FIG. 1.

High-dose interleukin-2 (HDIL2) induces albumin uptake by human endothelial cells (ECs). (a–e) Confocal images of FITC-albumin (green) and F-actin (red) in ECs treated with a vehicle (phosphate-buffered saline) (a) or 10,000 IU/mL IL-2 for 15 min (b), 1 h (c), or 3 h (d). FITC-albumin was added to ECs in the last 30 min of IL-2 incubation for the 1- and 3-h time points. For the 15 min time point, FITC-albumin was added 15 min before the addition of IL-2 for a total incubation time of 30 min. Serial confocal images were collected at a 0.5-μm interval, and a 2D projection image representing all slices was constructed using confocal microscope software. Data in (a–d) represent more than 6 independent experiments with similar results. (e) Quantitation of the HDIL2-induced albumin uptake shown is based on the average FITC fluorescence of multiple fields from 1 experiment representing 6 independent experiments with similar results. (f–j) Confocal images from the experiment described in (a–e) of FITC-albumin (green) and F-actin (red) in ECs pretreated with 50 μg/mL isotype control (IgG) (f, g) or anti-IL-2 antibody (h, i) for 30 min before being treated with a vehicle (f, h) or HDIL2 (g, i) for 3 h. (j) Quantitation of the HDIL2-induced albumin uptake shown is based on the average FITC fluorescence of multiple fields from 1 experiment representing 6 independent experiments with similar results. All scale bars: 10 μm. *P<0.01.