Objective:To explore the potential serum biomarkers of patients with lupus nephritis(LN)by using two-dimensional electrophoresis combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF/TOF MS),so as to lay the foundation for illuminating pathogenesis.Methods:A total of 40 LN patients were divided into two groups,the active LN group and the inactive LN group,with 20 in each.In addition,20 IgA nephritis patients and 20 healthy volunteers were enrolled as IgAN group and healthy control group.Two-dimensional gel electrophoresis was used to separate and analyze the serum proteins,and MALDI-TOF/TOF MS was applied to the identification of the differentially expressed pro-teins.Results:A total of fifty differentially expressed proteins were identified.Compared with that in healthy control group,23 differentially expressed proteins were discovered in active LN group and inactive LN group,among which,8 proteins were up-regulated and 1 5 proteins were down-regulated.And 1 8 differentially expressed proteins,compared with IgA nephritis group, were found in active LN group and inactive LN group,including 13 up-regulated proteins and 5 down-regulated proteins.Fur-thermore,the number of up-regulated and down-regulated proteins in active LN group,compared with those in inactive LN group,were 4 and 5,respectively.Among the 50 identified differentially expressed proteins,the expression of serum amyloid protein A(SAA )in active LN group was higher than that in the other groups while the expression of complement component C4A in active LN group was lower than that in the other groups.And the expression of chain B (solution structure of double super helix model)in the inactive LN group was higher than that in the other groups.Compared with that in healthy control group,the expression of vitamin D-binding protein isoform 1 precursor,chain A(crystal structure of uncomplexed vitamin D-binding protein)and chain B (a covalent dimer of transthyretin that affects the amyloid pathway)was up-regulated in both ac-tive LN group and inactive LN group,while the expression of the vitronectin precursor,ficolin-2 isoform a precursor and chain A (crystal structure of the catalytic domain of human complement C1 s protease)was down-regulated.Compared with that in IgA nephritis group,the expression of lipoprotein CIII and vitronectin precursor was up-regulated in both active LN group and inactive LN group.Conclusions:Combination of two-dimensional gel electrophoresis and MALDI-TOF/TOF MS is effective for screening and identification of differentially expressed proteins in serum from LN patients.These differentially expressed pro-teins could be used as biomarkers for noninvasive diagnosis and evaluation of LN.Further study on these proteins would be conducive to understanding the pathogenesis of LN.