α-actinin is a cross-reactive renal target for pathogenic anti-DNA antibodies
α-actinin is a cross-reactive renal target for pathogenic anti-DNA antibodies
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DOI：
10.4049/jimmunol.168.6.3072
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发表时间：
2002-03-15
影响因子：
4.4
通讯作者：
Putterman, C
中科院分区：
文献类型：
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作者：
Deocharan, B;Qing, XP;Putterman, C
在系统性红斑狼疮患者中常见的抗DNA抗体被认为在狼疮性肾炎中起着重要的致病作用。抗DNA抗体可能通过与肾脏AGS发生交叉反应而导致肾脏疾病，但其身份仍不明确。为了确定致病性抗DNA抗体的靶抗原，我们对狼疮易感的MRL-LPR/LPR小鼠和带有致病性抗DNA抗体R4A的非自身免疫性BALB/c小鼠的系膜细胞裂解物进行了免疫印迹和免疫沉淀。我们发现R4A(但不是R4A的非致病抗体突变体)与细胞表面和MRL-LPR/LPR系膜细胞裂解物中表达的100 kDa蛋白结合并免疫沉淀。DNA酶处理裂解物和R4A抗体不影响结合，表明R4A与100 kDa蛋白的结合是直接的，而不是通过含有DNA的抗原桥介导的。BALB/c裂解物结合能力显著降低，提示靶器官水平的抗原表达或可获得性可能是决定狼疮性肾炎易感性的一个因素。在鉴定该100 kDa蛋白为非肌肉α-肌动蛋白后，通过免疫印迹、酶联免疫吸附试验、抑制研究和免疫荧光证实R4A与α-肌动蛋白的结合。活动性肾炎狼疮小鼠血清和肾洗脱液中均有高滴度的抗α-肌动蛋白抗体。这些结果表明，某些抗DNA抗体的肾原性可能是通过与α-肌动蛋白的交叉反应而介导的。此外，不同个体之间靶标抗原显示的差异可能是对抗DNA抗体诱导的肾脏疾病的不同易感性的基础。
Anti-DNA Abs commonly found in patients with systemic lupus erythematosus are thought to play an important pathogenic role in lupus nephritis. Anti-DNA Abs may contribute to renal disease by cross-reactivity with renal Ags, the identity of which remain elusive. To identify a target Ag for pathogenic anti-DNA Abs, we performed Western blotting and immunoprecipitations of mesangial cell lysates from the lupus-prone MRL-lpr/lpr mouse and a nonautoimmune BALB/c mouse with the pathogenic anti-DNA Ab R4A. We found that R4A (but not a nonpathogenic Ab mutant of R4A) binds to and immunoprecipitates a 100-kDa protein expressed on the cell surface and in lysates of MRL-lpr/lpr mesangial cells. DNase treatment of the lysate and of the R4A Ab did not effect binding, indicating that the binding of R4A to the 100-kDa protein was direct and not mediated by an antigenic bridge containing DNA. Binding was greatly diminished in BALB/c lysates, suggesting that Ag expression or availability at the level of the target organ may be a factor in determining susceptibility to lupus nephritis. Following identification of this 100-kDa protein as nonmuscle alpha-actinin, binding of R4A to alpha-actinin was confirmed by Western blot, ELISA, inhibition studies, and immunofluorescence. High titers of anti-alpha-actinin Abs were present in sera and kidney eluates of lupus mice with active nephritis. These results indicate that the nephritogenicity of some anti-DNA Abs may be mediated via cross-reactivity with alpha-actinin. Furthermore, variations in target Ag display between individuals may underlie differential susceptibility to anti-DNA Ab-induced renal disease.