Clone REA765 recognizes the human CD137 antigen, a 30 kDa glycoprotein of the tumor necrosis factor (TNF) receptor superfamily, a group of cytokines that can cause cell death (apoptosis). CD137 is mainly expressed on activated CD4+
T cells, activated B cells, and natural killer cells, but can also be found on resting monocytes and dendritic cells. As a costimulatory molecule it is involved in the activation and survival of CD4+
T cells and NK cells. CD137 has been described to be a suitable marker for antigen-specific activation of human CD8+
T cells, as it is not expressed on resting CD8+
T cells and its expression is reliably induced after 24 hours of stimulation.