This gene encodes a glycoprotein coagulation factor that plays an important role in intrinsic pathway of blood coagulation and hemostasis. The encoded protein is an inactive zymogen that can be activated by coagulation factor XIIa, thrombin or factor XIa to generate active factor XIa protease. Mice lacking the encoded protein display a survival advantage during peritoneal sepsis and resist inflammation and bacterial accumulation upon infection with Listeria. [provided by RefSeq, Apr 2015]