Role of PS and CD14 in the uptake of early apoptotic cells by Mø1s and Mø2s. (A) CFSE-labeled early apoptotic cells were preincubated with 10 μg/mL or 50 μg/mL unlabeled annexin V or medium as control at 4°C for 20 minutes, before the coincubation with Mø2s. The percentage of uptake and/or binding was calculated as described in Figure 2. Data shown are representative of 3 independent experiments performed in duplicate. (B) CD14 expression on DCs, Mø1s, and Mø2s generated in parallel from the same donor. Bars show the mean fluorescence intensity (MFI). Data shown are the mean ± SD from 4 independent experiments. (C) After coincubation of apoptotic cells with Mø1s, cells were stained with a APC-conjugated anti-CD14 mAb, instead of anti-CD11b. CD14 expression was divided equally into 2 populations: CD14^high and CD14^low. Dot-plots of the FACS showed the distinct uptake of apoptotic cells by CD14^high and CD14^low cells. (D) Mø1s and Mø2s were preincubated with or without a blocking anti-CD14 antibody (mAb 61D3) at 4°C for 20 minutes, before the coincubation with early apoptotic cells for 2 hours. Relative uptake/binding was calculated as 100% × (% in the presence of anti-CD14)/(% in the absence of anti-CD14). Data are shown as mean ± SD from 4 (Mø1s) to 6 (Mø2s) independent experiments performed in duplicate. Similar results were obtained when etoposide-induced apoptotic cells were applied. **P < .001, 1 sample t test. Separate unrelated donors are used for each independent experiment. Dashed line indicates 100% of relative uptake.