Exosomes content

Dendritic cells, depending on their degree of maturation, may or may not secrete the contents of the MVE. Rather than being released in the extracellular medium, intralumenal vesicles contained in MIIC compartment can fuse back with the limiting membrane of the multivesicular structure (Kleijmeer et al. 2001). The tetraspanins CD9 and CD81, which have been shown to be involved in cell fusion regulation (Rubinstein etal. 2006), could participate in this cellular event. Moreover, this process of back fusion is related to activation and maturation of dendritic cells. As a consequence, the intracellular exosomal pool of MHC class II molecules (>50% of the total pool in immature DC) rapidly redistributes to the plasma membrane (Kleijmeer et al. 2001). Thus in both cases, dendritic cells and red cells use exosomes to remodel their surface as a function of their differentiation requirements. 

Exosomes are 30-120 nm in diameter membrane-bound vesicles sharing similar topology to the plasma membrane. Their contents include mRNA and miRNA. and a vast array of... 

The bioactivity of exosomes resides not only in their protein and RNA contents but also in their lipid molecules. The proteolipidic composition of a given type of exosome can change in time. This observation further supports the view that different pathways for the production of exosomes may be activated sequentially during the course of maturation of a reticulocyte. The maturation of reticulocytes into erythrocytes is the final step of erythropoiesis. Western blot analyses confirmed the prominence of class I MHC heavy chains and Hsc70 in Day 2 exosomes, whereas Hsp90 and proteasome core proteins were detected almost exclusively in Day 7 exosomes (Carayon et al., 2011). 

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