[Effect of CTL on K562 cell induced by exosomes and in combination with CPG OND]

To investigate the specific anti-leukemia effect of cytotoxic T lymphocytes (CTLs) induced by dendritic cells (DCs) activated by exosomes alone or in combination with CpG ODN in vitro and the feasibility of exosomes as remedial vaccine, the DCs induced from normal volunteer PBMNCs were divided into 7 groups. Three groups of them were added with the exosomes: Kexo (exosomes derived from K562 cells) or DCexo (exosomes derived from DCs induced from K562 cells) or FTexo (exosomes derived from DCs induced from K562 cells and pulsed by freeze-thawing antigen of K562 cells) as experimental groups (Kexo, DCexo and FTexo). The other three groups were added with CPG ODN while added the exosomes (Kexo, DCexo and FTexo), and were used as experimental groups also (Kexo+CpG, DCexo+CpG and FTexo+CpG). The seventh group DCs was added with nothing as blank control. These DCs above mentioned were cultured continuously for 72 hours. The T lymphocytes were co-cultured with DCs for another 72 hours to generate CTL. Then, the killing effects of them on K562 cells were determined by MTT assay. The results showed that all experimental groups pulsed by exosomes displayed stronger killing effect, compared with control group (p<0.05). DCexo and FTexo displayed stronger killing effect too, compared with Kexo (p<0.05). CPG ODN as an adjuvant could enhance the killing effect (p<0.05). It is concluded that the special killing effect on K562 cells can be induced by exosomes, CPG ODN as an adjuvant can enhance the killing effect. Exosome is hopeful as a remedial vaccine to be used for the leukemia therapy.