Semin Thromb Hemost 2017; 43(08): 814-826
DOI: 10.1055/s-0036-1598003
Review Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Factor XII Contact Activation

Clément Naudin1, 2, Elena Burillo1, 2, Stefan Blankenberg3, Lynn Butler1, 2, Thomas Renné1, 2
  • 1Clinical Chemistry, Department of Molecular Medicine and Surgery, Karolinska Institutet and University Hospital, Stockholm, Sweden
  • 2Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
  • 3Department of General and Interventional Cardiology, University Heart Center Hamburg-Eppendorf, Hamburg, Germany
Further Information

Publication History

Publication Date:
27 March 2017 (eFirst)


Contact activation is the surface-induced conversion of factor XII (FXII) zymogen to the serine protease FXIIa. Blood-circulating FXII binds to negatively charged surfaces and this contact to surfaces triggers a conformational change in the zymogen inducing autoactivation. Several surfaces that have the capacity for initiating FXII contact activation have been identified, including misfolded protein aggregates, collagen, nucleic acids, and platelet and microbial polyphosphate. Activated FXII initiates the proinflammatory kallikrein-kinin system and the intrinsic coagulation pathway, leading to formation of bradykinin and thrombin, respectively. FXII contact activation is well characterized in vitro and provides the mechanistic basis for the diagnostic clotting assay, activated partial thromboplastin time. However, only in the past decade has the critical role of FXII contact activation in pathological thrombosis been appreciated. While defective FXII contact activation provides thromboprotection, excess activation underlies the swelling disorder hereditary angioedema type III. This review provides an overview of the molecular basis of FXII contact activation and FXII contact activation–associated disease states.