PD-1 regulates extrathymic regulatory T-cell differentiation

Eur J Immunol. 2014 Sep;44(9):2603-16. doi: 10.1002/eji.201344423. Epub 2014 Aug 18.


Treg cells and the programed death-1/programed death ligand-1 (PD-1/PD-L1) pathway are both critical for maintaining peripheral tolerance to self-Ags. A significant subset of Treg cells constitutively expresses PD-1, which prompted an investigation into the role of PD-1/PD-L1 interactions in Treg-cell development, function, and induction in vivo. The phenotype and abundance of Treg cells was not significantly altered in PD-1-deficient mice. The thymic development of polyclonal and monospecific Treg cells was not negatively impacted by PD-1 deficiency. The suppressive function of PD-1(-/-) Treg cells was similar to their PD-1(+/+) counterparts both in vitro and in vivo. However, in three different in vivo experimental settings, PD-1(-/-) conventional CD4(+) T cells demonstrated a strikingly diminished tendency toward differentiation into peripherally induced Treg (pTreg) cells. Our results demonstrate that PD-1 is dispensable for thymic Treg-cell development and suppressive function, but is critical for the extrathymic differentiation of pTreg cells in vivo. These data suggest that Ab blockade of the PD-1/PD-L1 pathway may augment T-cell responses by acting directly on conventional T cells, and also by suppressing the differentiation of pTreg cells.

Keywords: PD-1; Treg cell; Treg-cell development; Treg-cell differentiation; Treg-cell function.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Differentiation / physiology*
  • Immune Tolerance / physiology*
  • Mice
  • Mice, Knockout
  • Programmed Cell Death 1 Receptor / genetics
  • Programmed Cell Death 1 Receptor / immunology*
  • T-Lymphocytes, Regulatory / cytology
  • T-Lymphocytes, Regulatory / immunology*
  • Thymus Gland / cytology
  • Thymus Gland / immunology*


  • Pdcd1 protein, mouse
  • Programmed Cell Death 1 Receptor