Phenotype of immature and mature DCs. After 5 days of differentiation in IL-4 and GM-CSF, monocyte-derived DCs were left immature or were matured for 48 hours by the activation of CD40. DCs were then analyzed by flow cytometry to determine levels of expression of CD1a, CD14, CD83, and HLA-DR. (A) Percentages of positive cells, set according to the isotype-matched controls (not shown), are shown in each quadrant. (B) Expression of PD-L1, SLAM, CD45RO, CD45RB, ILT-4, and ILT-3 was also determined. Results are representative of (A) 17 and (B) 6 independent experiments.