In order to verify whether p-nitrophenylalanine-containing BAFF vaccine can be used as a candidate molecule for the treatment of autoimmune diseases with BAFF over-expression,a soluble mutant of B cell activating factor belonging to the TNF Family (smBAFF) and its pNO2Phe mutant(pNO2Phe65smBAFF),which site specific incorporated pNO2Phe at position 65 of smBAFF,were expressed and purified.In order to evaluate the feasibility of using pNO2Phe65 smBAFF to treat BAFF-over-expressed autoimmune diseases,we investigate its Lymphocyte-stimulating capacity,immunogenicity and inhibitory effect of serum on biological activity of natural BAFF.The pharmacological activity of pNO2Phe65 smBAFF was evaluated using a cGVHD(graft-versus-host disease) induced SLE mouse model.Results indicated that pNO2Phe65 smBAFF,could bind to mouse lymphocytes but could not promote the proliferation of mouse lymphocytes.Moreover,the incorporation of pNO2Phe significantly increased the immunogenicity and induced cross-antibody,which can inhibit the biological activity of natural BAFF.In cGVHD induced SLE mouse model,pNO2Phe65 smBAFF can significantly reduce the symptoms of the disease and play a therapeutic role.Therefore,pNO2Phe65 smBAFF can be used as a candidate molecule for the treatment of autoimmune diseases with BAFF over-expression.