Intradermally injected peroxidase was found in the Langerhans' cell granules of the epidermal Langerhans' cells. As time elapsed, the number of stained granules increased, reaching the maximum at 22 hours, and tended to concentrate near the Golgi zone. Since the peroxidase molecule does not cross the plasma membrane, this suggested (1) ingestion of peroxidase by the Langerhans' cell granules at the cell periphery and (2) migration of such granules into the cell interior. At the cell periphery various types of close apposition of the plasma membrane with gap distance ranging from 30 Angstroms (gap junction) to 350 A (Langerhans' cell type) were found. They too migrated into the cell interior. This suggested that the so-called Langerhans' cell granule is just one type of plasma membrane apposition or invagination which this cell can produce.
Hashimoto K. Langerhans' Cell GranuleAn Endocytotic Organelle. Arch Dermatol. 1971;104(2):148-160. doi:10.1001/archderm.1971.04000200036007