CD27 antigen, also known as CD27L receptor, T-cell activation antigen CD27, T14, S152, Tp55, TNFRSF7 and Tumor necrosis factor receptor for superfamily member 7，belongs to the TNF-receptor superfamily. CD27 is a single-pass type I membrane protein and exists as a homodimer form, containing three TNFR-Cys repeats. CD27 transduces signals that lead to the activation of NF-KappaB and MAPK8/JNK. CD27 is involved in regulating B-cell activation and immunoglobulin synthesis, binding to the ligand CD70. TRAF2 and TRAF5 have been shown to mediate the signaling process of CD27. CD27-binding protein (SIVA), which is a proapoptotic protein, can bind to CD27 and is thought to play a key role in the apoptosis. CD27 is required for generation and long-term maintenance of T cell immunity.