Exosomes are nano-vesicles shed into the extracellular space from endosomes. They act as intermediaries for intercellular communication by providing a sample of the contents of the source cell to a target cell. Exosomes have been reported to have a role in diverse settings, such as cancer, malaria infection and gestational tolerance. In this issue, Skogberg et al. provide evidence that exosomes from the thymic epithelium may have an important role in negative selection, potentially broadening the availability of peripheral self-antigens to other antigen-presenting cells (APCs).
A unique property of thymic epithelial cells (TECs) is their broad expression of over 19 000 genes regulated, in part, by the autoimmune regulator (AIRE). Defects in this process in mice and humans lead to impaired tolerance and autoimmune disease that targets multiple tissue. Therefore, a conundrum in the field has been how central tolerance to individual TRA is so extensive when so few TECs express them. (read more…)