Regulated release of B cell-derived exosomes: do differences in exosome release provide insight into different APC function for B cells and DC?

The induction of CD4 T(H) cell activity is a crucial component of the mammalian acquired immune response. In order to activate T(H) cells, pathogen-derived peptides are displayed on the plasma membrane of specialized cells termed APC. As well as unravelling common mechanisms in this process, considerable attention has been given to the distinct roles of the various cell types involved. In this issue of the European Journal of Immunology, a study examining the release by B cells of small vesicles termed exosomes is presented. This commentary reports that the control of exosome release from B cells appears to differ from that seen in DC. How these differences may relate to important features that differentiate the antigen presenting cell function of B cells and DC in vivo is also discussed.