AA-Amyloid is cleared by endogenous immunological mechanisms

Objective: AA amyloidosis is a complication to longstanding inflammatory diseases, but reduction of amyloid mass has been reported as the inflammation ceases. Not much is known about the endogenous factors that contribute to this amyloid resolution. Herein, we describe the dynamics of amyloid degradation and resolution in experimental murine AA-amyloidosis. Methods: AA-amyloidosis was induced in mice with injections of amyloid enhancing factor (AEF) and by inflammation induced with injections of silver nitrate. Resolution of amyloid deposits was monitored over time. Results: Virtually all amyloid was cleared within 34 weeks. Using the ELISA-technique, antibodies directed against protein AA were detected in animals during amyloid clearance phase and macrophages were shown to internalize amyloid. Also, passive immunization with an amyloid specific monoclonal antibody, produced by a B-cell clone recovered from an animal with advanced AA-amyloidosis, reduced amyloid development in murine AA-amyloidosis. Conclusion: Immunoglobulins co-localize with amyloid deposits and can contribute to amyloid degradation by Fc-receptor mediated phagocytosis, and should be considered key players in the degradation process.