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Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 505 records · Page 28Linked to original sources
PubMed1984

Role of IgE receptors in effector function of human eosinophils.

After analysis of the technical parameters of the rosette assay with human IgE-coated erythrocytes, Fc epsilon receptors for IgE (Fc epsilon R) on human peripheral blood eosinophils were compared to Fc epsilon R on lymphocytes and monocytes. Antibodies directed against Fc epsilon R on lymphocytes and monocytes inhibited the IgE rosettes formed by eosinophils from hypereosinophilic patients, which suggests that Fc epsilon R on eosinophils were antigenically related to Fc epsilon R on lymphocytes and monocytes. Fc epsilon R on human eosinophils were shown to participate in the killing effect of Schistosoma mansoni schistosomula in vitro in the presence of purified eosinophils from highly hypereosinophilic patients (blood counts greater than 3000/mm3) and anti-schistosomula IgE antibodies present in S. mansoni-infected patient sera. Similar levels of inhibition of cytotoxicity were obtained after preincubation of eosinophils with aggregated human IgE or with anti-Fc epsilon R antibodies, whereas preincubation with aggregated IgG or with anti-C3b receptor antibodies did not decrease the killing effect for schistosomula targets. This IgE-dependent cytotoxic capacity seemed restricted to eosinophils with an abnormally low density ("hypodense" cells) present only in highly hypereosinophilic patients. These observations might be related to nonparasitic situations in which increased levels of IgE and tissue or blood eosinophils are observed.

Antilymphocyte Serum↗
PubMed1984

[Participation of the IgE receptor in the toxicity of blood platelets against schistosomes].

Human blood platelets, incubated with the serum from patients with schistosomiasis or allergic asthma, became cytotoxic for schistosome larvae, in an allergen-specific mechanism linked to surface bound IgE on platelets. Cytotoxic factors, among which oxygen metabolites might be involved, were able to kill schistosomula through platelet-retaining filters. Flow cytometry showed that platelets bearing IgE receptors represented a subpopulation, the percentage of which significantly increased in patients with high levels of circulating IgE.

Asthma↗
PubMed1984

Evaluation of ELISA and RAST using purified antigens for diagnosis of hydatidosis.

Purified Echinococcus granulosus antigens have been used in ELISA and RAST to improve the serodiagnosis of hydatidosis. Results in ELISA confirm the interest of purified antigens for a specific diagnosis and the particular relevance of antigen 5. Antigen B has been shown to be relevant in RAST since the highest correlation was obtained between total IgE and antigen B-specific IgE. Moreover, no false positive were shown as using RAST with antigen B. Such a study has now to be extended at a large scale to appreciate the evolutivity of the disease.

Antigens↗
PubMed1984

Heterogeneity of human eosinophils. II. Variability of respiratory burst activity related to cell density.

Recent work has suggested that there may be heterogeneity amongst human eosinophils. In order to study this further, blood and tissue eosinophils were separated by density gradient centrifugation in discontinuous gradients of metrizamide. Blood eosinophils were obtained from 16 patients with blood eosinophil counts above 1 X 10(9)/l. Resident eosinophils were isolated from alveolar fluid in three of these patients and from pleural effusion in two others. A large proportion of the eosinophils in these patients were of light buoyant density (hypodense) and a high percentage of these showed morphological evidence of hypogranulation. Hypodense eosinophils had a reduced capacity to reduce nitroblue tetrazolium or develop chemiluminescence after stimulation with phorbol myristate acetate. It was concluded that there is structural and metabolic heterogeneity amongst blood and tissue eosinophils in patients with a variety of eosinophilic disorders.

Centrifugation, Density Gradient↗
PubMed1984

Neutrophil-mediated killing of Dipetalonema viteae microfilariae: simultaneous presence of IgE, IgG antibodies and complement is required.

Neutrophils from the peripheral washings of normal rats in the presence of sera obtained from rats immune to circulating microfilariae adhered to and killed the microfilariae of Dipetalonema viteae in vitro within 16-24 hr. No significant adherence or cytotoxicity was mediated by sera collected from animals with a high microfilaraemia or from normal rats. Ultrastructural studies show that neutrophils, which are bigger than microfilariae, can easily internalize the small larvae resulting in the disintegration of the parasite. Immunoadsorption and inhibition experiments showed that the adherence-promoting activity resides both in IgG and IgE classes of antibody. However, the mere participation of these two antibodies is not sufficient to effect neutrophil adherence towards microfilariae, the presence of complement is also required. Samples of fresh immune rat serum (fIRS) depleted in alternative pathway components of complement by treatment with zymosan A failed to mediate cell adherence to the parasite. fIRS inactivated for the classical pathway of complement by the chelating agent EGTA partially retains its activity in mediating cytotoxicity to microfilariae. The striking antigenic specificity of D. viteae antibodies was shown by their ability to mediate cytotoxicity only to D. viteae but not towards Brugia malayi microfilariae.

Animals↗
PubMed1984

Allergens of Schistosoma mansoni. II. Fractionation and characterization of S. mansoni egg allergens.

The interaction of Schistosoma mansoni crude soluble egg antigen (SEA) with IgE antibodies in sera from S. mansoni-infected mice, rats and humans has been studied by the radioallergosorbent test (RAST) and the Prausnitz-Küstner (PK) technique. IgE antibodies recognizing egg antigens were present as early as day 21 after the infection in the mouse sera and day 28 in rat sera. IgE in sera of infected humans reacted with antigenic components in the Mr range 70,000-150,000 and focusing as a broad peak in the pH range 4.5-6.5 as measured by RAST. SDS-PAGE followed by western blotting showed the presence of major components at molecular weights of 117,000 and 35,000-43,000. In the PK test, using mouse sera, components focusing in the alkaline pH range also gave a positive reaction. Most of the allergenic activity was bound by concanavalin A-Sepharose and by wheat germ agglutinin-Ultrogel. IgE in serum from an infected non-permissive host (the Fischer rat) apparently recognized egg-stage-specific allergen as indicated by differences in the time course of the IgE response to egg allergens compared to the adult material. When analyzed by SDS-PAGE and western blotting with day 45-infected rat serum, SEA showed some qualitative and quantitative differences to adult worm antigen. Molecules at molecular weights between 25,000 and 30,000 and at about 43,000 in SEA reacted with rat serum IgE and were absent from adult worm antigen. The allergenic similarities between egg and adult worm are discussed.

Allergens↗
PubMed1984

Blocking activity of rat monoclonal antibodies in experimental schistosomiasis.

Rat IgG2c monoclonal antibodies have been produced after fusion of spleen cells from LOU/C rats infected with Schistosoma mansoni for 5 wk and IRF983F nonsecreting rat myeloma. The cell supernatant of an IgG2c-producing clone (IPLSm3), as well as ascitic fluids induced by this clone, revealed anti-S. mansoni activity detected by immunofluorescence on schistosomula sections. Antigenic analysis performed with IPLSm3 IgG2c antibody allowed to isolate onto the S. mansoni schistosomula surface a 38,000 dalton antigen previously characterized with the protective IPLSm1 IgG2a monoclonal antibody. Although IPLSm3 IgG2c did not exhibit any killing activity in vitro against schistosomula in the presence of complement, macrophages, or eosinophils, it was shown to strongly inhibit the eosinophil-dependent cytotoxicity mediated by IPLSm1 IgG2a antibodies. The blocking activity of IgG2c antibody was further demonstrated in vitro by the use of F(ab')2 fragments and in vivo by the inhibition of passively transferred immunity conferred by the IgG2a protective monoclonal antibody. These results indicate that blocking antibodies could play an important role in the expression of protective immunity during schistosome infection.

Animals↗
PubMed1983

Schistosoma mansoni: antigenic community between schistosomula surface and adult worm incubation products as a support for concomitant immunity.

The use of protective monoclonal antibodies has enabled us to demonstrate antigenic community between a 38-kDa schistosomula surface molecule and a 115-kDa component derived from adult worms. Injection of adult worms in rats also led to the production of antibodies specific for the 38-kDa antigen, suggesting that the 115-kDa adult worm molecule could act as an inducer of the protective immune response raised against young invading parasites.

Animals↗
PubMed1983

A new function for platelets: IgE-dependent killing of schistosomes.

Several killing mechanisms against schistosomes have been described in vitro, involving cellular and humoral factors. Neutrophils, eosinophils--with an accessory role for mast cells--monocytes and macrophages have been shown to exhibit cytotoxic properties against Schistosoma mansoni larvae, in association with antibodies of various isotypes or with complement (reviewed in ref. 1). Lymphocyte participation in effector functions is mediated mainly through lymphokines inducing cytotoxic macrophages, and, in certain cases, directly by T cells. The experiments reported here show that platelets, taken from rats after specific periods of infection with S. mansoni, were able to kill schistosomula, and that normal human or rat platelets acquired toxic properties towards the same target in the presence of serum from infected individuals. The humoral factor involved in this process was shown to be IgE, and evidence was obtained of a Fc receptor for IgE on human and rat platelets. The passive transfer of immune platelets to normal rats conferred a high degree of protection towards a challenge infection by the parasite.

Animals↗
PubMed1983

Stimulation of alveolar macrophages in asthmatic patients after local provocation test.

Dermatophagoîdes pteronyssinus allergen was instilled into the alveolar space of 7 allergic asthmatic patients during bronchoalveolar lavage. beta-glucuronidase concentration in the bronchoalveolar fluid from the challenged lung became significantly higher than that in the opposite control lung (3.90 +/- 1.88 nmol/h versus 0.86 +/- 0.55). The intracellular level of beta-glucuronidase in the alveolar macrophages in the challenged lung was 40.3% lower than that in the control lung. In 3 controls intracellular concentrations of beta-glucuronidase were similar before and after allergenic challenge and no enzyme activity could be detected in bronchoalveolar lavage fluid. These results suggest that alveolar instillation of an allergen in asthmatic patients rapidly stimulates alveolar macrophages, which may be involved in immediate hypersensitivity reactions in asthma.

Adolescent↗
PubMed1983

Characterization and synthesis of a macrophage inhibitory peptide from the second constant domain of human immunoglobulin G.

We have shown that IgG hydrolysed by Schistosoma mansoni schistosomula inhibited various macrophage functions, especially phagocytosis and anti-schistosome cytotoxicity. Here we show that a tripeptide, Thr289-Lys-Pro291, of the second constant domain of human immunoglobulin G (peptide 286-292) reproduced the inhibitory effect of a total hydrolysate. Indeed the beta-glucuronidase release from IgE-anti-IgE-stimulated rat and human macrophages decreased and its intracellular level did not rise after a prior incubation of the cells with Thr-Lys-Pro (500 nmol/ml). Moreover, the cell migration as well as the superoxide anion O2 generation were 50-80% reduced by the tripeptide. These results suggest that a single peptide set may be responsible for the decrease of the macrophage functions at the early stage of the parasite infection in the mammalian host. The pharmacologic properties of this tripeptide are under investigation.

Animals↗
PubMed1983

Ecdysone and 20 hydroxyecdysone: new hormones for the human parasite schistosoma mansoni.

The insect moulting hormones, ecdysone and 20 hydroxyecdysone, were detected by the combined use of radioimmunoassay and high performance liquid chromatography in the human parasite Schistosoma mansoni. On day 11 after infection only the ecdysone form is present, but, on day 40 after infection the ratio between ecdysone and 20 hydroxyecdysone changes with anatomic localization of the adult worms in mammalian host. In the eggs, the ratio of these two hormones is identical to the ratio found in sexually mature worms located in mesenteric veins. These data demonstrate for the first time that S. mansoni synthesizes the steroid hormones ecdysone and 20 OH ecdysone which are potent molecules in stimulating growth and vitello-genesis of this gonochoric trematode.

Aging↗
PubMed1983

Parasitological and immunological aspects of Trypanosoma cruzi infection in nude rats.

The role of the thymus on immunity of rats against Trypanosoma cruzi infection was investigated in vivo. The athymic (nu/nu) rats were shown to be significantly more susceptible to the acute phase of the infection than the control nu/+ rats, as measured by increased parasitemia and mortality. Specific anti-T. cruzi antibodies, complement, IgM and IgG2a serum levels were determined. The results would indicate the essential role of antibodies in immunity to acute Chagas' disease through T-dependent immune response.

Animals↗
PubMed1983

Schistosoma mansoni: surface membrane isolation by polycationic beads.

The Schistosoma mansoni surface membrane complex was isolated by binding polycationic beads to the worm surface in a sucrose- or sorbitol-acetate buffer, pH 5.0, at 4 C. The ratio of incorporation [3H]cholesterol/[14C]arachidonic acid was measured as well as the specific activities of the alkaline phosphatase (EC 3.1.3.1), Type I phosphodiesterase (EC 3.1.4.1), and Ca2+-adenosine triphosphatase (EC 3.6.1.3). The results indicated that membranes isolated on beads were of comparable or greater purity than membranes isolated by sucrose gradient centrifugation. The isolation procedure was rapid (30 min) and produced membrane fractions whose cytoplasmic surfaces were probably exposed.

Alkaline Phosphatase↗
PubMed1983

Messenger RNA extracted from Schistosoma mansoni larval forms codes for parasite antigens when translated in vitro.

Intact messenger RNA was extracted from three stages of development of the parasite Schistosoma mansoni, cercariae, 3 h (mechanically prepared) schistosomula and adults. Some of the in vitro translation products are precipitable with immune rat and human serum showing that these sera recognize protein determinants. Whereas the patterns of the total translation products show major proteins expressed at all three developmental stages, immunoprecipitation delineates patterns unique to each stage. Serum from chronically infected patients is likely to preferentially recognize proteins expressed by the adult parasite yet precipitates more products of translation of cercarial RNA than of adult RNA, suggesting that many of the same epitopes are already coded by cercarial messenger RNA. It seems, however, that antigens appear on lower molecular weight species in the adult. The experiments described here open the way to cloning the genes of antigens from S. mansoni.

Animals↗
PubMed1983

Detection of IgE antibodies in onchocerciasis using a semi-purified fraction from Dipetalonema viteae total antigen.

A Dipetalonema viteae extract was separated by gel filtration on ACA 34 Ultrogel into four fractions (A, B, C and D). The allergenic activity of the D. viteae extract and its various fractions was assayed by the passive cutaneous anaphylaxis (PCA) test in rats using mouse sera obtained from Balb/c mice transplanted with D. viteae. The PCA reaction showed that fraction B was the most potent allergenic fraction of the D. viteae extract. By the radioallergosorbent test (RAST) the use of fraction B coupled to CNBr-activated paper discs showed elevated binding of IgE antibodies in onchocerciasis human sera. A comparative study demonstrated the efficiency of the above fraction in the RAST technique in distinguishing between Onchocerca volvulus-infected patients and those infected with other human filarial worms or other helminth parasites. The binding of IgE to fraction B was confirmed by the radioimmunoelectrophoresis and radio-double diffusion methods using an 125I anti-human IgE. Since D. viteae antigens are more readily obtainable than those of O. volvulus, a further purification of fraction B to improve its specificity for the detection of IgE antibodies in human onchocerciasis is warranted.

Allergens↗
PubMed1983

Inhibition of cytotoxic T lymphocytes by a schistosome-derived inhibitory factor is independent of an inhibition of the production of interleukin 2.

Schistosome-derived inhibitory factor (SDIF) was shown to inhibit lymphocyte proliferation. While SDIF is not toxic to lymphoid cells, the generation of cytotoxic effector cells was inhibited by SDIF in a mixed lymphocyte culture. This inhibitory effect was not attributable to the induction of suppressor cells, as SDIF also inhibited the development of nonspecific suppressor cell activity in 7-day cultures of unstimulated spleen cells. The interleukine 2-dependent proliferation of cytotoxic T lymphocytes of or of blast cells was markedly reduced by the addition of SDIF. In contrast, the production of interleukine 2 itself was not impaired by SDIF. These results support the hypothesis of an inhibition by SDIF of a particular step of the mitotic cycle, probably posterior to the G0-G1 transition. An inhibitory activity of SDIF on the expression of the cytolytic activity of cytotoxic T lymphocytes was also observed.

Animals↗