The recombinant OKT8 antibody binds to the human CD8 protein (cluster of differentiation 8), a type I transmembrane glycoprotein and the co-receptor for the T-cell receptor (TCR). Along with the TCR, the CD8 co-receptor plays a role in T cell signaling and aiding with cytotoxic T cell-antigen interactions. The CD8 protein is predominantly expressed on the surface of cytotoxic T cells, but can also be found on natural killer cells, cortical thymocytes, and dendritic cells. The CD8 Molecule is a marker for cytotoxic T cell population.