C-reactive protein is a broad-spectrum capsule-binding receptor for hepatic capture of blood-borne bacteria

Area of Science:

• Immunology
• Microbiology
• Biochemistry

Background:

• Plasma C-reactive protein (CRP) is a key biomarker for bacterial infections.
• The precise biological function of CRP has remained largely undefined.
• Understanding CRP's role is crucial for developing new infection therapies.

Purpose of the Study:

• To elucidate the biological function of C-reactive protein (CRP).
• To investigate CRP's role in host defense against bacterial pathogens.
• To understand the mechanism by which CRP facilitates bacterial clearance.

Main Methods:

• In vivo mouse models of bacterial infection.
• Biochemical assays to assess CRP-pathogen interactions.
• Complement activation assays.
• Cryo-electron microscopy for structural analysis.
• Analysis of Kupffer cell function.

Main Results:

• CRP facilitates the capture and elimination of diverse bacteria by Kupffer cells.
• CRP binds to numerous Gram-positive and Gram-negative bacterial capsule types.
• CRP mediates bacterial clearance via complement-dependent and -independent pathways.
• Structural analysis revealed CRP's flexible recognition of bacterial polysaccharides.
• Human CRP exhibits similar broad capsule-binding activities.

Conclusions:

• CRP plays a vital role in innate immunity by enabling Kupffer cells to rapidly clear bacteremia.
• CRP's broad specificity for bacterial capsules explains its induction during infections.
• These findings provide a mechanistic basis for CRP's function in host defense.