Clone REA499 recognizes the human and mouse CD27 antigen, a single-pass type I membrane protein, also known as tumor necrosis factor receptor superfamily member 7 (TNFRSF7). CD27 is a member of the nerve growth factor receptor family and is exclusively expressed on cells of the lymphoid lineage, mostly in an activation-specific manner, and all enhance T cell receptor (TCR)–induced T cell expansion. CD27 and its ligand, CD70, have been defined at the protein, cDNA, and genomic level in both human and mouse. It is found on natural killer (NK), T, and B cell populations. In human and mice, the majority of CD4+
naive peripheral T cells express CD27 and expression is up-regulated upon TCR stimulation. Loss of CD27 expression is irreversible and seems to represent terminal effector T cell differentiation. In humans, naive B cells lack CD27 but antigen receptor stimulation induces expression. CD27+
B cells display all the functional and phenotypic characteristics of memory cells.