleukins are a potent group of molecules that is primarily involved in maintaining homeostasis. These molecules regulate the growth and function of many cells of the immune system including eosinophils, mast cells/basophils and others. Activation of the later cells by cytokines may play a crucial role in the development of allergic inflammation of the airways. The importance of cytokines in the pathogenesis of bronchial hyperreactivity and asthma has been reviewed in this paper.

Hematopoietic growth factors. Biology and clinical applications

The hematopoietic growth factors are potent regulators of blood-cell proliferation and development. The first phase of clinical trials suggests that they may augment hematopoiesis in a number of different conditions of primary and secondary bone marrow dysfunction. Future clinical use is likely to include combinations of these growth factors, in order to stimulate early marrow progenitors and obtain multilineage effects. An improved understanding of the biologic and clinical effects of hematopoietic growth factors promises future clinical applications for conditions of impaired function and reduced numbers of blood cells.

Identification of an alveolar macrophage-derived activity in bronchial asthma that enhances leukotriene C4 generation by human eosinophils stimulated by ionophore A23187 as a granulocyte-macrophage colony-stimulating factor

Incubation of eosinophils (EOS) with alveolar macrophage (AM) supernatants isolated from asthmatic subjects followed by stimulation with the calcium ionophore A23187 resulted in enhancement of the capacity of EOS to elaborate leukotriene C4 (LTC4) (mean enhancement 169 +/- 37%, n = 31). Pretreatment of EOS with AM supernatants derived from normal individuals did not enhance LTC4 generation as compared with control medium. Enhancement was maximal when EOS were preincubated with a 1:6 dilution of AM supernatants for 5 min at 37 degrees C and were then stimulated with 5 microM A23187 for 15 min. Separation of AM supernatants by size-exclusion HPLC using a TSK G3000 SW column resulted in a peak of enhancing activity with an estimated molecular mass of approximately 30,000 D. Further purification by anion exchange HPLC using a TSK DEAE 5PW column (pH 7.4) resolved the activity into a minor peak at 0.17 M NaCl and a major peak at 0.2 M NaCl. The activities were distinct from interleukin-1 and tumor necrosis factor. Resolution of the major peak of activity by reverse-phase HPLC using a C18 spherisorb ODS column and a slope gradient of 0 to 100% acetonitrile/0.1% trifluoroacetic acid demonstrated a single peak of activity that eluted at 41% acetonitrile. The enhancing activity was sensitive to trypsin and heat and was neutralized by a specific antibody to granulocyte-macrophage colony-stimulating factor (GM-CSF). Pretreatment of EOS with recombinant GM-CSF primed the cells for enhanced LTC4 generation following subsequent stimulation with A23187. GM-CSF may play a role in the amplification of the eosinophilic inflammation in asthmatic airways.

Human lung fibroblast-derived granulocyte-macrophage colony stimulating factor (GM-CSF) mediates eosinophil survival in vitro

Tissue eosinophilia has been reported to occur in pulmonary fibrosis, a disease characterized by chronic inflammation and lung fibroblast proliferation. We have examined the in vitro interaction of these two cell types by determining the in vitro survival of human peripheral blood eosinophils co-cultured with human lung fibroblasts. Survival of eosinophils cultured alone was 10% at day 3 and less than 1% at day 7. In contrast, survival of eosinophils that had been co-cultured with fibroblasts was 98, 90, 73, and 69% at days 3, 7, 10, and 14, respectively. Fibroblast-conditioned medium (CM) elicited a similar result in a dose-dependent fashion. Survival of eosinophils cultured with CM which had been preincubated with a monoclonal-neutralizing antibody to human GM-CSF was inhibited in a dose-dependent manner. Human recombinant-derived GM-CSF supported eosinophil survival in the dose-dependent fashion. Survival at day 7 of eosinophils treated with one single dose of GM-CSF (10 U/ml) was 64%. The effect of fibroblast-CM on eosinophils likely represents true survival since eosinophil proliferation as determined by [3H]thymidine incorporation did not occur. We also report that freshly isolated eosinophils had normal ultrastructural, scanning and transmission electron microscopy characteristics, and were normodense. In contrast, eosinophils co-cultured for 7 days with fibroblasts acquired irregular shapes and became hypodense and partially degranulated. Thus, our results indicate that human lung fibroblast-derived GM-CSF mediates the in vitro survival of human eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)

The cytokine network

The availability of pure recombinant cytokines and molecular probes for their genes has generated an avalanche of scientific information. These data show that cytokines have a broad and overlapping range of cell regulatory activity both in vitro and in vivo. New factors are added to the cytokine list, and new functions reported for existing cytokines, with such frequency that it is difficult to retain an overall picture. With this problem in mind, a large wallchart was designed and was displayed at the second meeting of the British Cytokine Group* whose members pooled their collective knowledge, to list the known biological activities of these cytokines. This wallchart of cytokine activity, now referenced, is reproduced for Immunology Today. It is not a final list: new information and cytokines are continually reported and space has been left for readers to make their own additions. A neutrophil-activating peptide variously named monocyte-derived neutrophil chemotactic factor (MDNCF), neutrophil-activating factor (NAF), lymphocyte-derived neutrophil-activating peptide (LYNAP), which has been suggested as a candidate for interleukin 8 (IL-8), is included.

Interleukin 3 activates human blood basophils via high-affinity binding sites

Pure populations of human basophilic granulocytes were obtained from chronic myeloid leukemia (CML) blood by negative selection using a mixture of monoclonal antibodies and complement. 125I-radiolabeled recombinant human interleukin 3 (rhIL-3) bound to purified basophils in a specific manner. Quantitative binding studies and Scatchard plot analyses performed on samples from two donors revealed the presence of a single class of high-affinity IL-3 binding sites (500 and 2100 sites per cell; dissociation constant at equilibrium, 230 and 160 pmol/liter, respectively). Purified CML basophils maintained in suspension in the presence of rhIL-3 (100 units/ml) incorporated up to 12 times more [3H]thymidine than basophils in control cultures. Furthermore, after preincubation in vitro with rhIL-3 (100 units/ml) for 30 min, normal blood basophils released 2- to 3-fold more histamine than basophils pretreated with control medium when exposed to various concentrations of an anti-IgE antibody. Together, these results show that rhIL-3 binds to a specific receptor on blood basophils and is a regulator of basophil function.

Interleukin 5 and phenotypically altered eosinophils in the blood of patients with the idiopathic hypereosinophilic syndrome

We report that the hypodense eosinophil population in three patients with corticosteroid-unresponsive IHES was uniquely long lived ex vivo in the absence of exogenous cytokines. Serum or plasma from these patients conferred prolonged viability ex vivo to normodense eosinophils from reference donors and converted them to a functionally activated hypodense phenotype. In that antibody against IL-5 neutralized this activity in IHES serum, excessive quantities of this cytokine may account for the characteristic eosinophilia and long-lived, functionally augmented eosinophil phenotype in this disorder.