Localization and characterization of N-cadherin–containing heterotypic AJ structures connecting human fibroblasts and hepatocellular carcinoma cells of line PLC. (A–C) Laser-scanning, double-label immunofluorescence microscopy (on a phase-contrast basis) of co-cultures of freshly dispersed transformed human fibroblasts (shown here is line SV80) and hepatocellular carcinoma cells of line PLC in a mixed cluster cell colony grown to confluency, after reaction with antibodies against N-cadherin (red) and the IF protein vimentin (green) as a marker of the fibroblasts. Punctate AJs containing N-cadherin occur not only as homotypic junctions formed between SV80 fibroblasts but also as heterotypic structures connecting N-cadherin AJs of fibroblasts and E–N-cadherin heterodimers of AJs of adjacent PLC cells. In the latter, the AJs are also positive for E-cadherin. Shown here are an overview (A) and details presenting special clarity at higher magnification (B and C), the latter allowing the resolution of an array of at least eleven variously sized AJ structures (red dot structures) connecting a fibroblastoid with a hepatocyte-derived cell. The yellow-stained structures are N-cadherin AJs located on the bottom side of the cells. Bars: (A) 20 µm; (B) 10 µm; (C) 5 µm.