Molecular and cellular characterization of Cord Blood derived, IDO expressing human fibrocystic Myeloid Derived Suppressor Cells

By restraining T cell activation and promoting regulatory T cell (Treg) expansion, myeloid-derived suppressor cells (MDSC) and tolerogenic dendritic cells (DC) (tDC) can control self-reactive and anti-graft effector T cells in autoimmunity and transplantation. Their therapeutic use and characterization, however, is limited by their scarce availability in the peripheral blood of tumor-free donors. In the present study we describe and characterize a novel population of myeloid suppressor cells, named fibrocytic MDSC (f-MDSC), that are differentiated from umbilical cord blood (UCB) precursors by a 4 day culture with FDA approved cytokines (rh-GM-CSF and rh-G-CSF). This MDSC subset, characterized by the expression of MDSC-, DC-, and fybrocyte-s associated markers, promotes Treg regulatory cells expansion and promote normoglycemia in a xenogeneic model of Type 1 Diabetes (T1D). In order to exert their pro-tolerogenic function, fibrocytic MDSC require direct contact with activated T cells, which leads to the induction and secretion of indoleamine 2,3 deoxygenase (IDO). This new myeloid subset may represent an important tool for the in vitro and in vivo production of Treg for the treatment of autoimmune diseases, and either prevention or control of allograft rejection.

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