Gastrointestinal Β2microglobulin amyloidosis in hemodialysis patients: Biochemical analysis of amyloid proteins in small formalin-fixed paraffin-embedded tissue specimens

Abstract

We present here a first report on the biochemical analysis of intestinal amyloid deposits found in two cases of hemodialysis-related amyloidosis. A new microtechnique was applied for extraction and immunochemical/chemical characterization of amyloid proteins in small amounts of fixed tissue, thus allowing precise identification of Β2microglobulin amyloid (AΒ2M) in both cases studied. The molecular mass of the identified amyloid Β2M was close to that of intact Β2M (12 kDa), with no evidence of the products of proteolytic fragmentation of these molecules. The isoelectrofocusing of the purified AΒ2M demonstrated a shift to more acidic pI as compared to the normal Β2M analyzed under the same experimental conditions. The obtained data suggest that the intestinal amyloid deposits in dialysis-related amyloidosis contain disease-specific Β2M isoforms, which could play a role in the pathogenesis of amyloid disease. The new methodology used might be useful in obtaining precise diagnosis of amyloidosis that is necessary for appropriate therapy, and also provide new important information on the chemical structure of amyloid proteins. © 2005 USCAP, Inc All rights reserved.