Autoantibodies against human calpastatin in rheumatoid arthritis: epitope mapping and analysis of patient sera.
Autoantibodies against human calpastatin in rheumatoid arthritis: epitope mapping and analysis of patient sera.
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类风湿性关节炎中针对人钙蛋白酶抑制剂的自身抗体：表位作图和患者血清分析。
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
G. Schmitz
中科院分区：
文献类型：
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作者：
K. Lackner;U. Schlosser;B. Lang;G. Schmitz
最近有报道称，抗钙调蛋白自身抗体在类风湿关节炎(RA)患者血清中非常普遍。用最新建立的酶联免疫吸附试验(EL ISA)检测45例RA患者血清中抗Calastatin自身抗体时，仅有4例(8.9%)阳性，与正常对照组无显著差异。由于该酶联免疫吸附试验是基于一种合成肽，该合成肽含有与固相结合的C-端27个氨基酸的钙调蛋白，所以这种阴性结果可能是使用了小的抗原所致。因此，我们利用RA患者和健康人的血清，对Calastatin中的自身抗体表位进行了系统分析。制备含Calastatin片段或完整蛋白的重组融合蛋白，并用Western blotts对血清进行分析。在N末端部分(氨基酸1-369)，至少存在两个主要表位，免疫印迹分析显示65%的正常血清和76%的RA血清对这两个表位具有反应性。这些表位对临床诊断没有用处。45份RA血清中只有5份(11.1%)与Calastatin的C末端部分(氨基酸363-708)发生反应，而52份对照血清中有4份(7.7%)表现出反应性。5份RA血清中有3份和4份对照血清中有2份有针对钙调蛋白C端27个氨基酸的自身抗体。这三份患者血清在酶联免疫吸附试验中已呈阳性。第4例ELISA阳性患者为Western印迹阴性。类风湿性关节炎患者组与对照组之间差异无统计学意义。当分析了4例抗钙调蛋白羧基末端自身抗体的患者的临床特征时，发现这4例患者的C反应蛋白均显著升高(>；50 mg/L)。这一观察结果可能表明，在疾病较活跃的类风湿关节炎患者中发现了钙调蛋白自身抗体。因此，虽然大多数类风湿性关节炎患者的钙调蛋白自身抗体的患病率没有增加，但不能确定地排除一小部分亚群可能以针对钙调蛋白C末端的自身抗体为特征。
Autoantibodies against calpastatin have recently been described to be highly prevalent in sera of patients with rheumatoid arthritis (RA). When the sera of 45 patients with RA were analysed for autoantibodies against calpastatin by a newly developed enzyme-linked immunosorbent assay (ELISA), only four sera (8.9%) tested positive, which is not significantly different from the frequency observed in healthy controls. Since the ELISA is based on a synthetic peptide containing the C-terminal 27 amino acids of calpastatin bound to the solid phase, this negative result might be the consequence of the small antigen used. Therefore, a systematic analysis of the epitopes for autoantibodies in calpastatin was performed using sera from RA patients and healthy individuals. Recombinant fusion proteins containing fragments of calpastatin or the complete protein were produced and sera analysed by Western blots. In the N-terminal portion (amino acids 1-369), at least two major epitopes exist, against which 65% of normal sera as well as 76% of RA sera show reactivity in Western blot assays. These epitopes are not useful for clinical diagnostics. Only five out of 45 (11.1%) RA sera reacted against the C-terminal portion (amino acids 363-708) of calpastatin, while four out of 52 (7.7%) control sera showed reactivity. Three of the five RA sera and two out of four control sera had autoantibodies against the C-terminal 27 amino acids of calpastatin. These three patient sera had already been tested positive in the ELISA. The fourth patient positive in the ELISA was Western blot negative. The differences between the group of RA patients and controls are not statistically significant. When the clinical characteristics of the four patients with autoantibodies against the carboxyl end of calpastatin were analysed, it became apparent that all four had significantly elevated C-reactive protein (>50 mg/l). This observation might indicate that calpastatin autoantibodies are found in RA patients with more active disease. Thus, while the majority of RA patients do not have an increased prevalence of calpastatin autoantibodies, it cannot be ruled out definitively that a small subgroup may be characterized by autoantibodies to the C-terminus of calpastatin.