"Figure 7-8Precipitation of peroxidase activity by sera from a patient with autoimmune thyroid disease and positive ""microsomal"" antibodies, and from a control subject without circulating antibodies.  TPO was precipitated by primary incubation with human sera, and removal of TPO Ig complexes was achieved by addition of Protein H Sepharose CL 4B.   Residual hTPO activity in the supernatant was assayed in a  guaiacol assay."