The article discusses the differentiation of effector and memory T cells after antigen stimulation, focusing on the signals required for commitment to this process and the factors influencing its progression. It highlights the importance of understanding these mechanisms for optimizing vaccine strategies. The authors review models of effector and memory T-cell differentiation, emphasizing the role of co-stimulatory molecules and cytokines in driving T-cell responses. They also explore the phenotypic and functional differences between CD4+ and CD8+ T cells, particularly in the context of memory formation. The article further examines the stages of T-cell responses, including expansion, contraction, and memory, and the thresholds of activation for CD4+ and CD8+ T cells. It discusses the stem-cell-like qualities of memory T cells, their proliferation rates, and the factors that regulate their turnover. The authors also delve into the commitment of T cells to effector differentiation and the role of extrinsic factors such as cytokines. They propose models of memory T-cell differentiation, including the decreasing-potential hypothesis, which suggests that the duration and level of antigenic stimulation determine the fate of effector T cells. Finally, the article discusses the implications of these findings for vaccine design, emphasizing the need to induce large effector T-cell populations and maintain memory T-cell numbers for long-term immunological protection.The article discusses the differentiation of effector and memory T cells after antigen stimulation, focusing on the signals required for commitment to this process and the factors influencing its progression. It highlights the importance of understanding these mechanisms for optimizing vaccine strategies. The authors review models of effector and memory T-cell differentiation, emphasizing the role of co-stimulatory molecules and cytokines in driving T-cell responses. They also explore the phenotypic and functional differences between CD4+ and CD8+ T cells, particularly in the context of memory formation. The article further examines the stages of T-cell responses, including expansion, contraction, and memory, and the thresholds of activation for CD4+ and CD8+ T cells. It discusses the stem-cell-like qualities of memory T cells, their proliferation rates, and the factors that regulate their turnover. The authors also delve into the commitment of T cells to effector differentiation and the role of extrinsic factors such as cytokines. They propose models of memory T-cell differentiation, including the decreasing-potential hypothesis, which suggests that the duration and level of antigenic stimulation determine the fate of effector T cells. Finally, the article discusses the implications of these findings for vaccine design, emphasizing the need to induce large effector T-cell populations and maintain memory T-cell numbers for long-term immunological protection.