Amyloid fibril protein related to prealbumin in familial amyloidotic polyneuropathy.

Amyloid fibrils were concentrated from the kidney, thyroid, and peripheral nerve of six patients with familial amyloidotic polyneuropathy (FAP). The fibril concentrates were solubilized in 6 M guanidine.HCl and fractionated on Sephadex G-100 columns. The elution profile of all FAP amyloid fibril concentrates revealed a protein of apparent Mr of 14,000, designated the FAP protein, that was absent from normal human tissues treated by the same procedure and from fibrils of a primary amyloidosis liver. Antisera against whole denatured fibril concentrates prepared in rabbits reacted with the FAP protein and a component in normal human serum corresponding to prealbumin. It was further established that the FAP protein shared common antigenic determinants with human prealbumin by its reaction of identity with normal prealbumin using commercial antisera against human prealbumin. Amyloid AL or AA proteins could not be identified in FAP fibrils by sensitive immunochemical assay methods. These results suggest that the FAP protein is a unique and significant component of the FAP amyloid fibrils and that it is closely related to the 13,745 Mr prealbumin subunit.