The crystal structure of the two immunoglobulin variable-like domains of the murine CD8αα homodimer complexed to the class I MHC H-2Kb molecule at 2.8 Å resolution shows that CD8αα binds to the protruding MHC α3 domain loop in an antibody-like manner. Comparison of mouse CD8αα/H-2Kb and human CD8αα/HLA-A2 complexes reveals shared as well as species-specific recognition features. In both species, coreceptor function apparently involves the participation of CD8 dimer in a bidentate attachment to an MHC class I molecule in conjunction with a T cell receptor without discernable conformational alteration of the peptide or MHC antigen-presenting platform.
Kern, P. S., Teng, M. kun, Smolyar, A., Liu, J. huan, Liu, J., Hussey, R. E., … Wang, J. huai. (1998). Structural basis of CD8 coreceptor function revealed by crystallographic analysis of a murine CD8αα ectodomain fragment in complex with H-2K. Immunity, 9(4), 519–530. https://doi.org/10.1016/S1074-7613(00)80635-4