"It can be thrown over the wall, it can be brought in by visitors - secreted in their bodily orifices - or in children's nappies… staff corruption is an issue in many prisons," he added.

The team also identified several genes that help regulate EV-DNA packaging, and found that when one of these, APAF1, was absent, the amount of EV-DNA secreted by tumor cells was sharply reduced.

Beta cells are isolated from a donor pancreas, purified and delivered to the patient's liver, where they can take up residence and begin secreting insulin.

For example, if a human disease involves a deficiency of secreted proteins, then bioengineers could hijack the system to deliver artificial snoRNAs to increase secretion of that protein.

In particular, goblet cells -- cup-shaped cells that secrete mucus -- expressed those genes only in the presence of ILC2s, a kind of immune cell.