Serum amyloid P component (SAP) is present in all types of amyloid deposits. Its histochemical significance is that it:

• A Is responsible for apple-green birefringence under polarized light
• B Acts as the structural subunit protein of AL amyloid fibrils
• C Induces Congo red staining by cross-linking fibril strands
• D Stabilizes amyloid fibrils and is targeted by SAP-scintigraphy for diagnosis ✓

Explanation

SAP is a serum pentraxin that binds non-covalently to amyloid fibrils in a calcium-dependent manner, protecting them from proteolysis and stabilizing deposits. SAP-scintigraphy using radiolabeled SAP localizes and quantifies amyloid deposits in vivo. Apple-green birefringence is a property of Congo red-stained amyloid fibrils due to the cross-beta pleated sheet structure, not SAP itself.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.