Description
Ox40 is a member of the tumor necrosis factor receptor (TNFR) family. It is a type I transmembrane protein expressed primarily on the surface of activated CD4+ T-cells. It is also expressed at low levels on the surface of activated CD8+ T cells, B cells, dendritic cells and eosinophils. Ox40 is a co-stimulatory molecule involved in T-cell activation and proliferation, the induction of cytokine production by effector T-cells, generation of memory T-cells, and arresting peripheral T-cell tolerance in vivo. Expression of Ox40 is induced following the initiation of a CD28 signal. It has been reported that the interaction of Ox40 with its ligand plays a role in the expansion of T-cell numbers at the height of the immune response as well as the generation of memory T-cells. Human Ox40 comprises a 186 amino acid extracellular domain containing four TNFR-Cys repeats, followed by a 21 amino acid transmembrane domain and a 42 amino acid cytoplasmic domain. Ox40 activity is mediated by NF-kappaB signaling via interaction of the intracellular domain of Ox40 with TRAF proteins