Abstract: This study was designed to investigate and compare the immune effect of different immunosuppressive mice models which were injected with cyclophosphamide (CTX) at different doses and adminstration times. 200 male Kunming mice aged 7 weeks were randomly divided into 5 groups, including the control group (normal saline, 0 mg/g CTX), groups injected with low dose (0.04 mg/g) and high dose (0.08 mg/g) CTX for three times, groups injected with low dose (0.10 mg/g) and high dose (0.16 mg/g) CTX for once, respectively. The mice in 3 injections groups were given intraperitoneal CTX for 3 days and the mice in the control group were given equal volume normal saline in the same way. In the single injection groups, mice were given intraperitoneal CTX injection once only on the 1st day of the experiment. All the mice were weighted every day. On the 1st, 2nd, 4th, 6th, 9th, 10th and 11th day of the experiment, 8 mice of each group were selected to test tail vein blood. On the 1st, 4th, 6th, 9th and 11th day, 8 mice of each group were executed and measured nucleated cells of femur marrow, thymus indexes and spleen indexes. The results showed that the immunosuppressive model could be established successfully at all doses. In terms of inhibition effect, 0.08 mg/g three injections had the best immunosuppression effects on white blood cells, bone marrow nucleated cells, weight gain, spleen and thymus, and the 0.16 mg/g once injection had the best immunosuppression effect on red blood cells. In terms of inhibition cycle, the duration of inhibition was different in various immune sites, the inhibition cycle of cyclophosphamide were shorter on leukocytes, bone marrow nucleated cells and spleen than that on erythrocyte and thymus. The multiple injections groups showed earlier hyperimmunity in leukocyte than once injection groups, while the effect on spleen was just on the contrary. In conclusion, different doses and adminstraion times of CTX administration had different effects on the immune status and immunosuppression cycle of different immune sites. This study could provide appropriate detection dose and time reference for different immune indexes in pharmacological experiments.

Key words: cyclophosphamide; immunosuppression; animal model preparation; drug evaluation