The Recognition of a Recombinant Human Fcε Fragment by the Subclasses of IgG Autoanti-lgE: Disproportional Subclass Distribution of Complexed Autoantibody
Circulating IgG autoanti-IgE is detectable in a large proportion of individuals with allergic asthma where it is suggested to be potentially involved in the removal of IgE-allergen complexes. Since such a putative role will largely be determined by the subclass profile of complexed (i.e. IgE-bound) IgG anti-IgE, a study was undertaken to determine the subclass distribution of complexed IgG anti-IgE antibody in the sera of asthmatic patients. The study exploits the heat-labile property of IgE by heating (30 min at 56°C) serum to liberate bound anti-IgE, pre- and post-heated sera are then assayed for IgG subclass anti-recombinant human Fcε (rFcε) activities by ELISA and any heat-induced increase in antibody activity is taken as a measure of complexed anti-IgE. This has revealed a disproportionately high amount of IgG4 in complexed (but not free) IgG anti-IgE. The propensity of IgG4 to form complexes with IgE has important biological consequences, particularly with regard to the activation of C1q and FcγR by other subclasses.