Which protein binds PSA and is increased in Alzheimer's disease?

• A. a1-Antichymotrypsin
• B. a1-Antitrypsin
• C. a1-Acid Glycoprotein
• D. Gc-Globulin

Answer: (A)

The main idea here is that Alzheimer’s disease features an increase of certain inflammatory, acute-phase proteins that interact with amyloid-beta. Alpha-1-antichymotrypsin is the protein that binds PSA and is elevated in Alzheimer’s disease. It belongs to the serpin family as a serine protease inhibitor and is produced in the liver but also localizes with amyloid plaques in the brain. In AD, levels of this protein rise in brain tissue and CSF and it co-localizes with plaques, highlighting its involvement in the disease process. This distinguishes it from the other options, which are not specifically elevated in AD or linked to amyloid plaque biology in the same way.