Rethinking peripheral T cell tolerance: checkpoints across a T cell's journey

Area of Science:

• Immunology
• Cellular Biology
• T cell biology

Background:

• T cells possess effector functions but must avoid harming host tissues.
• Peripheral tolerance checkpoints meticulously regulate T cell-mediated immunity quality and magnitude.

Purpose of the Study:

• To comprehensively review the mediators and networks governing the six primary peripheral tolerance checkpoints in T cells.
• To provide an integrated perspective on T cell peripheral tolerance and fate regulation throughout their lifespan.

Main Methods:

• Review and synthesis of existing literature on T cell tolerance checkpoints.
• Comparative analysis of quiescence, ignorance, anergy, exhaustion, senescence, and death pathways.

Main Results:

• Quiescence and ignorance actively maintain tolerance in naive T cells.
• Anergy induces unresponsiveness in co-stimulation-deficient T cell activation.
• Exhaustion and senescence limit inflammation and prevent immunopathology in effector T cells.
• Cell death acts as a universal checkpoint to control T cell expansion and terminate responses.

Conclusions:

• The six peripheral tolerance checkpoints (quiescence, ignorance, anergy, exhaustion, senescence, death) are critical for T cell fate regulation.
• These checkpoints operate across different T cell stages to maintain immune homeostasis and prevent autoimmunity.
• An integrated understanding of these checkpoints offers insights into managing T cell-mediated immunity.