Figure 3. Role of CD14⁺ monocytes in the development of CD56^brightCD11c⁺ cells.

(A) CD14⁺, CD56⁺, and CD11c⁺ cells were required for the development of CD56^brightCD11c⁺ cells. CD14⁺, CD56⁺, or CD11c⁺ cells were depleted from T cell-depleted PBMCs (2×10⁴ cells/0.5 ml) and stimulated with IL-2/ IL-18 for 7 days. The number of CD56^brightCD11c⁺ cells was counted based on trypan blue dye exclusion. Data show mean ± SD (n = 5), **p<0.01. (B) Effect of CD14⁺ monocytes on the division of CD56⁺ cells. CFSE-labeled CD56⁺ cells were cultured with purified CD14⁺ monocytes at a ratio of 1:1 at a cell density of 2×105/well. After co-culture for 4 days, proliferating cells were analyzed by CFSE, CD56 and CD11c expression. A representative result of three independent experiments is shown. Division of CFSE-labeled CD14⁺ cells is also shown (black line). (C) Formation of large aggregates of CD56^brightCD11c⁺ cells in the co-culture of CD56^intCD11c⁺ cells and CD14⁺ monocytes in the presence of IL-2/IL-18 for 7 days, not in cultures of individual cell types. Data show mean ± SD (n = 4), **p<0.01, and the morphological data are representative of three independent experiments. (D) IL-2/IL-18-dependent cell aggregation in culture of CD14⁺ monocytes and CD56^intCD11c⁺ cells. IL-4-DCs, IL-18-induced CD14⁺ monocytes and IFN-α-DCs were co-cultured with freshly isolated CD56^intCD11c⁺ cells (1×105 cells/well) at a ratio of 1:1, respectively. After 12 h incubation, cell aggregates were observed under a microscope. Flow cytometric analyses are carried out after 3 days of co-culture. A representative result of three independent experiments is shown.