AA-Amyloid is cleared by endogenous immunological mechanisms

• Reactive amyloidosis is a complication to longstanding inflammatory diseases.Protein amyloid A (AA), an N-terminal fragment of the acute phase protein serumamyloid A, undergoes conformational changes and is deposited as amyloid in tissue.AA-amyloidosis is reversible and reduction of amyloid mass has been reported as theinflammation ceases. Not much is known about the endogenous factors thatcontribute to amyloid resolution. Herein, we describe the dynamics of amyloiddegradation in experimental murine AA-amyloidosis and show that amyloiddegradation depends on macrophages and antibody formation. AA-amyloidosis wasinduced in mice and resolution of amyloid was monitored over time by histologicaltechniques. Internalized amyloid was present in macrophages that appeared at siteof deposition. At 9 months, when virtually all amyloid was cleared, amyloidosis wasre-induced in one group of animals by a single silver nitrate injection. This causedeposition of excessive amounts of amyloid, and indicate that even thoughundetectable the amyloid reseed in the body and can there act as amyloid enhancingfactor. Antibodies directed against protein AA were detected in animals duringamyloid clearance by ELISA-technique. Passive immunization with an amyloidspecific monoclonal antibody, produced by a B-cell clone recovered from an animalwith advanced AA-amyloidosis, diminish amyloid deposits in murine AA-amyloidosis.Immunoglobulins co-localize with amyloid deposits and can contribute to amyloiddegradation by Fc-receptor mediated phagocytosis.

Keyword

Amyloid A (AA)

Amyloid β(Aβ)

Amyloid light chain (AL)

Alzheimer’s disease (AD)

amyloid enhancing factor (AEF)

serum amyloid A (SAA)

tumour necrosis factor (TNF)

MEDICINE

MEDICIN

Publication and Content Type

ref (subject category)

art (subject category)