Figure 1. Superior immunostimulatory activity of TLR-activated dendritic cells. (A) In the presence of immature dendritic cells (iDCs), regulatory T cells (Tregs) inhibit the proliferation of conventional T cells. (B) DCs matured in the presence of Toll-like receptor (TLR) agonists (DC1s) secrete an unknown soluble factor that abolish the immunosuppressive functions of Tregs, hence allowing for T-cell proliferation. DC1s also secrete biologically active interleukin-12 (IL-12), which converts Tregs into T-bet+ interferon γ (IFNγ)-secreting TH1-like cells.