Immunoelectron microscopic localization of gp-Fy in kidney glomerulus. Antibody 6615 was used for labeling. (a) Low magnification of the glomerular capillaries (original magnification × 6,000) and (b through e) higher magnification showed strong labeling (original magnification × 60,000). Endothelial cells (E) showed labeling of the apical and basal plasma membranes, including fenestration and caveolae. In contrast epithelial cells (podocytes, P) were unlabeled. (e) When preimmune serum was used, no labeling was observed. BM, basement membrane.