The immunosuppressive effect of embryonic stem cells and mesenchymal stem cells on both primary and secondary alloimmune responses

Recently, both embryonic stem cells and mesenchymal stem cells have been demonstrated to have immunosuppressive effects. The purpose of this study was to elucidate whether the embryonic stem cells and/or mesenchymal stem cells modulate both primary and secondary alloimmune responses. Both stem cells suppressed in vitro proliferation and cytokine production in primary alloimmune responses. They also suppressed in vitro proliferation and cytokine production of the allosensitized CD44+ memory T cells. However, they failed to prolong skin graft survival across both a major mismatch barrier (BALB/C, C57BL6/J) and a minor mismatch barrier (male to female). In conclusion, both embryonic stem cells and mesenchymal stem cells can suppress secondary alloimmune response in vitro as well as primary alloimmune responses; however, neither embryonic stem cells nor mesenchymal stem cells suppressed allograft rejection in stringent murine skin transplantation models.