As a proof of concept, we show that tailored gp350+ exosomes can co-transfer functional CD154 as immune accessory molecule to B-CLL cells, which are subsequently stimulated to express surface molecules like CD54, CD80, CD86 and CD95 and stimulate autologous tumor- and EBV-specific T cells. The gene discussed is CD40LG; the disease is B-cell chronic lymphocytic leukemia.