Characterization of a conduit system containing laminin-5 in the human thymus: a potential transport system for small molecules

Drumea-Mirancea M., Wessels J.T., Müller C.A., Essl M., Eble J.A., Tolosa E., Koch M., Reinhardt D.P., Sixt M., Sorokin L., Stierhof Y-D., Schwarz H., Klein G.
Journal of Cell Science, 2006

T cells develop in the thymus in a highly specialized cellular and extracellular microenvironment. Laminin-332 is predominantly found in the medulla of the human thymic lobules. Here, the authors show that laminin-332 is localized in a bi-membranous conduit-like structure, together with matrix components, such as collagen type IV, nidogen, perlecan, fibrillin-1 or -2, tenascin-C or fibrillar collagen types. 3D confocal microscopy suggested a tubular structure, whereas immunoelectron and transmission electron microscopy showed that the core of these tubes contained fibrillar collagens enwrapped by the laminin-332-containing membrane. These medullary conduits are surrounded by thymic epithelial cells, which in vitro were found to bind laminin-332. Dendritic cells were also detected in close vicinity to the conduits.