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M Etievant

Publications and source records attributed to M Etievant.

9 recordsLinked to original sources
PubMed1995

Human auto-anti-idiotypic antibodies to mite-specific IgE can degranulate human basophils in vitro.

BACKGROUND: Anti-idiotypic antibodies (anti-Ids) to specific IgE antibodies are formed spontaneously during an anti-allergen immune response and can be induced by immunotherapy. Although anti-Ids can down-regulate the production of IgE antibodies, at least in experimental models, their possible role in the modulation of target cell reactivity remains ill-defined. OBJECTIVE: The capacity of human anti-Ids to modulate the release of histamine was examined in an in vitro system of human basophil degranulation. Anti-Ids were prepared from the serum of six Dermatophagoides pteronyssinus (Dp)-hypersensitive patients suffering from atopic dermatitis and who had never been desensitized. Basophils were obtained from the blood of atopic donors. The extent of histamine release was determined using a fluorometric assay. RESULTS: We show that: anti-Ids trigger the release of histamine in an allergen-specific, dose- and IgE-dependent manner; the release is not due to the presence of allergen and/or anti-IgE antibodies; and that the degranulating activity can be removed by absorption with affinity-purified anti-Dp antibodies of the corresponding patient. CONCLUSION: These results indicate that spontaneously produced human anti-Ids can modulate the reactivity of human basophils.

Allergens↗
PubMed1994

Binding of serum autoantibodies to sialidase-treated tracheal epithelial cells. Determination of autoantibodies isotypes in normal and influenza virus infected guinea pig sera.

Cultured epithelial cells isolated from guinea pig trachea were treated with Vibrio cholerae sialidase. The treatment was not cytotoxic and resulted in membrane desialylation as assessed by measurement of sialic acids released, along with an increased fixation of the galactose-specific lectin peanut agglutinin. After incubation in serum from normal guinea pigs, membrane-bound immunoglobulins were detected using peroxidase-labelled antibodies. Sialidase-treated cells bound significantly more IgM than controls (P < 0.0005), whereas binding of IgG was not significantly different between treated and untreated cells (0.1 < P < 0.375); IgA were never detected. In influenza-infected guinea-pigs, as assessed by reactivity with peanut agglutinin, the tracheal and lung epithelium, as well as alveolar cells were hyposialylated. In these animals, the level of serum IgG autoantibodies capable to bind sialidase treated cultured cells increased, while the level of IgM autoantibodies did not change. These autoantibodies may participate in cellular dysfunctions and modified bronchoreactivity that occur during infection of the respiratory tract by sialidase-producing microorganisms, either through activation of the complement system, or subsequently to their reaction with cells expressing membrane complement and/or Fc receptors.

Animals↗
PubMed1988

In vitro inhibition of the classical and alternate pathways of activation of human complement by N acetyl aspartyl glutamic acid (NAAGA).

A synthetic dipeptide, magnesium salt of N-acetyl-L-aspartyl-glutamic acid (NAAGA) identical to a natural dipeptide found as traces in cerebral tissues of mammalian brains, was shown to inhibit, in vitro, the hemolytic activity of both classical and alternate pathways complement; the required concentration of NAAGA was 2 to 10 mM. Cross immuno electrophoretic analysis demonstrated an inhibition of C3 cleavage by both classical and alternate pathway C3 convertases with 24 mM NAAGA. As expected, if C3 convertases were really the target of inhibition, the release of highly inflammatory C3a, C5a fragments scored by R.I.A. was impaired when complement was incubated with activators of classical and alternate pathways. Such a low molecular weight dipeptide, quite atoxic and inhibiting the complement dependent cytotoxicity and release of phlogistic by-products could be interesting for pharmacological manipulation of complement activation in inflammatory processes.

Complement Activation↗
PubMed1985

Specific binding of endotoxin to human monocytes and mouse macrophages: serum requirement.

Specific binding of Bordetella pertussis and Neisseria meningitidis endotoxins to human monocytes and murine macrophages was demonstrated. Binding of B. pertussis endotoxin could be inhibited by endotoxins of Salmonella minnesota, Escherichia coli, and Klebsiella pneumoniae, the extent of inhibition being dependent on the origin of the lipopolysaccharides and on the origin of the mononuclear phagocytic cells. The binding of B. pertussis and N. meningitidis endotoxins which was mediated by the polysaccharide region of the endotoxins was serum dependent. The results indicated that the binding of endotoxin was promoted neither by natural antibodies directed against the endotoxin nor by proteins known to combine with endotoxins: immunoglobulins, albumin, or fibronectin; we have provided some evidence that complement components may play a role in the specific binding of endotoxins to the monocyte/macrophage membrane.

Animals↗
PubMed1979

Immuno-enzymatic study of IgG subclasses specific for allergen in house dust immediate hypersensitivity.

Investigation of the serum-specific IgE by the RAST technique and of the four specific subclasses of IgG in house dust allergy by an immuno-enzymatic assay was made among healthy control subjects, non-treated atopic patients and hyposensitized patients. There was evidence that the titer of specific IgE remains high in the treated patients regardless of their improvement or non-improvement clinically. A good prognostic significance, however, correlates with a low specific IgG4 titer in the serum, but the pathogenic significance of IgG4 cannot be determined until these immunoglobulins can be studied on the membrances of circulating basophils of hyposensitized patients.

Allergens↗