Contact system revisited: an interface between inflammation, coagulation, and innate immunity

Area of Science:

• Biochemistry and Molecular Biology
• Immunology
• Hematology

Background:

• The contact system is a plasma protease cascade involving factor XII (FXII).
• It initiates both the kallikrein-kinin system (inflammation) and the intrinsic coagulation pathway (clotting).
• Anionic surfaces and bacterial components activate FXII, highlighting its role in host defense.

Purpose of the Study:

• To review the multifaceted role of the contact system.
• To explore its function at the intersection of inflammation, coagulation, and innate immunity.
• To discuss FXIIa as a potential therapeutic target for thrombotic diseases.

Main Methods:

• Literature review of experimental and clinical studies.
• Analysis of the mechanisms of FXII activation.
• Examination of the therapeutic implications of targeting the contact system.

Main Results:

• FXII activation by anionic surfaces and bacterial components.
• Involvement of platelet-derived inorganic polyphosphate in FXII activation and pathological thrombosis.
• Evidence for thromboprotection via FXII inhibition with minimal bleeding risk.

Conclusions:

• The contact system serves as a critical nexus for inflammatory and coagulation processes.
• FXIIa represents a promising therapeutic target for managing thrombotic events.
• Understanding the contact system is key to developing novel host defense and antithrombotic strategies.