CD134, also known as TNFRSF4 or OX40, is a member of the tumor necrosis factor receptor superfamily. It is a co-stimulatory molecule primarily expressed on activated CD4+ and CD8+ T cells, as well as other immune cells such as natural killer (NK) cells and dendritic cells. Structurally, CD134 contains four TNFR-Cys repeats and interacts with its ligand, OX40L (TNFSF4), to activate downstream signaling pathways, including the NF-魏B pathway through adaptor proteins like TRAF2 and TRAF5. This interaction promotes T cell proliferation, cytokine production, and enhances the survival of CD8+ T cells, playing a crucial role in immune responses. Additionally, CD134 has been implicated in various diseases, including cancer and autoimmune conditions, making it a target for immunotherapy and other therapeutic interventions.