Human OX40 Ligand/TNFSF4 Antibody

OX40 Ligand (OX40L), also known as gp34, is a type II transmembrane glycoprotein belonging to the TNF superfamily. Human OX40L cDNA encodes a 183 amino acids (aa) polypeptide with an amino-terminal cytoplasmic domain (aa 1-23) and a carboxy-terminal extracellular domain (aa 51-183). It shares 46% aa sequence identity with the mouse counterpart. OX40L is expressed on the surface of activated B cells, T cells, dendritic cells, and endothelial cells. Similarly to other TNF superfamily members, membrane-bound OX40 Ligand exists as a homotrimer. OX40L binds to OX40 (CD134), a member of the TNF receptor superfamily that is expressed predominantly on activated CD4⁺ T cells. OX40 Ligand is one of the co-stimulatory molecules in the immune system that includes B7, CD40 Ligand, CD30 Ligand, CD27 Ligand, and 4-1BB Ligand. Because OX40 appears as a late activation-induced T cell surface antigen, it has been speculated that the major function of OX40-OX40L interaction is to transmit a late co-stimulatory signal to promote the survival and proliferation of activated CD4⁺ T cells and prolong the immune response. Engagement of OX40 on activated T cells in situ in tumors has been shown to augment immune responses and subsequent tumor regression.