A soluble form of PROCR (sEPCR) fully retains the ability to bind Protein C and Activated protein C (Kurosawa et al. 1997). This form increases up to 5-fold in patients with sepsis or systemic lupus erythematosus (Kurosawa et al. 1998), either from vascular injury or through a regulated proteolytic release of soluble receptor (Gu et al. 2000). sEPCR inhibits protein C activation over large vessel endothelium in culture, reflecting competition between the soluble and cell surface forms of PROCR (Liaw et al. 2000).