Elastic fibers associated with collagenous fibrils surrounded by reticular cells in lymph nodes of the rat as revealed by electron microscopy after orcein staining.

Electron microscopy of the rat lymph node disclosed reticular cells in close association with bundles of collagenous fibrils 30-45 nm in diameter, and electron lucent "amorphous" substances surrounded by microfibrils 11 nm in diameter, with junctional complexes. The amorphous substances, distinctly revealed by orcein staining, and the microfibrils showed morphological characteristics of elastic fibers. Since elastase digestion of 2% glutaraldehyde fixed specimens induced the selective disappearance of the orcein-stainable substances, it was concluded that they are elastin. Elastin often had a close contact with the plasma membrane of reticular cells. It is suggested that reticular cells synthesize elastic fibers.