Mesenchymal stem cells suppress T cells by inducing apoptosis and through PD-1/B7-H1 interactions

Area of Science:

• Immunology
• Cell Biology

Background:

• Mesenchymal stem cells (MSCs) are known for their immunosuppressive properties, particularly on T cells.
• The precise molecular mechanisms underlying MSC-mediated T cell suppression remain incompletely understood.

Purpose of the Study:

• To investigate the role of the programmed cell death-1 receptor (PD-1)/B7-H1 pathway in MSC-induced suppression of conventional CD4(+)CD25(-) T cells (Tconv).
• To elucidate the relationship between PD-1 up-regulation, T cell apoptosis, and immunosuppressive cytokines in MSC-Tconv co-cultures.

Main Methods:

• Co-culture assays of MSCs and Tconv with and without transwell systems.
• Flow cytometry to assess PD-1 expression on activated Tconv.
• Analysis of T cell apoptosis and levels of IL-10 and TGF-β1.

Main Results:

• MSCs significantly increased PD-1 expression on activated Tconv.
• The PD-1/B7-H1 pathway was implicated in the suppression of Tconv by MSCs.
• Elevated PD-1 expression correlated with increased Tconv apoptosis.
• The PD-1/B7-H1 pathway's effect was independent of IL-10 and TGF-β1.

Conclusions:

• The PD-1/B7-H1 pathway is a key mechanism mediating MSC-induced T cell suppression and apoptosis.
• IL-10 and TGF-β1 do not appear to mediate PD-1 up-regulation in this context.