Thyroid microsomal antibodies (Anti-M-Abs) have been recently proved to be directed to thyroid peroxidase (TPO). The present study evaluates the significance of antibodies against TPO (Anti-TPO-Abs) in the patients with systemic lupus erythematosus (SLE) with respect to their correlation with Anti-M-Abs and to their influence on TPO activity. When measured by immunoprecipitation using crude microsomal prepation, anti-TPO-Abs were highly correlated with microsomal antibodies (r=0.78 p<0.01). When evaluating the direct influence of anti-TPO-Abs on the activity of TPO. We found no significant inhibition of the enzymatic activity by lupus sera. In conclusion, the findings indicate that the specificities of anti-TPO-Abs in SLE are different from those in patients of thyroid disorders.
