Contribution of TNF-α in the maturation of dendritic cells. T cell–depleted blood mononuclear cells were cultured for 7 days in GM-CSF/IL-4 as described in Materials and Methods. From day 7 to 11 they were cultured in conditioned medium (MCM) or no additional supplementation (−MCM). TNF-α (50 ng/mL) was added every other day from days 0 to 8. On day 11, the cells were analyzed for CD83 expression. Residual cells were washed twice and returned to culture for 3 more days in RPMI containing 1% plasma. On day 14 the cells were tested for T cell–stimulatory capacity in the allo MLR (left panel) and reevaluated for CD83 expression. The recovered cell yields from a starting volume of 40 mL of blood are given in the upper right hand corner of each FACS panel. The results are representative of two experiments.