Search PubMed⌕ Search

Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 451 records · Page 25Linked to original sources
PubMed1986

Protection against experimental Schistosoma mansoni schistosomiasis achieved by immunization with schistosomula released products antigens (SRP-A): role of IgE antibodies.

Schistosomula-released products (SRP-A) have been shown to induce preferentially a significant IgE response against Schistosoma mansoni schistosomula when injected into rats, in the absence of adjuvant. The present work provides additional evidence of the in vivo relevance of the anti-SRP-A target antigens. Two strains of rat (Brown Norway and Fischer) were immunized with SRP-A and infected percutaneously. A significant level of protection (up to 83% reduction in worm burden) was observed. Passive transfer experiments carried out with anti-SRP-A or IgE-depleted anti-SRP-A sera suggested the preponderant role of antibodies and particularly of IgE in the protective immunity developed by Fischer rats. Platelets and macrophages recovered from such immunized rats had surface IgE as demonstrated by immunofluorescence analysis with FITC anti-IgE, and have been shown to be directly cytotoxic for schistosomula. The chemiluminescence observed when the macrophages were incubated with anti-IgE suggested the presence of IgE on the surface of these cells.

Animals↗
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

Use of a monoclonal antibody in a double-sandwich ELISA for detection of IgM antibodies to Toxoplasma gondii major surface protein (P30).

A double-sandwich ELISA, developed for detection of IgM antibodies to the major surface protein of Toxoplasma gondii (P30), is proposed for the diagnosis of acute acquired toxoplasmosis. The method is based on the capture of serum IgM antibodies, which are revealed indirectly by the sequential addition of a Toxoplasma extract and a beta-galactosidase-conjugated anti-P30 monoclonal antibody. All 57 patients tested with serological characteristics of recently acquired toxoplasmosis showed high levels of IgM anti-P30 antibodies. In addition, 5 out of the 24 patients with chronic toxoplasmosis and all 7 patients with a clinical acute infection in which the classical IgM serology was negative, also presented significant anti-P30 IgM antibodies. Patients with either rheumatoid factor or antinuclear antibodies were all negative. In view of its simplicity, specificity and sensitivity, this method is recommended for the current diagnosis of T. gondii infection.

Animals↗
PubMed1985

Major surface protein of Toxoplasma gondii (p30) contains an immunodominant region with repetitive epitopes.

Four monoclonal antibodies (mAb) against surface antigens of tachyzoites of Toxoplasma gondii were produced. Immunoprecipitation of extracts of 125I-labeled tachyzoites identified the same polypeptide with apparent molecular weight of 30 000 (p30). A competition binding assay indicated that a single region of p30 was recognized by all 4 of the mAb. Furthermore, we found that single mAb inhibited 25-50% of the specific binding of antibodies of patients with toxoplasmosis to the antigenic extract of tachyzoites. It appears, therefore, that p30 is the most immunogenic constituent of tachyzoites, and that a single region of this molecule contains most of the immunogenic activity. Finally, a two-site/one-antibody immunoradiometric assay with the same mAb indicated that the p30 molecule is multivalent with respect to the expression of a single epitope.

Animals↗
PubMed1985

Trypanosoma cruzi: modulation of parasite-cell interaction by plasma fibronectin.

Treatment of either rat peritoneal macrophages (RPM), cloned 3T3 fibroblasts (3T3FR) or Trypanosoma cruzi trypomastigote culture forms with human plasma fibronectin (huFN) enhanced their association with the untreated counterpart and this related to the concentration of huFN used. When treatment was performed at 4 degrees C, the enhancing effect of huFN on parasite-cell interaction was greater than that observed at 37 degrees C. This observation could be related to the indirect immunofluorescence antibody assay showing that a significant increase of fibronectin staining was observed on the cell and parasite surfaces upon incubation with huFN and that the extent of fibronectin staining was greater at 4 degrees C. Incubation of huFN-treated or nontreated parasites or cells with anti-huFN antibodies exerted an inhibitory effect on the parasite-cell association. The region of fibronectin that interacts with the trypomastigote surface is unknown. Inhibition experiments suggested that the domain of fibronectin which interacts with parasite surface receptors would probably be localized close to the NH2-terminal region of the molecule. Taken together, these results suggest that fibronectin may play a role in the binding of parasites to the vertebrate host cell surface.

Animals↗
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

Infectivity of Leishmania promastigotes is associated with surface antigenic expression.

Differentiation between a non-infective and an infective Leishmania promastigote population was demonstrated. Promastigotes in the stationary phase (day 5) were found to be highly infective in vitro to BALB/c mouse peritoneal macrophages, compared with those of the logarithmic phase (day 3). The infective promastigotes showed surface antigenic determinants different from non-infective ones. Polyclonal anti-3 day and anti-5 day antibodies were bound specifically to the surface of corresponding promastigotes in both SRIA and IFAT; no strong cross-reactions were observed otherwise. Also, polyclonal anti-5 day but not anti-3 day antibodies recognized efficiently the antigenic molecules on the surface of late stage (day 7) sandfly promastigotes. This clearly indicates the appearance of new antigenic molecules on the surface of infective promastigote forms. Intracellular multiplication of Leishmania was significantly inhibited by anti-5 day antibodies compared with anti-3 day antibodies. The presence of new surface molecules on late stage promastigotes may contribute to Leishmania infectivity.

Animals↗
PubMed1985

Renewal of the membrane complex of Schistosoma mansoni is closely associated with lipid metabolism.

Metabolic pathways leading to lipid biosynthesis in four different developmental stages of Schistosoma mansoni were explored and quantified by incubation in the presence of labeled precursors in a chemically defined medium. At the schistosomulum stage and in male, female, or paired worms, glycerol and oleate incorporation into neutral lipids, mainly in the form of triacylglycerols, was greater than into phospholipids, whereas in 11-and 15-day-old worms, synthesis mainly led to phospholipids. Incorporation into phospholipids was recovered largely in phosphatidylcholine, and distribution into other phospholipids depended on the developmental stage. Incorporation of choline and ethanolamine into their respective phospholipids represented up to 15% of the parasitic phospholipid content. The formation of phosphatidylcholine by phosphatidylethanolamine methylation occurred mainly in the immature parasitic stages. Inositol incorporation was also measurable, whereas [14C]serine incorporation was low or undetectable. Addition of 1-palmitoyl-2-[14C]oleyl phosphatidylcholine revealed a very high uptake of this phospholipid by the immature stages but further metabolism was not detectable. In contrast, adult S. mansoni were completely unable to take up or absorb this exogenous phospholipid. The most striking aspect of this study was the relatively high metabolic activity in 11-day-old worms and the lower but sustained activity on day 15 and at the schistosomulum stage. By comparison, biosynthetic activity in adult S. mansoni, on which research studies have been focused until now, was very low. We also discuss the participation of lipid metabolism in the constant renewal of the membrane complex which is essential to parasitism by S. mansoni.

Aging↗
PubMed1985

Biochemical studies on the 30-40 kDa Schistosoma mansoni surface antigens.

Biochemical studies of the previously identified 30-40 kDa surface antigens of Schistosoma mansoni schistosomula confirmed that four molecules could be discriminated in this antigenic group. The antigens presented slightly different molecular mass in sodium dodecyl sulfate polyacrylamide gel electrophoresis (40, 38, 37 and 32 kDa) but were all found in isoelectric focusing at the same pH (6.2-6 and 7.5). The four antigens bound to concanavalin A and only the 32 kDa molecule had affinity for the Lens culinaris agglutinin. These results indicated almost similar biochemical characteristics of the 30-40 kDa antigens and partial hydrolysis of the 38 and 32 kDa antigens suggested that they were affected by a similar cleavage process. The possibility of a structural homology between these two components is discussed.

Animals↗
PubMed1985

Translation of Schistosoma mansoni antigens in Xenopus oocytes microinjected with mRNA from adult worms.

Oocytes from Xenopus laevis microinjected with RNA isolated from Schistosoma mansoni adult worms translated antigens recognized by sera from infected rats, humans, and from immunized rabbits. The pattern of immunoprecipitated proteins analysed by SDS-polyacrylamide gel electrophoresis was species specific in rats. Serum from infected Fischer rats recognized antigens of 20, 27 and several bands in the 50-60 kDa range whereas serum from infected Brown Norway rats also immunoprecipitated major bands at 29, 43 and 100 kDa. Human infection sera gave a very variable pattern of immunoprecipitation not apparently dependent on the patients' age. At least 20 different antigenic species could be identified ranging from 14 to 150 kDa. Some S. mansoni antigenic proteins could be isolated from the membrane fraction of the oocytes whereas notably the 29 kDa band was present mainly in the soluble fraction. N-Glycosylation of S. mansoni antigens occurred as evidenced by the effects of tunicamycin treatment and concanavalin A binding. A multiple series of bands between 50 and 60 kDa, present in the membrane fraction, were glycosylated and secreted from the oocytes. Monoclonal antibodies to larval stage surface antigens failed to immunoprecipitate oocyte translation products, but sera absorbed with live schistosomula identified at least three putative surface antigens of 100, 43 and 29 kDa. However, the 29 kDa molecule was neither synthesized into membranes, nor secreted from oocytes.

Animals↗
PubMed1985

In vitro synthesis of a 28 kilodalton antigen present on the surface of the schistosomulum of Schistosoma mansoni.

Adult Schistosoma mansoni proteins were fractionated on polyacrylamide slab gels, recovered by electrophoretic elution and used for immunization of Fischer rats. Three antisera recognizing, respectively, 28, 78 and 85 kDa antigens were obtained. The 28 kDa antigen was found among the in vitro translation products from adult worm RNA, and among the 125I-labelled surface antigens of S. mansoni schistosomula. The isoelectric point of the 28 kDa antigen was 6.3-6.5. The 28 kDa antiserum mediated a cytotoxic activity against schistosomula when used in an in vitro assay in the presence of a purified eosinophil cell population.

Animals↗