AIM: To investigate the effect of bone marrow-derived monocytes transfected with RNA of CT-26 (a cell line of mouse colon carcinoma) on antitumor immunity. METHODS: Mouse bone marrow-derived monocytes were incubated with mouse granulocyte macrophage colony stimulating factor (mGM-CSF) in vitro, and the purity of monocytes was detected by flow cytometry. Total RNA of CT-26 was obtained by TRIzol’s process, and monocytes were transfected by TransMessenger in vitro. The activity of cytotoxic T lymphocytes (CTL) in vivo was estimated by the modified lactate dehydrogenase (LDH) release assay. Changes of tumor size in mice and animal’s survival time were observed in different groups. RESULTS: Monocytes from mouse bone marrow were successfully incubated, and the positive rate of CDllb was over 95%. Vaccination of the monocytes transfected with total RNA induced a high level of specific CTL activity in vivo, and made mice resistant to the subsequent challenge of parental tumor cells. In vivo effects induced by monocytes transfected with total RNA were stronger than those induced by monocytes pulsed with tumor cell lysates. CONCLUSION: Antigen presenting cells transfected with total RNA of CT-26 can present endogenous? tumor antigens, activate CTL, and effectively induce specific antitumor immunity. A: To investigate the effect of bone marrow-derived monocytes transfected with RNA of CT-26 on a cell line of mouse colon carcinoma on antitumor immunity. METHODS: Mouse bone marrow-derived monocytes were incubated with mouse granulocyte macrophage colony stimulating factor mGM-CSF) in vitro, and the purity of monocytes was detected by flow cytometry. Total RNA of CT-26 was obtained by TRIzol’s process, and monocytes were transfected by TransMessenger in vitro. The activity of cytotoxic T lymphocytes (CTL) in vivo was estimated by the modified lactate dehydrogenase (LDH) release assay. Changes of tumor size in mice and animal’s survival time were observed in different groups. RESULTS: Monocytes from mouse bone marrow were successfully incubated, and the positive rate of CD11b was over 95% Vaccination of the monocytes transfected with total RNA induced a high level of specific CTL activity in vivo, and made mice resistant to the subsequent challenge of parental tumor cells. In vivo e ffects induced by monocytes transfected with total RNA were stronger than those induced by monocytes pulsed with tumor cell lysates. CONCLUSION: Antigen presenting cells transfected with total RNA of CT-26 can present endogenous? tumor antigens, activate CTL, and effectively induce specific antitumor immunity .