Fas expression is quickly upregulated on CD8+ T cells following stimulation, while FasL expression is limited to Tcm and later. A phenomenon of T cell differentiation via paracrine Fas signal has been previously described. Here, we describe such differentiation in a pool fits the Feed-forward model which can correct for disturbances in the system, as seen during in vitro T cell stimulation. This feed-forward controller exerts control via Fas/ FasL expression, and the effect is uncoupled with use of lz-FasL. Interestingly, the feed-forward model provides us with evolutionary insight as to why Fas stimulation becomes apoptotic at terminal differentiation, in order to exhibit a perfect and extinguished control and response.