Figure 1.

Downregulation of CD6 surface expression in response to different T-cell receptor-mediated activation stimuli. (A–C) PBLs (10⁵/well) were cultured for 4 days in the presence of PHA (5 μg/mL), αCD3/CD28 beads (2 μL/10⁵ cells), PMA (10 ng/mL), or rhIL-2 (10 ng/mL). Cells were then stained with labeled specific mAbs for CD3 (UCHT1), CD4 (MT310), CD8 (SK1), and CD6 (M-T605) and analyzed by flow cytometry at different days (d). (A) Representative dot plots of CD6⁺ cells in the CD3⁺CD4⁺ (top panel) or CD3⁺CD8⁺ (bottom panel) subsets at days 0 and 4 post-stimulation. (B) Bar chart representing mean ± SD of geometric mean of fluorescence intensity (Geo MFI) values for CD6 expression on CD3⁺CD4⁺ (top panel) and CD3⁺CD8⁺ (bottom panel) cells over time post-stimulation, from three independent experiments. (C) Line chart representing the percentage of CD6⁺ cells over time post-stimulation in the CD3⁺CD4⁺ (left hand) or CD3⁺CD8⁺ (right hand) subsets from three independent experiments. (D) Staphylococcal enterotoxin B-pulsed mature DCs (2 × 10³/well) co-cultured with CFSE-labeled PBL (10⁵/well) for 5 days were analyzed for CD6 expression on proliferating (CFSE^lo) and non-proliferating (CFSE^hi) cells. Left, representative histogram of CD6 expression on CFSE^lo and CFSE^hi cells is. Right, bar chart representing percent (mean ± SEM) of CD6⁺ cells in the CFSE^lo and CFSE^hi subsets from 10 independent experiments. ***p < 0.001 (unpaired t test).