Requirement for CD8 β chain in positive selection of CD8-lineage T cells

CD8 is either an αα homodimer or an αβ heterodimer, although most peripheral CD8-lineage T cells express only the CD8αβ heterodimer. The physiological function of CD8β was elucidated with mice that were chimeric for the homozygous disruption of the CD8β gene. The CD8β(-/-) T cells developed normally to CD4⁺CD8⁺ stage, but did not efficiently differentiate further, which resulted in few peripheral CD8⁺ T cells. The number of peripheral CD8⁺ T cells was restored by transfer of an exogenous CD8β gene into CD8β-deficient T cells. Thus, CD8β is necessary for the maturation of CD8⁺ T cells.