CD63 is a type II membrane protein belonging to tetraspanin superfamily and it play key roles in the activation of several cellular signaling cascades along with acting as TIMP1 receptor. It is expressed by activated platelets, monocytes, macrophages, granulocytes, T /B cells, and different type of cancer cells. CD63 localizes to endosomes, lysosomes and on the cellular surfaces, and is often considered as a marker for late endosomes as well as for lysosomes.
