CD30, also known as TNFRSF8 (TNF receptor superfamily member 8), is a cell membrane protein of the tumor necrosis factor receptor family and a tumor marker. This receptor is expressed by activated, but not by resting, T and B cells. TRAF2 and TRAF5 can interact with this receptor, and mediate the signal transduction that leads to the activation of NF-kappaB. It is a positive regulator of apoptosis, and also has been shown to limit the proliferative potential of autoreactive CD8 effector T cells and protect the body against autoimmunity. Two alternatively spliced transcript variants of this gene encoding distinct isoforms have been reported. CD30 is associated with anaplastic large cell lymphoma. It is expressed in embryonal carcinoma but not in seminoma and is thus a useful marker in distinguishing between these germ cell tumors. CD30 and CD15 are also expressed on Reed-Sternberg cells typical for Hodgkin's lymphoma.