Biology of factor XI

• Published in: Blood Vol. 143; no. 15; pp. 1445 - 1454
• Main Authors: Moellmer, Samantha A., Puy, Cristina, McCarty, Owen J. T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 11.04.2024
• ISSN: 0006-4971; 1528-0020; 1528-0020
• DOI: 10.1182/blood.2023020719

[Display omitted] Unique among coagulation factors, the coagulation factor XI (FXI) arose through a duplication of the gene KLKB1, which encodes plasma prekallikrein. This evolutionary origin sets FXI apart structurally because it is a homodimer with 2 identical subunits composed of 4 apple and 1 catalytic domain. Each domain exhibits unique affinities for binding partners within the coagulation cascade, regulating the conversion of FXI to a serine protease as well as the selectivity of substrates cleaved by the active form of FXI. Beyond serving as the molecular nexus for the extrinsic and contact pathways to propagate thrombin generation by way of activating FIX, the function of FXI extends to contribute to barrier function, platelet activation, inflammation, and the immune response. Herein, we critically review the current understanding of the molecular biology of FXI, touching on some functional consequences at the cell, tissue, and organ level. We conclude each section by highlighting the DNA mutations within each domain that present as FXI deficiency. Together, a narrative review of the structure-function of the domains of FXI is imperative to understand the etiology of hemophilia C as well as to identify regions of FXI to safely inhibit the pathological function of activation or activity of FXI without compromising the physiologic role of FXI. Introduced by Associate Editor Thomas Ortel, this Review Series focuses on factor XI (FXI). The series opens with a review of the biology of FXI, proceeds to a discussion of congenital FXI deficiency, and concludes with a discussion of the use of therapies targeting FXI and factor XIa as active anticoagulants with a decreased risk of bleeding complications.