AIM:To investigate the potential role of Active Chinese mistletoe lectin-55 (ACML-55) in tumor immune surveillance.METHODS:In this study,an experimental model was established by hypodermic inoculating the colon cancer cell line CT26 (5×105 cells) into BALB/c mice.The experimental treatment was orally administered with ACML-55 or PBS,followed by the inoculation of colon cancer cell line CT26.Intracellular cytokine staining was used to detect IFN-y production by tumor antigen specific CD8+ T cells.FACS analysis was employed to profile composition and activation of CD4+,CD8+,γδ T and NK cells.RESULTS:Our results showed,compared to PBS treated mice,ACML-55 treatment significantly delayed colon cancer development in colon cancer-bearing Balb/c mice in vivo.Treatment with ACML-55 enhanced both Ag specific activation and proliferation of CD4+ and CD8+ T cells,and increased the number of tumor Ag specific CD8+ T cells,it was more important to increase the frequency of tumor Ag specific IFN-γ producing-CD8+ T cells.Interestingly,ACML-55 treatment also showed increased cell number of NK,and γδT cells,indicating the role of ACML-55 in activation of innate lymphooltes.CONCLUSION:Our results demonstrate that ACML-55therapy can enhance function in immune surveillance in colon cancer-bearing mice through regulating both innate and adaptive immune responses.