pDC expression of GrB is negatively regulated by ligands for TLR7, TLR9, and CD40. pDCs were activated for 16 hours in the presence of IL-3 alone or IL-3 and IL-10 as well as the TLR9 ligand ODN 2006 or the TLR7 ligand imiquimod. Then they were stained with fluorescently labeled antibodies to pDC markers and GrB, and analyzed by FACS. (A) Histograms show GrB expression in pDCs from 1 representative donor. (B) Bar graphs illustrate average MFI for GrB expression from 3 independent experiments. (C) Zebra plots from pDCs activated in the presence of IL-3 and combinations of imiquimod with CD40L, PGE₂, or VIP illustrate the percentages of GrB⁺ pDCs (representative for n = 3).