Figure 1.

Classical models of memory CD8 T-cell formation during acute infection. (A) Linear differentiation decreasing potential model. The responding population differentiates into effector cells, but some cells accumulate more differentiation signals than others, which drives terminal differentiation. (B) Separate fate with progressive differentiation model. Activated cells initially diverge into distinct effector and memory developmental paths based on early signal strength. Cells in the memory pathway that continue to receive stimulation progressively differentiate and ultimately join the effector pathway. (C) Linear differentiation, stochastic model. Individual naive cells unpredictably commit to a proliferative fate that is coupled to the degree of differentiation. Naive cells first develop into slow cycling central memory precursors (Tcmp), then faster dividing effector memory precursors (Temp), and ultimately highly proliferative terminally differentiated progenies.