Antibodies induced to the LHR are not specific for the receptor, unlike antibodies induced to mouse TPO. (A) Flow cytometry was compared in the same serum for antibody binding (IgG class) to LHR-CHO cells versus untransfected CHO cells. Sera were tested from BALB/c mice that had received three injections of rat-LHR-Ad, rat-LHR-289-Ad, or Con-Ad. Symbols indicate values for sera from individual mice. For most sera, binding was higher to LHR-CHO than to CHO cells, particularly those from Con-Ad immunized mice. (B) Flow cytometry was compared in the same serum for antibody binding (IgG class) to mouse-TPO-CHO cells versus untransfected CHO cells. In this experiment, we re-tested sera from C57BL/6 mice immunized three times with mouse-TPO-Ad (7) and examined sera from mice immunized three times with mouse TPO-ECD-Ad (present study). The horizontal dashed line indicates the mean + 2SD for Con-Ad immunized mice. Note the difference in magnitude of the geometric means (Y axis): 0 to >200 (B) versus only 0 to 14 (A). TPO, thyroid peroxidase.