Immunofluorescence staining of CD31 and vβ3 integrin on IL-4–stimulated vascular endothelial cells. HUVEC monolayers grown on the well of 24-well tissue culture plates were stimulated with IL-4 (100 ng/mL) for 8 hours at 37°C. IL-4–stimulated HUVECs were then incubated with anti-CD31 MoAb NIH31-1 (right panels; B, D, and F) or control mouse IgG (left panels; A, C, and E) (10 μg/mL each) for 10 minutes at 37°C, fixed in acetone, and stained with anti-CD31 MoAb-FITC (C and D), anti-vβ3 integrin MoAb-FITC (E and F), or control mouse IgG-FITC (A and B) (10 μg/mL each) for 60 minutes at room temperature. (Original magnification × 1,000.)