Amyloid fibril protein from medullary carcinoma of the thyroid--biochemical and immunochemical characterizations.

A unique amyloid fibril protein (Nis) was extracted from a patient with medullary carcinoma of the thyroid (MCT). This amyloid protein has a molecular weight of approximately 17,000 daltons, and has different amino acid composition from AA, AL or AF type amyloid fibril proteins. Immunochemical analysis using antiserum raised against Nis-DAM and Nis-GAM proteins disclosed that positive reactions were obtained only with degraded amyloids of MCT and with sera from patients with MCT. In contrast, there were negative reactions for other type of amyloid proteins, sera from other type of amyloid, normal sera or urinary proteins. Therefore Nis-amyloid fibril protein has some antigenic determinants characteristic of MCT-related amyloid fibril protein.