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Biomedical subjects

M Capron

Publications and source records attributed to M Capron.

At least 163 records · Page 9Linked to original sources
PubMed1986

Human eosinophils express CR1 and CR3 complement receptors for cleavage fragments of C3.

The functional and antigenic characteristics of C3 receptors expressed on human eosinophils were investigated using rosette assays with sheep erythrocytes coated with C3 fragments and flow cytometric analysis of cells stained with anti-receptor antibodies. Purified peripheral blood eosinophils from 13 patients with hypereosinophilia expressed CR1 antigens. In 8 patients, a mean of 14 + 9.5% eosinophils formed C3b-dependent rosettes that were inhibited by F(ab')2 anti-CR1 antibodies. This number increased to 33% following stimulation with leukotriene B4 (LTB4) (10(-7) M). Similar numbers of C3b rosettes were formed by hypodense and normodense eosinophils. Eosinophils from 2 patients from this group expressed 20,000 125I-labeled monoclonal anti-CR1 antibody binding sites/cell. In another group of patients, 55 +/- 9% eosinophils spontaneously formed C3b-dependent rosettes that could not be enhanced by LTB4. In all patients, a mean of 16 +/- 9% eosinophils formed cation-dependent rosettes with C3bi-bearing intermediates that were inhibited by anti-CR3 antibody OKM1. All eosinophils stained with monoclonal antibodies against the alpha chain of CR3. There was no C3d-dependent rosette formation with eosinophils and no eosinophils stained with monoclonal anti-CR2 antibody. Thus, human eosinophils express CR1 and CR3. Since CR3 is required for the adhesion of granulocytes to surfaces and antibody-dependent cellular cytotoxicity of neutrophils, the interaction of C3 fragments with CR3 and CR1 on eosinophils may be of importance in eosinophil-mediated damage of opsonized targets.

Antibodies, Monoclonal↗
PubMed1986

A role for glycoprotein IIb-IIIa complex in the binding of IgE to human platelets and platelet IgE-dependent cytotoxic functions.

A possible relationship between binding sites for Immunoglobulin E (IgE) on human platelets, involved in IgE-dependent cytotoxic functions of platelets against helminth parasites, and well-characterized platelet constituents involved in haemostasis, was investigated. We first explored the interaction with IgE of platelets from patients with rare inherited deficiencies of defined platelet constituents and functions: Glanzmann's thrombasthenia, Bernard-Soulier and grey platelet syndromes. We report that only type I and II thrombasthenic platelets, which lack the membrane glycoproteins (GP) IIb and IIIa, failed to bind IgE and to exhibit IgE-dependent effector functions. Since thrombasthenic monocytes, however, showed normal interaction with IgE, this defect appeared restricted to platelets. Polyclonal and monoclonal antibodies directed against GP IIb-IIIa complex, but not monoclonal antibody directed against GP Ib, inhibited the binding of IgE to normal platelets, and their IgE-dependent cytotoxicity. Taken together, these findings indicate a relation between the GP IIb-IIIa complex and the expression of IgE binding sites and IgE-dependent effector functions in human platelets.

Blood Platelets↗
PubMed1986

Therapeutic efficacy of the transplantation of isolated hepatocytes in rats with surgically induced acute hepatic failure: a study of the mechanism.

In this study, the beneficial effect of intrasplenic transplantation of hepatocytes or splenocytes was shown in animals with 75% hepatectomy and portacaval shunt but not in animals with total dehepatization by hepatic vascular exclusion. No enhancement of the phagocytic activity was observed in the animals with 75% hepatectomy and portacaval shunt after injection of hepatocytes or splenocytes. This study confirms the efficacy of hepatocytes for the treatment of experimental liver failure but shows that nonhepatic cells may be equally as effective. Metabolic activity of the transplanted cells and stimulation of the phagocytic activity of the reticuloendothelial system probably do not explain the therapeutic effect of the transplanted cells.

Animals↗
PubMed1986

Detection and quantification of circulating antigen in schistosomiasis by a monoclonal antibody. I. Specificity analysis of a monoclonal antibody with immunodiagnostic capacity.

Monoclonal antibodies were obtained after immunization of mice with Schistosoma mansoni excretory/secretory antigen, previously shown to contain the circulating cathodic (M) antigen. Among these, the 40:B1 monoclonal antibody proved to be specific for the schistosome genus and to detect only adult worm-derived antigens as shown both by immunoprecipitation and with a two-site immunoradiometric assay using the monoclonal as both the solid-phase and the labelled antibody. The two-site immunoradiometric assay allows a sensitive measurement (detection limit: 5 ng) of circulating schistosome antigen in blood and in urine from patients with schistosomiasis. The amount of circulating schistosome M antigen is correlated with schistosome egg excretion in stool.

Animals↗
PubMed1986

Monoclonal antibodies to human eosinophil plasma membrane antigens enhance the secretion of eosinophil cationic protein.

This study was done to examine the nature of the membrane constituents involved in the secretion of eosinophil cationic protein (ECP) from human blood eosinophils. Three mouse monoclonal antibodies were used, which showed greater binding to membrane antigens on activated, and light density eosinophils from patients with an eosinophilia, than on nonactivated or normal density eosinophils. All three antibodies (EoN4, EoN5 & EoN6) stimulated normal density human eosinophils to secrete ECP, either alone or in association with sepharose-C3b. The antibodies bound to at least two separate sites on the membrane, which were distinct from the receptors for immunoglobulins, C3b, and eosinophil activating factor. One combination of antibodies increased the amount of ECP which was secreted. The membrane antigen recognized by antibody EoN4 was a glycoprotein, molecular weight 75 kD. These findings showed that ECP secretion may be induced by a wider range of stimuli than has been previously recognized, and that the antigens recognized by these monoclonal antibodies may play an important role in the induction of eosinophil degranulation.

Antibodies, Monoclonal↗
PubMed1986

Presence of factors chemotactic for granulocytes in hypereosinophilic syndrome sera: relation with alterations in eosinophil migration.

Recent work has underlined a structural and metabolic heterogeneity amongst blood eosinophils in various hypereosinophilic diseases. Little is known about the factors responsible for this variability. We have identified granulocyte chemotactic factors, termed GCFs in the sera of five patients with hypereosinophilic syndrome (HES). Sera from normal controls or from 20 patients with blood hypereosinophilia of various causes, but with little or no hypodense blood eosinophils, did not demonstrate any chemotactic activity. Two distinct GCFs were characterized, either by gel filtration or isoelectric focusing (molecular weights of 600 kD and 240 kD; pIs of approximately 5 and 7). These fractions are sensitive to proteolytic enzymes and to heating to 100 degrees C but not to 56 degrees C. The activity of GCFs has been tested towards neutrophils and eosinophils. The fractions of 240 kD and pI 7 appear more selective for the eosinophil lineage. Checkerboard analysis shows that such fractions are primarily chemotactic. In addition, hypodense eosinophils appear defective in random motility and chemotaxis towards chemotactic agents which are effective on normodense eosinophils. Moreover, preincubation of normodense eosinophils with HES sera rendered these cells unresponsive to very efficient chemotactic agents such as leukotriene B4 (LTB4) (decrease in migration of 91%; P less than 10(-3), formyl methionyl leucyl phenylalanyl (Fmlp) (decrease of 95%; P less than 10(-2)), HES sera (decrease of 91 to 93%). These findings suggest a process of deactivation of blood eosinophils with the possible retention within the circulation of activated hypodense eosinophils in HES.

Adolescent↗
PubMed1986

Eosinophilic lung disease: immunological studies of blood and alveolar eosinophils.

Five patients with eosinophilic lung diseases and blood hypereosinophilia (PIE syndrome) were investigated clinically and by bronchoalveolar lavage (BAL). Comparative studies on blood and alveolar eosinophils were carried out after purification and selection of eosinophil subpopulations according to their density. A predominant 'hypodense' alveolar eosinophil population was found in BAL fluids of active chronic eosinophilic pneumonia (CEP). In addition, supernatants of alveolar macrophages obtained from CEP are able to enhance spontaneously the generation of eosinophil oxygen metabolites. Such eosinophil stimulation emphasizes a probable tissue cell cooperation. In addition, BAL permitted the study of membrane immunological markers on eosinophilic inflammatory cells endowed with migratory properties. An increase in eosinophils carrying surface IgE was demonstrated in alveolar cells from PIE Syndrome particularly with hypodense eosinophils from CEP patients. Although no specific stimulus is known at the present time, this work underlines the potential implication of IgE-mediated hypersensitivity processes in the pathogenesis of eosinophilic lung diseases.

Adult↗
PubMed1985

Defined antigens secreted by the larvae of schistosomes protect against schistosomiasis: induction of cytotoxic antibodies in the rat and the monkey.

The study of the immunology of schistosomiasis has allowed a clear understanding of the basic mechanisms of resistance, emphasizing the important role played by cellular and humoral factors. Whereas the production of polyclonal or monoclonal antibodies and the precise inventory of immune effector mechanisms in the rat and in man have led to the identification of potentially protective antigens, immunization with soluble schistosome components has not allowed a successful control of the destruction of schistosomula after infection. The experiments reported here show that schistosomulum-released products (SRP) were able to induce the production of antibodies, in the rat and the monkey, highly cytotoxic in antibody-dependent cellular cytotoxicity, using monocyte monolayers, platelets or eosinophils as effector cells. The immunization of rats with either total SRP or 25-30-kDa molecules purified from schistosomula conferred a significant protection towards a challenge infection by the parasite. IgE and to a lesser extent IgG antibodies represented the major humoral factors of cell activation leading to the schistosomulum killing when anti-SRP antisera, obtained after immunization of the monkey, were incubated with human effector cells.

Animals↗
PubMed1985

Eosinophil activation by lymphokines and T cell clone products in the rat.

T cell lines and T cell clones derived from inbred Fischer rats and specific for Schistosoma mansoni antigens were established. Cell-free supernatants from the T cell lines demonstrated a marked capacity to enhance IgE- and IgG2a-dependent eosinophil-mediated killing of S. mansoni larvae in vitro. In addition, supernatants from cloned T cells stimulated with concanavalin A or specific antigen, or unstimulated, enhanced IgE-dependent eosinophil-mediated helminthotoxicity. The enhancing activity in both cases was very heat-stable (100 degrees C, 10 min). We also found that clone-derived supernatants enhance eosinophil peroxidase release upon stimulation with homologous IgE and anti-IgE as well as inducing a more delayed spontaneous release of peroxidase. In view of the established thymus dependency for the development of immunity to schistosomiasis in the rat, the availability of these S. mansoni-specific cloned T cells has enabled the relationship between eosinophils, lymphocytes and anaphylactic antibodies to be examined more closely.

Animals↗
PubMed1985

Immunity after treatment of human schistosomiasis mansoni. II. Identification of resistant individuals, and analysis of their immune responses.

Intensities of re-infection were monitored at three-monthly intervals after treatment of Schistosoma mansoni infections in a group of 119 Kenyan schoolchildren, whose levels of water contact were also observed. 22 children showed high reinfection intensities (greater than 100 eggs per gram of faeces) by 12 months after treatment, and were considered to be susceptible. Out of 70 children who showed low reinfection intensities during the same period (less than 30 eggs per gram), 35 showed high levels both of total water contact and of contact with sites containing infected snails. In these children, the relative lack of reinfection could not be attributed to a lack of exposure, and they were classified as resistant to reinfection. Comparison of the two groups, resistant and susceptible, revealed no difference in pretreatment intensities of infection. However, there was a marked difference in age, the mean age of the resistant group being two years greater than that of the susceptible group, within a restricted starting age range. These findings indicated that resistance was an acquired and age-dependent phenomenon, not obviously related to previous egg-induced pathology. Studies of immune responses revealed no clearcut correlate of resistance, but there were interesting differences between the two groups. Whereas anti-egg antigen responses declined after treatment to a greater extent in the resistant than in the susceptible group, antibodies mediating eosinophil-dependent killing of schistosomula rose markedly in both groups, strongly suggesting that the resistant children were being exposed to cercariae. Anti-adult worm antibodies rose sharply in both groups immediately after treatment, and thereafter declined to pretreatment levels. Although some individual children showed high levels of IgE anti-schistosomulum antibodies, there were no significant differences between the two groups. Since all children showed detectable levels of antibodies mediating eosinophil-dependent killing of schistosomula, the possibility was considered that such antibodies might be a necessary, but not a limiting, factor in immunity. Instead, the functional state of the effector cells mediating antibody-dependent killing might be limiting. Eosinophil levels, measured as an indirect estimate of eosinophil functional activity, did not differ between the two groups. There were, however, marked differences between different individuals in their capacity to produce eosinophil-stimulating monocyte mediators, and although this cannot yet be related to resistance, this aspect is worth further study.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Effects of hyperthermia on normal or neoplastic rat liver.

An experimental study was conducted in rats to evaluate the sensitivity of the liver to infrared hyperthermia. A 15-min hyperthermia session treating only the liver was done in rats with a normal hepatic parenchyma and in rats with hepatocarcinoma induced by chronic 3'-diethylaminoazobenzene intoxication, at various ranges of intrahepatic temperature. In normal rats, 40-42 degrees C hyperthermia was well tolerated, but the mortality rate increased when the intrahepatic temperature exceeded 42 degrees C. In rats with tumors, a 40-42 degrees C hyperthermia session was well tolerated in case of small tumors, but resulted in a high mortality rate in case of large tumors. In all cases, death occurred as a consequence of liver injury. This study using a simple method of hyperthermia defines the thermosensitivity of the neoplastic or normal rat liver and provides a basis for further investigations on the effect of hyperthermia on experimental liver tumors.

Animals↗
PubMed1985

Cytophilic IgE on human blood and tissue eosinophils.

Flow microfluorometry (FMF) was used to investigate the presence of cytophilic Ig (IgE or IgG) and the proportion of Fc receptor (Fc epsilon R or Fc gamma R)-bearing eosinophils among eosinophils from 21 hypereosinophilic patients. In 75% of the cases, it was possible to detect cytophilic IgE, significantly associated with serum IgE levels. Moreover, when lung and blood eosinophils were compared, the proportion of occupied Fc epsilon R was significantly increased on lung eosinophils, whereas very few cells had cytophilic IgG. This work provides further evidence that cytophilic IgE is not restricted to cells with high-affinity Fc epsilon R but can also be detected on the cell populations with low-affinity IgE receptors. These findings support the view that eosinophils can act as effector cells in immediate hypersensitivity reactions and in diseases associated with increased IgE production and hypereosinophilia.

Eosinophilia↗
PubMed1985

Cytophilic IgE on human blood and tissue eosinophils: detection by flow microfluorometry.

Flow microfluorometry (FMF) was used to investigate the presence of cytophilic Ig (IgE or IgG) and the proportion of Fc receptor (Fc epsilon R or Fc gamma R)-bearing eosinophils among eosinophils from 21 hypereosinophilic patients. In a large majority of the cases, it was possible to detect cytophilic IgE significantly associated with serum IgE levels. Moreover, when lung and blood eosinophils were compared, the proportion of occupied Fc epsilon R was significantly increased on lung eosinophils, whereas very few cells had cytophilic IgG. This work provides further evidence that cytophilic IgE is not restricted to cells with high affinity Fc epsilon R, but can also be detected on the cell populations with low affinity IgE receptors. These findings support the view that eosinophils can act as effector cells in immediate hypersensitivity reactions and in diseases associated with increased IgE production and hypereosinophilia.

Cell Separation↗
PubMed1985

Fc gamma receptors on rat eosinophils: isotype-dependent cell activation.

Fc receptors for rat IgG subclasses (IgG2a, IgG2c, and IgG1) were studied on rat eosinophils by rosette formation with erythrocytes coated with monoclonal immunoglobulin (Ig) or anti-Ig antisera in a reverse assay. Inhibition experiments revealed that IgG2a and IgG2c bind to the same receptor (IgG2a/IgG2c Fc receptor), distinct from the receptor for IgG1. In addition to the recent demonstration of the blocking effect of IgG2c antibodies in immunity to schistosomes, the present results show that the existence of this common receptor led to the specific inhibition by IgG2c of IgG2a-mediated eosinophil peroxidase release. Kinetic experiments on Schistosoma mansoni-infected rat eosinophils indicate that the IgG2a/IgG2c Fc receptors were occupied by cytophilic antibodies of the IgG2a isotype during the early phase of infection and by IgG2c thereafter. By rosette experiments it was possible to displace both in vivo and in vitro cytophilically bound IgG2a from its receptor. These results confirm, therefore, the major role played by antibodies in the modulation of eosinophil effector function during schistosomiasis. They underline, moreover, the possible isotypic regulation of cell activation.

Animals↗
PubMed1985

Extracellular release of rat eosinophil peroxidase (EPO) I. Role of anaphylactic immunoglobulins.

The release of intracellular peroxidase (EPO) was investigated in order to evaluate rat eosinophil activation by various immunoglobulin (Ig) isotypes. After successive incubations with purified rat IgG1, IgG2a, IgG2b, IgG2c, IgE, or IgM and their respective anti-Ig antisera, eosinophils released significant amounts of EPO (up to 26% of the intracellular content) only in the case of Ig with anaphylactic activities (IgG2a and IgE). Other classes and subclasses were unable to induce EPO exocytosis. Selective depletion and reconstitution experiments suggested that mast cells were not required in this process. Similar levels of EPO could be released after interaction of eosinophils with antigen-antibody complexes (IgG2a monoclonal antibody and Schistosoma mansoni antigen) immobilized on nonphagocytosable surfaces. These results indicate that EPO exocytosis can be obtained after cell activation with specific antibodies, and that this mechanism is independent of phagocytosis. A kinetic study of eosinophils from S. mansoni-infected rats revealed that IgG2a and IgE cytophilic antibodies induced EPO release after incubation with either specific antisera or specific antigen, which suggests the in vivo relevance of such findings. The present work underlines the parallelism of interaction of anaphylactic-type Ig with eosinophils and with mast cells. Moreover, EPO release seems to represent an interesting marker of eosinophil activation, because close relationships were established between the present findings and previous work on the effector function of rat eosinophils.

Anaphylaxis↗
PubMed1984

Rat IgE directed against schistosomula-released products is cytotoxic for Schistosoma mansoni schistosomula in vitro.

The immunogenicity of molecules shed by schistosomula into culture medium (antigens present in schistosomula-released products, SRP-A) has been studied. The results obtained show that SRP-A preferentially induce an IgE response when injected into rats, without the need for adjuvants. Moreover, anti-SRP-A IgE is cytotoxic in vitro for the larvae in the presence of macrophages, eosinophils or platelets, which have previously been demonstrated as being the three efficient killer cells for schistosomula in the presence of specific IgE. Immunofluorescence analysis locates the target antigens at the schistosomulum surface. Among the antigens recognized by anti-SRP-A IgE, two molecules of 26 and 22 kDa have been identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by western blotting.

Animals↗