On the function and heterogeneity of extracellular vesicles
Both, prokaryotic and eukaryotic cells contain the ability to communicate with cells in their environment. Classically, intercellular cell communication was thought to be mainly mediated by direct cell-cell contacts and by soluble factors including cytokines, growth factors and hormones. In 1996 Raposo and colleagues showed that intercellular communication can also be mediated by vesicles; specifically they reported that B lymphoblastoid cells release MHC class II carrying vesicles which are able to induce antigen-specific MHC class II-restricted T cell responses (1). Since then, an exponentially increasing amount of studies demonstrates the importance of extracellular vesicle (EV) mediated intercellular signaling in a huge variety of different cellular systems and organisms ranging from bacteria and yeast to plants and humans. It became evident that EV-mediated intercellular communication is essentially involved in many physiological and pathophysiological processes (2). Thus, EV-mediated intercellular communication provides a third, very complex mode of intercellular communication. Unraveling the basic principles of this novel intercellular communication system and gaining insight in its complexity will for sure have large impacts on the overall understanding of biological processes and certainly will pave the way for novel diagnostic and therapeutic approaches (2-4).