TCR affinity is a quantitative measurement of the binding strength of the TCR to its target. So far, it has been shown that TCR affinity determines the fate and efficacy of T cells in immune responses. However, effective TCR affinity for cellular therapy is also dependent on the disease context and differs between autoimmune disease, infections or cancer. Therefore, our goal is to elucidate the mechanistic connection between optimal affinity and efficacy to improve T-cell therapy.