F2R (Coagulation factor II thrombin receptor) is a Proteinase-Activated Receptor involved in the regulation of thrombotic response. Proteolytic cleavage leads to the activation of the receptor. Thrombin induces RANTES expression via a PAR-1 mediated pathway and influences inflammatory cell migration to the synovium in patients with rheumatoid arthritis. It is important for vascular development, and functions as a negative regulator of hematopoietic differentiation of stem cells during embryogenesis and development. In immunohistochemistry, it has membranous positivity at variable levels in a wide range of tissues and is present in blood vessels. References: Ann Rheum Dis. 2002 Sep;61(9):834-7, PMID: 12176812; Developmental Cell. 2012. 22(5), 15 May 2012:1092-1100;