CD42b is a platelet activation marker involved in the process of coagulation as an aggregating factor. It interacts with extracellular matrix as well as with adhesion molecules. CD42b expression and activation seems to be regulated by VEGF and PDGF. CD42b composes together with GPIb beta, GPIX and GPV the GPIb-IX-V receptor complex critical in the process of platelet-rich thrombus formation by tethering the platelet to a thrombogenic surface. CD42b binds to von Willebrand factor (VWF) exposed at a site of vascular injury, as well as to thrombin, coagulation factors XI and XII, high molecular wight kininogen, TSP-1, integrin Mac-1 and P-selectin. The extracellular domain of CD42b by its interactions also contributes to metastasis. Further, CD42b antigen is expressed on platelets and on megakaryocytes in bone marrow. Several polymorphisms and mutations have been described in the CD42b, some of which are the cause of Bernard-Soulier syndromes and platelet-type von Willebrand disease.
Antigen CD42b-alpha; CD42b; Glycocalicin; glycoprotein Ib (platelet), alpha polypeptide; GP-Ib alpha; GPIB; GPIb alpha; GPIX; MGC34595; mutant platelet membrane glycoprotein Ib-alpha; Platelet glycoprotein Ib alpha chain; Platelet GPIX; platelet membrane glycoprotein 1b-alpha subunit; platelet membrane glycoprotein Ib-alpha