IL-3–activated pDCs secrete large amounts of GrB. Purified pDCs were cultured for 16 hours in the absence or presence of IL-3 with or without IL-10. (A) GrB in supernatants was measured by ELISA. Bar graphs illustrate average GrB concentrations from 5 independent experiments (values normalized to 10⁴ pDCs per well). (B) GrB secretion was determined by a GrB-specific ELISPOT using purified pDCs treated with IL-3 with or without IL-10 or using T cells treated with PHA (positive control). No spots were observed in samples with 4 × 10³ pDCs per well in the presence of PHA (not shown). (C) GrB ELISA was performed from supernatants of purified pDCs treated with ODN 2006 or imiquimod. Bar graphs illustrate GrB concentrations normalized to 10⁴ pDCs per well (n = 10).