Coexistence of beta2 microglobulin and lambda light chain in amyloid fibrils of dialysis-unrelated plasma cell dyscrasia-associated systemic amyloidosis

BACKGROUND: Systemic amyloidosis occurs as a result of amyloid deposition in various tissues. The amyloid fibrils in systemic amyloidosis have been reported to originate from immunoglobulin light chains. OBJECTIVE: We studied the composition of amyloid fibrils from two patients with plasma cell-associated systemic amyloidosis (PASA). METHODS: A double immunofluorescence study of the lesional skin of PASA was undertaken. Amyloid proteins were extracted with distilled water from one case of PASA. RESULTS: The double immunofluorescence study showed that anti-lambda light chain and anti-beta2 microglobulin antibodies mostly reacted with the same area of amyloid deposit. Amyloid deposits from two patients with PASA who had never undergone haemodialysis showed a positive reaction with the antibodies for beta2 microglobulin as well as immunoglobulin lambda light chain. By the use of immunoblot assay of amyloid fibril proteins, polypeptides immunoreactive with antigamma light chain antibody (29 kDa) and with anti-beta2 microglobulin antibody (12 kDa) were detected. CONCLUSIONS: These results indicate that beta2 microglobulin is a component of amyloid fibrils in PASA.