Anti-human GpIb alpha Antibody against glycoprotein Ib alpha (GPIbα), also known as CD42, a transmembrane protein of 135 kDa. Together with GPIbβ, GPIX and GPV, it forms the non-covalent GPIb-V-IX complex on megakaryocytes and platelets. GPIbα is present at 25.000 copies per platelet. Platelet activation is accompanied by a transient clearance of GPIb from the platelet surface, which is followed by a slow reappearance to a normal surface expression level within 30 to 60 min. Also, deficiency of a single subunit dramatically decreases the surface expression of the whole complex.The GPIb-V-IX complex functions as a receptor for von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. Additionally, GPIb contains a binding site for P-selectin, Mac-1, coagulation factor XI and XII, thrombin and high molecular-weight kininogen. Hence, GPIb is an omnivalent receptor that links primary and secondary hemostasis.Defects in the gene encoding for GPIbα, in addition to the genes for GPIbβ and GPIX, give rise to a serious bleeding diathesis, which is accompanied by morphological platelet anomalies, including giant platelets. Collectively, this is defined as Bernard-Soulier Syndrome (BSS), a rare hereditary thrombocytopathy. A gain-of-function mutation causes platelet-type von Willebrand disease.
