Requirement of cognate CD4+ T-cell recognition for the regulation of allospecific CTL by human CD4+ CD127- CD25+ FOXP3+ cells generated in MLR

PLoS One. 2011;6(7):e22450. doi: 10.1371/journal.pone.0022450. Epub 2011 Jul 22.


Although immunoregulation of alloreactive human CTLs has been described, the direct influence of CD4(+) Tregs on CD8(+) cytotoxicity and the interactive mechanisms have not been well clarified. Therefore, human CD4(+)CD127(-)CD25(+)FOXP3(+) Tregs were generated in MLR, immunoselected and their allospecific regulatory functions and associated mechanisms were then tested using modified (51)Chromium release assays (Micro-CML), MLRs and CFSE-based multi-fluorochrome flow cytometry proliferation assays. It was observed that increased numbers of CD4(+)CD127(-)CD25(+)FOXP3(+) cells were generated after a 7 day MLR. After immunoselection for CD4(+)CD127(-)CD25(+) cells, they were designated as MLR-Tregs. When added as third component modulators, MLR-Tregs inhibited the alloreactive proliferation of autologous PBMC in a concentration dependent manner. The inhibition was quasi-antigen specific, in that the inhibition was non-specific at higher MLR-Treg modulator doses, but non-specificity disappeared with lower numbers at which specific inhibition was still significant. When tested in micro-CML assays CTL inhibition occurred with PBMC and purified CD8(+) responders. However, antigen specificity of CTL inhibition was observed only with unpurified PBMC responders and not with purified CD8(+) responders or even with CD8(+) responders plus Non-T "APC". However, allospecificity of CTL regulation was restored when autologous purified CD4(+) T cells were added to the CD8(+) responders. Proliferation of CD8(+) cells was suppressed by MLR-Tregs in the presence or absence of IL-2. Inhibition by MLR-Tregs was mediated through down-regulation of intracellular perforin, granzyme B and membrane-bound CD25 molecules on the responding CD8(+) cells. Therefore, it was concluded that human CD4(+)CD127(-)CD25(+)FOXP3(+) MLR-Tregs down-regulate alloreactive cytotoxic responses. Regulatory allospecificity, however, requires the presence of cognate responding CD4(+) T cells. CD8(+) CTL regulatory mechanisms include impaired proliferation, reduced expression of cytolytic molecules and CD25(+) activation epitopes.

Publication types

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

MeSH terms

  • Apoptosis / immunology
  • CD4 Antigens / metabolism*
  • Cell Differentiation / immunology
  • Forkhead Transcription Factors / metabolism*
  • Humans
  • Interleukin-2 Receptor alpha Subunit / metabolism*
  • Interleukin-7 Receptor alpha Subunit / deficiency*
  • Lymphocyte Culture Test, Mixed
  • T-Lymphocytes, Cytotoxic / cytology
  • T-Lymphocytes, Cytotoxic / immunology*
  • T-Lymphocytes, Cytotoxic / metabolism
  • T-Lymphocytes, Regulatory / cytology
  • T-Lymphocytes, Regulatory / immunology*
  • T-Lymphocytes, Regulatory / metabolism


  • CD4 Antigens
  • FOXP3 protein, human
  • Forkhead Transcription Factors
  • Interleukin-2 Receptor alpha Subunit
  • Interleukin-7 Receptor alpha Subunit