Fantastic IgA plasma cells and where to find them.

IgA is produced in large quantities at mucosal surfaces by IgA plasma cells (PC), protecting the host from pathogens, and restricting commensal access to the subepithelium. It is becoming increasingly appreciated that IgA PC are not constrained to mucosal barrier sites. Rather, IgA PC may leave these sites where they provide both host defense and immunoregulatory function. In this review, we will outline how IgA PC are generated within the mucosae and how they subsequently migrate to their "classical" effector site, the gut lamina propria. From there we provide examples of IgA PC displacement from the gut to other parts of the body, referencing examples during homeostasis and inflammation. Lastly, we will speculate on mechanisms of IgA PC displacement to other tissues. Our aim is to provide a new perspective on how IgA PC are truly fantastic beasts of the immune system and identify new places to find them.