A current perspective on the role of eosinophils in dermatologic diseases

Effect of benralizumab on inflammation in skin after intradermal allergen challenge in patients with moderate-to-severe atopic dermatitis

Background

Atopic dermatitis (AD) is a skin barrier dysfunction characterized by tissue eosinophilia.

Objective

In patients with AD, we evaluated the effect of eosinophil depletion with benralizumab on markers of inflammation in skin after intradermal allergen challenge.

Methods

A total of 20 patients with moderate-to-severe AD completed a randomized, double-blind, placebo-controlled parallel-group study comparing 3 doses of benralizumab (30 mg each) administered subcutaneously every 4 weeks (n = 9) with placebo (n = 11). Allergen and saline control intradermal challenges were conducted before and after treatment, with skin biopsy samples collected 24 hours after challenge. Early and late cutaneous responses were measured by skin wheal size. Levels of eosinophils and IL-5 receptor-α-bearing cells, including eosinophil progenitor (EoP) cells, basophils, and mast cells, in papillary dermis were measured by immunofluorescence microscopy, and levels of EoP cells, hematopoietic progenitor cells, and type 2 innate lymphoid cells in the blood were measured by flow cytometry. Outcomes were compared between the placebo and benralizumab treatment groups by using the Mann-Whitney U test.

Results

Benralizumab reduced eosinophil counts in the blood (P < .0001) and allergen-challenged skin, as measured by hematoxylin and eosin staining and eosinophil cationic protein antibody concentration (P < .05). Benralizumab lowered the levels of EoP cells, mast cells, and basophils in the skin, as well as the levels of EoP cells, hematopoietic progenitor cells, and type 2 innate lymphoid cells in the blood (all P < .05). There was a trend toward improvement in the early cutaneous response (P = .095) but no effect on the late cutaneous response.

Conclusion

In patients with moderate-to-severe AD, benralizumab treatment significantly inhibited accumulation of eosinophils and other IL-5 receptor-α-expressing cells in the papillary dermis after intradermal allergen challenge. Targeting IL-5 receptor-α-positive cells did not modulate the size of the allergen-induced skin wheal (ClincialTrials.gov identifier NCT03563066).

Apoptosis of Eosinophil Granulocytes

Simple Summary

Eosinophil granulocytes (eosinophils) belong to the family of white blood cells that play important roles in the development of asthma and various types of allergy. Eosinophils are cells with a diameter of 12–17 µm and they originate from myeloid precursors. They were discovered by Paul Ehrlich in 1879 in the process of staining fixed blood smears with aniline dyes. Apoptosis (programmed cell death) is the process by which cells lose their functionality. Therefore, it is very important to study the apoptosis of eosinophils and their survival factors to understand how to develop new drugs based on the modulation of eosinophil apoptosis for the treatment of asthma and allergic diseases.

Abstract

In the past 10 years, the number of people in the Czech Republic with allergies has doubled to over three million. Allergic pollen catarrh, constitutional dermatitis and asthma are the allergic disorders most often diagnosed. Genuine food allergies today affect 6–8% of nursing infants, 3–5% of small children, and 2–4% of adults. These disorders are connected with eosinophil granulocytes and their apoptosis. Eosinophil granulocytes are postmitotic leukocytes containing a number of histotoxic substances that contribute to the initiation and continuation of allergic inflammatory reactions. Eosinophilia results from the disruption of the standard half-life of eosinophils by the expression of mechanisms that block the apoptosis of eosinophils, leading to the development of chronic inflammation. Glucocorticoids are used as a strong acting anti-inflammatory medicine in the treatment of hypereosinophilia. The removal of eosinophils by the mechanism of apoptosis is the effect of this process. This work sums up the contemporary knowledge concerning the apoptosis of eosinophils, its role in the aforementioned disorders, and the indications for the use of glucocorticoids in their related therapies.

T-Helper Type 2 Cells Direct Antigen-Induced Eosinophilic Skin Inflammation in Mice

Eosinophilic inflammation in combination with immunoglobulin E (IgE) production is a characteristic feature of atopic dermatitis. Although activated T-helper type (Th) 2 cells play critical roles in the local accumulation and activation of eosinophils, whether they induce eosinophilic skin inflammation, independent of the IgE-mediated pathway has been unclear. To address the functional role of T cells in allergic skin diseases, we herein transferred Th1/Th2-differentiated or naive DO11.10 T cells into unprimed BALB/c mice. Ovalbumin-specific Th2 cells, as well as eosinophils, accumulated in the skin upon antigen challenge, despite the absence of antigen-specific IgE. Neither antigen-specific Th1 nor naive T cells induced eosinophil accumulation, although Th1 cells by themselves migrated into the skin. Interleukin (IL)-4, IL-5, and eotaxin were specifically produced in the skin of antigen-challenged, Th2 cell-transferred mice, whereas interferon (IFN)-γ and regulated on activation, normal T cell expressed and secreted (RANTES) were preferentially produced in Th1 cells-transferred mice. Production of monocyte chemoattractant protein (MCP)-1 and MCP-3 was enhanced by both Th1 and Th2 cells. The accumulation of eosinophils and Th2 cells in the skin was suppressed by both dexamethasone and FK506, indicating an essential role of Th2 cells in eosinophil recruitment. We conclude that Th2 cells can induce eosinophilic infiltration into the skin in the absence of antigen-specific IgE.

Clinico-immunological profile and their correlation with severity of atopic dermatitis in Eastern Indian children

OBJECTIVE

To study the clinical features, absolute eosinophil count, and total immunoglobulin E (IgE) level and their association with severity of atopic dermatitis in Eastern Indian children (Bihar).

DESIGN

Prospective hospital-based study.

SETTINGS

Pediatrics out-patient Department (OPD) and Dermatology OPD of a Tertiary Care Teaching Hospital located in Rohtas District of Bihar. The study was carried out over a period of 2 years during January 2010 to December 2011.

PARTICIPANTS

One hundred and thirty two children aged 0 month to 15 years were diagnosed with atopic dermatitis.

MAIN OUTCOME

Demographic profile, common clinical features, absolute eosinophil count, and total IgE level and their correlation with severity of atopic dermatitis in Eastern Indian children.

RESULTS

Out of a total 1829 pediatric patients aged 0 month to 15 years with some pediatric dermatoses, 132 (7.21%) had atopic dermatitis. Of 132 patients, 57 (43.2%) were boys and 75 (56.8%) were girls, with a male to female ratio 1:1.3. Of these 29 were infants and 103 were children. Two (62.1%) patients belonged to rural area whereas 50 (37.9%) belonged to urban area. Personal history, family history (up to third degree relatives), and both personal and family history of atopy were present in 43.18%, 33.34%, and 12.1% of the subjects respectively. Majority (89.4%) of patients had onset before 5 years of age. In infantile Atopic dermatitis (AD), mean age ± SD at onset was 5.2 months ± 3.01 months. In infantile group, 8 (27.6%) had mild, 14 (48.3%) moderate, and 7 (24.1%) had severe atopic dermatitis. Infantile AD had statistically significant higher SCORing Atopic Dermatitis (SCORAD) index score in all three grades of severity of the disease. One hundred and three patients had childhood AD, out of which 40 (38.8%) were boys and 63 (61.2%) were girls, with a male to female ratio 1:1.57. In childhood AD, mean age ± SD at onset of the disease was 3.47 years ± 3.02 years. Sixty three (61.1%) belonged to rural area whereas 40 (38.9%) were from urban area. One hundred and thirty (98%) patients presented with itching. Ninety two (69.7%) patients had high absolute eosinophils count (AEC) with mean ± SD of 1004.1 ± 596.2 (range 325-2510). Eighty seven (65.9%) patients had increased total serum immunoglobulin E (TsIgE) with mean ± SD value of 1127.11 IU/ml ± 731.69 IU/ml (range: 125-2680 IU/ml).

CONCLUSION

Epidemiological data on atopic dermatitis in India are mainly hospital-based, true-point prevalence in community is still scanty. Although the prevalence of AD is considered to be increasing, it still remains low in comparison to developed countries. In Indian children, the disease is relatively milder than children of developed countries. This study identified that both AEC and TsIgE increased significantly in about 66% patient and directly correlated with the severity of the AD.

Blood eosinophils and serum eosinophil cationic protein in patients with acute and chronic urticaria

We have analysed the relationship of blood eosinophil count and serum eosinophil cationic protein (ECP) levels in patients with acute and chronic idiopathic urticaria. The ECP levels and eosinophil counts were measured in the peripheral blood of 15 patients with acute urticaria, 25 with chronic idiopathic urticaria and 10 normal healthy subjects. Blood eosinophil counts and serum ECP levels increased in all patients with acute urticaria. Concerning patients affected by chronic urticaria, taking into account the recrudescence of the disease at the moment of taking the blood sample, only symptomatic patients showed increased eosinophil blood values whereas serum ECP levels were increased both in symptomatic and asymptomatic patients. Furthermore, serum ECP levels in chronic urticaria did not correlate with the peripheral eosinophil counts, as they did in acute urticaria. The results of the present study indicate that eosinophils may play a role in the inflammatory mechanisms in patients with acute and chronic urticaria showing a positive correlation between serum ECP levels and disease activity.

Analysis of serum total IgE, specific IgE and eosinophils in children with acute and chronic urticaria

BACKGROUND/PURPOSE

Increased IgE and eosinophil levels are frequently observed in cutaneous inflammation and are thought to provoke the occurrence of urticaria. However, the relationship of these factors with the disease duration of urticaria remains unclear. The aim of this study was to compare serum total IgE levels, specific IgE sensitization rates and eosinophil percentages between acute and chronic urticaria in children.

METHODS

A total of 165 patients (104 with acute and 61 with chronic urticaria) from a tertiary referral hospital were enrolled in this study. Serum levels of total IgE, prevalence of sensitization to food and aeroallergens and blood eosinophil percentages were compared by the disease duration of urticaria.

RESULTS

There were no statistical differences in total IgE production, positive sensitization to specific allergens and eosinophil percentages between the patients with acute and chronic urticaria. There is a higher prevalence of sensitization to aeroallergens than food allergens in children with urticaria. In terms of gender, males had significantly higher serum IgE levels than females.

CONCLUSION

Boys potentially have a higher serum IgE expression than girls children with urticaria. IgE levels and eosinophil percentages are not good indicators for a prolonged course of urticaria. The prevalence of sensitization to aeroallergens was significantly higher than that of food allergens in children with urticaria. Routine laboratory analysis for common allergens is not appropriate, and it could be a feasible approach to detect a predilection for atopy when respiratory infections are causative factors of urticaria occurrence.

IgE, mast cells, and eosinophils in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific immune and inflammatory mechanisms. Atopy is among the major features of the diagnosis criteria for AD but is not an essential feature. Thus, patients diagnosed with AD can be atopic or non-atopic. This review focuses on the role of IgE, mast cells, and eosinophils in the pathogenesis of AD. The known functions of IgE in allergic inflammation suggest that IgE and IgE-mediated mast cell and eosinophil activation contribute to AD, but direct evidence supporting this is scarce. The level of IgE (thus the degree of allergic sensitization) is associated with severity of AD and contributed by abnormality of skin barrier, a key feature of AD. The function of IgE in development of AD is supported by the beneficial effect of anti-IgE therapy in a number of clinical studies. The role of mast cells in AD is suggested by the increase in the mast cell number and mast cell activation in AD lesions and the association between mast cell activation and AD. It is further suggested by their role in mouse models of AD as well as by the effect of therapeutic agents for AD that can affect mast cells. The role of eosinophils in AD is suggested by the presence of eosinophilia in AD patients and eosinophil infiltrates in AD lesions. It is further supported by information that links AD to cytokines and chemokines associated with production, recruitment, and activation of eosinophils.

Dermal fibroblasts from acute inflamed atopic dermatitis lesions display increased eotaxin/CCL11 responsiveness to interleukin-4 stimulation

BACKGROUND

The presence of eosinophils and/or eosinophil-derived products in the dermis is characteristic for involved skin of patients with atopic dermatitis and contributes to the observed tissue injury. CCL11 is a potent chemoattractant and activator of human eosinophils and interleukin (IL)-4 is a potent inducer of CCL11 expression in dermal fibroblasts.

OBJECTIVES

As increased fibroblast CCL11 expression may explain eosinophilic infiltration of involved skin areas in atopic dermatitis, we asked whether dermal fibroblasts from atopic patients differ from fibroblasts of healthy individuals in their ability to express CCL11.

METHODS

We compared IL-4-induced CCL11 mRNA expression using reverse transcription-polymerase chain reaction from cultured dermal fibroblasts derived from biopsies of chronic lesional and acute lesional atopic skin as well as from skin biopsies derived from normal skin of healthy donors.

RESULTS

Considerable variability in IL-4-induced relative CCL11 mRNA expression was detected in fibroblasts derived from biopsies of different individuals. The lowest median IL-4 concentration inducing half maximal CCL11 mRNA expression (EC(50)) was found in fibroblasts derived from acute inflamed atopic lesions.

CONCLUSIONS

Inducibility of CCL11 in dermal fibroblasts upon stimulation with Th2 cytokines explains the tissue eosinophilia observed in the presence of Th2 cytokines and the localization of eosinophils to the dermis. Decreased EC(50) values of IL-4-induced CCL11 expression in fibroblasts from acute inflamed atopic skin lesions indicates increased IL-4 responsiveness in these lesions and further substantiates the special role for IL-4-induced dermal fibroblast CCL11 expression in acute lesions. Variable CCL11 expression in fibroblasts from different patients with atopic dermatitis indicates heterogeneity of factors determining atopic phenotype in atopic dermatitis.

Increase effect of transforming growth factor on eotaxin production by normal cultured dermal fibroblasts stimulated with interleukin-4: inhibitory effect of suplatast tosilate on eotaxin production

Eotaxin plays a central role in the development of allergic disease, including atopic dermatitis, asthma, and nasal allergy. Interleukin (IL)-4 induces eotaxin production in normal human dermal fibroblasts. On the other hands, Transforming growth factor-beta (TGF-beta), a multifunctional regulatory cytokine, affects many biological functions, including fibroblast growth and differentiation and Th2 cytokine regulation. In this study, we investigated the effect of TGF-beta on IL-4-induced eotaxin production by normal human fibroblasts, as well as the effect of suplatast tosilate, an antiallergic drug that selectively inhibits Th2 cytokine production. Dermal fibroblast treatment with IL-4 and TGF-beta for 24 h increased eotaxin production and expression of eotaxin mRNA, as measured by enzyme-linked immunosorbent assay (ELISA) and reverse-transcriptase polymerase chain reaction (RT-PCR), respectively. TGF-beta synergistically up-regulated eotaxin production and eotaxin mRNA expression when stimulated with IL-4. Suplatast tosilate dose-dependently inhibited eotaxin production induced by IL-4 or IL-4 plus TGF-beta. These results suggest that TGF-beta may regulate skin allergic inflammation by up-regulating eotaxin production in dermal fibroblasts. Suplatast tosilate might suppress this inflammation by inhibiting eotaxin production.

Oral mucosa lesions in hypereosinophilic syndrome--an update

Hypereosinophilic syndrome (HES) is a rare disorder characterized by persistent and marked eosinophilia. Some HES forms have a poor prognosis, either because of end-organ damage (particularly endomyocardial fibrosis), or because of associated myeloid leukemia or malignant T-cell lymphoma. Oral mucosa ulcerations can be early clinical signs in severe forms. They are discrete, round or oval, sometimes confluent ulcers or erosions, located on non-keratinized, unattached oral mucosa. In the last 15 years a better understanding of eosinophil biology has led to a new clinical classification of HES. The lymphocytic form is characterized by T-lymphocyte clonality, IL-5 production, and a possible progression to T-cell lymphoma. Oral lesions are more frequently associated with the myeloproliferative form, characterized by an increased risk of developing myeloid malignancies and a good response to a recent anti-tyrosine kinase therapy (imatinib mesylate). The target of imatinib is a novel kinase resulting from an 800-kb deletion on chromosome 4. Recently, the resulting FIP1L1-PDGFRalpha fusion gene was characterized as a marker of response to imatinib. Exclusion of other erosive ulcerative oral disease and early recognition of HES in patients with oral ulcerations, and precise characterization of the lymphocytic or myeloproliferative form are therefore important to rapidly initiate an effective therapy.

Serum eosinophil cationic protein in children with atopic dermatitis

BACKGROUND

Eosinophil cationic protein (ECP) is a cytotoxic agent secreted by activated eosinophils during allergic and inflammatory processes. The aim of the study was to determine the ECP level, absolute and relative eosinophil count and IgE antibodies in children with atopic dermatitis (AD) compared with those of nonatopic children, and to assess the correlation of these laboratory parameters with the clinical severity of AD.

METHODS

This prospective study comprised 70 children. There were 49 children with AD aged 3-36 months, and the control group comprised 21 children with a negative personal and family history for atopic diseases. Detailed history, serum ECP levels (UniCAP FEIA), relative and absolute eosinophil counts and total serum IgE antibodies were determined in both groups. In the children with AD, skin involvement was measured by the SCORAD index.

RESULTS

The calculated SCORAD index was between 16 and 83. IgE antibodies, relative and absolute eosinophil counts showed a significantly wider range of values and a statistically higher median (P < 0.001) in the patients with AD compared with the control group. These laboratory parameters did not correlate with the severity of AD. The serum ECP median level, in the children with AD, was 16.2 microg/L (range 3.01-65.30) compared with 5.92 microg/L (range 2.76-21.90) in the control group. Correlation of the total SCORAD index and the serum ECP levels was negative, weak (r = -0.065) and statistically not significant (P > 0.05). The same was found for the correlation of serum ECP and intensity of skin changes (r = -0.095) and serum ECP and subjective symptoms (r = -0.045). The correlation was positive, but weak and statistically not significant for the serum ECP and extent of the skin lesions (r = 0.079, P > 0.05).

CONCLUSION

Elevated levels of ECP, relative and absolute eosinophil counts, as well as IgE antibodies were determined in the patients with AD. As these laboratory findings did not correlate with the severity of AD, they can be considered only as additional methods in the evaluation of patients with AD.

Mechanistic analysis of experimental food allergen-induced cutaneous reactions

Individuals with food allergy often present with uritcaria and atopic dermatitis. Indeed, susceptibility to food allergy may predispose to the development of these cutaneous allergic disorders. Recently, we developed a model of food allergy, whereby oral consumption of food [pea Pisum sativum L.; expressing alpha-amylase inhibitor-1 (alphaAI) from the common bean Phaseolus vulgaris L. cv Tendergreen (pea-alphaAI)] promotes a T helper cell type 2 (Th2) inflammatory response and predisposes to cutaneous allergic reactions following subsequent food allergen (alphaAI) exposure. To delineate the kinetics of food allergen-induced cutaneous reactions and examine the inflammatory mechanisms involved in this allergic reaction, we used interleukin (IL)-13-, IL-4 receptor alpha-, and eotaxin-1-deficient mice and performed serum transfer and CD4+ T cell depletion studies. We demonstrate that consumption of pea-alphaAI promotes an alphaAI-specific immunoglobulin G1 (IgG1) and IgE antibody response. Furthermore, we show that subsequent food allergen (alphaAI) challenge in the skin induced an early (3 h)- and late-phase (24 h) cutaneous allergic reaction. The early-phase response was associated with mast cell degranulation and the presence of Ig, whereas the late-phase response was characterized by a lymphoid and eosinophilic infiltrate, which was critically regulated by CD4+ T cells, IL-13, and eotaxin-1. Collectively, these studies demonstrate that food allergy can predispose to cutaneous inflammatory reactions, and these processes are critically regulated by Th2 immune factors.

Eosinophils and urticaria

Previously believed to have an exclusive role in the release of cytotoxic mediators in the defense against helminthic infections, eosinophils are now considered key players in inflammatory reaction and regulation of immune response. Through activation of a large variety of membrane receptors and production of various pharmacologically active mediators, eosinophils may exert a detrimental role in tissues in which they have been recruited and may contribute to the perennization of inflammatory processes. The crucial role of eosinophils has been documented in several eosinophilic skin diseases, such as hypereosinophilic syndrome and bullous pemphigoid, and the literature provides strong evidence for their role in urticaria. The aim of this article is to discuss the mechanisms of specific tissue recruitment of eosinophils, the factors of eosinophil activation, and the contribution of these cells to inflammation and immunoregulation in urticaria. Recent advances in the knowledge of eosinophils will certainly help toward developing new strategies for the management of antihistamines resistant to urticaria.

Sarcoptic mange in free-ranging raccoon dogs (Nyctereutes procyonoides) in Japan

Sarcoptes scabiei infestation was diagnosed in three freshly dead free-ranging raccoon dogs (Nyctereutes procyonoides) in Kanagawa Prefecture, Japan. The dogs presented with an alopecic pruritic skin disease, with signs of alopecia on the ears, muzzle, around the eyes, elbow, thigh and the neck, and hyperpigmented and crusted skin lesions, which had a severe malodour. Skin scrapings revealed the presence of the mite Sarcoptes scabiei. Histopathology of lesions demonstrated marked acanthosis, hyperkeratosis, parakeratosis and fungal elements, which were subsequently identified as Acremonium sp., Alternaria sp. and an unknown fungus. Mite segments were located mainly in the stratum corneum and also in the stratum granulosum. Tunnels could be observed in the hyperkeratotic stratum corneum. Scanning electron microscopy (SEM) revealed the tortoise-like Sarcoptes scabiei with four long bristles, suckers and blade-like claws on legs 1 and 2, cuticular spines, prominent body striations and a terminal anus. SEM also revealed an adult female mite digging a tunnel with the head wedged into the very end of the closed burrow. Tunnels filled with eggshells, corneocyte debris and faecal pellets were also observed.

A prospective study of the clinical findings, treatment and histopathology of 44 cases of pyotraumatic dermatitis

Pyotraumatic dermatitis (hot spot) is a common clinical syndrome in dogs but there are few prospective scientific studies related to it. The aim of this study was to investigate correlations among clinical pyotraumatic dermatitis, histopathology of the lesions and possible predisposing causes. The relationship of these with breed, age, sex and location of lesion was assessed statistically. A clinical diagnosis of acute pyotraumatic dermatitis was made in 44 privately owned dogs. Males exceeded females (P = 0.0348) and lesions were more common in dogs aged 4 years or less (P < 0.0001). Lesions were most often seen on the cheek, neck and lateral thigh with a significant correlation between breed and site of lesion (P < 0.0001). In 31 cases a possible underlying cause was found or suspected. In contrast to previous studies, no otitis externa was recorded and the study was conducted in an area without endemic fleas. Fourteen breeds were represented of which Rottweiler, German shepherd dog and golden retriever were most common. There was no significant seasonal incidence and no correlation among site of lesion and cause, time of year, age or sex. Histopathologically, the dogs could be separated into four patterns by the presence or absence of eosinophils and/or folliculitis. Eosinophils have not previously been recorded in pyotraumatic dermatitis but were seen in 29 cases. Acute folliculitis was seen in 20 cases. However, no correlation was seen among age, sex, breed, underlying cause or site of lesion and histopathology. Twenty-seven cases were cultured for bacteria of which 25 grew Staphylococcus intermedius and two were negative.

In situ eosinophil activation in 26 primary cutaneous T-cell lymphomas with blood eosinophilia

Blood and tissue eosinophils can be associated with Hodgkin and non-Hodgkin lymphomas in that they have prognostic value. Tissue eosinophils in T-cell lymphoma patients with blood eosinophilia have not been systematically assessed. The objective of this research was to study the presence, density, and activation of tissue eosinophils in patients with primary cutaneous T-cell lymphomas (CTCLs) with blood eosinophilia and a possible relationship between features of the disease and prognosis. With skin biopsy specimens from 26 CTCL patients with blood eosinophilia, tissue eosinophils were studied with electron microscopy, extracellular eosinophil peroxidase deposits, and interleukin-5 expression. Tissue eosinophils, found in 22 of 26 cases, were constantly activated. Both density and activation of tissue eosinophils were significantly related to disease progression. The state of activation of tissue eosinophils in CTCL might reflect inflammatory flare-ups associated with aggressive lymphomas. Further studies are needed to confirm the value of eosinophil density as a simple and reliable marker of CTCL progression.

Eosinophil infiltration and activation at the gastric ulcer margin in rats

BACKGROUND

Recruitment and activation of eosinophils have been studied intensely in asthma and other allergic diseases. Less is known about the infiltration and behaviour of eosinophils during gastric ulcer healing.

AIM

To examine the tissue infiltration and activation of eosinophils in the ulcer margin at different time points after ulcer induction (days 1-15).

METHODS

Eosinophil peroxidase (EPO) staining and transmission electron microscopy (TEM) were used to observe eosinophil infiltration and activation in rats with acetic-acid-induced ulcer in the oxyntic mucosa. The distribution of macrophages was evaluated by immunocytochemistry using the macrophage-specific antibodies ED1 and ED2.

RESULTS

There was a prominent increase in eosinophils around the ulcer margin at day 1 after ulcer induction, which peaked at day 5. TEM revealed characteristic signs of eosinophil activation, including cytolysis and piecemeal degranulation. Eosinophil cytolysis was the major form of activation, seen most frequently at day 5. A few scattered apoptotic eosinophils could also be observed. In normal controls and sham-operated rats, activated eosinophils were detected rarely. The distribution pattern of infiltrated eosinophils closely resembled that of macrophages at the ulcer margin. However, in the central part of the granulation tissue (at day 5) only macrophages could be found.

CONCLUSIONS

There is marked infiltration and signs of activation of eosinophils together with macrophages at the margin of newly formed ulcers.

Tissue eosinophilia in acute and chronic atopic dermatitis: a morphometric approach using quantitative image analysis of immunostaining

BACKGROUND

The frequency and amount of tissue eosinophilia in spontaneous lesions of acute and chronic atopic dermatitis (AD) are still a matter of controversy, and little is known about the distribution of eosinophilia in skin.

OBJECTIVES

To give a quantitative description of tissue eosinophilia in spontaneous lesions of acute and chronic AD based on morphometric data.

METHODS

Thirty-one lesional skin biopsies of AD were evaluated using our recently described method for the quantitative assessment of eosinophilic granule protein (EGP) deposition by image analysis of immunostaining using the antibodies EG1, EG2, MBP, EPO and neutrophil elastase (NE). The frequency, amount and distribution of protein deposition including extracellular EGP deposition as an indicator of complete activation and degranulation of eosinophils were determined. Eosinophil count was performed in addition. Histopathological parameters of acute dermatitis (spongiosis) and chronic dermatitis (epidermal hyperplasia) were scored to look for a correlation with tissue eosinophilia.

RESULTS

Tissue eosinophilia was found in nearly all biopsies (30 of 31). The most protein was detected by EG2, followed by EG1, MBP and EPO, with very small amounts of NE. A superficial tissue distribution of eosinophilia was found, with < 10% of total EGP deposition below a depth of 1.39 mm from the epidermis. Eosinophils were involved in acute, spongiotic dermatitis, but more tissue eosinophilia including EGP deposition was detected in lesions with pronounced epidermal hyperplasia than in biopsies without.

CONCLUSIONS

These data provide further evidence for the involvement of activated eosinophils in acute and chronic AD by a new quantitative in situ approach. Pronounced tissue eosinophilia, especially EGP deposition as the result of complete activation of eosinophils, is found in chronic AD and may be involved in the development or maintenance of chronicity.

Urine eosinophil protein X (EPX) is an in vitro parameter of inflammation in atopic dermatitis of the adult age

BACKGROUND

Eosinophils are important effector cells in several atopic diseases. The levels of eosinophil granule-derived mediators (ECP, EPX) in serum and body fluids have been proven to be correlated with disease activity in atopic respiratory diseases and atopic dermatitis. The study aimed to demonstrate an interrelationship between urine EPX and disease activity in adult patients with atopic dermatitis.

METHODS

We determined urine EPX concentration, serum ECP concentration, and peripheral blood eosinophil count in 40 adult patients with mild to severe atopic dermatitis and compared it with the disease activity as assessed with the SCORAD index.

RESULTS

Urine EPX and serum ECP concentrations were significantly higher in patients with severe atopic dermatitis than in patients with mild or moderate disease (median values 123.5 vs 78.3 microg/mmol creatinine, P<0.0001; 25.4 vs 14.9 microg/l, P<0.0001, respectively). We found a significant correlation between urine EPX levels, serum ECP levels, and the SCORAD (r=0.36, P<0.0001 and 0.34, P<0.0001, respectively).

CONCLUSION

Urine EPX is a useful in vitro parameter of inflammation in atopic dermatitis of the adult age.

Secretion and tissue content of eosinophil cationic protein in Crohn's disease

To define further the role of eosinophils in the pathogenesis of Crohn's disease, the secretion rate and tissue content of eosinophilic cationic protein (ECP) were measured in colorectal samples. Mucosal biopsies were obtained from 22 controls and 20 patients with Crohn's disease during colonoscopy. After measurement of the initial basal ECP, release samples were incubated using a mucosa oxygenation system. Spontaneous and antiimmunoglobulin E (anti-IgE)-induced secretions of ECP were measured at different time points. For detection of the remaining tissue, ECP amount samples were mechanically homogenized after the incubation period. ECP measurement was performed by radioimmunoassay. Spontaneous ECP secretion rates during the incubation period were similar in all patient groups, whereas the initial basal ECP secretion was significantly increased in tissue affected by Crohn's disease. After stimulation with anti-IgE, ECP secretion was increased two-fold in controls and three-fold in patients with Crohn's disease. In tissue affected by Crohn's disease, ECP levels were found to be significantly increased in most segments of the lower gastrointestinal tract with the highest ECP concentrations in affected mucosa. This functional study demonstrates an enhanced immunologically mediated ECP secretion and an accumulation of ECP in the intestinal mucosa of Crohn's disease, indicating a local upregulation of eosinophils.

Advances in the immunobiology of eosinophils and their role in disease

Eosinophils play a protective role in host immunity to infections by parasitic worms and, detrimentally, are involved in the pathophysiology of asthma and other allergic diseases. Airway inflammation is central to the pathology of asthma and is characterized by infiltration of the bronchial mucosa by large numbers of proinflammatory cells, amongst which the eosinophil is prominent despite being a minority constituent of circulating leukocytes. Crucial steps in eosinophilic inflammation include augmented production of eosinophils in the bone marrow, their increased release into the circulation, and their selective accumulation in the conducting airways. The eosinophil has a potent armory of proinflammatory mediators, including cytotoxic granule proteins, cytokines and lipid mediators with considerable potential to initiate and sustain an inflammatory response. Thus there is much interest in the elucidation of the mechanisms responsible for eosinophil accumulation, persistence, activation and ultimate fate. This article reviews our current understanding of the role of the eosinophil in human disease and the immunobiology of this important proinflammatory cell.

The role of chemokines in cutaneous allergic inflammation

Eosinophils are the major effector cells that kill helminthic parasites and are - for unknown reasons present in the dermal part of atopic skin. This review summarizes our knowledge on the chemotactic factors involved in eosinophil tissue recruitment, focusing on the role of eosinophil-chemotactic chemokines. It is the current view that the chemokines RANTES and eotaxin represent the most important eosinophil-attracting chemokines. The inducibility of eotaxin in dermal fibroblasts only upon stimulation with Th2-cytokines IL-4 and IL-13 may explain why eosinophils appear only in the dermis and why the presence of Th2-cytokines is always linked with tissue eosinophilia.

Production of singlet oxygen by eosinophils activated in vitro by C5a and leukotriene B4

Using the trans-methoxyvinylpyrene analogues of benzo[a]pyrene-7,8-dihydrodiol (MVP) as a singlet oxygen ((1)O2) chemiluminescence probe, we have demonstrated that guinea pig eosinophils release (1)O2 when activated with the physiological agonists C5a and leukotriene B4. This release, which occurs at agonist concentrations as low as 10(-7) M, occurs more rapidly than activation with phorbol ester (10(-6) M), is similar in level, but is more transitory. In addition, the release of (1)O2 occurs in the absence of added bromide ions and represents, we propose, an important feature of eosinophil-mediated inflammatory damage.

Norm values for eosinophil cationic protein in nasal secretions: influence of specimen collection

BACKGROUND

Eosinophil granulocytes play an important role in allergic inflammation of the nasal mucosa. Eosinophil cationic protein (ECP) is a specific eosinophil granule protein released upon activation of these cells. ECP concentration in nasal secretions has been demonstrated to be a good marker for the activity of eosinophilic nasal mucosal inflammation. The clinical use of such a marker requires defined values which are regarded as pathological or within normal range. In analyses of nasal secretion samples, the sampling method has an important influence on the data obtained.

OBJECTIVE

We investigated ECP levels in nasal secretions (NS) of healthy volunteers obtained by seven different methods of sample collection to define norm values and to evaluate the clinical use of the different methods.

METHODS

A total of 839 healthy individuals were evaluated using blowing the nose (Bl: n = 82), suction (Suc: n = 69), Okuda microsuction technique (MSuc: n = 93), absorbent cotton wool samplers (CWS: n = 156), rubber-foam samplers (RFS: n = 193), nasal lavage (Lav: n = 112) and nasal spray washing (NSW: n = 134).

RESULTS

Missing values occurred in more than 60% in Bl, Suc and MSuc, so that no norm range was defined for these methods. Norm range for ECP in NS was 5-46 ng/mL for CWS, 7-41 ng/mL for RFS, 4-51 ng/mL for NSW, and 3-31 ng/mL for Lav.

CONCLUSIONS

When comparing seven different methods used in this study to collect nasal secretions and determine ECP levels, the method based upon absorption or nasal washing was the best.

Dystrophic epidermolysis bullosa associated with eosinophilic infiltrate and elevated serum IgE

An infiltrate of eosinophils is rarely seen in epidermolysis bullosa. We describe a child with dystrophic epidermolysis bullosa associated with a marked eosinophilic tissue infiltrate and elevated serum IgE.

Soluble E-selectin and eosinophil cationic protein are distinct serum markers that differentially represent clinical features of atopic dermatitis

The serum levels of eosinophil cationic protein (ECP), soluble E-selectin (sE-selectin), soluble CD14 (sCD14) and interleukin (IL)-4 are known to be elevated in patients with atopic dermatitis (AD). However, little is known of the mutual relationship between these factors. To elucidate the clinical and mutual relevance of these markers, we examined the serum levels of ECP, sE-selectin, sCD14 and IL-4 as compared with eruption scores, itch scores, total IgE and numbers of peripheral eosinophils in patients with AD (n = 43), non-atopic eczema (n = 24) and urticaria (n = 13) and in normal individuals (n = 45). In 27 patients with AD the levels of these markers were compared before and after treatment. Levels of ECP were elevated only in the patients with AD, whereas the sE-selectin levels were higher not only in AD but also in non-atopic eczema in a severity-dependent manner. The levels of both markers significantly diminished after treatment. Significant correlations existed between ECP levels and numbers of eosinophils, sE-selectin levels and itch scores, and sE-selectin levels and IgE levels. No significant changes were observed in the sCD14 and IL-4 levels. Taken together, sE-selectin and ECP are good but distinct serum markers that reflect different clinical features of AD.

Allergic skin disease: atopic dermatitis as a prototype

The skin is the largest immune organ in the body. It is strategically positioned as an interface between a hostile antigenic world and a complex immune system characterized by inflammatory cells, mediators, lymphocytes, and a panoply of cytokines. These cytokines act as subcellar messengers that direct effector lymphocytes, eosinophils, mast cells, and a host of other cells to target the skin in allergic inflammation. Just as asthmas and allergic rhinitis are prototypes of IgE-mediated respiratory disease, atopic dermatitis is the prototype allergic skin disease. This article focuses on an understanding of the pathogenic mechanisms involved in atopic dermatitis and outlines the clinical spectrum of cutaneous allergic disease. Finally, a state-of-the-art approach to treatment is offered to the clinician confronted with the management of this difficult disorder.

Exaggerated arthropod-bite lesions in patients with chronic lymphocytic leukemia: a clinical, histopathologic, and immunopathologic study of eight patients

BACKGROUND

Unusual papulovesicular lesions resembling arthropod bites have been described in patients with chronic lymphocytic leukemia (CLL).

OBJECTIVE

Our purpose was to describe and characterize further the clinical, histopathologic, and immunopathologic features of these lesions.

METHODS

Eight patients were identified retrospectively who had CLL and characteristic skin lesions. Clinical and histologic features were recorded. Skin biopsy specimens were analyzed immunohistochemically for eosinophil granule major basic protein, eosinophil-derived neurotoxin, neutrophil elastase, and mast cell tryptase.

RESULTS

The clinical features, including the lesional distribution, suggested arthropod bites, although most patients could not recall having been bitten. Mixed T- and B-cell lymphoid cell infiltrates were present within lesions, along with prominent eosinophil infiltration and eosinophil granule protein deposition.

CONCLUSION

Exuberant papulovesicular lesions develop in patients with CLL apparently as an exaggerated response to arthropod bites. Prominent eosinophil infiltration and degranulation within these lesions likely contribute to the severity of symptoms.

Mast Cells Enhance Eosinophil Survival In Vitro: Role of TNF-α and Granulocyte-Macrophage Colony-Stimulating Factor

Mast cell-eosinophil interactions in allergy have not yet been completely defined. To determine whether mast cells influence eosinophil survival, human peripheral blood eosinophils were incubated with rat peritoneal mast cell sonicate. After 3 days, viable eosinophils in medium were 21.3% compared with 44% with mast cell sonicate. Like sonicate, supernatants of compound 48/80-activated mast cells enhanced eosinophil survival, demonstrating that the factor(s) involved is stored preformed and rapidly released. Increased eosinophil survival was due to an inhibition of apoptosis (morphologic analysis; annexin V/PI). Neutralizing Abs to granulocyte-macrophage CSF (GM-CSF), but not to IL-3 or IL-5, decreased by 61.7% the enhancing effect on eosinophil viability. Eosinophils are the source of GM-CSF since its release in the culture medium was inhibited by their incubation with the mast cell sonicate together with dexamethasone. In addition, eosinophils incubated with the sonicate expressed mRNA for GM-CSF. To partially characterize the mast cell-derived factor(s) increasing eosinophil survival, the sonicate was heated (56°C/30 min or 100°C/10 min) or preincubated with antihistamines or with anti-TNF-α-neutralizing Abs. Most of the activity was heat labile. TNF-α was found to be predominantly (70%) responsible, while histamine had no role. Mast cell sonicate also caused eosinophils to release eosinophil peroxidase and to display morphologic signs of activation. In conclusion, we have demonstrated that mast cells enhance eosinophil survival in part through their activation to produce and release the autocrine survival cytokine GM-CSF.

Familial eosinophilic cellulitis, dysmorphic habitus, and mental retardation

BACKGROUND

Eosinophilic cellulitis is a polymorphous, chronic disease characterized by eosinophil infiltration and granulomatous inflammation.

OBJECTIVE

Our purpose was to describe the clinical, histologic, and immunohistologic findings in three family members who have had eosinophilic cellulitis since childhood associated with mental retardation and abnormal body habitus.

METHODS

Family members were evaluated. Multiple skin biopsy specimens were obtained and examined after hematoxylin-and-eosin staining, by immunofluorescence and by electron microscopy. Blood specimens were analyzed by immunoassays for eosinophil granule proteins and eosinophil active cytokines.

RESULTS

Three short-statured, mentally retarded family members with abnormal body habitus in at least two generations had recurrent eosinophilic cellulitis. Peripheral blood and bone marrow eosinophilia was present. Plasma eosinophil granule major basic protein and eosinophil-derived neurotoxin levels were elevated with normal plasma eosinophil cationic protein levels. Eosinophil survival in culture was increased by patients' plasma and was blocked with monoclonal interleukin-5 antibody. The level of plasma interleukin-5 was elevated. Lesional skin biopsy specimens showed massive staining for three eosinophil granule proteins. Electron microscopy showed eosinophil disruption.

CONCLUSION

Eosinophilic cellulitis, mental retardation, and abnormal body habitus were likely inherited as a dominant syndrome in this family in which eosinophil involvement was striking.

Prevalence of IgE-mediated food allergy among children with atopic dermatitis

OBJECTIVE

There is a growing body of clinical and laboratory evidence to support the notion that food allergy plays a role in the pathogenesis of atopic dermatitis (AD). However, the incidence of IgE-mediated food allergy in children with AD is not well established.

DESIGN

A prospective study to determine the prevalence of IgE-mediated food hypersensitivity among patients referred to a university-based dermatologist for evaluation of AD.

SETTING

University hospital pediatric dermatology clinic.

PATIENTS

A total of 63 patients with AD were recruited (35 male; 32 white, 24 African-American, 7 Asian).

METHODS

Patients were assigned an AD symptom score (SCORAD) and were screened for food-specific serum IgE antibodies to six foods (milk, egg, wheat, soy, peanut, fish) known to be the most allergenic in children. The levels of food-specific serum IgE were determined by the CAP System fluoroscein-enzyme immunoassay (CAP); patients with a value >/=0.7 kIUa/L were invited for an additional allergy evaluation. Those with CAP values below the cutoff were considered not food allergic. Patients were considered to be allergic if they met one of the following criteria for at least one food: 1) reaction on food challenge; 2) CAP value more than the 95% confidence interval predictive for a reaction; 3) convincing history of an acute significant (hives, respiratory symptoms) reaction after the isolated ingestion of a food to which there was a positive CAP or prick skin test.

RESULTS

A total of 63 patients (median age, 2.8 years; median SCORAD, 41.1) were recruited; 22 had negative CAP values (without a significant difference in age or SCORAD score, compared with the 41 with positive specific IgE values). Further allergy evaluation was offered to the 41 remaining patients; 10 were lost to follow-up and 31 were evaluated further. Of these, 19 underwent a total of 50 food challenges (36 double-blind, placebo-controlled, and 14 open), with 11 patients experiencing 18 positive challenges (94% with skin reactions). Additionally, 6 patients had a convincing history with a predictive level of IgE; 5 had a convincing history with positive, indeterminate levels of IgE; and 1 had predictive levels of IgE (to egg and peanut) without a history of an acute reaction. Overall, 23/63 (37%; 95% confidence interval, 25% to 50%) had clinically significant IgE-mediated food hypersensitivity without a significant difference in age or symptom score between those with or without food allergy.

CONCLUSIONS

Approximately one third of children with refractory, moderate-severe AD have IgE-mediated clinical reactivity to food proteins. The prevalence of food allergy in this population is significantly higher than that in the general population, and an evaluation for food allergy should be considered in these patients.

Th2-like cytokine activity in dermatitis herpetiformis

Dermatitis herpetiformis (DH) is a chronic subepidermal blistering disease, in which a perivascular cellular infiltrate, composed mainly of CD4+ T lymphocytes together with a varying number of neutrophils and eosinophils, is thought to be important in the pathogenesis of blister formation. The aim of this study was to investigate the potential role of cytokines such as the interleukins IL-4 and IL-5 and to quantify the distribution of T cells as well as their state of activation using alkaline phosphatase-antialkaline phosphatase and reverse transcriptase-polymerase chain reaction (RT-PCR) procedures in seven patients with typical clinical and histological features of DH. A strong extracellular staining with anti-IL-4 monoclonal antibody was detected in the upper dermis with a prevalent perivascular pattern in perilesional areas, whereas in the dermal-epidermal separation sites there was an intense, scattered distribution. IL-5 was intensely expressed, mainly at the intracellular level, by eosinophils and lymphocytes. Concerning RT-PCR, five DH patients showed a strong positive signal for both IL-4 and IL-5 cytokines while two patients showed a faint signal for both IL-4 and IL-5; these last two cases were histologically poor in inflammatory cells. In view of these results, it can be hypothesized that the recruitment of eosinophils and neutrophils in DH may be induced not only by granulocyte macrophage colony-stimulating factor and IL-8 as previously demonstrated, but also by Th2 cytokines as well.

IL-4 Induces Eotaxin: A Possible Mechanism of Selective Eosinophil Recruitment in Helminth Infection and Atopy

A common feature of some parasitic infections and allergic and atopic skin diseases is the involvement of Th2 lymphocytes and the dermal appearance of eosinophils (Eos). Because Th2 lymphocytes apparently do not release Eo attractants, we addressed the question of whether the Th2 cytokine IL-4 induces its production in dermal fibroblasts. We therefore stimulated fibroblasts with IL-4. HPLC investigation of supernatants revealed a single Eo chemotactic protein, which was purified to homogeneity giving a single 13-kDa band upon SDS-PAGE analyses. Peptide mapping with subsequent amino acid sequencing revealed an Eo-selective chemotaxin, which consists of a mixture of N-terminally truncated and O-glycosylated forms of the chemokine eotaxin. Other chemokines such as RANTES, MCP-3, MCP-4, or MIP-1α were not detected as Eo chemotaxins under these conditions. Using reverse transcriptase-PCR techniques, we found that IL-4 dose and time dependently induces eotaxin mRNA in dermal fibroblasts. Stimulation with IL-4 and TNF-α caused a 10- to 20-fold increase of the release of three biochemically different eotaxin forms, each consisting of a mixture of N-terminally truncated and O-glycosylated variants having the same backbone amino acid sequence but different specific activities. Our findings support the hypothesis that eosinophil recruitment seen in IL-4-mediated skin reactions, at least in part, may be due to Th2 cytokine-mediated induction of eotaxin in dermal fibroblasts.

In vivo relevance of CD30 in atopic dermatitis

CD30 expression was evaluated by immunohistochemistry in lesional skin biopsies of eight patients with active atopic dermatitis (AD) and three patients with allergic contact (nickel-induced) dermatitis (ACD). CD30 expression was also assessed in a large panel of CD4+ and CD8+ T-cell clones generated from the skin biopsies of four patients with AD. Finally, the levels of soluble CD30 (sCD30) were measured in the serum of 41 patients with AD, 19 patients with ACD, and 60 healthy controls. In all specimens of lesional AD skin, where the great majority of infiltrating cells were CD4+ T cells, remarkable numbers of cells were CD30+, whereas virtually no CD30+ cells were found in the skin of patients with ACD. In CD4+ T-cell clones generated from the lesional AD skin, most of which produced both interleukin (IL)-4 and interferon-gamma (IFN-gamma) (Th0-like cells) or IL-4 and IL-5, but not IFN-gamma (Th2-like cells), CD30 expression directly correlated with the ability to produce IL-4 and IL-5, but was inversely related to IFN-gamma production. High levels of sCD30 (correlated with disease activity: r = 0.618) were detected in the serum of most AD patients, whereas there was no increase of sCD30 levels in the serum of patients with ACD. These data support the view that Th0/Th2-type responses predominate in the skin of patients with AD and suggest that the presence of CD30+ T cells in tissues and/or increased levels of sCD30 in biologic fluids are indicative of Th2-dominated responses.

Eosinophil cationic protein (ECP) level and its correlation with eosinophil number or IgE level of peripheral blood in patients with various skin diseases

Eosinophil cationic protein (ECP) is a cationic protein derived from eosinophil granulocytes, and has been studied mainly in atopic diseases and considered as a useful marker of disease activity in atopic dermatitis. We measured the serum ECP levels in patients with various skin diseases (n = 875) and in normal healthy controls (n = 79), and evaluated the correlation between ECP level and blood eosinophil number, or ECP and IgE levels. Serum ECP levels were significantly higher in patients with drug eruption (15.8 +/- 1.7 micrograms/l), psoriasis (15.1 +/- 6.0 micrograms/l), acute urticaria (13.9 +/- 1.4 micrograms/l) than in healthy controls (4.5 +/- 0.3 micrograms/l) (P < 0.05) and also significantly elevated in patients with elevated eosinophil numbers (15.2 +/- 1.0 micrograms/l) compared to those in patients with normal eosinophil numbers (8.8 +/- 0.3 micrograms/l) (P < 0.001). Serum ECP level and eosinophil number in peripheral blood were also correlated in patients with psoriasis (gamma = 0.82, P < 0.01), drug eruption (gamma = 0.31, P < 0.01) and acute urticaria (gamma = 0.20, P < 0.05). However, no correlation between ECP and IgE levels in all of the patients was found. Among the patients with chronic urticaria, ECP levels showed an increasing trend in patients with angioedema, cold urticaria and dermographic urticaria as compared with those in healthy controls. Our results suggest that, even though the role of ECP released from activated eosinophils is still unknown, its measurement might be of help to understand the pathogenesis of some skin disorders.

The effect of the selectin binding polysaccharide fucoidin on eosinophil recruitment in vivo

1. In order to accumulate at sites of inflammation, leukocytes initially roll on endothelial cells of postcapillary venules before becoming firmly attached. This process of rolling is mediated by selectins which bind to carbohydrate counter-ligands present on the surface of both leukocytes and endothelial cells. The polysaccharide fucoidin has been previously shown to inhibit leukocyte rolling in the mesenteric circulation and to reduce neutrophil accumulation in the skin and meninges in experimental inflammation. 2. In the present study we have assessed the effects of fucoidin on eosinophil function in vitro and eosinophil accumulation at sites of inflammation in guinea-pig skin. 3. At concentrations of up to 1200 micrograms ml-1, fucoidin inhibited phorbol myristate acetate (PMA)-induced eosinophil homotypic aggregation by up to 60% but had no inhibitory effect on PMA-induced eosinophil adhesion to serum-coated plates. 4. Fucoidin effectively reduced the binding of the anti-L-selectin mAb MEL-14 to guinea-pig eosinophils. Binding of a P-selectin-IgG chimera to eosinophils was also partially inhibited by fucoidin, but binding of an anti-CD18 or an anti-VLA-4 mAb were unaffected. 5. When given systemically to guinea-pigs, fucoidin suppressed 111In-labelled eosinophil recruitment to sites of allergic inflammation. 111In-labelled eosinophil accumulation induced by platelet-activating factor (PAF) and zymosan-activated plasma (as a source of C5a des Arg) was also inhibited. 6. These results demonstrate a role for fucoidin-sensitive selectins in mediating eosinophil recruitment in vivo.