Fig. 2.

Models of memory development according to memory programming. a Two-lineage model. Upon priming, the naive T cell is stimulated by TCR, costimulatory and inflammatory signals/IL-2. It commits to become either a short-lived effector or a memory precursor that has acquired effector characteristics but is able to further differentiate into an effector memory T cell (T_EM) and a central memory T cell (T_CM). b Linear differentiation model/“Goldilocks model”. Signals that are too weak or too strong result in cells that differentiate into a short-lived end-stage effectors. Intermediate signal strengths support T_EM and T_CM. differentiation passing by an effector phase