Serum anti-double-stranded (ds)DNA antibody in the NZB/WF1 mice before and after treatment with vehicle or the ethyl acetate (EA) extract of Tripterygium wilfordii Hook F. (a) Serum was collected before, 7 and 14 weeks after starting treatment. Anti-dsDNA antibody was determined by ELISA as described in Materials and methods. The mean of relative titers of anti-dsDNA antibody of serum obtained from normal C57BL/6j mice was 0.23 (0.1 to 0.3). Numbers in parentheses indicate the mice evaluated. Data are the mean ± standard error of the mean of the optical density (OD) readings on 1:20 diluted serum of each group. **p < 0.01, ***p < 0.001 at time 0 versus at 7 weeks or 14 weeks of treatment for the same group. (b) The same data were analyzed as the change in anti-dsDNA antibody titers from the baseline at 28 weeks of age. Original magnification × 400.