Figure 7: UC-MSCs transferred mitochondria to activate T cells. PBMCs from SLE patients were labeled with carboxyfluorescein succinimidyl amino ester (CFSE) and treated with anti-CD3/CD28 antibodies for two days. Then they were cocultured with UC-MSCs for 12 h, which had been prelabeled with respiratory mitochondrion specific probe Mitotracker Deep Red (MDR). PBMCs were cultured with UC-MSCs through transwell as control. Then PBMCs were stained with anti-CD3, anti-CD4, or anti-CD8 dye and detected for MDR fluorescence with flow cytometry. Fluorescence microscopy was carried out similarly with anti-CD3/28 stimulation for 12 h and then cocultured for 6 h. All experiments were performed in triplicate. (a) T cells (CD3 positive) rather than non-T cells (CD3 negative) got MDR staining. (b–d) T cells cultured with UC-MSCs directly rather than through transwell got transferred mitochondria (). Arrows indicated transferred mitochondria within lymphocytes.  .