We describe a method of detecting a therapeutic exosome, the method comprising detecting an activity of an exosome. The activity may be selected from the group consisting of: (a) immunodulatory activity； (b) complement inhibition activity； (c) proteasome activity； (d) glycolytic enzyme activity； (e) anti-oxidative activity； (f) extracellular matrix (ECM) modifying activity； (g) NT5E (CD73) ecto-5'-ectonucleotidase activity； (h) ion homeostasis activity； and (i) chaperone activity. If the exosome is detected as having one or more such activities, the exosome is likely to comprise a therapeutic exosome having therapeutic activity.
