Mouse Factor XII Total ELISA Kit This mouse coagulation Factor XII antigen assay is intended for the quantitative determination of total Factor XII antigen in mouse plasma. Factor XII (aka Hageman Factor) is a single-chain, 615 amino acid glycoprotein zymogen. Factor XII is activated by kallikrein. Factor XIIa converts prekallikrein to kallikrein during the intrinsic pathway of the coagulation cascade. Although Factor XII is not thought to play an essential role in normal hemostasis, lack of Factor XII in a mouse model resulted in a severe defect in thrombus formation.