Lineage relationship and protective immunity of memory CD8 T cell subsets

Memory CD8 T cells can be divided into two subsets, central (T-CM) and effector (T-EM), but their lineage relationships and their ability to persist and confer protective immunity are not well understood. Our results show that T-CM have a greater capacity than T-EM 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, T-EM convert to T-CM and that the duration of this differentiation is programmed within the first week after immunization. We propose that T-CM and T-EM do not necessarily represent distinct subsets, but are part of a continuum in a linear naive effector --> T-EM --> T-CM differentiation pathway.