Abstract: Objective To explore the prophylaxis of dangguibuxue decoction, a traditional Chinese medicine made from Angelica sinensis and Radix astragalus, on immunosuppressed mice infected by Cryptosporidium parvum. Methods 48 BALB/c mice were randomly divided into 4 groups: normal control （A）, immunosuppressed control （B）, high dose （C）, and low dose （D）. Mice in groups B, C and D were intragastrically administered with dexamethasone （DXM） for 8 days, and in the same time mice in groups C and D were given high dose （2 g/kg） and low dose （1 g/kg） dangguibuxue decoction respectively. On the ninth day all mice in groups B, C and D were orally inoculated by 1×10 oocysts of C. parvum. The amount of oocysts in feces was examined daily since being infected. 11 days after infection, the subset of T lymphocytes in peripheral blood was analyzed with flow cytometry, sIL-2R in serum and sIgA of intestinal fluid were detected by ELISA. Pathological change of duodenum and jejunum was observed microscopically. Results Compared with the immuno-suppressed control group， there were less oocysts in feces （35.0±4.21） （P＜0.01） and lighter injury in the intestinal mucosa in mice of the high dose dangguibuxue decoction group. Both the number of CD4+ T lymphocytes （47.483±4.082） and the ratio of CD4+/CD8+ （2.271±0.378） increased, sIgA [（320.19±1.94） ng/ml] in the intestinal fluid elevated and sIL-2R [（321.34±6.66) ng/ml] in peripheral blood decreased in the high dose group, with a significant difference in comparison to the immunosuppressed group（P＜0.01）. All the above-mentioned indices in low dose dangguibuxue decoction group showed no significant difference with the immunosuppressed control group （P＞0.05）. Conclusion Administration of high dose dangguibuxue decoction plays a role of prophylaxis on the infection of C. parvum in immunosuppressed mice through improving the immune status.

Key words: angguibuxue decoction, Immunosuppression, Cryptosporidium parvum, Prophylaxis