title: The blocking activity of birch pollen-specific immunotherapy-induced IgG4 is not qualitatively superior to that of other IgG subclasses.
abstract: Allergen-specific IgG antibodies induced by specific immunotherapy (SIT) interfere with the allergen-IgE interaction, and act as blocking antibodies in vitro. It has been hypothesised that IgG4, as opposed to other IgG subclasses, is particularly important in this function, which may play a role for the clinical efficacy of SIT. In this study, fractionated serum samples from 14 SIT-treated birch pollen allergic individuals enabled determination of the inhibitory capacity of IgG4 alone versus non-IgG4 IgG. Allergen-binding activities of IgG and the IgG-mediated inhibition of allergen binding to autologous IgE were detected using 125I-labelled rBet v 1.2801, a recombinant variant of the major allergen of Betula verrucosa pollen. Results show that IgG4-depletion resulted in equivalent reductions in binding and blocking activities. In contrast, a significant but less than two-fold higher relative blocking activity was found in the purified IgG4 fraction. There was no significant difference in the binding avidities (1/K(d)) measured in the two IgG fractions. Thus, it appears that SIT-induced specific IgG4 contributes to the IgG blocking of allergen binding to IgE in a simple quantitative manner and not by a particular intrinsic blocking activity.
authors.affiliation: ALK-Abelló, Department of Biological Research, Horsholm, Denmark.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Ejrnaes
authors.forename: Uffe
authors.initials: U
authors.lastname: Bodtger
authors.forename: Jørgen N
authors.initials: JN
authors.lastname: Larsen
authors.forename: Morten
authors.initials: M
authors.lastname: Svenson
mesh_terms: D000485:Allergens / Q000276:immunology / Q000627:therapeutic use; D000906:Antibodies / Q000097:blood / Q000276:immunology; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D052179:Antigens, Plant; D029662:Betula / Q000276:immunology*; D001667:Binding, Competitive; D003429:Cross Reactions / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000628:therapy; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood / Q000145:classification / Q000276:immunology*; D007167:Immunotherapy; D011058:Pollen / Q000276:immunology*; D011994:Recombinant Proteins
chemical_list: D000485:Allergens; D000906:Antibodies; D052179:Antigens, Plant; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D007073:Immunoglobulin E