Immunogold labeling of occludin and caveolin-1 in jejunal enterocytes of untreated wild-type mice. High pressure–frozen, freeze-substituted, cryoembedded specimens were immunolabeled. (A) Antioccludin, detected with 10 nm gold-conjugated secondary antisera, shows tight junction–specific labeling (best appreciated in the enlarged region [right]). (B) Anti–caveolin-1, detected with 10 nm gold-conjugated secondary antisera, shows labeling at the adherens junction (AJ) and, to a lesser extent, the tight junction (TJ). (C) Antioccludin and anti–caveolin-1, detected with 10 nm and 15 nm gold-conjugated secondary antisera, respectively, label at the tight junction and adherens junction as in A and B. Controls for double labeling are shown in Fig. S1. Mv, microvilli. Bars: (left) 300 nm; (right) 50 nm.