During the last 20 years my research group has studied general molecular mechanisms that regulate endosome dynamics and sorting in these organelles of medically relevant cargo molecules, such as MHC class II. In professional antigen presenting cells, MHC class II is instrumental to initiate adaptive immune responses. Newly synthesised MHC class II is first loaded in endosomal compartments with antigen derived peptides and thereafter deposited at the cell surface. Regulation of these processes is one of the major elements of our current research. MHC class II is also incorporated into exosomes, which are small vesicles that are generated and secreted by endosomes. We study the immunological role of MHC class II carrying exosomes from antigen presenting cells. Another focus of our research group is the role of prostasomes, which are prostate epithelial cell derived exosomes found in semen.