Figure 1

Coexistence of anti-snRNPs antibodies in anti-topo I-positive sera. (a)12.5% SDS-PAGE. (b) 8% SDS-PAGE. Six sera with anti-topo I and-snRNPs (two anti-Sm + U1RNP; four anti-U1RNP) were identified by immunoprecipitation of [³⁵S]-methionine-labeled K562 cell extract. Positions of Topo I, components of snRNPs (U5RNP-200 kDas; U1-70 kDa; U1-A, B'/B, U1-C, D1/D2/D3, E, F, and G), and molecular weight are indicated. U1, Sm, Topo I, prototype sera for each specificity; Topo I+Sm, anti-topo I with anti-Sm and U1RNP-positive SSc sera; Topo I+U1RNP, anti-topo I and U1RNP-positive SSc sera; NHS, normal human serum. (c) Analysis of RNA components in anti-topo I-positive patients with coexisting anti-snRNPs. RNA components immunoprecipitated by human autoimmune sera were analyzed with urea-PAGE and silver staining. Six anti-topo I-positive patients had coexisting anti-UsnRNPs (two anti-Sm (U1, 2, 4 to 6, and 5; lanes 1 and 2) and four anti-U1RNP (lanes 3 to 6)) were identified. Total, total RNAs; U1, Sm, prototype human serum for each specificity; Topo I + Sm, anti-topo I with anti-Sm and U1RNP-positive SSc sera; Topo I + U1RNP, anti-topo I and U1RNP-positive SSc sera; NHS, normal human serum; positions of 7S, 5.8S, and 5S rRNA, tRNAs, and U1, 2, 4, 5, and 6 snRNAs are shown.