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Amyloid P component (AP) has been recognized as a beta-amyloid-associated protein but the pathological role is not known. In the present experiments, it has been shown that AP promotes the aggregation of Alzheimer's beta-amyloid peptide (A beta) in the presence of a physiological concentration of Ca2+. The aggregation promotion was observed at a concentration of soluble A beta 1-40 in human cerebrospinal fluid. The results suggest that AP is possibly a pathogenic factor of the cerebral amyloidosis.

Human serum amyloid P component (SAP) was found to agglutinate erythrocytes in the presence of calcium ion. The hemagglutination was strongly inhibited by hyaluronic acid as well as by heparan sulfate and dermatan sulfate, but not by chondroitin 4-sulfate and keratan sulfate. A specific binding of SAP to hyaluronic acid, heparan sulfate, and dermatan sulfate was also confirmed by the fact that these glycosaminoglycans blocked the binding of SAP to agarose, a specific ligand of SAP.