Pre-division TCF1 drop determines long-term CD8 T cell fates.

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• T Cell Factor 1 (TCF1) is crucial for T cell development and differentiation.
• TCF1 is downregulated during effector T cell differentiation.
• The role of TCF1 during T cell priming before cell cycle entry was previously unknown.

Purpose of the Study:

• To investigate the role and dynamics of TCF1 during the early stages of CD8 T cell activation.
• To understand how TCF1 regulation impacts T cell fate decisions.

Main Methods:

• Analysis of TCF1 expression dynamics in murine and human CD8 T cells post-antigen encounter.
• Transcriptomic and epigenetic analyses to identify TCF1-regulated pathways.
• siRNA-mediated TCF1 knockdown to assess functional consequences.

Main Results:

• TCF1 expression rapidly downregulated within hours after antigen encounter, preceding cell cycle entry.
• TCF1 levels rebound upon cell cycle entry, then decline with proliferation.
• Pre-division TCF1 drop magnitude, influenced by TCR signaling and cytokines, regulates long-term effector and memory cell fates.
• TCF1-regulated chromatin remodeling occurs rapidly, activating effector and inflammatory pathways.
• Transient TCF1 downregulation before division induces long-term effector cell skewing.

Conclusions:

• Dynamic pre-division regulation of TCF1 is a novel mechanism controlling CD8 T cell fate commitment.
• TCF1 acts as a critical checkpoint regulating T cell responses in infection, cancer, and autoimmunity.