CD56⁺CD14⁺ cells can be induced to differentiate into fully mature CD83⁺ DCs. (A) CD56⁺ cells (10⁶/mL) were cultured for 3 days in either GM-CSF alone (800 U/mL) or in GM-CSF plus IL-4 (500 U/mL). From day 3 to day 5 maturation was induced by the addition of TNF-α (1000 U/mL) and PGE2 (1 μM). Flow cytometric analysis showed that IL-4 was required to allow the development of homogenously CD83⁺ DCs (B) with the typical cytoplasmic extensions (veils, white arrows).