Unique Amyloid Protein Subunit common to Different Types of Amyloid Fibril

Abstract

IT has been shown by Glenner et al.¹ that certain amyloid fibrils, chiefly derived from primary amyloidosis or amyloidosis associated with myelomatosis, consist of immunoglobulin chains or their fragments. The principal component of these fibrils seems to be derived from the variable part of monoclonal κ or λ light chains (Bence-Jones proteins). In addition, a “non-immunoglobulin” amyloid fibril protein with a molecular weight of 85,000, named by us protein AS (amyloid subunit), which comprises an essential part of some secondary amyloid fibrils, has been detected by Benditt et al.² and by other groups^3–5. The protein AS is found in secondary amyloid, chiefly associated with chronic inflammations, and has been suggested to be a fragment of a hitherto unknown larger protein⁴. Except for the detection of some light chain material connected with amyloid fibrils of the “non-immunoglobulin” type^6,7, no chemical link between the primary (“light chain”) and secondary (“non-immunoglobulin”) classes of amyloid substances has been established. On the contrary, the question has been raised whether there are two completely different chemical classes of amyloid⁸.