CD4+ memory T cell survival.

Memory CD4+ T cells specific for a given antigen are generated during the primary response from the effector lymphoblast progeny of naïve precursors. How memory CD4+ T cells differentiate from the effector population is not understood but new tools to assess transcription factor and cytokine expression are allowing for a more careful assessment of this process. Here we review the factors that allow some effector CD4+ T cells to survive the contraction phase of the primary response and become memory cells, and consider whether parallels can be drawn between T and B cells.