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

Nat Rev Immunol. 2021 Apr;21(4):257-267. doi: 10.1038/s41577-020-00454-2. Epub 2020 Oct 19.

Abstract

Following their exit from the thymus, T cells are endowed with potent effector functions but must spare host tissue from harm. The fate of these cells is dictated by a series of checkpoints that regulate the quality and magnitude of T cell-mediated immunity, known as tolerance checkpoints. In this Perspective, we discuss the mediators and networks that control the six main peripheral tolerance checkpoints throughout the life of a T cell: quiescence, ignorance, anergy, exhaustion, senescence and death. At the naive T cell stage, two intrinsic checkpoints that actively maintain tolerance are quiescence and ignorance. In the presence of co-stimulation-deficient T cell activation, anergy is a dominant hallmark that mandates T cell unresponsiveness. When T cells are successfully stimulated and reach the effector stage, exhaustion and senescence can limit excessive inflammation and prevent immunopathology. At every stage of the T cell's journey, cell death exists as a checkpoint to limit clonal expansion and to terminate unrestrained responses. Here, we compare and contrast the T cell tolerance checkpoints and discuss their specific roles, with the aim of providing an integrated view of T cell peripheral tolerance and fate regulation.

Publication types

  • Review

MeSH terms

  • Apoptosis / immunology*
  • Cell Death / immunology
  • Cellular Senescence / immunology*
  • Clonal Anergy / immunology*
  • Humans
  • Immunologic Memory / immunology*
  • Peripheral Tolerance / immunology*
  • T-Lymphocytes / immunology*