Human peripheral blood was collected into heparin vacutainer tubes (BD Bioscience, Franklin Lakes, NJ) from healthy individuals. Peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll-Paque density gradient centrifugation (GE Healthcare, Uppsala, Sweden). A final suspension was made in complete RPMI 1640 (Hyclone), supplemented with 10% [v/v] FBS, 100 U/ml penicillin, 100 mg/ml streptomycin, 0.25 mg/ml and fungizone. Cell viability (greater than 95%) was determined by trypan blue exclusion. Human monocytes were purified from PBMC using the Monocyte Isolation Kit II (Miltenyi Biotec, Auburn, CA), according to the manufacturer's recommendations. These monocytes were then used to produce Monocyte Derived Dendric Cells (MDDC) as described below.