Postproliferative differentiation model. (a) Schematic presentation of the culture system. After leukapheresis and subsequent elutriation, monocytes (MO) were cultured either in the presence of IL-4, granulocyte-macrophage colony-stimulating factor (GM-CSF) and FCS to generate DCs or with human AB-serum to obtain macrophages (MAC) for 7 days. (b) Microarray expression profiles of several marker genes that are preferentially expressed in macrophages (CHI3L1, CHIT1), monocytes (KLF4, FOSB) or DCs (CD1A, CCL17) and control genes (VDR, SPI1) showing constant mRNA levels during differentiation. Shown are median-normalized microarray signal intensities derived from ten (monocytes) or six (DCs and macrophages) independent donors. (c) DCs and U937 cells were cultured with [3H]-thymidine for 20 h at different time points (day 0 to 1, day 1 to 2, day 2 to 3, day 3 to 4) during culture. Values represent mean ± standard deviation of three independent experiments. The U937 leukemia cell line served as positive control showing high thymidine incorporation levels.