['Cationized gelatin nanoparticles (GNPs) were used as carrier to improve delivery of immunostimulatory CpG oligonucleotides (CpG ODN) both in vitro and in vivo.', 'Uptake of CpG ODN-loaded cationized gelatin nanoparticles (CpG-GNPs) into murine myeloid dendritic cells (DCs) and their respective immunostimulatory activity was monitored. In vivo, induction of cytokine secretion by CpG-GNPs was measured. For experiments on primary human cells, prototypes of the three CpG ODN classes were adsorbed onto GNPs. Uptake and induction of proinflammatory cytokines were assessed in human plasmacytoid DCs and B cells, the only existing human target cells for CpG ODN.', 'In the murine system, gelatin nanoparticle formulations enhanced the uptake and immunostimulatory activity of CpG ODN both in vitro and in vivo. Furthermore, delivery by cationized gelatin nanoparticles of CpG ODN of the classes B and C to primary human plasmacytoid DCs increased production of IFN-alpha, a key cytokine in the driving of both the innate and adaptive immune responses.'] Does delivery by cationic gelatin nanoparticles strongly increase the immunostimulatory effects of CpG oligonucleotides?