ANTIGEN-SPECIFICITY OF ANTIHISTONE ANTIBODIES IN LOCALIZED SCLERODERMA

Background and Design: Recently, we detected antihistone antibodies (A HAs) in patients with localized scleroderma. However, the exact antige n specificity of AHAs in this disease is still unknown. Therefore, we determined the reactivity of AHAs with five individual histones and th e correlation of AHAs with rheumatoid factor in localized scleroderma by means of enzyme-linked immunosorbent assay. Twenty patients with lo calized scleroderma who had IgG and/or IgM AHAs, as determined by enzy me-linked immunosorbent assay, were examined. These patients were clas sified into the following three subgroups: patients with generalized m orphea (n=11), patients with linear scleroderma (n=6), and patients wi th morphea (n=3). Results: In generalized morphea, IgG AHAs strongly r eacted with histones H1, H2A, and H2B; and IgM AHAs strongly reacted w ith H1 and H2B, as determined by means of enzyme-linked immunosorbent assay. The pattern of reactivity in linear scleroderma and morphea was similar to that in generalized morphea. A homogeneous immunofluoresce nt pattern on HEp-2 cells, which was produced by localized scleroderma sera, was completely abolished by absorption with total histones. By employing a latex agglutination test, IgM rheumatoid factor was detect ed in 60% of the 20 patients with localized scleroderma and at a frequ ency of 82% in those with generalized morphea. However, an absorption test of rheumatoid factor activity with human IgG revealed no cross-re activity of AHAs with rheumatoid factor. Conclusions: Our data suggest that AHAs in localized scleroderma are directed against native chroma tin, since H1, H2A, and H2B occupy a relatively exposed portion of chr omatin.