On the MHC class I molecule, where is the binding site for CD8?

The binding site for CD8 on the MHC class I molecule is located in the α3 domain. CD8 is a co-receptor that is specifically expressed on cytotoxic T cells, and it interacts with MHC class I molecules to enhance the recognition of antigen-presenting cells. The α3 domain of the MHC class I molecule provides a stable region for the binding of CD8, facilitating a stronger and more effective immune response.

The α1 and β1 domains do not contain the specific binding site for CD8; instead, they are involved in binding peptide antigens and forming the overall structure of the MHC molecule. The β2 domain is a part of the MHC structure that associates with the α chain, but it does not play a role in binding CD8. Understanding the specific interactions between these molecules is crucial for grasping the principles of T cell activation and the immune response.