Phagocytic cells engulf exosomes, process their proteins in lysosomes and present epitops in association with MHC class II molecules to CD4+ T cells [10] . To further utilize the potential of gp350+ exosomes to specifically transfer exogenous proteins to B cells, which, in turn, may activate specific T cells, we generated exosomes that carried BNRF1, the major tegument protein of EBV, either alone (BNRF1+) or together with gp350 (BNRF1+/ gp350+). We then incubated purified CD19+ B cells with these exosomes overnight and used these PBMC as stimulators for an autologous BNRF1-specific CD4+ T-cell clone. As shown in Figure 1D , B cells incubated with BNRF1+/gp350+ exosomes activated the T-cell clone in a concentration-dependent manner whereas B cells incubated with BNRF1+ exosomes did not activate the T-cell clone. This result demonstrates the potential of gp350+ exosomes to transfer immunogenic foreign proteins to B cells that then can activate specific CD4+ T lymphocytes.