Haemodialysis-associated amyloidosis: beta 2-microglobulin alone or associated with globin chains?

1. The protein constituents of amyloid fibrils were characterized in amyloid deposits extracted from surgical material obtained from a 66-year-old patient undergoing maintenance haemodialysis and operated for a carpal tunnel syndrome. 2. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis disclosed the presence of bands at 12 and 14 kDa. Two-dimensional electrophoresis and Western blotting confirmed that the proteins were beta 2-microglobulin (beta 2M) and globin chains. 3. When the effluent of high-performance gel filtration chromatography corresponding to molecular masses of 10-15 kDa was subjected to Edman degradation, only one amino acid residue was found at each step. The 18 residues determined corresponded to the N-terminal sequence of beta 2M. 4. Although globin chains were clearly present in the amyloid material, they were not accessible for sequence determination. The identification of the other protein constituents present in the amyloid material, along with beta 2M, should provide a better understanding of haemodialysis-associated amyloidosis, the mechanisms of formation of which have not yet been completely determined.