An Extragranular Compartment of Blood Eosinophils Contains Eosinophil Protein X/Eosinophil-Derived Neurotoxin (EPX/EDN)

Serum and plasma profiles of eosinophil protein X (EPX/EDN) and those of other eosinophil proteins differ in various conditions, suggesting a different mobilisation from storage granules. This work studied the subcellular localisation of EPX/EDN in non-primed and in vivo primed blood eosinophils from healthy and allergic subjects, during and out of the pollen season. Primed eosinophils contain easily mobilisable secretory proteins. By fractionation on sucrose density gradients, EPX/EDN localised in the specific granules as well as in a cytoplasmic extra-granular compartment of low equilibrium density that partially overlapped with vesicular structures, cytosolic proteins and plasma membranes. This compartment was clearly separate from the low density peak of ECP that increases during the pollen season. There were no significant differences in the amounts of EPX/EDN present in the low density peak of healthy and allergic subjects. Immuno-gold labelling electron microscopy showed EPX/EDN in specific granules, cytoplasm and associated to plasma membranes. In conclusion, substantial amounts of EPX/EDN localise in an extra-granular, low equilibrium density compartment of human eosinophils.     

PI3-Kinase Regulates Eosinophil and Neutrophil Degranulation in Patients with Allergic Rhinitis and Allergic Asthma Irrespective of Allergen Challenge Model

The PI3K pathway plays a major role in many vital cell processes. Our primary aim was to investigate signalling through PI3K for in vitro degranulation from allergen-primed eosinophils and neutrophils in allergic rhinitis and allergic asthma after seasonal and experimental allergen challenge. Nine patients with allergic rhinitis, eight with allergic asthma and four controls were studied during birch pollen season and after nasal and bronchial allergen challenge. Primed blood eosinophils and neutrophils were stimulated for in vitro degranulation with C3b-coated Sephadex particles, after prior incubation with Wortmannin, a PI3K inhibitor. The released amounts of eosinophil cationic protein (ECP), eosinophil peroxidase (EPO) and myeloperoxidase (MPO) were measured by radioimmunoassay. Wortmannin (10⁻⁶ to 10⁻⁹ M) inhibited ECP, EPO and MPO release in a dose-dependent manner in allergic rhinitis and allergic asthma in all three allergen challenge models. Inhibition of ECP release tended to be lower in the asthmatics in all allergen challenge models, statistically significant compared to the controls during season for 10⁻⁸ M Wortmannin (p = 0.01). A clear propensity towards less inhibition in the rhinitic patients was seen after nasal and bronchial challenge compared to seasonal exposure, significant for ECP (10⁻⁸ M Wortmannin; p = 0.034 and 0.002, respectively). Signalling through PI3K is clearly involved in ECP, EPO and MPO release in allergic rhinitis and allergic asthma irrespective of allergen challenge model. Allergic asthma demonstrated less inhibition of ECP release via PI3K during pollen season, indicating that other pathways play a greater role in eosinophil degranulation in allergic asthma than allergic rhinitis.     

Eosinophil cationic protein and myeloperoxidase in nasal secretion as markers of inflammation in allergic rhinitis

The inflammatory component of allergic rhinitis was studied by measuring the concentration and content of eosinophil cationic protein (ECP, specific for eosinophils) and myeloperoxidase (MPO, specific for neutrophils) in samples of nasal secretion from 20 pollen-allergic subjects. All secretion samples contained measurable concentrations of both proteins. The mean ECP concentrations on two occasions without pollen exposure were 950 and 1170 micrograms/l. The ECP concentration during the pollen season without any therapy (mean 1160 micrograms/l) did not differ significantly from the baseline values, but intranasal corticosteroid therapy resulted in a significant decrease (mean 530 micrograms/l). The concentration of MPO was about 10 times higher than that of ECP, but the changes in MPO were nonsignificant throughout the observation period. An inverse correlation was found between the threshold dose in histamine challenges and the ECP level expressed either as concentration or as content. Furthermore, the ECP concentration and content 1 day after a positive allergen challenge were both significantly correlated with the strength of the challenge reaction. Measurements of ECP in nasal secretions are useful for studying the presence and activity of eosinophils in the nasal mucosa, and may prove of value in clinical investigations on patients with allergic rhinitis.     

Ragweed-specific IgA in nasal lavage fluid of ragweed-sensitive allergic rhinitis patients: increase during the pollen season

Because the secretions of asthma and rhinitis contain toxic eosinophil granule proteins and because secretory IgA is the most potent immunoglobulin stimulus for eosinophil degranulation, we measured eosinophil-derived neurotoxin and ragweed-specific IgA and IgE antibodies in nasal lavage before and during the ragweed pollen season in 44 hay fever patients. We found IgA antibody in nanogram/milliliter concentrations before the season and rising 20-fold by the end of the season. IgE antibody was present in picogram/milliliter concentrations and did not change. Eosinophils and eosinophil-derived neurotoxin also increased. We conclude that IgA is the predominant antibody in allergic nasal secretions and increases with allergen exposure. The hypothesis that secretory IgA antibody-allergen complexes contributes to allergic inflammation by stimulating eosinophil degranulation warrants further study.     

Circulating eosinophils in asthma, allergic rhinitis, and atopic dermatitis lack morphological signs of degranulation

BACKGROUND: In allergic diseases, eosinophils in affected tissues release granule proteins with cytotoxic, immunoregulatory, and remodelling-promoting properties. From recent observations, it may be assumed that eosinophils degranulate already in circulating blood. If degranulation occurs in the circulation, this could contribute to widespread systemic effects and provide an important marker of disease. OBJECTIVE: To determine the degranulation status of circulating eosinophils in common allergic diseases. METHODS: Using a novel approach of whole blood fixation and leucocyte preparation, the granule morphology of blood eosinophils from healthy subjects, non-symptomatic patients, symptomatic patients with asthma, asthma and Churg-Strauss syndrome, allergic rhinitis, and atopic dermatitis was evaluated by transmission electron microscopy (TEM) and eosinophil peroxidase (TEM) histochemistry. Plasma and serum levels of eosinophil cationic protein were measured by fluoroenzymeimmunoassay. Selected tissue biopsies were examined by TEM. RESULTS: Regardless of symptoms, circulating eosinophils from allergic patients showed the same granule morphology as cells from healthy subjects. The majority of eosinophil-specific granules had preserved intact electron-density (96%; range: 89-98%), while the remaining granules typically exhibited marginal coarsening or mild lucency of the matrix structure. Abnormalities of the crystalline granule core were rarely detected. Furthermore, granule matrix alterations were not associated with any re-localization of intracellular EPO or increase in plasma eosinophil cationic protein. By contrast, eosinophils in diseased tissues exhibited cytolysis (granule release through membrane rupture) and piecemeal degranulation (loss of granule matrix and core structures). CONCLUSION: In symptomatic eosinophilic diseases, circulating blood eosinophils retain their granule contents until they have reached their target organ.     

Monitoring nasal allergic inflammation by measuring the concentration of eosinophil cationic protein and eosinophils in nasal secretions

Quantitative measurement of the eosinophil cationic protein (ECP) concentration and the percentage of eosinophils in nasal secretions has greatly improved our understanding of the inflammatory process after natural allergen exposure. ECP and eosinophils were measured in the nasal secretions of 40 symptomatic patients with seasonal allergic rhinitis during the pollen season. Results showed a significant relationship between a high concentration of ECP (median: 410 ng/g, range: 6–2380 ng/g) and a high percentage of eosinophils (median: 13.5%, range: 1–85%). This quantitative study again demonstrated that infiltration by eosinophils and release of ECP play a key role in allergic rhinitis. It also suggests that the combined measurement of the percentage of eosinophils together with the ECP concentration in nasal secretions seems to be a very useful model in monitoring and assessing the condition of chronic nasal inflammation in patients with allergic rhinitis.     

Albumin, bradykinins, and eosinophil cationic protein on the nasal mucosal surface in patients with hay fever during natural allergen exposure

This study examined plasma- and eosinophil-derived products in nasal lavage fluids obtained from patients with hay fever during natural allergen exposure. Nine patients with strictly seasonal allergic rhinitis and five normal, nonallergic subjects (control group) were studied. Nasal lavages were performed twice weekly, starting 1 week before the expected birch-pollen season and continuing for 6 weeks, thereby covering the entire birch-pollen season. Nasal symptoms and pollen counts were recorded daily. The lavage fluid was analyzed for it content of albumin, bradykinins, and eosinophil cationic protein (ECP). During the pollen season, each of these solutes was significantly increased in the nasal lavage fluid from the allergic patients (p less than 0.05) but not from the control subjects. Albumin, bradykinins, and ECP generally correlated better between themselves than with symptoms and pollen counts. We conclude that natural exposure to allergens induces plasma exudation and increased levels of ECP on the human nasal mucosa.     

A sensitive high throughput ELISA for human eosinophil peroxidase: A specific assay to quantify eosinophil degranulation from patient-derived sources

Quantitative high throughput assays of eosinophil-mediated activities in fluid samples from patients in a clinical setting have been limited to ELISA assessments for the presence of the prominent granule ribonucleases, ECP and EDN. However, the demonstration that these ribonucleases are expressed by leukocytes other than eosinophils, as well as cells of non-hematopoietic origin, limits the usefulness of these assays. Two novel monoclonal antibodies recognizing eosinophil peroxidase (EPX) were used to develop an eosinophil-specific and sensitive sandwich ELISA. The sensitivity of this EPX-based ELISA was shown to be similar to that of the commercially available ELISA kits for ECP and EDN. More importantly, evidence is also presented confirming that among these granule protein detection options, EPX-based ELISA is the only eosinophil-specific assay. The utility of this high throughput assay to detect released EPX was shown in ex vivo degranulation studies with isolated human eosinophils. In addition, EPX-based ELISA was used to detect and quantify eosinophil degranulation in several in vivo patient settings, including bronchoalveolar lavage fluid obtained following segmental allergen challenge of subjects with allergic asthma, induced sputum derived from respiratory subjects following hypotonic saline inhalation, and nasal lavage of chronic rhinosinusitis patients. This unique EPX-based ELISA thus provides an eosinophil-specific assay that is sensitive, reproducible, and quantitative. In addition, this assay is adaptable to high throughput formats (e.g., automated assays utilizing microtiter plates) using the diverse patient fluid samples typically available in research and clinical settings.     

Regulation of the release of eosinophil cationic protein by eosinophil adhesion

BACKGROUND: Varying release of eosinophil granule proteins depending on the stimulus and environmental factors has previously been reported. OBJECTIVE: To investigate the degranulation from adherent eosinophils by using mixed granulocytes. METHODS: Granulocytes isolated by Percoll gradient centrifugation were incubated on plates coated with plasma and tissue fibronectin, fibrinogen or human serum albumin (HSA) and stimulated with Mn2+, phorbol-myristate-acetate (PMA), formyl-methionyl-leucyl-phenylalanine (f-MLP) and combinations thereof, respectively. The release of eosinophil cationic protein (ECP) was measured by radioimmunoassay. RESULTS: Unstimulated eosinophils incubated in wells coated with plasma and tissue fibronectin, fibrinogen or HSA did not release any ECP. Furthermore, Mn2+ (5 mmol/L) did not induce release of ECP despite the fact that adhesion of eosinophils to these four proteins was induced. PMA stimulated a dose-dependent release of ECP. Contemporaneous stimulation of eosinophils with PMA and Mn2+ induced a dramatically increased release of ECP regardless of which protein the eosinophils were adhering to. A small but significant release of ECP was found when eosinophils incubated on plates coated with fibrinogen and HSA were stimulated by f-MLP. Contemporaneous stimulation of eosinophils with f-MLP and Mn2+ did not induce any synergistic effect on the release of ECP. On the contrary, Mn2+ inhibited the release of ECP induced by f-MLP from eosinophils. Serum-opsonized Sephadex particles stimulated a potent increase of the release of ECP up to 12%-14% in the presence of plasma fibronectin and, in particular, fibrinogen. The kinetics of eosinophil adhesion and degranulation showed that the cellular adhesion preceded the degranulation response and that the degranulation patterns depend on the stimuli and environment. CONCLUSION: The present study indicated that cellular adhesion plays an important role in the regulation of eosinophil degranulation, but that adhesion and degranulation can be induced separately.     

Mechanisms of eosinophil secretion: large vesiculotubular carriers mediate transport and release of granule-derived cytokines and other proteins

Eosinophils generate and store a battery of proteins, including classical cationic proteins, cytokines, chemokines, and growth factors. Rapid secretion of these active mediators by eosinophils is central to a range of inflammatory and immunoregulatory responses. Eosinophil products are packaged within a dominant population of cytoplasmic specific granules and generally secreted by piecemeal degranulation, a process mediated by transport vesicles. Large, pleiomorphic vesiculotubular carriers were identified recently as key players for moving eosinophil proteins from granules to the plasma membrane for extracellular release. During secretion, these specialized, morphologically distinct carriers, termed eosinophil sombrero vesicles, are actively formed and direct differential and rapid release of eosinophil proteins. This review highlights recent discoveries concerning the organization of the human eosinophil secretory pathway. These discoveries are defining a broader role for large vesiculotubular carriers in the intracellular trafficking and secretion of proteins, including selective receptor-mediated mobilization and transport of cytokines.     

Evidence for eosinophil degranulation in acute appendicitis

Finding of increased numbers of eosinophils in the muscle in cases of acute appendicitis has led to the hypothesis that it may have an allergic origin. This study aimed to measure the eosinophil degranulation resulting in a rise in the serum of eosinophil granule proteins that would be expected in such cases. The levels of serum eosinophil cationic protein (ECP) measured by chemiluminescence assay in acute appendicitis were compared, with those of appropriate controls. Mean (95% CI) serum ECP (microg/L) levels were: acute appendicitis 45.3 (27.7-63.0); normal appendix 22.7 (16.0-29.3); asthma 24.2 (4.6-43.8); and healthy volunteers 13.2 (8.3-18.1). In cases of acute appendicitis, there is an inverse relationship between duration of symptoms and serum ECP. However, this was not statistically significant. Significant local eosinophil activation and degranulation occurs in acute appendicitis, enough to cause a rise in serum levels of eosinophil chemotactic protein.     

Major basic protein, but not eosinophil cationic protein or eosinophil protein X, is related to atopy in cystic fibrosis.

Increased eosinophil granule proteins have been described in serum and sputum samples of patients with cystic fibrosis (CF). It has been assumed that eosinophil degranulation is enhanced in atopic subjects - as in asthmatics. Since in CF no differences in eosinophil cationic protein (ECP), eosinophil protein X (EPX), and eosinophil peroxidase between atopic and nonatopic subjects have been detected, we investigated whether major basic protein (MBP) is increased in serum and sputum samples derived from atopic (n = 14) compared with nonatopic CF subjects (n = 26). In CF patients, high mean serum (sputum) levels of ECP 29.7 microg/l (2.7 mg/l), EPX 53.7 microg/l (7.9 mg/l), and MBP 984.6 microg/l but low sputum MBP levels (57.4 microg/l) were measured. In addition, in serum and in sputum samples, a significant correlation between MBP and ECP (P<0.03 and P<0.0001, respectively) or EPX (P<0.05 and P<0.0004, respectively) was detected. By subdivision of the patients into allergic and nonallergic subjects, significant differences were found for serum MBP values only(mean 1382.2 microg/l vs. 770.5 microg/l; P<0.0001), but not for ECP or EPX serum levels or for eosinophil proteins in sputum. Although no differences between atopic and nonatopic CF patients in ECP and EPX were found, serum MBP levels were higher in patients sensitized to inhalant allergens than in nonsensitized subjects. These results indicate differential release of eosinophil granule proteins in peripheral blood from eosinophils, and they also indicate that MBP in serum likely is to be a better discriminator of atopy in CF.     

Effect of natural seasonal pollen exposure and repeated nasal allergen provocations on elevation of exhaled nitric oxide

Background:  Exhaled nitric oxide (FENO) is a marker for allergic airway inflammation. We wondered whether in patients with intermittent allergic rhinitis only (i) natural pollen exposure and (ii) artificial pollen exposure by repeated nasal allergen provocations may lead to an elevation of FENO.
Methods:  In two prospective studies, we compared the FENO of nonatopic controls with the FENO of nonasthmatic individuals with mild intermittent rhinitis to tree and/or grass pollen. Study I: 13 atopic individuals and seven controls had measurements of FENO, blood eosinophils and eosinophilic cationic protein (ECP) before, during and after pollen season. Study II: 16 atopic individuals and 12 controls had nasal allergen provocations on four following days out of pollen season, with daily measurements of FENO before, 2 and 6 h after provocation, and determination of blood eosinophils, ECP and FEV1 at baseline, on days 5 and 10–12.
Results:  Natural pollen exposure (study I) caused a significant elevation of FENO in allergic individuals. Nasal allergen provocations (study II) did not elicit a statistically significant rise neither of FENO nor of blood eosinophils between baseline and day 5. However, a subgroup of four individuals with a rise of blood eosinophils during nasal allergen provocations showed also a rise of FENO.
Conclusions:  We suppose that in allergic rhinitis a concomitant reaction of the bronchial system is dependent on a strong local inflammation leading to a generalized immune stimulation.     

The degree of natural allergen exposure modifies eosinophil activity markers in the circulation of patients with mild asthma

We have previously found that CD9, CD11b, and intracellular ECP (EG2) may be used as activity markers for eosinophils in vitro . The main object of the present study was to determine whether these markers can reflect eosinophil activation in vivo in relation to allergen exposure. For this purpose, six patients with a history of allergic rhinitis and occasional asthma symptoms during the pollen season participated. Blood donors served as controls. Peripheral blood eosinophils were analyzed according to the FOG method and flow cytometry, before and during one birch pollen season with high pollen load (HPL) and one with low pollen load (LPL). The CD9 expression on peripheral eosinophils from the patients was significantly increased both before (P<0.05) and during (P<0.01) HPL season, and CD11b expression solely during HPL season (P = 0.01) as compared to controls. The intracellular expression of the EG2 epitope was increased before (P<0.01) and during (P<0.05) HPL season, and increased significantly (P<0.05) during season as compared to before. No changes were observed before and during LPL season. The proportion of eosinophils was increased both before (P<0.05) and during (P<0.001) the HPL season as compared to controls. The markers CD9, EG2, and, to a lesser extent, CD11b seem to detect activated eosinophils in the circulation, whereas EG2 may also reflect increased antigen exposure during season.     

Immunofluorescence analysis of cytokine and granule protein expression during eosinophil maturation from cord blood–derived CD34 progenitors

Background: In allergic inflammation and asthma, eosinophils are major effector cells. They have been shown to synthesize at least 23 cytokines, some of which are stored intracellularly in their unique crystalloid granules together with cationic granule protein. Little is known about the synthesis and storage of cytokines relative to cationic granule proteins in maturing eosinophils during eosinophilopoiesis. Objective: Our purpose was to analyze the expression of eosinophil-derived mediators, major basic protein (MBP), eosinophil cationic protein (ECP), IL-6, and RANTES, during early stages of eosinophil maturation in CD34⁺ cell-derived colonies. Methods: Purified human cord blood CD34⁺ cells were grown in methylcellulose cultures in the presence of recombinant human IL-3 and IL-5. By confocal laser scanning microscopy, the coexpression of eosinophil granular proteins MBP and ECP was determined concurrently with IL-6 and RANTES during eosinophil maturation on days 16, 19, 23, and 28 of culture. Results: Immunoreactivity against MBP, ECP, IL-6, and RANTES was not detectable in freshly purified CD34⁺ cells. Maturing eosinophils (>95%) exhibited positive immunostaining for all these proteins between days 16 and 28 of culture. At early stages of culture, discrete immunostaining was observed around the periphery but not in the center of granular structures. By day 28 cultured eosinophil-like cells showed evidence of the acquisition of crystalloid granule-like structures, analogous to those observed in mature peripheral blood eosinophils. Conclusions: Eosinophils express and store cytokines simultaneously with cationic granule proteins during the process of maturation. We propose that the storage of cytokines during the development of eosinophils is an early event and it may be integral to inflammatory responses involving these cells. The results of this study suggest a potential immunoregulatory function for maturing eosinophils. (J Allergy Clin Immunol 2000;105:1178-84.)     

The formation of eosinophil and neutrophil chemotactic activity during a pollen season and after allergen challenge

Heat-stable (HS) and heat-labile (HL) neutrophil chemotactic activities (NCAs) have been demonstrated in serum after allergen challenge of subjects with asthma. In this investigation, we have studied the possible occurrence of similar activities in 20 atopic individuals on natural exposure to allergen, that is, during the birch-pollen season. Since eosinophil accumulation is a hallmark of an ongoing allergic inflammation in the respiratory tract also, the possible production of eosinophil chemotactic activity (ECA) was examined in serum after allergen challenge and at natural exposure to pollen. Both HL-NCA and HL-ECA were produced to a significant extent (p less than 0.001) during the season, with the peak of activities occurring simultaneously with the peak pollen count. HL-ECA was produced after allergen challenge of subjects with asthma in the laboratory, as has been demonstrated for NCA previously. The activity of the HS-NCA was unaltered during season. Gel-filtration studies of the major HL-NCA and HL-ECA indicated a molecular weight for both activities of 100 to 150,000, and the activities produced during season cochromatographed with the HL-NCA and HL-ECA produced after allergen challenge in the laboratory, suggesting that all these activities are due to one and the same molecule. The results suggest that the heat-labile chemotactic activity found in serum of atopic subjects and subjects with asthma after allergen exposure may be involved in the attraction of eosinophils and neutrophils to the site of allergic inflammation.     

Characterization of eosinophils and detection of eotaxin in skin chamber fluid after challenge with relevant allergen in patients with mild asthma

BACKGROUND: A selective recruitment of eosinophils to sites of allergic inflammation is suggested to be controlled by regulation of cytokines, chemokines and adhesion molecules. OBJECTIVE: The aim of this study was to examine whether allergen challenge in skin chambers, applied on patients with allergic rhinitis and mild asthma, results in a selective influx of activated eosinophils and detectable levels of cytokines/chemokines related to eosinophil recruitment, such as interleukin (IL)-5 and eotaxin. METHODS: A skin blister was induced on the volar aspect of each forearm; one contained PBS-heparin buffer (control) and the other was challenged with relevant allergen. Peripheral blood was drawn before the allergen was applied to the skin chamber, and the expression of CD9, CD11b and EG2-epitope on intracellular eosinophil cationic protein (ECP) was analysed in eosinophils. Chamber fluid was collected 8 h after allergen application and analysed for differential cell counts, expression of eosinophil activity markers, the presence of ECP, eotaxin, and IL-5. RESULTS: The number of recruited leucocytes was equal in the allergen-challenged chambers and in controls. However, the number of eosinophils was significantly increased in the allergen-challenged chambers, and elevated levels of released ECP were measured. Moreover, the eosinophils recruited were activated, as shown by increased expression of EG2 and CD11b, and decreased expression of CD9, in comparison with blood eosinophils. In the skin chamber fluids, higher levels of eotaxin were detected in the allergen-challenged chambers than in controls, but there were no detectable levels of IL-5. CONCLUSION: We have demonstrated a selective recruitment of eosinophils, and higher levels of released ECP and eotaxin, in skin chambers stimulated with allergen, as compared with control chambers. Allergen challenge in skin chambers is a useful tool for studies of eosinophil recruitment, their state of activation, and their involvement in the allergic inflammatory response.     

Oxygen radical production by blood eosinophils is reduced during birch pollen season in allergic patients

Background The eosinophil granulocyte takes part in allergic inflammatory diseases, like asthma and rhinitis. The aim of this study was to investigate the oxidative metabolism of the blood eosinophils and neutrophils from birch pollen allergic patients, during and after exposure to their allergen. Methods Thirteen birch pollen allergic patients, with seasonal symptoms of rhinitis, with or without asthma, were followed. The cells were purified using a percoll gradient and the MACS system. The eosinophil purity in all samples was >95%. The oxidative metabolism of both the PMN and the eosinophils was measured by means of a chemiluminescenee (CL) assay, with luminol or lucigenin as the amplifier, and using PMA (16nM) as the activator. Results In relative terms, the lucigenin CL by the eosinophils was 5-10-foId higher than that of the PMN, P= 0.002. The eosinophils of the birch pollen allergic patients produced less oxygen radicals during the season, compared to the reference group, measured both with luminol CL and lucigenin CL, P=0.01 and P= 0.02 respectively. Out of season, there was no difference. There was also no difference, during either period, between patients and references in PMN CL. Separating the eosinophils into hypodense and normodense fractions, showed a decreased oxidative metabolism by the hydrodense eosinophils. Conclusion We conclude that the eosinophils of birch pollen allergic patients have reduced production of oxygen radicals when the patients are exposed to their allergen, which could depend on higher amounts of hypodense eosinophils in the blood during season.     

Immunoelectron microscopic evidence for release of eosinophil granule matrix protein onto microfilariae of Onchocerca volvulus in the skin after exposure to amocarzine

The involvement of eosinophils in the host reaction to microfilariae (mf) of Onchocerca volvulus was studied by immunohistochemistry and immunoelectron microscopy. Skin biopsies were obtained from patients after transepidermal administration of the microfilaricide amocarzine. At 20–28 h after the application of amocarzine, mf were degenerated or dead and a marked eosinophil-parasite adherence (EPA) reaction was seen, with intense staining for intra- and extracellular eosinophil granule proteins such as eosinophil cationic protein (ECP) surrounding the mf. Immunoelectron microscopically the eosinophil granule matrix in intact and necrotic eosinophils was specifically labeled, whereas granules whose matrix had dissolved showed no specific gold particle binding. As specific labeling was seen on lowly electron-dense material adjacent to matrix-depleted granules, the material was regarded as released eosinophil granule matrix material. Intact and necrotic eosinophils, matrix-containing as well as matrix-depleted eosinophil granules, and released eosinophil granule matrix material were observed on the surface of damaged mf and between collagen fibers. The coincidence of mf degeneration, EPA reaction, and release of eosinophil granule matrix material on damaged mf and collagen fibers indicated a role of eosinophils and eosinophil granule matrix protein in the host reaction to mf after amocarzine application. Received: 3 March 1998 / Accepted: 13 March 1998