Also called vesicular transport, transcytosis is a form of intracellular vesicular traffic in which endocytosed macromolecules are transferred across the cell and released via exocytosis at the opposite plasma membrane domain. In other words, transcytosis is a mechanism for transcellular transport in which a cell encloses extracellular material in an invagination of the cell membrane to form a vesicle, then moves the vesicle across the cell to eject the material through the opposite cell membrane by the reverse process.
Vesicles are employed to intake the macromolecules on one side of the cell, draw them across the cell, and eject them on the other side. While transcytosis is most commonly observed in cells of an epithelium, the process is also present elsewhere. Blood capillaries are a well-known site for transcytosis, though it occurs in other cells, including neurons and intestinal cells.