Extracellular vesicles: important players in immune homeostasis
Exosomes are nano-sized extracellular vesicles (EVs) released from cells that act as mechanisms of cellular communication both between the surrounding cells that make up the cellular mileu and cells at distant locations in the body (1). Not only do they play many different roles in normal physiology, exosomes have been shown to exacerbate the progression of numerous different pathologies (1), including playing dual roles in immune regulation (2). Exosomes activate immunity by way of transferring antigens and promoting activation of antigen presenting cells. They also have been shown to participate in immunosuppression under different circumstances (2). For example, exosomes released from intestinal epithelial cells have the ability to suppress global immune function and are critical players in immune evasion in tumor models. Additionally, exosomes released by mesenchymal stem cells suppress immune function in various animal models of disease and tissue damage when used for therapeutic cellular regeneration (2).