Expression of GrB in pDCs is associated with phosphorylation of JAK/STAT members. pDC precursors were purified and evaluated either unstimulated or after stimulation with IL-3 with or without IL-10. Stimulation was performed for 16 hours for GrB detection, 10 minutes for pJAK detection, and 30 minutes for pSTAT detection. Protein was extracted and Western immunoblotting performed. Loading of equal protein amounts was assured by parallel blotting for β-actin. PBMCs stimulated with PHA served as positive controls (data not shown). One representative experiment of 3 is shown.