title: Isotypic analysis of grass pollen-specific antibodies in human plasma. 4. Biological activity of allergen-specific and autoanti-IgE antibody fractions on basophil histamine release.
abstract: BACKGROUND
  Blocking antibodies are defined as antibodies that compete with IgE for binding to allergens due to their specificity for those allergens. Thus, they may inhibit allergen-induced basophil and mast cell IgE-dependent mediator release both in vivo and in vitro.
  
  
  OBJECTIVE
  The present study was designed to evaluate the ability of antibodies isolated from human plasma samples on a Dactylis glomerata (Cocksfoot) pollen affinity-column to inhibit the Dactylis pollen-induced histamine release from human basophils (BHR) in vitro.
  
  
  METHODS
  Antibodies from Ig pools containing either high or low IgG4 anti-Dactylis pollen were purified on a Dactylis pollen affinity-column and then separated on an antihuman IgE column. Obtained Ig fractions were incubated for 30 min with Dactylis pollen allergens prior to incubation with basophils from Dactylis pollen-allergic donors. Cell supernatants were assessed for histamine content and the inhibition of BHR was calculated.
  
  
  RESULTS
  Unlike control non-isolated Igs, the antibodies isolated on the Dactylis pollen column were able to inhibit efficiently and in a dose-dependent manner Dactylis pollen-induced BHR. The inhibitory activity was increased in isolated antibody samples that had high IgG4 levels. Antibodies isolated on the Dactylis pollen column, however, consisted not only of true allergen-specific (potentially blocking) antibodies but also of autoanti-IgE binding to allergen-specific IgE and mistaken for allergen-specific antibodies thus opening to question the involvement of the true allergen-specific antibodies in the BHR-inhibitory activity. Unlike the true allergen-specific antibodies, the autoanti-IgE were retained on and eluted from the anti-IgE column. Results showed that both the autoanti-IgE-depleted and the autoanti-IgE-containing fractions accounted for the inhibition observed with the related non-depleted sample that had been isolated on the Dactylis pollen column.
  
  
  CONCLUSIONS
  For the first time, the true blocking activity of allergen-specific antibodies is demonstrated, that is, in the absence of the autoanti-IgE which can also inhibit BHR.
authors.affiliation: Laboratoire Français du Fractionnement et des Biotechnologies (LFB), Les Ulis, France.
authors.forename: T
authors.initials: T
authors.lastname: Batard
authors.forename: A
authors.initials: A
authors.lastname: Weyer
authors.forename: A
authors.initials: A
authors.lastname: Laroze
authors.forename: M R
authors.initials: MR
authors.lastname: Ickovic
authors.forename: B
authors.initials: B
authors.lastname: David
authors.forename: G
authors.initials: G
authors.lastname: Peltre
authors.forename: B
authors.initials: B
authors.lastname: Basuyaux
mesh_terms: D000485:Allergens / Q000276:immunology; D000888:Antibodies, Anti-Idiotypic / Q000097:blood; D019138:Antibodies, Blocking / Q000276:immunology; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology; D001491:Basophils / Q000378:metabolism; D002846:Chromatography, Affinity; D004797:Enzyme-Linked Immunosorbent Assay; D006636:Histamine Release / Q000502:physiology; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000097:blood*; D011058:Pollen / Q000276:immunology*
chemical_list: D000485:Allergens; D000888:Antibodies, Anti-Idiotypic; D019138:Antibodies, Blocking; D001323:Autoantibodies; D007132:Immunoglobulin Isotypes; D007073:Immunoglobulin E