Ultrastructural localization of TF in fibroblasts and loss of caveolar structure on cholesterol depletion. Fibroblasts (WI-38 cells) were fixed and immunostained with TF mAb as described in “Materials and methods” (A-D). TF was localized on the cell membrane (A), on cellular processes (B), and in caveolae (C). The tip of a cellular process that was in contact with other cell/cellular process are stained densely for TF (D). Thin arrows point out gold particles, whereas arrowheads point out caveolae. Monolayers of WI-38 fibroblasts were treated with a control vehicle (E) or mβCD (10 mM) (F) for 45 minutes at 37°C. The cells were then fixed, sectioned, stained, and viewed under transmission electron microscope. Bar indicates 200 nm.