Objective:To observe the expression and localization of CD4+T cell and its co-stimulator factors（CSF） in the mucosa of ulcerative colitis（UC）rat with damp-and-heat syndrome

and to explore the conceivable immunology mechanism of Huangqin decoction to treat the disease.Method:The model of UC rats with damp-andheat syndrome were established by giving the high sugar fat food and put into an artificial bioclimatic chamber

resulting in damp-and-heat body constitution and then clysmaed with 2

4

6-trinitro-benzene-sulfonic acid.After that the rats were divided into the model group

Huangqin decoction group and mesalazine group.SP of Immunohistochemistry was used to determine the expression and localization of CD4+T cell

CD28

CD152

OX40 T cell subsets in mucosa.The above antigens were tested using Image pro plus 6.0

an image acquisition system based on the digital camera and software

by analyzing their mean density.Result:Compared with the normal rats（n=15）

the expression of CD4 + T cell

CD28

CD152 and OX40 T cell subsets in mucosa increased for the model rats（n=38 in total and P<0.05）

and targeted to distribution in the submucosa and inherent layers.Compared with the model control group（n=12）

CD4+T cell

CD28 and OX40 in both Huangqin decoction（n=13） and mesalazine group（n=12） decreased（P<0.05）

but CD152 did not

kept in the level of model gruop.There was no statistical difference of the level of the above antigens between Huangqin decoction（n=13） and mesalazine group（n=12

P>0.05）.Conclusion: It is possible that the expression of the CSF for CD4+T cells maybe the immunology mechanism of the decotion to treat UC.