Protein AA in primary and myeloma associated amyloidosis.

Protein AA, the main fibril constituent in secondary systemic amyloidosis, was demonstrated by the peroxidase-anti-peroxidase method in kidney sections from five out of 14 cases of primary and myeloma associated amyloidosis, all having an immunoglobulin light chain derived protein as a major subunit. In three of these cases, protein AA was also demonstrated in double immunodiffusion of dissolved amyloid preparations. The protein had the characteristics of protein AA in elution position, immunodiffusion and isoelectric focussing pattern. The significance of protein AA in primary and myeloma associated amyloidosis is unknown.