Homozygous serum amyloid P component-deficiency does not enhance regression of AA amyloid deposits

Serum amyloid P component (SAP) is a common protein constituent of all type s of amyloid deposits. Using SAP-deficient mice generated through gene targ eting, we and others have shown that SAP significantly promotes amyloid dep osition. It has been speculated that SAP protects amyloid fibrils from degr adation by coating their exterior surface. To assess potential ways of trea ting individuals with amyloidosis, we examined the persistence of splenic A A amyloid fibrils in SAP-deficient and wild-type mice. No enhancement in th e rate of regression of splenic AA amyloid was observed in the SAP-deficien t mice relative to wildtype mice. These results present, for the first time , evidence that lack of SAP in AA amyloid deposits does not enhance regress ion of the deposits in vivo and suggest that dissociation of bound SAP from AA amyloid deposits would not significantly accelerate regression of the d eposits in vivo.