Immune complexes exposed on mast cell-derived nanovesicles amplify allergic inflammation

Extracellular vesicles (EVs) are released by different cell types in- cluding mast cells (MCs) and are involved in intercellular communication thanks to their complex cargo of bioactive molecules. Among them, exosomes represent nanovesicles (<150 nm) secreted from endosomal compartments upon their fusion with the plasma membrane. Through both constitutive and induced exocytosis, MCs release exosomes that deliver several molecules including mRNA/miRNA and subunits of the high-affinity IgE receptor (FcεRI). However, the role of MC-derived vesicles in the context of allergic reactions is still controversial. A recent study provides evidence that exosomes re- leased from unstimulated mouse bone marrow-derived mast cells (mBMMCs) bind to free IgE and decrease circulating IgE levels, thus inhibiting the allergic response. In contrast, several evidences support a positive regulatory role of MC-derived exosomes, suggesting that depending on MC activation status they can either attenuate or stimulate the inflammatory responses.