Normodense Eosinophils Research Articles

Interleukin-5, interleukin-3 and granulocyte-macrophage colony-stimulating factor prime actin-polymerization in human eosinophils: A study with hypodense and normodense eosinophils from patients with atopic dermatitis

Characteristic features of atopic diseases (AD) are immigration and local activation of eosinophils. Reorganization of the cytoskeleton modulates the function of leukocytes and is a prerequisite for the motility response. In this work, the regulation of actin polymerization has been investigated by flow cytometry using NBD-phallacidin and right angle light scatter measurements in purified eosinophils isolated from patients with atopic dermatitis and normal individuals. Stimulation of eosinophils with chemotaxins such as complement fragment C5a (C5a), CC chemokine RANTES/ CCL5 and platelet activating factor (PAF) induced a reversible polymerization of actin. Normodense eosinophils purified from patients with AD showed a decreased chemotaxin-induced actin response as compared to normodense eosinophils from healthy subjects and hypodense eosinophils from patients. Stimulation of eosinophils with Th2-cytokines such as interleukin-3 (IL-3), interleukin-5 (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF) did not exert a significant effect on actin polymerization. However, pretreatment with IL-3, IL-5 or GM-CSF potentiated the chemotaxin-induced actin polymerization and graded the differential responsiveness between normodense and hypodense eosinophils. We demonstrate a different actin responsiveness in eosinophils from atopic patients and healthy subjects which could be overcome by modulating effects of Th2-cytokines.

Murine hypodense eosinophils induce tumour cell apoptosis by a granzyme B-dependent mechanism.

Eosinophils have been shown to potentiate anti-tumour cytotoxicity in both clinical and animal studies. The mechanism by which eosinophils induce tumour cell damage, however, has largely been speculative. The purpose of this study was to identify the mechanisms involved in eosinophil-induced tumour cell cytotoxicity. To investigate eosinophil cytotoxicity, eosinophils were isolated from the peritoneal cavity of Mesocestoides corti-infected BALB/c mice, and were separated into normodense (ND) and hypodense (HD) populations using discontinuous Percoll density gradient centrifugation. The tumoricidal activity of ND and HD eosinophils was assessed using the [51Cr]-release cytotoxicity assay (a measure of cytolytic activity) and the JAM assay (a measure of apoptotic activity). Investigation of apoptosis-inducing molecules in HD eosinophils was undertaken by RT-PCR. The calcium chelator EGTA, serine protease inhibitor aprotinin and a competitive substrate for granzyme B were used to assess the role of perforin and granzyme B in HD eosinophil killing. Cytotoxic activity induced by HD eosinophils was significantly greater than that of ND eosinophils, and apoptosis was the principal killing mechanism. RT-PCR analysis revealed that HD eosinophils express mRNA for perforin, granzyme B and Fas ligand. Furthermore, HD eosinophil killing was markedly inhibited by EGTA, intracellular aprotinin and the granzyme B competitive substrate. These data are consistent with a hypothesis that murine HD eosinophils elicit tumoricidal activity via a granzyme B-dependent mechanism.

Distinct amplification of the C5a-receptor pathways in normodense and hypodense eosinophils of patients with atopic dermatitis.

In patients with atopic dermatitis two different types of blood eosinophils with distinct density can be isolated. The normodense cells represent the huge majority in count, whereas the hypodense eosinophils are characterized by higher effector activity. To understand the altered functional responsiveness of these two cell subtypes, the expression of C5a receptors as well as C5a-induced signal pathways and the production of reactive oxygen metabolites have been analyzed. Chemiluminescence measurements revealed significant higher production of reactive oxygen metabolites in hypodense eosinophils in comparison to normodense cells. However, no difference in the expression level of C5a receptors as well as in the C5a-induced Ca2+-transients between normodense and hypodense eosinophils were found. In contrast, hypodense eosinophils showed a significantly higher actin polymerization response and phosphatidylinositol 4,5 bisphosphate 3-kinase activation after stimulation with C5a than normodense eosinophils. Therefore, normodense and hypodense eosinophils from the blood of patients with atopic dermatitis are characterized by differential amplification of C5a-receptor signal pathways, which might explain the differences in their proinflammatory activity.

Regulation of ICAM-3 and other adhesion molecule expressions on eosinophils in vitro. Effects of dexamethasone.

ICAM-3 has been recently identified as the third leukocyte-function associated-1 (LFA-1) ligand. ICAM-3 is expressed in eosinophils, but its regulation has not been studied. The objective of this study was to investigate the differential expression of ICAM-3 and other adhesion molecules (AM) on the surface of eosinophils. We also evaluated the effects of dexamethasone on AM expression. Normodense eosinophils were isolated from peripheral blood and incubated with calcium ionophore A23187 (calcimycin) with and without dexamethasone. Expression of AM was assessed by flow cytometry and expressed as fluorescence mean intensity (FMI). Peripheral blood eosinophils constitutively expressed low levels of ICAM-1 and ICAM-2 (<10 FMI), moderate levels (10-50 FMI) of CD29 and L-selectin, and high levels (>50 FMI) of ICAM-3, LFA-1, and Mac-1. Calcium ionophore (1 microM) significantly increased Mac-1 and ICAM-1 expression at 6 and 24 h. L-selectin expression decreased at 6 and 24 h, but ICAM-2, ICAM-3, LFA-1, and CD29 expression did not show any significant change after calcium ionophore stimulation. Dexamethasone decreased ICAM-3 and increased L-selectin basal expression, and it caused a dose-related inhibition of calcium ionophore-induced ICAM-1 expression. These findings suggest that some AM, such as ICAM-1, Mac-1, and L-selectin, may be involved in adhesion during eosinophil activation and that glucocorticoids may prevent airway inflammation by regulating the expression of AM in eosinophils. The role of ICAM-3, a leukocyte AM highly expressed in resting eosinophils, remains to be clarified.

Effect of topical anti-inflammatory drugs on epithelial cell-induced eosinophil survival and GM-CSF secretion.

Topical anti-inflammatory drugs decrease eosinophil infiltration. This action may be due to an effect on the release of epithelial cell products responsible for promoting eosinophil survival. We investigated the effect of fluticasone propionate, budesonide, beclomethasone dipropionate and nedocromil sodium on the release of granulocyte/macrophage colony-stimulating factor (GM-CSF) and on eosinophil survival induced by secretions from cultured nasal epithelial cells. Human epithelial cell-conditioned media (HECM) were generated by cultured epithelial cells obtained from healthy subjects undergoing corrective nasal surgery. Normodense eosinophils isolated from peripheral blood were incubated with HECM generated with and without the drugs. All of the drugs tested inhibited eosinophil survival, and response was dose-dependent. Fluticasone propionate had the highest inhibitory potency (25% inhibitory concentration (IC25) 1x10(-9) M), followed by budesonide (IC25 3.3x10(-8) M), beclomethasone dipropionate (IC25 1.5x10(-6) M), and nedocromil sodium IC25 5x10(-6) M). Likewise, fluticasone was the strongest steroid in inhibiting release of GM-CSF (IC25 8.4x10(-11) M), followed by budesonide (IC25 2x10(-9) M), beclomethasone dipropionate (IC25 13x10(-8) M), and nedocromil sodium (IC25 >10(-5) M). A significant correlation was found between both inhibitory effects (r=0.955; p<0.05). Topical anti-inflammatory drugs may decrease eosinophil survival by abrogating the promoting effect of epithelial cells. These drugs may exert part of their therapeutic effect by modulating GM-CSF release. The following rank of potency was observed: fluticasone propionate > budesonide > beclomethasone dipropionate > nedocromil sodium. The study of the interaction between epithelial cells and eosinophils may be a useful method for investigating and comparing the potency of topical drugs.

Differentiation of eosinophils from cord blood cell precursors: kinetics of Fc epsilon RI and Fc epsilon RII expression.

Expression of Fc epsilonRI and Fc epsilonRII/CD23 was examined by immunocytochemistry and flow cytometry on eosinophils differentiated from human cord blood cells in the presence of human interleukin-3 (rhIL-3), granulocyte/macrophage colony stimulating factor (rhGM-CSF) and interleukin-5 (rhIL-5) and on blood eosinophils purified from normal donors or patients with idiopathic hypereosinophilic syndrome (HES). On cord blood derived eosinophils, Fc epsilonRI expression started at 1 week of culture and increased to reach a plateau at 3 weeks of culture. Fc epsilonRII/CD23 appeared slightly later, after 2 weeks of culture, and the percentage of Fc epsilonRII/CD23-positive eosinophilic cells increased and stayed in plateau. Fc epsilonRI expression on cord blood derived eosinophils was downregulated after culture with interleukin-2 (rhIL-2), interleukin-4 (rhIL-4), rhIL-5, interferon-alpha (rhIFN-alpha), interferon-gamma (rhIFN-gamma). In contrast, the expression of Fc epsilonRII/CD23 on cord blood derived eosinophilic cells was upregulated after culture with rhIL-4, rhIL-5 and rhIFN-gamma, and downregulated with rhIL-2 and rhIFN-alpha. Fc epsilonRI was expressed on about 30% normal donor eosinophils as well as on normodense eosinophils from HES patients but significantly decreased on hypodense eosinophils. In contrast, Fc epsilonRII/CD23, expressed on a very small proportion of normal donor eosinophils, increased from normodense to hypodense eosinophils. These results suggest that Fc epsilonRI on eosinophils might represent one differentiation antigen expressed relatively early, with decreased expression through maturation or activation, whereas Fc epsilonRII/CD23 might rather be considered as a marker of eosinophil activation.

Increased hypodense eosinophils after activation with PAF-acether and calcium ionophore in asthmatic subjects.

Eosinophils play a major role in the pathogenesis of bronchial asthma. In this study, we examined the density characteristics of blood eosinophils from 9 normal healthy individuals and 9 allergic asthmatic patients. Furthermore, the effect of platelet-activating factor, a potent mediator of inflammation, and calcium ionophore, A23187, on the density of normodense eosinophils (density > 1.085 g/ml) has also been examined. Initially, asthmatic patients had 27.0 +/- 1.1% eosinophils of lighter density (density < or = 1.081 g/ml), significantly greater than that in the normal individuals (7.5 +/- 0.5%). After exposure to platelet-activating factor (1 microM) or calcium ionophore (A23187, 1 microgram/ml), the normodense eosinophils switched to hypodense in both groups: 16.7 +/- 2.1% and 54.2 +/- 3.7%, respectively, in normal individuals, and 30.6 +/- 5.7% and 77.4 +/- 2.3%, respectively, in asthmatic patients. These data demonstrated that a certain percentage of normodense eosinophils from asthmatics and normal subjects switched to hypodense after activation with platelet-activating factor or calcium ionophore. Furthermore, eosinophils from asthmatics switched to a greater degree than in normal subjects, suggesting that the normodense eosinophils in asthmatics become primed probably by endogenously released mediators.

The effect of cetirizine on the integrin-dependent respiratory burst of normodense eosinophils.

It has been proposed that cetirizine inhibits eosinophil migration and adherence. We evaluated the possible effect of cetirizine on integrin-induced eosinophil proinflammatory activation. Normodense eosinophils were triggered with monoclonal antibodies to integrins in the presence of different concentrations of certirizine. Proinflammatory activation was measured by evaluation of O2- production. Only at high concentrations (250 micrograms/ml) and in the first 15 min did certirizine significantly inhibit (p < 0.02) the eosinophil respiratory burst. No effect was shown for lower concentrations (50 and 100 micrograms/ml) or after 15 min. These data suggest that, only at very high concentrations, cetirizine may induce a transient inhibition of the integrin-induced eosinophil respiratory burst.

Blood eosinophil leukotriene C4 production in asthma of different severities

In asthma, activation and recruitment of eosinophils to the bronchial mucosa amplifies many cellular functions. The blood eosinophil count and the number of hypodense eosinophils increase with asthma severity. Eosinophils produce numerous proinflammatory mediators in response to a variety of agonists, notably the peptido-leukotriene (LT) C4, a potent bronchoconstrictor. In this study, we have evaluated blood eosinophil LTC4 release and its modulation by cytokines in normal individuals and in subjects with asthma of various severities: mild (beta 2-agonist on demand); moderate (inhaled steroids on a regular basis); and severe (inhaled and oral steroids on a regular basis). Eosinophils were isolated using a modified Percoll gradient technique, which recovers both hypodense and normodense eosinophils in a global cell population. Eosinophils released detectable amounts of LTC4 only in the presence of the stimulus (calcium ionophore A23187, 2 microM). The ionophore-induced LTC4 release was greater in moderate asthmatics (mean +/- SEM 5.7 +/- 1.3 pg x 10(3)/250,000 eosinophils) than in normal individuals (1.6 +/- 0.4 pg x 10(3)/250,000 eosinophils), mild asthmatics (1.8 +/- 0.3 pg x 10(3)/250,000 eosinophils) and severe asthmatics (2.0 +/- 0.3 pg x 10(3)/250,000 eosinophils). Granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin-5 (IL-5) amplified the ionophore-induced LTC4 release in the four groups from 1.9 to 2.6 and 1.9 to 2.8 fold, respectively. Interleukin-3 (IL-3) did not increase LTC4 production except by the eosinophils of the severe asthmatics whose ionophore-induced LTC4 production was enhanced by 1.9 fold. These data demonstrate that the asthmatic bronchial inflammatory process may modify blood eosinophil LTC4 release and its modulation by cytokines according to asthma severity and treatment.

The skin as a model to study the pathogenesis of IgE-mediated acute and late-phase responses

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Incorporation of radioactive phosphate from adenosine triphosphate into phosphatidylinositol-4-phosphate in human peripheral blood hypodense eosinophils is less than in the normodense eosinophils.

Peripheral blood eosinophils from patients with atopic dermatitis and normal healthy controls were isolated on a Percoll gradient and incubated with [gamma 32P]ATP in the presence of Mg2+. After stopping the reaction, lipid extraction was performed with acidic medium and phospholipids were separated by thin-layer chromatography on 1% (w/v) oxalic acid-impregnated silica gel plates. In the autoradiographs considerable amounts of the radioactivity were found to be incorporated into phosphatidylinositol-4-phosphate. 32P incorporation into phosphatidylinositol-4-phosphate in hypodense eosinophils from atopic dermatitis patients was less than in normodense eosinophils from the same patients and controls.

1,1'-Ethylidenebis(tryptophan) (Peak E) induces functional activation of human eosinophils and interleukin 5 production from T lymphocytes: association of eosinophilia-myalgia syndrome with a L-tryptophan contaminant.

This study was designed to clarify the important association between eosinophilia-myalgia syndrome (EMS) and the L-tryptophan contaminant, "Peak E." To determine the functional activation of eosinophils induced by Peak E, eosinophil cationic protein (ECP) release was examined. Peak E augumented the release of ECP from peripheral blood normodense eosinophils by degranulation. Proliferative analysis using the human eosinophilic leukemia cell line EoL-3 showed prominent cellular replication in the presence of Peak E. Moreover, Peak E upregulated interleukin 5 (IL-5) receptor levels on normodense eosinophils. Of particular interest, Peak E-stimulated human splenic T cells produced bioactive and immunoreactive IL-5. Marked induction of IL-5 mRNA in Peak E-stimulated T cells was also shown by reverse-transcriptase polymerase chain reaction (RT-PCR). In contrast, L-tryptophan without the contaminant showed none of these effects. Thus, these data suggest that Peak E might be involved in the pathogenesis of EMS through bimodal mechanism including IL-5 generation by T cells and potentiation of eosinophil functional activation.

Induction of lung eosinophilia and neutrophilia in guinea pigs following injection of sephadex beads.

We have developed a method of induction of airway eosinophilia and neutrophilia in guinea pigs by intravenous injection of various types of Sephadex beads. In the first series of experiments, we have shown that G-50 Sephadex beads (Superfine, 24 mg/kg in conscious animals) induced a large accumulation of inflammatory cells in alveolar walls. The bronchoalveolar lavage (BAL) fluid from animals treated with this dose of Sephadex beads contained about 85 x 10(6) cells as compared to 20 x 10(6) cells in control animals. The eosinophils corresponded to 41% of the BAL cell population as assessed with Wright-Giemsa staining. However, in the BAL fluid from these bead-treated animals, a significant increase of monocytes, lymphocytes, and neutrophils was also observed. We have also tested the potency of G-75, G-100, and G-200 Sephadex beads (Superfine) to induce eosinophilia in guinea pig. Nonlethal intravenous doses of G-75 (14.27 mg/kg), G-100 (8.0 mg/kg), and G-200 (10.71 mg/kg) Sephadex beads were selected and induced variable levels of airway eosinophilia and neutrophilia in conscious guinea pigs. The percentage of eosinophil recovered in the BAL fluid corresponded to 35, 61, and 44% of total cells for G-75, G-100, and G-200, respectively. The neutrophils corresponded to 24, 2, and 12% of the total BAL cells for G-75, G-100, and G-200, respectively. Since the size of the beads did not seem to correlate with the intensity of airway eosinophilia and neutrophilia, the effect of lower doses of the G-50 Sephadex beads (9.86-0.43 mg/kg) on the inflammatory cell infiltration was also tested. Results showed that there was a correlation between the neutrophil number and the number of beads (r = 0.996), whereas the number of eosinophils was less directly correlated to the bead number (r = 0.812). The alveolar eosinophils were purified from BAL fluid by centrifugation on a continuous Percoll gradient (65%) to separate eosinophils from neutrophils. Normodense eosinophils (density 1.087-1.100 g/ml) obtained from Sephadex-treated animals were found at the bottom of the continuous Percoll gradient (25 x 10(6); 98% purity). These highly purified eosinophils released thromboxane A2 (TxA2) following stimulation with 2 microM ionophore A23187. The method of accumulation and purification of guinea pig alveolar eosinophils is simple, rapid, and provides a large number of pure normodense cells for further biological studies.(ABSTRACT TRUNCATED AT 400 WORDS)

A simple and rapid method for isolation of eosinophilic granulocytes from human blood

A simple and rapid method for the purification of morphologically and functionally intact eosinophils from human blood of both normal and eosinophilic subjects is described. The method is based on a single centrifugation of total blood leukocytes suspended in Percoll with specific gravity 1.0853 g/ml, after erythrocyte removal by dextran sedimentation. The peculiarity of this isolation technique is the maintenance of strictly physiological values of pH and osmolality throughout the entire procedure. Moreover, the cells are not subjected to measures aimed at changing the physical properties of either neutrophils or eosinophils. Because of such characteristics, this isolation method could be usefully exploited for comparative studies of normal and eosinophilic normodense eosinophils and of neutrophils and eosinophils from the same noneosinophilic subject.

Nasal Tissue Eosinophils in Allergic Rhinitis

The density characteristics and functional heterogeneity of nasal tissue eosinophils were studied. The density distribution profiles of eosinophils from patients with allergic rhinitis (AR) showed peaks at densities of 1.068 to 1.084 g/ml, significantly lower than the densities of eosinophils in non-allergic patients with nasal polyps and chronic sinusitis (p < 0.01). The proportion of hypodense eosinophils in patients with AR was 43%; this was significantly greater than that in non-allergic subjects (p < 0.001). Patients with AR tended to have more EG2-positive tissue eosinophils. Furthermore, normodense eosinophils in nasal tissue tended to show a higher percentage of EG2-positive cells than hypodense eosinophils. On the other hand, circulating hypodense eosinophils showed a higher percentage of EG2-positive cells than normal density eosinophils. These results suggest that tissue eosinophils may be activated, and that the functional heterogeneity of eosinophils is dependent on factors other than cell density.

A simple and rapid method for isolation of eosinophilic granulocytes from human blood.

A simple and rapid method for the purification of morphologically and functionally intact eosinophils from human blood of both normal and eosinophilic subjects is described. The method is based on a single centrifugation of total blood leukocytes suspended in Percoll with specific gravity 1.0853 g/ml, after erythrocyte removal by dextran sedimentation. The peculiarity of this isolation technique is the maintenance of strictly physiological values of pH and osmolality throughout the entire procedure. Moreover, the cells are not subjected to measures aimed at changing the physical properties of either neutrophils or eosinophils. Because of such characteristics, this isolation method could be usefully exploited for comparative studies of normal and eosinophilic normodense eosinophils and of neutrophils and eosinophils from the same noneosinophilic subject.

Activation of human eosinophils in vitro by respiratory syncytial virus.

To determine the nature of the interaction between viruses and eosinophils, normodense eosinophils were separated from the blood of healthy volunteers and incubated in vitro with respiratory syncytial virus (RSV). After incubation for 2 h with the virus, 29.5 +/- 15.8% of the eosinophils demonstrated specific binding of the virus to the cell membrane, as detected by fluorescent staining with an anti-RSV MAb. Superoxide production and leukotriene C4 release were measured as determinants of cell activation. Using a cytochrome c reduction assay, superoxide could be detected in the supernatant 30 min after exposure to RSV. Maximal release was reached at 3 h postexposure (5.88 +/- 2.19 nmol cytochrome c reduction/5 x 10(5) cells). The virus-induced superoxide generation varied in magnitude among different subjects and ranged from 0.6 to 11.5 nmol cytochrome c reduction/5 x 10(5) cells. RSV also appeared to prime eosinophils to the effects of other known cell activators, as demonstrated by an increase in superoxide production upon subsequent stimulation of RSV-primed cells with phorbol-12-myristate-13-acetate (21.4 +/- 5.8 versus 9.4 +/- 2.7 nmol cytochrome c reduction/5 x 10(5) cells for primed and unprimed cells, respectively) (p less than 0.04). RSV did not directly induce leukotriene C4 release from the eosinophils but primed the cells to exhibit a more vigorous response on subsequent challenge with the calcium ionophore A23187 (9.16 +/- 1.04 versus 4.2 +/- 1.3 ng leukotriene C4/1 x 10(6) cells) (p less than 0.005). These findings indicate that RSV can activate or prime eosinophils to release various inflammatory mediators.(ABSTRACT TRUNCATED AT 250 WORDS)

Formation of LTB4 by fMLP-stimulated alveolar macrophages accounts for eosinophil migration in vitro.

Guinea pig alveolar macrophages obtained by bronchoalveolar lavage were isolated by adherence for 2 h and stimulated with 1 microM of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) for different time intervals. The supernatants then were tested for their chemotactic effect on guinea pig peritoneal normodense eosinophils and for release of thromboxane B2, leukotriene B4 (LTB4), and platelet activating factor (PAF). The supernatant from fMLP-stimulated alveolar macrophages induced a significant eosinophil attraction (96.0 +/- 11.9, number of migrating eosinophils [mean +/- SEM], n = 17) as compared to unstimulated macrophages (4.8 +/- 1.4, n = 15). This effect was not accounted for by fMLP carry-over to the macrophages because, in contrast to human eosinophils, fMLP has no chemotactic effect on guinea pig eosinophils. Pretreatment of eosinophils with BN 52021 (100 microM), a specific PAF antagonist, and with indomethacin (10 microM), a cyclooxygenase inhibitor, failed to inhibit migration of eosinophils induced by supernatants from either stimulated or unstimulated alveolar macrophages. In contrast, inhibition of the 5-lipoxygenase enzyme with N-(3-phenoxycinamyl)-acetohydroxamic acid (1 microM) suppressed eosinophil migration by alveolar macrophage supernatants (94.1 +/- 2.6% of inhibition, n = 6). Desensitization of eosinophils by and to LTB4 (10 nM) inhibited migration induced by supernatants from stimulated alveolar macrophages (87.5 +/- 5.4% of desensitization toward LTB4 and 83.1 +/- 5.4% of desensitization toward supernatants, n = 5). Under the present experimental conditions, LTB4 is the only agent implicated in eosinophil migration induced by supernatants from fMLP-stimulated alveolar macrophages.

Opposing effects of tumor necrosis factor-alpha and nerve growth factor upon leukotriene C4 production by human eosinophils triggered with N-formyl-methionyl-leucyl-phenylalanine.

Tumor necrosis factor (TNF) as well as the hematopoietic growth factors interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor affect several eosinophil functions. We previously reported (J. Exp. Med. 1989. 170: 467; 1990. 172: 1577) that the hematopoietic growth factors also potentiate leukotriene C4 (LTC4) formation by eosinophils as well as basophils stimulated with soluble chemotactic peptides such as N-formyl-methionyl-leucyl-phenylalanine (FMLP), but whether TNF also modulates lipid mediator generation in normodense eosinophils triggered with FMLP is unknown. Here we show that a short preincubation (10 min) of human eosinophils purified from healthy donors with low concentrations of TNF (5-150 pM) strongly enhances LTC4 formation in response to FMLP. However, basophil mediator release is not affected by TNF preincubation. Nerve growth factor (NGF), the receptor of which is structurally related to the TNF receptors, tended to suppress lipid mediator synthesis in eosinophils, in contrast to its profound potentiating capacity on basophil mediator release. Thus, the present study demonstrates a first difference in susceptibility of eosinophils and basophils towards cytokines, indicating that TNF and NGF may regulate the relative importance of effector functions of these otherwise closely related cell types.

Density profile of bronchoalveolar lavage eosinophils in the guinea pig model of allergen-induced late-phase allergic responses.

Inhalation of aerosolized ovalbumin by guinea pigs both during sensitization and upon challenge induces a pulmonary eosinophilia as assessed by cells recovered in bronchoalveolar lavage fluid (BALF). In comparison with BALF eosinophil numbers in naive animals of 0.82 +/- 0.2 x 10(6) cells, those in sensitized animals before challenge and 17 and 72 h after challenge were 1.48 +/- 0.2 x 10(6), 2.60 +/- 0.6 x 10(6), and 4.2 +/- 0.7 x 10(6) cells, respectively. BALF eosinophils from all these groups were notable for their heterogeneity with respect to density, size, and appearance under the electron microscope. In comparison with peritoneal eosinophils, which had a single mean density peak of 1.088 +/- 0.001 g/ml, BALF cells comprised hypodense (less than 1.080 g/ml), normodense (1.080 to 1.096 g/ml), and hyperdense (greater than 1.096 g/ml) eosinophils. The percentage of hypodense eosinophils rose from 25% in naive animals to 63% in sensitized animals (P less than 0.001) and fell after challenge. In contrast, challenge induced the appearance of hyperdense eosinophils, which rose from 6% in sensitized animals to 42% 72 h after challenge (P less than 0.001). Blood eosinophils in naive animals showed a similar profile to those in the lung, but after sensitization and challenge no gross changes in the proportion of either hypodense or hyperdense eosinophils were observed. Flow cytometric analysis of BALF eosinophils indicated that hypodense eosinophils, with a mean diameter of 15.8 microns, were larger than both normodense and hyperdense eosinophils, which had mean diameters of 14.3 and 11.6 microns, respectively. Although the numbers and size of granules were not reduced in hypodense BAL eosinophils, electron microscopy morphology indicated a reduced granular content.(ABSTRACT TRUNCATED AT 250 WORDS)