TCR signal-enhancing mutation alters lipid metabolism of thymocytes and impairs antitumor immunity of mature T cells.

The T cell receptor (TCR), a master regulator of adaptive immunity, serves as a molecular transducer that converts antigen recognition into precisely modulated intracellular signals, orchestrating both T cell development and effector functions. In this study, we leveraged a germline CD3εI173A mutation, a previously characterized alteration that amplifies TCR signaling through the disruption of inhibitory lipid interactions, to dissect how thymocyte-intrinsic TCR signaling amplification influences the fate of mature T cells. Remarkably, thymic double-positive cells in CD3εI173A mice with altered TCR repertoires demonstrated a significant downregulation of the phosphatidylserine decarboxylase homolog gene AC149090.1. This modulation triggered a comprehensive rewiring of lipid metabolic pathways, establishing a systemic compensatory mechanism to counterbalance excessive TCR signaling. These metabolic adaptations culminated in functionally compromised mature T cells, characterized by diminished activation potential, reduced proliferative capacity, and impaired antitumor efficacy in CD3εI173A mice. Our results underscore the critical role of thymic TCR signaling in T cell development for sustaining immune homeostasis and orchestrating mature T cell functionality, unveiling the lipid metabolic plasticity during thymocyte development that acts as a critical regulatory checkpoint for maintaining immune homeostasis.