CD8 is a set of glycoproteins expressed on the surface of all cytotoxic T lymphocytes (CTLs) and various innate immune cells (e.g. DCs, macrophages, monocytes, and NK cells). It is a protein dimmer comprised by two CD8α chains (homodimer) or a combination of CD8α and CD8β chains (heterodimer)
The CD8 dimmer is a co-receptor of TCR-CD3 complex and it functions by interacting with the complex and subsequently binds to MHC-1 for T cell activation. Two “subunits” of the CD8 dimmer play unique roles in immune modulations. CD8α recruits Lck or LAT to trigger subsequent signaling pathways while CD8β enhances the avidity of the CD8/MHC/TCR complex to increase IL-2 production in response to stimulator immune cells. In mouse, the CD8α homodimer also serves as an immuno-modulator and binds to MHC I-like molecule (TL) without TCR. For immune cells that lack TCR, FcγR is an alternative pathway that is co-activated by CD8 for amplifying immune responses.
Current evidence has showed that immune responsiveness could be drastically reduced by blocking CD8, rendering it a viable target for the development of biotherapeutics to regulate immune responses mediated by CD8 and treat diseases such as auto-immune disorders, allergies, and a variety of cancers.
CD8 genes are highly conversed during the course of evolution in different species. Sino Biological has developed a panel of active recombinant CD8 proteins to facilitate the research in the immunology and physiology of CD8.