ANALYSIS OF IGG SUBCLASSES OF HUMAN ANTITOPOISOMERASE-I AUTOANTIBODIES SUGGESTS CHRONIC B-CELL STIMULATION

Antitopoisomerase I autoantibodies are highly specific of scleroderma and are mainly IgG. The present study was designed to evaluate the pre valence of each IgG antitopoisomerase I subclass. An ELISA for the det ection of IgG antitopoisomerase I subclasses was standardized and used to study the antibodies from 49 antitopoisomerase I-positive patients identified from a total of 541 patients, Correlations and multivariat e analysis were performed to determine the frequency of associations b etween the IgG; antitopoisomerase I subclasses. All IgG antitopoisomer ase I subclasses were found, Twelve patients (24.5%) had all four IgG antitopoisomerase I subclasses, 13 (26.5%) had three, 16 (32.7%) had t wo, and 7 (14.3%) had only one antitopoisomerase I subclass. The prese nce of all four IgG antitopoisomerase I subclasses suggests that this specific B-cell is the target of multiple activation pathways which in dicate that there is a complex T-cell-cytokine-driven process. Togethe r with the absence of other autoantibodies in these sera, our results support the concept of a multiple but highly selected and chronic B-ce ll activation in scleroderma patients with antitopoisomerase I. (C) 19 97 Academic Press.