Fig. 1. Generation, characteristics, and mechanisms of action of tolDCs. Human tolDCs are mostly produced from peripheral blood monocytes by culturing with GM-CSF, IL-4, and an agent(s) known to confer tolerogenic properties. In murine systems, immature DCs are first generated by culturing bone marrow cells with GM-CSF and IL-4, and then induced to tolDCs by additional culturing with an agent(s) known to confer tolerogenic properties. TolDCs induce several subtypes of regulatory lymphocytes such as CD4⁺CD25⁺Foxp3⁺ Tregs, and CD25⁺Foxp3^+/− Tr-1 cells from precursor T cells (pTh). DC, dendritic cell; tolDCs, tolerogenic DCs; GM-CSF, granulocyte macrophage-colony stimulating factor; IL, interleukin; MHC, major histocompatibility complex; PD-L1, programmed death-ligand 1; ICOSL, inducible costimulator ligand; TNF, tumor necrosis factor; IFN, interferon; TLR, toll-like receptor; IDO, indoleamine 2,3-dioxygenase; FasL, Fas ligand; TGF, transforming growth factor.