Fig. 1.

CD46 co-stimulation down modulates surface expression of CD46. (A) Flow histograms of baseline CD46 surface expression (open histograms) on CD3⁺CD8⁺ and CD3⁺CD4⁺ T cells from four different donors, stained with αCD3-FITC, αCD4-Brilliant Violet 421, αCD8-PC5, and αCD46-PE. An isotype control stained with IgG1-PE (closed gray histogram) from one representative donor is shown for comparison. The right panel shows the summarized CD46 median fluorescence intensity (MFI) values for the 4 donors. (B) Surface expression of CD46 on isolated CD8⁺ and CD4⁺ T cells following activation with αCD3 or αCD3/αCD46 for 2 h measured by flow cytometry using αCD46-PE for staining. An isotype control stained with IgG1-PE (closed gray histogram) is shown for comparison. Data are representative of 2 independent experiments.