Abstract
Current models of T-helper-cell differentiation depict the generation of effector cells from a naïve T cell based on the cytokine environment upon T-cell-receptor engagement. We propose a new model of CD4(+) T-cell activation, differentiation, and function whereby the outcome of antigen recognition is dictated by mTOR activity and the subsequent up-regulation of selective metabolic function. Such a model more readily explains the generation of effector and memory cells including the concept of effector and memory Foxp3(+) regulatory cells.