Internalised Material Fate-Transcytosis
Transcytosis is the transfer of surface receptors from one side of the cell to the other in polarised epithelial cells, i.e. from the apical to the basolateral part or vice versa. This route is indirect, since receptors move first from the early endosome, to an intermediate compartment, the recycling endosome. Unique about recycling endosomes is they can regulate the exit of proteins, meaning that they can regulate the concentration of specific plasma membrane proteins, in either the apical or the basolateral part of the cell.
An Example of Transcytosis - of natural passive immunity
- Antibodies from a mother's milk are transferred to a baby across the epithelium of the baby's gut during breast feeding.
At the acidic pH in the gut, antibodies in the milk bind to surface receptors on the apical side of the gut epithelial cells.- The receptor and antibodies are internalised via clathrin coated vesicles and are delivered to the early endosome.
- They are retrieved in transport vesicles that bud from the early endosome and then these fuse with the basolateral side of the epithelial cell.
- Here the pH is neutral causing the antibodies to dissociate from their receptors and ultimately enter the baby's bloodstream.
Image 2 courtesy of Instablog Network 2005 under Creatice Commons License