Comparison of topo I staining in cultured fibroblasts of normal controls and SSc patients. A. Topo I immunostaining with anti-topo I monoclonal antibodies showed multiple speckles in the nucleoplasm of SSc fibroblasts, which is differentiated from that in normal fibroblasts (relatively homogenous stain of topo I) at both 7 and 14 days of cultures. Some SSc fibroblasts show cytoplasmic staining of topo I protein (marked with red arrow heads). B. Topo I immunostaining with anti-topo I positive sera from SSc patients show the expected nuclear/nucleolar staining as well as cytoplasmic staining of SSc fibroblasts. At Day 14, the cytoplasmic staining appeared to increase relative to the nucleoplasm and nucleolar staining.