Factor XI in haemostasis and thrombosis: past, present and future.

Thromb Haemost 2007; 98: 84–89 The discipline of haemostasis and thrombosis has set an example, perhaps more than other disciplines of Medicine, in discoveries based on observations of the so called “experiments of nature”. During a relatively short time of 13 years (1947 – 1960), most coagulation factors were identified in patients who presented with a bleeding tendency and were worked up by rather simple laboratory assays.This era of discoveries was followed by the characterization of the biochemical reactions involved in blood coagulation, delineation of the sequence of reactions in the coagulation pathways and more recently by unraveling the molecular genetic aspects of the various coagulation components. The objective of this review is to describe some of the major developments in understanding the role of factor (F)XI in haemostasis and thrombosis that have occurred over more than 50 years of research, and to highlight recent evidence which suggests that FXI deficiency can have an antithrombotic effect.