BACKGROUND: The graft versus host disease (GVHD) is the main reason for allogeneic hematopeic stem cell transplantation (allo-HSCT) failure, and oral tolerization is a newly developed treating method.OBJECTIVE: To evaluate the inhibition effect of acute GVHD induced by feeding donors with recipient splenocytes orally before allo-HSCT in a murine model and to compare the immune tolerance with immunosupression agents currently used in clinical treatment.DESIGN, TIME AND SETTING: A randomized grouping design of contrast observation was performed at the Center Laboratory of School of Medicine, Southeast University in December 2008.MATERIALS: The male C57BL/6J(H-2~b) mice were served as donors, and the female (BALB/C) mice (H-2~d) were served as recipients.METHODS: The mice were prepared allo-HSCT/GVHD models, and divided into 5 groups, which received prevent scheme. ①Oral tolerization group: C57BL/6J mice were fed with BALB/C (H-2~d) splenocytes before the transplantation, with dose of 10 μg per time, 1 day interval, for 3 times. ②Rapamycin group: mice were intragastric administrated rapamycin from the 1st after transplantation with dose of 1.5 mg/(kg·d). ③Ciclosporin A+ methotrexate group: mice were intragastric administrated ciclosporin A with 1.5 mg/(kg·d), increased to 5 mg/(kg·d) when mice were recovered the gastrointestinal function, and received intragastric administrated 0.4 mg/(kg·d) methotrexate at days 1, 3, 6 and 11 after transplantation. ④Blank control group: no medication after transplantation. ⑤Irradiation group: mice were received no transplantation.MAIN OUTCOME MEASURES: The presence of GVHD after allo-HSCT, and the difference of immune tolerance index.RESULTS: Typical GVHD symptoms occurred in all mice after transplantation. In the blank control group, most mice dead at days 14-18 and the mortality was nearly 100%. Compared to the blank control group, the symptoms were significantly ameliorated and the median survival times were extended in the other 3 transplantation groups (P < 0.05). The pathological structures in liver, intestine and skin tissue in the oral tolerization group were significantly decreased. Flow cytometry assay showed that oral tolerization significantly increased the CD4~+/CD8~+ lymphocyte ratio and the percentage of the CD4~+CD25~+ cells.Oral tolerization also induced the decrease of GVHD-related cytokine level. The MTT results also showed that the immunologic tolerance in the oral tolerization group was significantly enhanced and the proliferation of lymphocyte was suppressed.CONCLUSION: Oral tolerization has obviously inhibitory effect towards GVHD after allo-HSCT, its exact mechanism may be due to the suppressing the proliferation of lymphocyte and increase the immunologic tolerance in recipients. Compared to the widely used immunosuppressive drugs, oral tolerization exhibits strong ability in ameliorating GVHD.