Kallikrein directly interacts with and activates Factor IX, resulting in thrombin generation and fibrin formation independent of Factor XI.
Kearney KJ, Butler J, Posada OM, Wilson C, Heal S, Ali M, Hardy L, Ahnström J, Gailani D, Foster R, et al. Proc Natl Acad Sci U S A. 2021 Jan 19; 118(3).