Cell proliferation and differentiation of CD34⁺ progenitor cells in different culture conditions. (A) After 14 days, the total number of cells expanded in vitro in the presence of IL-16 added to the basal cocktail was higher than in the presence of the other cytokine combinations. The mean fold increase over cell number plated on day 0 is shown. Mean ± SEM from 16 independent experiments. Comparison between treatments performed with the 2-tailed t test. (B) Morphology of the cells after 14 days of culture. The majority of the cells showed lobulated nuclei and numerous fine cytoplasmic projections, as assessed by AO staining. Photographs were taken under a Leitz-DIALUX22 fluorescence microscope (Leica, Milan, Italy) equipped with a Kodak DX7590 camera (Kodak-italia, Milan, Italy). Original magnification × 400. No differences were observed among the different culture conditions. (C) Down-regulation of CD34 and up-regulation of CD1a expression after 7 and 14 days of culture in the presence of the different cytokine combinations. IL-16 (♦) added to the basal cocktail (▵) appeared to be more efficient than SCF (▴), TPO (•), and IL-16 plus TPO (▪) in inducing the differentiation of CD34⁺ cells into DCs. The mean of 9 independent experiments is shown. (D) After 14 days, the number of DCs expanded in vitro in the presence of IL-16 added to the basal cocktail was higher than in the presence of the other cytokine combinations. The mean fold increase, obtained by multiplying the percentage of CD1a⁺ cells for the absolute number of viable cells, is shown. Mean ± SEM from 16 independent experiments. Comparison between treatments performed with the 2-tailed t test.