Immunochemical and immunohistochemical studies on the 27 S iodoprotein of dog thyroid with reference to thyroglobulin-like reaction of the parafollicular cells.

Our earlier finding that the thyroglobulin-like material responsible for the immunoreaction of parafollicular cells obtained in peak I fraction of Bio-Gel A-5m was followed up in the present study by an investigation of the immunochemical and immunohistochemical reactions of 27 S iodoprotein which was the most prominent material in the peak I fraction. The antibody was raised against completely purified 27 S iodoprotein which was obtained as follows: Thyroglobulin was extracted from dog thyroids and chromatographed initially on Bio-Gel A-5m and then on Bio-Gel A-50m. The area of 27 S migrated as a single bank on polyacrylamide gel slab electrophoresis. This was cut and eluted. Anti-27 S antiserum showed the same immunochemical patterns to 27 S and 19 S as anti-19 S antiserum with three different immunochemical methods: double diffusion test, one dimensional and two dimensional immunoelectrophoresis. The immunoperoxidase reactions of the anti-27 S antiserum and anti-19 S antiserum were restricted to follicular cells and luminal colloids. No reaction of the parafollicular cells was obtained by these antisera. Thus, 27 S iodoprotein shared common immunochemical and immunohistochemical properties with 19 S thyroglobulin. It was concluded that 27 S iodoprotein was not responsible for the thyroglobulin-like reaction of the parafollicular cells.