Glycoprotein Ib

Glycoprotein Ib (GPIb), also known as CD42, is a component of the GPIb-V-IX complex on platelets. The GPIb-V-IX complex binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury.

It is deficient in the Bernard-Soulier syndrome. A gain-of-function mutation causes platelet-type von Willebrand's disease.