Isolation and characterization of a 60-kDa IgE-binding component derived from sera of atopic patients (atopic dermatitis).

Abstract

The low-affinity receptor for IgE (Fc epsilon RII, CD23) and the related soluble IgE-binding factors (IgE-BF; sCD23) play an important role in IgE regulation. Sera of patients suffering from atopic dermatitis (AD) were reported to contain an IgE-binding component with a molecular weight of 60 kD. The aim of our studies was the isolation and characterization of the 60 kD component. Sera of patients with AD were fractionated by ammonium sulfate precipitation (10-90%). The fractions were analyzed with regard to their IgE and their IgE-BF contents. Furthermore, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and subsequent autoradiography with 125I-labeled human IgE (PS) was performed to detect IgE-binding activity. The major amount of IgE as well as IgE-BF was obtained within the 30-50% ammonium sulfate precipitation. In addition, IgE-binding activity was precipitated at 60% saturation. Separation by gel filtration under physiological conditions indicated IgE-BF with molecular weight of greater than 100, 60, 25 and 15 kD. Rechromatography of the greater than 100-kD fraction led to IgE-binding activity with a molecular weight of 60 kD which is not present within normal sera. The data demonstrate that the 60-kD component is partially bound to serum IgE. One may suggest that the complex is involved in the induction and persistence of allergic disorders.