Tumor necrosis factor receptor superfamily member 4 (TNFRSF4) is also known as ACT35 antigen, OX40L receptor, TAX transcriptionally-activated glycoprotein 1 receptor, CD antigen CD134, OX40. OX40 / TNFRSF4 contains four TNFR-Cys repeats. TNFRSF4 is receptor for TNFSF4 / OX40L / GP34 and can interacts with TRAF2, TRAF3 and TRAF5.The interaction between OX40 and OX40L plays an important role in antigen-specific T-cell expansion and survival. OX40 and OX40L also regulate cytokine production from T cells, antigen-presenting cells, natural killer cells, and natural killer T cells, and modulate cytokine receptor signaling. In line with these important modulatory functions, OX40-OX40L interactions have been found to play a central role in the development of multiple inflammatory and autoimmune diseases, making them attractive candidates for intervention in the clinic.Conversely, stimulating OX40 has shown it to be a candidate for therapeutic immunization strategies for cancer and infectious disease.