Cluster of Differentiation 70 (CD70), also known as CD27 ligand (CD27L/CD27LG), TNFSF7, or TNFSF7G, is a type II transmembrane glycoprotein belonging to the TNF superfamily. It is expressed on activated T and B lymphocytes and mature dendritic cells. CD70 binds to its receptor CD27, inducing T-cell priming, effector functions, differentiation, and memory formation. This interaction is critical for T-cell activation, co-stimulated T-cell proliferation, and the generation of cytolytic T-cells. CD70 on T cells provides essential co-stimulatory signals for T-cell proliferation and clonal expansion, promoting effector T-cell formation. In mouse B cells, CD70 inhibits terminal differentiation into plasma cells and enhances memory B-cell responses. Additionally, CD70 stimulates NK cell proliferation and IFNγ production.