Anti-Sm antibodies stain the nuclei of HEp-2 cells in a coarse nuclear speckled pattern

Human serum containing anti-Sm antibodies stain the nuclei of HEp-2 cells in a coarse nuclear speckled pattern (A and C). DAPI staining in panels B and D indicate the location of nuclei. In contrast to anti-DNA antibodies, in dividing cells (indicated by white arrow in C and D) anti-Sm antibodies do not stain the chromosomes. The anti-Sm antibody reference serum was obtained from the Centers for Disease Control repository of ANA standards.