Selectin and Lewis(x) are required as co-receptors in antibody-dependent cell-mediated cytotoxicity of human eosinophils to Schistosoma mansoni schistosomula

Killing of Schistosoma mansoni larvae by human eosinophils via antibody-dependent cell-mediated cytotoxicity (ADCC) mechanisms requires adherence between effector cells and parasite targets. The role of adhesion molecules in this mechanism was investigated using blocking monoclonal antibodies (mAb) and soluble ligands. We show that, along with the Mac-1 alpha chain, interactions between selectins and LewisX-related structures, both expressed by eosinophils and parasite targets, play a critical part in the antibody-dependent cytotoxic function of eosinophils. To further elucidate the interactions between adhesion molecules and eosinophil Fc receptors, ADCC was performed with IgG1 or IgA mAb. We found that mAb directed against Mac-1 alpha chain or against LewisX could significantly inhibit the IgG1-, but not IgA cytotoxicity. This result might be explained, at least in part, by the inhibitory effect of these mAb on the release by eosinophils of eosinophil cationic protein, one of the major mediators involved in target killing. Taken together, these results suggest novel interactions between Fc receptors and selectins and LewisX-related structures which might act as co-receptors for eosinophil-mediated cytotoxicity.

Expression of Th1 and Th2 immunoregulatory cytokines by human eosinophils

Besides cytotoxic mediators, human eosinophils can produce proinflammatory and anti-inflammatory cytokines, as well as growth factors and chemokines. The demonstration that eosinophils from patients could produce IL-5, IL-4 and IL-2 suggested their participation in the regulation of immune response. In the present work, we have examined the presence of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-5, IL-10 and IL-13) cytokines in eosinophils from patients or donors by intracellular flow cytometry, and by immunocytochemistry. Whereas almost 100% eosinophils expressed intracellular IFN-gamma, IL-2 and IL-10, the expression of IL-4, IL-5 and IL-13 is more variable and increased in patients versus donors. The differential release by eosinophils of Th2 versus Th1 cytokines is suggested both by the decrease of the intracellular content after culture, restricted to IL-4, IL-5 and IL-13, associated with an accumulation of IL-4 and IL-5 in the presence of Brefeldin. These results indicate that, through the preferential release of Th2 cytokines, human eosinophils can participate in the polarization of the immune response.

Relationship between interleukin-5 production and variations in eosinophil counts during HIV infection in West Africa: influence of Mycobacterium tuberculosis infection

Eosinophils are important effectors of the non-specific immune response and we studied whether perturbations in the production of the type 2 cytokine, interleukin-5 (IL-5), could account for the variations in eosinophil counts observed in human immunodeficiency virus (HIV) infection. HIV-infected patients without helminthiasis were investigated in a cross-sectional study in West Africa. Eosinophil counts were significantly higher in CDC-B patients than in controls, but were dramatically decreased at the CDC-C stage. Phorbol 12-myristate 13-acetate (PMA)+ ionomycin-induced IL-5 production by peripheral blood mononuclear cells (PBMC) was decreased from the A stage of the disease, and significant correlations were observed between IL-5 production and eosinophil counts in tuberculosis (TB)-negative HIV-1-positive, TB-positive HIV-1-positive and TB-positive HIV-negative patient groups. Nevertheless, the production of IL-5 was not decreased in HIV-positive patients with TB, in contrast to HIV-positive patients without TB presenting with the same ranges of CD4+ counts. Our data suggest that, during HIV infection, the impairment in IL-5 production is one of the factors associated with the 'paradoxal' eosinopenia observed in tropical areas, but that IL-5 production during active TB is compensated by cellular subsets, yet to be identified.

Expression of rat interleukin-5 and generation of neutralizing antiserum: a comparative study of rat IL-5 produced in Escherichia coli and insect cells

A cDNA coding for rat IL-5 was obtained by RT-PCR from total spleen RNA. With the exception of a single a.a. replacement at position 85 (L-P), it is identical to the published sequence obtained by retroviral gene transfer. This cDNA was used to express biologically active recombinant IL-5 in E. coli and in insect cells using a baculovirus system. Rat IL-5 is more active on B13, an IL-5 dependent cell line, when produced in insect cells (specific activity 1.47 x 10(11)UI/mg compared to 4.28 x 10(6)UI/mg). This increased activity seems to be associated with the presence of IL-5 homodimers in recombinant protein preparations. A rabbit antiserum raised against recombinant bacterial IL-5 specifically inhibited B13 proliferation induced by bacterial and baculoviral IL-5. The availability of such reagents should facilitate studying the role of IL-5 in different infectious diseases, experimental allergic encephalomyelitis and in transplantation biology where the rat represents a more suitable model than mice.

Circulating growth-regulator oncogene alpha contributes to neutrophil priming and interleukin-8-directed mucosal recruitment into chronic lesions of patients with Crohn's disease

Crohn's disease (CD) lesions are characterized by a marked neutrophilic infiltrate associated with enhanced mucosal IL-8, contrasting with low serum IL-8 levels. The aim of this study was to investigate the effects of circulating GROalpha and IL-8 on neutrophil priming and migration. The expression of surface molecules involved in rolling (CD62L, CD15) and firm adhesion (Mac-1 and LFA-1) to endothelial cells was assessed by flow cytometry, while the chemotactic response of PMN to IL-8 and to fMLP was investigated in a Boyden chamber assay. In addition, IL-8 and GROalpha levels were determined by ELISA in plasma samples and in culture supernatants of purified polymorphonuclear neutrophils (PMN) and peripheral blood mononuclear cells (PBMC) from patients with CD and healthy blood donors. This study revealed an upregulation of CD11b (Mac-1) membrane expression on circulating PMN from patients with CD, as assessed by the mean fluorescence intensity which reflects antigen density. Furthermore, an enhanced chemotactic response towards both fMLP and IL-8 of PMN from CD patients was observed. Despite often undetectable levels of circulating IL-8, all plasma samples were positive for GROalpha, with a significant increase in CD patients when compared to donors. In vitro, equivalent concentrations of GROalpha were able to increase the IL-8 driven chemotaxis of PMN. In conclusion, blood PMN from patients with CD showed an enhanced capacity to be recruited into inflammed intestinal mucosa, which could be due to an increased expression of CD11b (Mac-1) as well as an increased chemotactic response toward fMLP or IL-8. This priming effect of PMN in CD may partly occur through elevated circulating GROalpha levels.

[Eosinophils: protection or pathology: a cell with two personalities]

Expression of various membrane receptors on human eosinophils for immunoglobulin, complement, certain cytokines and chemotaxis factors, and adherence molecules as well as CD4 and class II major histocompatibility complex antigens has led to a reconsideration of the role of the eosinophil in the immune response. Eosinophils are able to present antigen and become infected by HIV. Eosinophils are not to only source of cytotoxic and proinflammatory mediators but can also release different cytokines and growth factors including their own differentiation factors. The recent demonstration that eosinophils can express IgE-binding molecules belonging to different multigenic families as well as two different IgA receptors which participate equally to the protective and to the pathological inflammatory responses reinforces the concept of a dual functionality for the eosinophil.

From allergy to schistosomes: role of Fc receptors and adhesion molecules in eosinophil effector function

The dual function of eosinophils has been evidenced in protective immunity against parasites as well as in pathological manifestations during allergic disorders. We have demonstrated that a new class of IgE receptors, Fc epsilon RII/CD23, was involved in the functional duality of eosinophils and other proinflammatory cells. More recently, we have shown that Fc epsilon RI, the high affinity IgE receptor thought to be only expressed by basophils and most cells, was involved in eosinophil-mediated cytotoxicity against schistosomes as well as in mediator release. These results favour the view that both IgE and its receptors have been primarily associated to a protective immune response, rather than to pathology. Not only IgE receptors but also members belonging to the family of adhesion molecules can participate as co-receptors in eosinophil effector function. The inhibitory role of monoclonal antibodies to Lewis(X) (Le(X) CD15) or to selectins in eosinophil-mediated cytotoxicity towards schistosomes and the detection of Le(X) and selectin-like molecules on schistosomula surface indicate a double interaction mediated by selectins and their carbohydrate ligands between eosinophils and schistosomula. These results suggest new functions for these adhesion molecules, previously known to be involved mainly in cell infiltration.

Similar IL-5, IL-3, and GM-CSF syntheses by eosinophils in the jejunal mucosa of patients with celiac disease and dermatitis herpetiformis

Celiac disease (CD) and dermatitis herpetiformis (DH) are gluten-sensitive diseases with different clinical features that can initiate similar intestinal changes. The flat-destructive stage corresponds to severe lesions involving activated T-cells. However, other inflammatory cells such as eosinophils are also abundant. The mechanisms for the intestinal recruitment of eosinophils in patients with CD and DH remain unknown. Eosinophil recruitment and activation are induced in vitro by three main cytokines: interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte-macrophage colony-stimulating factor (GM-CSF). In this study, IL-3, IL-5, and GM-CSF were detected by immunohistochemistry in all patients with CD and DH but not in the control group. By ultrastructural immunogold staining, these three cytokines had the same subcellular localization in the granule matrix of eosinophils. This result suggests that eosinophils may be involved in the immune response at the flat-destructive stage of both CD and DH.

Inhibitory effects of lodoxamide on eosinophil activation

Recent reports describe the beneficial use of lodoxamide, an anti-allergic compound, for the treatment of asthma and allergic conjunctivitis. Lodoxamide is known as a mast cell stabilizer, however, the association of a significant clinical improvement with a specific decrease in eosinophil infiltrate suggested possible direct effects of lodoxamide on eosinophils. The chemotactic response of eosinophils to fMLP as well as to IL-5, in vitro, was very significantly and dose-dependently inhibited by Lodoxamide. Lodoxamide was also able to strongly inhibit the release of eosinophil peroxidase after IgA-dependent activation and, to a lesser extent, the release of eosinophil cationic protein and eosinophil-derived neurotoxin. Moreover, the release of cytotoxic mediators evaluated in an antibody-dependent cytotoxicity assay against parasitic targets was also significantly reduced, not only in the case of human eosinophils but also in a rat eosinophil-mast cell model of cytotoxicity. Taken together, these results indicate that lodoxamide can exert potent inhibitory effects on eosinophil activation in vitro combined with a strong inhibition of eosinophil attraction, leading therefore to a reduction in their pathological potential in vivo.

In vivo expression of cytokine mRNA in rats infected with Schistosoma mansoni

As an animal model, rat schistosomiasis mansoni has provided considerable knowledge of immune mechanisms involved in the expulsion of worms and in a subsequent development of immunity to reinfection. Although it is clear that ADCC mechanisms participate in immunity to reinfection; the nature of the cytokines involved in immunity is unknown. To analyse the pattern of cytokines involved, the mRNA levels of different cytokines were assessed by RT-PCR as they occur within tissues during the course of infection. In spleens from infected rats, a significant elevation in IL-2 and IL-5 mRNA was observed during the early phase of infection (day 7). Analysis of pulmonary cytokine responses showed a dramatic increase in IL-4 and IL-5 on day 7. This was accompanied with a low but significant increase in IL-2 (day 11) and IL-12 (day 7) in the absence of augmented IFN-gamma expression. The cytokine expression patterns of draining lymph nodes (LN) from infected rats showed a significant increase of IL-2, IL-4 and IL-5 on day 21. Analysis of IL-10 expression showed exclusively a significant increase in LN on day 11, IFN-gamma mRNA was not detected in any tissue sample. Thus, rats develop a predominately Th2-type cytokine response during a primary infection which may be involved at least in part, in the expression of immunity against Schistosoma mansoni infection.

Modulation of cell adhesion molecules on human endothelial cells by eosinophil-derived mediators

Mechanisms that allow a selective eosinophil emigration in different eosinophilic lung diseases remain poorly understood. In this study, we tested the hypothesis that eosinophils might participate in their own recruitment, particularly through adhesion molecule expression on human endothelial cells (EC). Blood eosinophils from donors with blood eosinophilia were purified and maintained in culture medium for 1 and 18 h. The expression of ICAM-1, E-selectin, and VCAM-1 on human umbilical vein endothelial cells (HUVEC) was evaluated by ELISA and flow cytometry analysis after addition of eosinophil supernatants. Eosinophil supernatants collected after 1 h induced a weak increase of CAM expression on HUVEC. In contrast, supernatants from eosinophils cultured for 18 h considerably amplified ICAM-1, E-selectin, and VCAM-1 expression on the surface of EC. These levels of CAM expression (in optical density determined by ELISA) were about two- or threefold more important than those obtained with eosinophil supernatants collected after a 1-h culture. The characterization of the implicated molecules showed that anti-IL-1beta antibodies significantly inhibited ICAM-1, E-selectin, and VCAM-1 expression, whereas anti-TNF-alpha antibodies only induced a moderate inhibition. Our data support the hypothesis that eosinophils, through the release of at least IL-1beta and TNF-alpha, might participate in the amplification of the inflammatory reaction by activating the vascular endothelium.

[Recent data on the physiopathology of respiratory allergies]

Mechanisms of the allergic inflammatory reaction in the respiratory tract, such as those involved in chronic asthma and allergic rhinitis involve a complex and integrated cellular cascade. After allergen inhalation, the response is initiated by the airway epithelial dendritic cells which are responsible after transportation to regional lymph nodes, for the presentation to naïve CD4+ T helper (Th0) cells. After the first phase of allergen sensitization, CD4+ T cells give rise in atopic patients to lymphocytes CD4+ with a cytokine profile of Th2-type (secretion of IL-4, IL-5 and IL-13). Both cytokines IL-4 and IL-13 favor the IgE antibody production towards inhaled allergens, while IL-5 allows the differentiation, activation and survival of eosinophils. Among effector cells, two are predominant: mast-cells and activated eosinophils. During the initiation phase of the allergic reaction the dominant phenomena is represented by IgE mediated mast cell/basophil activation which leads to the release of granular mast cell mediators but also to the secretion by mast cells of cytokines also offering a Th2 profile. Moreover in chronic asthma histopathological, immunocytochemical studies and in situ hybridization techniques demonstrate a large recruitment of inflammatory cells, mainly of activated eosinophils that similarly produce Th2 type cytokines and participate in the development of the local allergic inflammation. Several additive environmental factors such as viruses or aeropollutants are susceptible to amplify the Th2 type response; conversely specific immunotherapy has been shown to allow a shift from the Th2 to Th1 profile, which explains at least for a part its therapeutic effects.

Streptococcal pyrogenic exotoxin A (SPE A) superantigen induced production of hematopoietic cytokines, IL-12 and IL-13 by human peripheral blood mononuclear cells

A quantitative and kinetic study of the release of the hematopoietic cytokines IL-3, IL-5 and GM-CSF, the immunoregulatory cytokine IL-12 heterodimer (and its p40 subunit) and IL-13 by human peripheral blood mononuclear cells (PBMC) stimulated in vitro with the superantigen streptococcal pyrogenic (erythrogenic) exotoxin A (SPE A) from Streptococcus pyogenes is reported. PBMC were stimulated in parallel with heat-killed group A streptococcal cells, E. coli lipopolysaccharide (LPS) and with concanavalin A (Con A) in certain experiments for comparative purposes. The cytokines were assayed in the supernatant fluids by ELISA. IL-13 expression was also determined by a quantitative competitive PCR. IL-3, IL-5, GM-CSF, IL-12 p40, IL-12 heterodimer and IL-13 expression was induced by SPE A in a time- and dose-dependent manner in rather substantial amounts except the IL-12 heterodimer, which was released in small quantities. In contrast to SPE A, IL-3, IL-5 and IL-13 were not or poorly elicited by streptococcal cells or LPS whereas these two stimulants induced relatively high amounts of GM-CSF. Interestingly, both IL-12 p40 and IL-12 heterodimer were released in much higher amounts by streptococcal cells. Con A induced IL-3, IL-5, GM-CSF and IL-13 production in amounts comparable to those elicited by SPE A. The possible pathophysiological relevance of the elicitation by SPE A and streptococcal cells of these cytokines is discussed.

Expression and functions of the high-affinity IgE receptor on human platelets and megakaryocyte precursors

Platelets can be activated by IgE and are therefore involved in IgE-mediated effector mechanisms against parasites and in allergic disorders. Here we show that, besides the low-affinity IgE receptor (Fc epsilon RII/CD23), platelets express the high-affinity receptor for IgE (Fc epsilon RI). Flow cytometry analysis revealed the existence of surface Fc epsilon RI on platelets with a large heterogeneity among individual donors, and a low proportion of platelets co-expressing Fc epsilon RI and FC epsilon RII/CD23. Northern hybridization and reverse transcription polymerase chain reaction confirmed the presence of mRNA encoding the alpha, beta and gamma chains of Fc epsilon RI in platelets and in their megakaryocytic precursors. Cross-linking of Fc epsilon RI with monoclonal antibody (mAb) to alpha chain using either the whole molecule or F(ab')2 triggered platelet cytotoxicity for Schistosoma mansoni larvae. Anti-Fc epsilon RII/CD23 mAb significantly inhibited IgE- or Fc epsilon RI-mediated cytotoxicity, indicating down-regulatory effects of Fc epsilon RII/CD23 on Fc epsilon RI-dependent functions. These results demonstrate functional properties for Fc epsilon RI on platelets and indicate unsuspected interactions between the low- and the high-affinity IgE receptors.

Role of adhesion molecules of the selectin-carbohydrate families in antibody-dependent cell-mediated cytoxicity to schistosome targets

The role of adhesion molecules in antibody-dependent cell-mediated cytotoxicity (ADCC) of macrophages toward the extracellular parasite Schistosoma mansoni was investigated by using 1) a panel of blocking mAbs directed against adhesion molecules and 2) different soluble ligands as candidate inhibitors of ADCC. The results show that the beta2-integrin Mac-1 (CD11b/CD18), L-selectin (CD62-L), and the carbohydrate determinant sialyl Lewis(x) (sLe(x); sCD15) are required for macrophage effector function toward schistosomula targets. On the other hand, the parasite counter-receptors involved in ADCC were found to share common motifs with the mammalian selectin-carbohydrate families. One family of parasite receptor(s) involved in ADCC carries the Lewis(x) (Le(x); CD15) carbohydrate structure, whereas a second family of receptor(s) appears to display selectin-like properties with affinity for the sLe(x) tetrasaccharide. Immunostaining experiments confirmed that schistosomula express on their surface hostlike molecules recognized by anti-Le(x) (CD15) and by anti-human E-selectin (CD62-E) mAbs. The double receptor-ligand interaction between macrophages and parasite targets provides new insights into the biologic roles of selectins and Le(x)-related structures in immunity against helminthic parasites.

Role of adhesion molecules of the selectin-carbohydrate families in antibody-dependent cell-mediated cytoxicity to schistosome targets

The role of adhesion molecules in antibody-dependent cell-mediated cytotoxicity (ADCC) of macrophages toward the extracellular parasite Schistosoma mansoni was investigated by using 1) a panel of blocking mAbs directed against adhesion molecules and 2) different soluble ligands as candidate inhibitors of ADCC. The results show that the beta2-integrin Mac-1 (CD11b/CD18), L-selectin (CD62-L), and the carbohydrate determinant sialyl Lewis(x) (sLe(x); sCD15) are required for macrophage effector function toward schistosomula targets. On the other hand, the parasite counter-receptors involved in ADCC were found to share common motifs with the mammalian selectin-carbohydrate families. One family of parasite receptor(s) involved in ADCC carries the Lewis(x) (Le(x); CD15) carbohydrate structure, whereas a second family of receptor(s) appears to display selectin-like properties with affinity for the sLe(x) tetrasaccharide. Immunostaining experiments confirmed that schistosomula express on their surface hostlike molecules recognized by anti-Le(x) (CD15) and by anti-human E-selectin (CD62-E) mAbs. The double receptor-ligand interaction between macrophages and parasite targets provides new insights into the biologic roles of selectins and Le(x)-related structures in immunity against helminthic parasites.

Distinct cytokine patterns in early and chronic ileal lesions of Crohn's disease

BACKGROUND & AIMS

Chronic intestinal lesions of patients with Crohn's disease (CD) are associated with a T helper (Th) 1-type cytokine profile, including high levels of interleukin 2 (IL-2) and interferon gamma (IFN-gamma). However, the mechanisms involved in the pathogenesis of the early mucosal lesions are poorly known. The aim of this study was to examine the pattern of Th1- and Th2-type (IL-4, IL-5, and IL-13) cytokines in the early ileal lesions occurring in patients with CD 3 months after ileal resection and ileocolonic anastomosis. Cytokines were also examined in the chronic ileal lesions to look for cytokine patterns related to disease progression.

METHODS

Ileal biopsy specimens were obtained from 17 patients with CD and 11 controls. Mucosal IL-2, IFN-gamma, IL-4, IL-5, and IL-13 messenger RNA (mRNA) was evaluated by competitive reverse-transcription polymerase chain reaction.

RESULTS

The early ileal lesions of patients with CD were associated with a significant increase of IL-4 mRNA and a decrease of IFN-gamma mRNA compared with the normal mucosa of patients with CD or controls. A Th1-type pattern was observed in the chronic ileal lesions.

CONCLUSIONS

Divergent cytokine patterns are observed during different clinical stages of CD. These observations need to be considered in the development of newer specific therapeutic agents to prevent CD recurrences.

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.

Eosinophils in allergic reactions

Mainly located in the skin or mucosa of patients with allergic diseases, eosinophils contribute directly to tissue damage and chronic inflammation. The past year has seen significant advances in the study of the factors involved in the specific tissue recruitment of eosinophils, including chemoattractants and their receptors. New data have been obtained on the synthesis by eosinophils of various cytokines mostly released by immune complexes.

Induction by interferons of human eosinophil apoptosis and regulation by interleukin-3, granulocyte/macrophage-colony stimulating factor and interleukin-5

The effects of recombinant human interferon alpha (rhIFN-alpha) and interferon gamma (rhIFN-gamma) were examined on the apoptosis of human cord blood derived eosinophils, obtained after 4 weeks of culture with recombinant human interleukin-3 (rhIL-3), granulocyte-macrophage-colony stimulating factor (rhGM-CSF) and interleukin-5 (rhIL-5). Eosinophil viability decreased remarkably after 1 week culture with rhIFN-alpha and rhIFN-gamma. Recombinant rhIFN-alpha also decreased the viability of co-existing monocytes/macrophages, whereas in contrast, rhIFN-gamma increased the percentage of viable monocytes/macrophages. There was no synergistic or additional effect of rhIFN-alpha and rhIFN-gamma on eosinophil viability. Apoptotic eosinophils, detected by their morphological characteristics, or by DNA nick end labeling in situ, increased remarkably after incubation with rhIFN-alpha and increased to a lesser extent with rhIFN-gamma. The numbers of eosinophil-phagocytosing macrophages increased after culture with rhIFN-alpha and also with rhIFN-gamma. In contrast, eosinophilopoietic cytokines such as rhIL-3, rhIL-5 and specially rhGM-CSF, significantly increased eosinophil viability, and partially rescued the effects of rhIFNs. They also decreased apoptotic eosinophil numbers and eosinophil-phagocytosing macrophage numbers. These results indicate that eosinophil viability, at least in vitro, can be differentially regulated by cytokines produced during the immune response.

Synthesis of type 1 (IFN gamma) and type 2 (IL-4, IL-5, and IL-10) cytokines by human eosinophils

Eosinophils are not only the source of cytotoxic and proinflammatory mediators but they can also generate cytokines and growth factors, including their own factors of differentiation, namely IL-3, GM-CSF, and IL-5. Synthesis of IL-5 by eosinophils was demonstrated by in situ hybridization and immunostaining in a variety of diseases, such as coeliac disease, asthma, hypereosinophilic syndrome, or skin diseases. However, IL-5 synthesis by eosinophils was not shown in Crohn's disease, whereas in other diseases, it was restricted to a subpopulation of eosinophils, suggesting some heterogeneity in cytokine-producing eosinophils. Here, we report that human eosinophils, in addition to the synthesis of IL-5, and Th2 cytokine, can synthesize IFN gamma, a Th1 cytokine, as well as IL-10 and IL-4, known to be mainly produced by Th2 cells. Double immunostaining procedures reveal the coexpression of IL-5, IL-4, and IL-10 by the same eosinophil populations, different from IFN gamma-producing eosinophils. We propose that distinct subpopulations of human eosinophils express Th2 or Th1 cytokines. These results point to the importance of cytokines derived from non T cells in the regulation of the immune response.

IgE autoantibodies directed against the major bullous pemphigoid antigen in patients with a severe form of pemphigoid

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease characterized in part by circulating and tissue-bound IgG autoantibodies directed against the basement membrane zone. In addition, most of the patients with BP have increased serum IgE levels which seem to be correlated with the disease activity, whereas the presence of circulating anti-basement membrane zone IgE Abs has been reported in some patients. To elucidate whether IgE-dependent mechanisms play a role in the physiopathology of BP, we looked for the presence of IgE Abs specifically directed against the major BP Ag (BPAg1) in sera of BP patients at the onset and after remission of the disease. A radioimmunoassay and a 55-kDa recombinant protein (rBP55) obtained from a cDNA sequence, encoding the C-terminal region of the BPAg1 and containing the BPAg1 immunodominant epitopes, were used. Anti-rBP55 IgE Abs were found in 12 of the 19 sera tested. When the patients were divided into two groups according to the disease severity, anti-rBP55 IgE Abs were found only in patients with a severe form of the disease. Cytophilic IgE was detected on approximately 20% of peripheral blood eosinophils purified from BP patients. Immunohistochemistry studies suggested that some of the IgE-bearing cells in the lesional skin of BP patients are eosinophils. Immunostaining experiments revealed the existence of FcepsilonRI on both peripheral blood and tissue eosinophils. Taken together, these results suggest that IgE-dependent mechanisms could participate in the constitution of the lesions in BP.