The 53-6.7 monoclonal antibody specifically reacts with Ly-2, the 38 kDa alpha chain, and with Lyt-2, the 34 kDa alpha’ chain, of the mouse CD8 antigen. The alpha’ chain is the truncated form of alpha chain, encoded by the same CD8a gene. In CD8a, the alpha and alpha’ chains form heterodimers with CD8b (the beta chains) or homodimers (alpha-alpha), which occur as receptors on the surface of the majority of thymocytes. A subpopulation of mature T lymphocytes expresses the CD8 alpha beta (alpha beta TCR T cells), and a subpopulation of intestinal intraepithelial lymphocytes and dendritic cells express CD8a without CD8b. CD8 interacts with the mouse major histocompatibility complex class I (MHC class I) molecules on antigen-presenting cells or epithelial cells. Its function seems to be to attenuate the CD8-mediated signal for the stimulation of intrathymic T-cell maturation.

The 53-6.7 antibody is useful for depleting CD8+ peripheral T lymphocytes. It cross reacts with the alpha- and alpha’-like polypeptides on some thymic and peripheral lymphocytes.