Presence of nucleosome‐restricted antibodies in patients with systemic lupus erythematosus

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Abstract
Objective. To assess whether nucleosome-restricted antibodies, i.e., antibodies that react with the whole nucleosome particle but not with its individual components (double-stranded DNA [dsDNA] and his-tones), are present in the sera of patients with systemic lupus erythematosus (SLE). Methods. Antibodies were detected by enzyme-linked immunosorbent assay using purified nucleo-somes, dsDNA, or histones. These tests were applied to the sera of 40 patients with SLE. Protein G–purified IgGs of representative sera were sequentially adsorbed on dsDNA-and histone-conjugated solid-phase supports and further assayed for their nucleosome, dsDNA, and histone reactivities. Results. Of the 40 sera tested, 16 displayed anti-dsDNA and/or antihistone antibody activity, which was always associated with significant antinucleosome reactivity. In addition, 3 sera showed antinucleosome activity that was not associated with concomitant anti-dsDNA or antihistone activity. The presence of true nucleosome-restricted antibodies was demonstrated, after solid-phase adsorption, in representative SLE sera that showed anti-dsDNA or antihistone antibody activity, and also in sera that did not show these activities. Conclusion. Our results provide evidence for the presence of nucleosome-restricted antibodies in patients with lupus. These nucleosome-restricted antibodies, along with anti-dsDNA and antihistone antibodies, appear to belong to a broad set of antinuclear antibodies, the antinucleosome family.