Objective    To investigate the induction of antitumor response and its immune mechanism of H

22

cell-derived exosomes.     Methods    Fifteen BALB/c mice were immunized by H

22

cell-derived exosomes three times at weekly intervals

then inoculated with the wild-type H

22

. Another 15 BALB/c mice that were injected with PBS were used as controls. In the 80-day observation period

the tumor growth and survival time were observed. MTT was used to determine lymphocyte proliferation and specific cytotoxicity of mice splenic cells. Immunohistochemical staining of CD4

+

and CD8

+

was performed for lymphocyte infiltr

ation in tumor tissues.     Results    Immunization with exosomes derived from H

22

delayed the tumor growth and promoted the survival rate of the mice bearing the tumor

and also induced lymphocyte proliferation and triggered strong specific cytotoxic response of spleen lymphocytes and activated CD4

+

and CD8

+

T cells.     Conclusion    Vaccination of H

22

cell-derived exosomes is effective in inducing the protective immunity. Furthermore

those exosomes have strong antitumor activities.