| [Background and Objective] Systemic lupus erythematosus(SLE) is acommon autoimmune disease involving multi-organs and multi-systems. Kidney is one of the organs frequently involved in SLE. Amounts of immune deposits in the mesangial area could been seen pathologically in lupus nephritis(LN). Production of autoantibodies is one of the characteristic manifestations of patients with SLE. Many autoantibodies can be detected in sera of SLE patients, such as anti-nuclear antibodies(ANA), anti-double stranded DNA antibodies(anti-dsDNA) and anti-Smith antibodies(anti-Sm). The previous studies showed that the immune deposits in mesangial area of LN were mainly associated with DNA and their autoantibodies. But current researches have also comfirmed some patients with negative anti-dsDNA accompanied with pathological characterizations of LN typically; or with positive anti-dsDNA accompanied with few immune deposits containing anti-dsDNA. It was reported that many other autoantibodies excluding anti-nuclear antibodies(ANA) such as anti-neutrophil cytoplasmic autoantibodies(ANCA) and anti-endothelial autoantibodies might play a role in the pathogenesis of LN. So we hypothesize that the intrinsic components of glomerular mesangial cells might have participated in the formation of in situ immune complexes and initiation of autoimmune reactions as autoantigens.Anti-mesangial cells autoantibodies(anti-MC) which could bind to mesangial cells directly have been found in patients with primary IgA nephropathy and Henoch-Schonlein purpura. But there were no coincident reports which were capable of elucidating the pathogenesis of mesangial cells impairment mediated by anti-mesangial cells autoantibodies and their target antigens completely. Up to now, there are no widely accepted conclusions. Especially there are no reports about anti-MC autoantibodies and their target antigens in patients with lupus nephritis.The purpose of this study was to detect the anti-MC autoantibodies in sera from patients with lupus nephritis and analyze their clinical associations, meanwhile, to primarily purify and localize the target antigens.[Methods] 100 sera from LN patients proven by renal biopsy with integrateclinical and pathological data, 100 sera from normal blood-donors, 25 sera from patients with primary IgA nephropathy and 12 sera from SLE patients without nephritis were collected. Anti-mesangial cell autoantibodies were examined by cellular ELISA taking cultured human mesangial cells in vitro as antigens; their soluble proteins in non-reducing conditions were used as antigens in Western-blot to detect anti-MC, and the associations between the various anti-MC and clinical manifestations were analyzed; Then the soluble proteins of human mesangial cell line(HMCL) were primarily isolated by Mono Q anionic chromatograph at pH 7.5 in fast protein liquid chromatography (FPLC) system, and the localizations of the antigens recognized by positive LN sera were confirmed in Western-blot; HMC membrane proteins were extracted by double liquid-phase system of Dextran T-500/PEG 3350, the target antigens were identified by Western-blot analysis.[Results] (1) Cellular ELISA: the positive percentage of anti-MC in sera frompatients of LN group and SLE without nephritis group were 36% and 17%, respectively. The relative binding ratio of anti-MC in LN group and SLE without nephritis group were significantly higher than that in normal blood-donors group (0.68±0.24 vs 0.42±0.17, P<0.001; 0.65±0.15 vs 0.42±0.17, P<0.001) and primary IgA nephropathy group (0.68±0.24 vs 0.35±0.15, P<0.001; 0.65±0.15 vs 0.35±0.15, P<0.001), respectively; there was no significant difference comparing the relative binding ratio of anti-MC in LN group with that in SLE withoutnephritis group (0.68±0.24 vs 0.65±0.15, P>0.05); there was no significant difference between primary IgA nephropathy group and normal blood-donors group (0.35±0.15 vs 0.42±0.17, P>0.05). (2) Western blot: 97.9% of sera from patients with LN had anti-MC autoant... |
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