Differential responses of human regulatory T cells (Treg) and effector T cells to rapamycin

PLoS One. 2009 Jun 22;4(6):e5994. doi: 10.1371/journal.pone.0005994.


Background: The immunosuppressive drug rapamycin (RAPA) promotes the expansion of CD4(+) CD25(high)Foxp3(+) regulatory T cells via mechanisms that remain unknown. Here, we studied expansion, IL-2R-gamma chain signaling, survival pathways and resistance to apoptosis in human Treg responding to RAPA.

Methodology/principal findings: CD4(+)CD25(+) and CD4(+)CD25(neg) T cells were isolated from PBMC of normal controls (n = 21) using AutoMACS. These T cell subsets were cultured in the presence of anti-CD3/CD28 antibodies and 1000 IU/mL IL-2 for 3 to 6 weeks. RAPA (1-100 nM) was added to half of the cultures. After harvest, the cell phenotype, signaling via the PI3K/mTOR and STAT pathways, expression of survival proteins and Annexin V binding were determined and compared to values obtained with freshly-separated CD4(+)CD25(high) and CD4(+)CD25(neg) T cells. Suppressor function was tested in co-cultures with autologous CFSE-labeled CD4(+)CD25(neg) or CD8(+)CD25(neg) T-cell responders. The frequency and suppressor activity of Treg were increased after culture of CD4(+)CD25(+) T cells in the presence of 1-100 nM RAPA (p<0.001). RAPA-expanded Treg were largely CD4(+)CD25(high)Foxp3(+) cells and were resistant to apoptosis, while CD4(+)CD25(neg) T cells were sensitive. Only Treg upregulated anti-apoptotic and down-regulated pro-apoptotic proteins. Treg expressed higher levels of the PTEN protein than CD4(+)CD25(neg) cells. Activated Treg+/-RAPA preferentially phosphorylated STAT5 and STAT3 and did not utilize the PI3K/mTOR pathway.

Conclusions/significance: RAPA favors Treg expansion and survival by differentially regulating signaling, proliferation and sensitivity to apoptosis of human effector T cells and Treg after TCR/IL-2 activation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibiotics, Antineoplastic / pharmacology
  • Apoptosis
  • CD28 Antigens / biosynthesis
  • CD3 Complex / biosynthesis
  • CD4-Positive T-Lymphocytes / drug effects
  • CD4-Positive T-Lymphocytes / metabolism*
  • Cell Proliferation
  • Cross-Linking Reagents / pharmacology
  • Humans
  • Interleukin Receptor Common gamma Subunit / metabolism
  • Interleukin-2 / metabolism
  • Interleukin-2 Receptor alpha Subunit / biosynthesis
  • Leukocytes, Mononuclear / cytology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Signal Transduction
  • Sirolimus / pharmacology*
  • T-Lymphocytes, Regulatory / drug effects
  • T-Lymphocytes, Regulatory / metabolism*


  • Antibiotics, Antineoplastic
  • CD28 Antigens
  • CD3 Complex
  • Cross-Linking Reagents
  • IL2RG protein, human
  • Interleukin Receptor Common gamma Subunit
  • Interleukin-2
  • Interleukin-2 Receptor alpha Subunit
  • Phosphatidylinositol 3-Kinases
  • Sirolimus