The 2.43 monoclonal antibody specifically reacts with mouse CD8 antigen. CD8a (the 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.