Analysis of Biological Functions of a 60-kD IgE-Binding Component Derived from Sera of Patients with Atopic Dermatitis.

CD23 and its soluble components (sCD23) play an important role in IgE regulation. Sera of patients with atopic dermatitis (AD) were reported to contain an IgE-binding component with a molecular weight of 60 kD. The aim of our study was to analyze the biological functions of the 60-kD component. Sera of patients with AD were fractionated by ammoniumsulfate precipitation, gel filtration, affinity chromatography on IgE-Sepharose or anti-CD23 Sepharose and electroelution from SDS/PAGE. The sCD23-containing preparations were used in cell culture experiments to stimulate peripheral blood lymphocytes of normal donors. Binding studies with IgE peptides demonstrated that CD23 and the 60-kD IgE-binding components bind to the same site. Further experiments were performed to analyze the induced mRNA pattern in the presence of the 60-kD components by polymerase chain reaction (PCR). These data demonstrated that signals for IgE-germ line transcripts and IFN-γ were induced in the presence of the IgE-binding factor preparations from normal peripheral blood lymphocytes whereas there was no signal obtained for IL-2 or IL-4. In addition, it was shown by flow cytometry that the 60-kD component enhanced the expression of adhesion molecules (CD11α, CD18, CD54) whereas the expression of CD23 was reduced.