Anti-F(ab')_2 and anti-dsDNA-F(ab'):fragment(idiotype)Were prepared from digested normal human IgG and anti-dsDNA antibody with pepsin.Anti-F(ab')_2 antibody was determined by ELISA in 46 patients with SLE.A significant correlation between titers of anti-dsDNA-F(ab')_2 and anti-F(ab'):antibodies was observed.Results show high levels of anti-F(ab')_2 and low levels of anti-dsDNA antibodies in patients with remisson SLE activity.These findings suggest that the general IgG-F(ab')_2 antibodies and the anti-dsDNA-F(ab')_2 idiotypes in SLE sera may express some common structural epitopes.The measurement of anti-F(ab')_2 antibody levels may prove usefuladditional parameters assessing the clinical status.

Using human spleen purified SSA antigen,we set up a new technique of dot immunobinding assay(DIBA)for detection of anti—SSA antibody.The specificity of DIBA is better than that of double immunodiffusion method.The positive rate of anti—SSA antibody in Sjogren syndrome is 76.9%,while that in systemic lupus erythematosus is 33.3%.We found that anti—SSA antibody and RF usually appeared in same patient with Sjo-gren syndrome or rheumatoid arthritis.