Internalization of anti-PECAM/NCs is inhibited in PECAM-1 ΔCD cells. (A) The kinetics of internalization of FITC-labeled anti-PECAM/NCs by REN cells transfected with human wild-type PECAM-1 (RhP) (●), and PECAM-1 lacking the cytoplasmic domain (ΔCD) (○) was determined by fluorescence microscopy after counterstaining surface nanocarriers with a Texas red secondary antibody. Internalization was quantified as the percentage of internalized anti-PECAM/NCs relative to total number of nanocarriers associated per cell. The percentage of internalized anti-PECAM/NCs was significantly lower for ΔCD cells at each time point (*P < .001). (B) Anti-PECAM/NC uptake was assessed in RhP and ΔCD cells incubated with either control media or media containing amiloride, an inhibitor of CAM-mediated endocytosis. Internalization was calculated as in panel A and normalized to RhP control cells. Data are mean plus or minus SD (n ≥ 25 cells; *P < .001).