The present invention relates to compositions and methods for producing antigen-presenting cells, in vitro, ex vivo or in vivo. This invention relates more particularly to methods and compositions for producing dendritic cells using interleukin-15, preferably in combination with a growth factor such as GM-CSF. This invention is particularly suited for producing immature dendritic cells and activated cells from precursors, in vitro, ex vivo or in vivo. The invention also relates to compositions for implementing these methods, as well as compositions comprising antigen-presenting cells and uses thereof. Dendritic cells or membrane vesicles derived thereforom have utility in many applications, including diagnostic, therapy, vaccination, research, screening and gene delivery.