Activation-induced T cell apoptosis by monocytes from stem cell products

Int Immunopharmacol. 2001 Jul;1(7):1307-19. doi: 10.1016/s1567-5769(01)00062-5.


We recently found that mobilized peripheral blood stem cell (PSC) products (from both cancer patients and normal donors) contain high levels of CD14+ monocytes, which can inhibit the proliferation of allogeneic and autologous T cells. We found in our studies that using CD14+ monocytes from mobilized PSC products (from normal and cancer patient donors), normal apheresis products or normal peripheral blood (PB) can affect lymphocyte function and apoptosis-dependent T cell activation. However, it appears that the apoptosis is dependent on the frequency of monocytes, which is increased by both mobilization and apheresis. Both phytohemagglutinin (PHA)- and interleukin (IL)-2-induced proliferation of steady-state peripheral blood mononuclear cells (PBMC) were markedly inhibited by co-culture with irradiated CD14+ monocytes, although inhibition was significantly greater with PHA than with IL-2 stimulation. IL-2 (predominately CD56+ NK cells) or anti-CD3 monoclonal antibody (mAb) and IL-2-expanded lymphocytes (activated T cells) were inhibited by PSC monocytes to a significantly greater level as compared to steady-state lymphocytes. Indeed, no inhibition of T cell proliferation was observed when lymphocytes were co-cultured in the absence of mitogenic or IL-2 stimulation. In contrast, an increased proliferation was observed in co-cultures of CD14+ monocytes and steady-state or activated lymphocytes without mitogenic stimulation. Cell cycle analysis by flow cytometry revealed a significant increase in hypodiploid DNA, in a time-dependent manner, following co-culture of monocytes and PBMC in PHA, suggesting that T cell apoptosis occurred during PHA-induced activation. These results demonstrate that PSC-derived monocytes inhibit T cell proliferation by inducing the apoptosis of activated T cells and NK cells, but not steady-state cells. This suggests a potential role for monocytes in the induction of peripheral tolerance following stem cell transplantation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Monoclonal / pharmacology
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • CD3 Complex / immunology
  • Cell Division
  • Flow Cytometry
  • Fluorescent Antibody Technique
  • Humans
  • In Vitro Techniques
  • Interleukin-2 / pharmacology
  • Monocytes / drug effects
  • Monocytes / physiology*
  • Neoplastic Stem Cells / physiology*
  • Phytohemagglutinins / pharmacology
  • Stem Cells / physiology*
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / physiology*


  • Antibodies, Monoclonal
  • CD3 Complex
  • Interleukin-2
  • Phytohemagglutinins