Effect of lactic acid and low doses of M-CSF and IL-6 on CD1a expression (A). Monocytes were differentiated in the presence of IL-4 and GM-CSF for 7 days with or without the addition of 10 to 15 mM lactic acid or low-dose M-CSF (1 ng/mL) and IL-6 (10 U/mL). As a control, the medium with IL-4 and GM-CSF was titrated to pH 6.0 to 6.5 with HCl (pH). In some samples, the pH of the lactic acid-containing cultures (10 mM lactic acid pH 6.5, 15 mM lactic pH 6.3) was adjusted to pH 7.4. Cells were stained with an antibody against CD1a and analyzed with a FACScan. The figure shows the mean and SEM of the median fluorescence intensity (isotype subtracted) of at least 3 experiments. (B) Phenotypical characterization of DCs cultured under different conditions. Monocytes were differentiated in the presence of IL-4 and GM-CSF for 7 days with or without the addition of 10 mM lactic acid, low-dose M-CSF (1 ng/mL), and IL-6 (10 U/mL), or a combination of lactic acid, low-dose M-CSF, and IL-6. As a control, monocytes were cultured in a medium with pH 6.0. Cells were stained with an antibody against CD1a, HLA-DR, and CD86 and analyzed with a FACScan. Filled histograms represent the specific staining.