Issues

Cover picture: Small, soluble, lymph-borne molecules (e.g., chemokines, antigen) move rapidly from the subcapsular sinus to the high endothelial venules through the fibers of the reticular network, rather than percolating diffusely through the lymph node. Low molecular weight dextran labeled with Texas Red (10 kD; red) was injected subcutaneously into a rat, and the draining lymph node was excised and fixed within 5 min of the injection. This confocal image shows that lymph-borne dextran rapidly filled the subcapsular sinus (red band across the top) and highlighted the fibers of the reticular network (vertical) as well as associated blood vessels (capillaries and high endothelial venules; horizontal), with little dextran visible between lymphocytes. Topical counterstaining with the FITC-labeled lectin (green) wheat germ agglutinin resulted in a fine green outline of the fibers and associated blood vessels consistent with staining of the fibroblastic reticular cells, known to ensheathe the reticular fibers. Therefore, the fibers of the reticular network act as conduits for the delivery of small, lymph-borne molecules such as chemokines to the high endothelial venules, where the delivered chemokines would facilitate lymphocyte binding to endothelium and transmigration. See related article in this issue by Gretz et al., pp. 1425-1439.