T-bet or Not T-bet

Abstract
We depend on the efficiency of our adaptive immune system to combat pathogen invaders. Part of this protective response includes development of CD4 and CD8 effector T cells. As Hatton and Weaver discuss in their Perspective, key transcription factors regulating CD4 effector T cell development have been identified, whereas those governing the development of CD8 effectors have not. Hatton and Weaver describe new work showing that cooperation between two T-box transcription factors, T-bet and Eomesodermin, instigates the CD8 effector program ( Pearce et al.).