A laboratory reports a serum level rising sharply three days after surgery, reaching concentrations hundreds of times above baseline. This molecule is synthesized by hepatocytes under interleukin-6 stimulation, binds phosphorylcholine on bacterial surfaces, and activates complement through which pathway?

• A Alternative pathway by spontaneous hydrolysis of its thioester bond
• B It fixes complement only when complexed with specific antibody
• C Lectin pathway through mannose-binding lectin association
• D Classical pathway after binding C1q as a pattern recognition molecule ✓

Explanation

C-reactive protein is the prototype acute phase reactant, induced by IL-6 in hepatocytes. It binds phosphorylcholine exposed on pneumococci and apoptotic cells and then engages C1q, initiating the classical complement cascade independent of antibody. It is itself a pattern recognition molecule of the innate immune system, so it does not require antibody complexing, distinguishing it from conventional immunoglobulin-mediated classical activation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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