Memory CD8 T cells can be divided into two subsets, central (TCM) and effector (TEM), but their lineage relationships and their ability to persist and confer protective immunity are not well understood. Our results show that TCM have a greater capacity than TEM to persist in vivo and are more efficient in mediating protective immunity because of their increased proliferative potential. We also demonstrate that, following antigen clearance, TEM convert to TCM and that the duration of this differentiation is programmed within the first week after immunization. We propose that TCM and TEM do not necessarily represent distinct subsets, but are part of a continuum in a linear naive → effector → TEM → TCM differentiation pathway.
Bibliographical noteFunding Information:
for helpful discussions. Supported by National Institutes of Health grant AI30048 and AI44644 (to R.Ahmed), a Cancer Research Institute fellowship (to E.J.W. and D.M.) and a Damon Runyon-Walter Winchell fellowship (to S.M.K.).