Regulation of asymmetric division and CD8+ T lymphocyte fate specification by protein kinase Cζ and protein kinase Cλ/ι.

During an immune response against a microbial pathogen, activated naive T lymphocytes give rise to effector cells that provide acute host defense and memory cells that provide long-lived immunity. It has been shown that T lymphocytes can undergo asymmetric division, enabling the daughter cells to inherit unequal amounts of fate-determining proteins and thereby acquire distinct fates from their inception. In this study, we show that the absence of the atypical protein kinase C (PKC) isoforms, PKCζ and PKCλ/ι, disrupts asymmetric CD8(+) T lymphocyte division. These alterations were associated with aberrant acquisition of a pre-effector transcriptional program, detected by single-cell gene expression analyses, in lymphocytes that had undergone their first division in vivo and enhanced differentiation toward effector fates at the expense of memory fates. Together, these results demonstrate a role for atypical PKC in regulating asymmetric division and the specification of divergent CD8(+) T lymphocyte fates early during an immune response.