IgV_CD8_beta: immunoglobulin (Ig)-like domain in CD8 beta. The CD8 glycoprotein plays an essential role in the control of T-cell selection, maturation and the T-cell receptor (TCR)-mediated response to peptide antigen. CD8 is comprised of alpha and beta subunits and is expressed as either an alpha/alpha or alpha/beta dimer. Both dimeric isoforms can serve as a coreceptor for T cell activation and differentiation, however they have distinct physiological roles, different cellular distributions, unique binding partners etc. Each CD8 subunit is comprised of an extracellular domain containing a V-type Ig-like domain, a single pass transmembrane portion and a short intracellular domain.