Recent evidence indicates that artesunate has immunomodulatory properties that might be useful for treating autoimmune disease. In this study, we conducted a pilot study and explored the effect and mechanism of artesunate on the treatment of systemic lupus erythematosus using an MRL/lpr murine model. MRL/lpr mice were divided into control, cyclophosphamide (CTX) and artesunate treatment groups. Blood was collected to measure serum levels of creatinine, antinuclear antibody (ANA) and anti-double-stranded DNA (anti-dsDNA) antibody. Twenty-four-hour urine was collected to measure levels of proteinuria. The concentration of monocyte chemotactic protein-1 (MCP-1) in serum and urine was measured. The expression of MCP-1 in kidney was detected by West blot and immunohistochemistry assay, respectively. The expression of B cell activating factor (BAFF) in spleen was determined by real time-PCR and immunoblotting. We found that artesunate significantly increased the survival rate, body weight and blood leukocyte counts, and reduced the serum levels of ANA and anti-dsDNA antibody titer, 24 h urinary protein, and serum creatinine. Our results indicated that artesunate could decrease MCP-1, major pro-inflammation cytokine, in serum, urine and kidney. We also found that the level of BAFF, the major B cell activation factor, was decreased in artesunate ~reated MRL/lpr mice. Its efficacy was comparable with that of CTX in this study. Taken together, we have demonstrated that artesunate can inhibit the progression of disease and reverse the pathologic lesion of lupus nephritis. Cellular & Molecular Immunology. 2009;6(6):461-467.