CD70, also known as CD70 antigen, is a transmembrane protein in the TNF receptor superfamily. It functions as a co-stimulatory molecule that supports lymphocyte activation and survival. This protein binds to the transmembrane glycoprotein CD27 ligand/CD70 which is expressed on activated B cells, activated T cells, and dendritic cells. Binding of CD70 to its receptor CD27 induces in priming, effector functions, differentiation and memory formation of T cell activation, and thus is proliferation of co-stimulated T cells, as well as the generation of cytolytic T cells.