Demonstration of the Langerhans Granule by Lanthanum

The term Langerhans granule has been introduced recently as a designation for a characteristic structure in the Langerhans cell of the epidermis and in the infiltrating histiocyte in histiocytosis X (1, 2). This unusual structure is found within the cytoplasm or attached to the plasma membrane, is in the form of a plate or disc, and is composed of two dense membranes separated by a central core of moderate density. Its dimensions vary, and the central core may have a repeating period. No function is known for this granule, which appears to originate from the plasma membrane or from vacuoles of the smooth endoplasmic reticulum in the region of the Golgi zone. A new method for defining the extracellular space in ultrathin sections by means of a lanthanum complex has been described by Revel and Karnovsky (3). With this technique, they were able to demonstrate in intercellular junctions hexagonal arrays that were not evident with conventional methods of preparation for electron microscopy (3, 4). Since the Langerhans granule is frequently continuous with the extracellular space, the probability that it too could be demonstrated with lanthanum and that additional information could be obtained about its structure seemed likely. This report describes our findings with this technique. MATERIALS AND METHODS Granuloma tissue obtained in the operating room from a 4 yr-old girl with a solitary eosinophilic granuloma of the skull was immediately fixed in 3% glutaraldehyde in 0.1 M phosphate buffer at pH 7.4. After 6 hr fixation it was washed and stored in the buffer. The tissue was later postfixed for 2 hr in an Os04-collidine-lanthanum solution at room temperature as described by Revel and Karnovsky (3), dehydrated in graded alcohols, and embedded in Araldite. Other tissue was postfixed in 1 % osmium tetroxide and embedded in Epon 812. Thin sections were cut with a diamond knife, stained briefly in an aqueous solution of uranyl acetate, and photographed