Tethered exosomes and their role in MHC-II presentation

Exosomes are vesicles that are released from cells upon fusion of internal compartments (endosomes) with the surface of cells. It has been assumed that upon their release from cells, exosomes deliver their contents to adjacent cells, providing communication between cells. I have recently shown that exosomes can be retained in clusters on the surface of cells following their discharge, opening up potential new roles for exosomes. The retention of exosomes is dependent on a protein called tetherin, which plays a similar role in the tethering of newly budded viruses. The function of tethering exosomes is unknown. Cells of the immune system generate high levels of tetherin and present clusters of exosomes on their surface, but why? I will test the hypothesis that tethered exosomes contribute to a functional immune system. Further, I will define where and how exosomes fuse when they come into contact with another cell.