Fig. 3. Electron microscopic analysis of the conduits. (A) Ultrathin thymic cryosections were labeled with antibodies against the laminin 2 chain, which were detected by nanogold-coupled secondary antibodies. After silver enhancement, labeling of a membrane surrounding an area rich in fibrillar collagens could be observed. (B) Transmission electron microscopy of the thymic medulla revealed densely packed collagen bundles surrounded by a basement membrane. These conduit-like structures are enwrapped by a cell that is rich in intermediate filaments. Note the desmosome at the top of the right conduit. Bars, 1 µm.