Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a large production of autoantibodies and deficient clearance of cellular waste. The disease typically oscillates between episodes of elevated disease activity and quiescent disease. C-reactive protein (CRP) is a pentameric acute-phase protein usually reflecting inflammation and tissue damage. However, despite increased inflammation and elevated interleukin-6, the levels of CRP typically remain low or only slightly raised in SLE. Under certain conditions, pentameric CRP (pCRP) can dissociate into its monomeric isoform (mCRP), which mainly has been ascribed pro-inflammatory properties. The present study aims to investigate the potential relationship between pCRP and mCRP, respectively, with disease activity and clinical features of SLE. The levels of pCRP and mCRP were measured, by turbidimetry (high-sensitive) and sandwich enzyme-linked immunosorbent assay (ELISA) respectively, in serum samples from 160 patients with SLE and 30 patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Twenty-two of the SLE cases were selected for analysis at two time-points; quiescent disease and active disease. The two CRP isoforms were evaluated in relation to disease activity and clinical features in the two diseases. Levels of pCRP and mCRP were significantly lower in SLE than AAV (p < 0.001) and the ratio of mCRP/pCRP was higher in SLE compared to AAV. The mCRP/pCRP ratio was higher for patients in remission and able to significantly separate between active/quiescent disease in paired, but not in non-paired, samples from patients with SLE. Significant correlations were observed with SLICC/ACR damage index for pCRP levels as well as inversely with the mCRP/pCRP ratio. Lower mCRP levels associated with malar rash. As the interrelationship between the two isoforms appear to (a) discriminate between quiescent and active SLE and (b) differ between SLE and AAV, our data indicates that the two CRP isoforms could exert contrasting immunological effects and/or reflect different milieus. Given the biological effects of mCRP, it is possible that altered levels may indicate increased opsonization of immune complexes and apoptotic debris, and thereby prevent their deposition outside the reticuloendothelial system and manifestations such as lupus nephritis and lupus-related skin disease.

中文翻译：

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C反应蛋白亚型与系统性红斑狼疮表型和疾病活动的关联

系统性红斑狼疮 (SLE) 是一种自身免疫性疾病，其特征是自身抗体大量产生和细胞废物清除不足。该疾病通常在疾病活动性升高和疾病静止期之间波动。C 反应蛋白 (CRP) 是一种五聚体急性期蛋白，通常反映炎症和组织损伤。然而，尽管炎症增加和白细胞介素 6 升高，但 SLE 中 CRP 水平通常保持低水平或仅略微升高。在某些条件下，五聚体 CRP (pCRP) 可以解离成单体异构体 (mCRP)，这主要归因于促炎特性。本研究旨在分别研究 pCRP 和 mCRP 与 SLE 的疾病活动和临床特征之间的潜在关系。分别通过比浊法（高灵敏度）和夹心酶联免疫吸附试验（ELISA）测定了 160 名 SLE 患者和 30 名抗中性粒细胞胞浆抗体相关血管炎（AAV）患者的血清样本中 pCRP 和 mCRP 的水平。在两个时间点选择了 22 个 SLE 病例进行分析；静止病和活动病。评估了两种 CRP 同种型与两种疾病的疾病活动性和临床特征的关系。SLE 患者的 pCRP 和 mCRP 水平显着低于 AAV（p < 0.001），并且 SLE 患者的 mCRP/pCRP 比值高于 AAV。缓解期患者的 mCRP/pCRP 比率较高，并且能够显着区分 SLE 患者的配对样本中的活动/静止疾病，但在非配对样本中则不然。pCRP 水平与 SLICC/ACR 损伤指数显着相关，与 mCRP/pCRP 比率呈负相关。与颧骨皮疹相关的 mCRP 水平降低。由于两种亚型之间的相互关系似乎（a）区分静止和活动 SLE 和（b）SLE 和 AAV 之间的差异，我们的数据表明两种 CRP 亚型可以发挥对比免疫学作用和/或反映不同的环境。鉴于 mCRP 的生物学效应，改变的水平可能表明免疫复合物和凋亡碎片的调理作用增加，从而防止它们在网状内皮系统外沉积以及狼疮肾炎和狼疮相关皮肤病等表现。与颧骨皮疹相关的 mCRP 水平降低。由于两种亚型之间的相互关系似乎（a）区分静止和活动 SLE 和（b）SLE 和 AAV 之间的差异，我们的数据表明两种 CRP 亚型可以发挥对比免疫学作用和/或反映不同的环境。鉴于 mCRP 的生物学效应，改变的水平可能表明免疫复合物和凋亡碎片的调理作用增加，从而防止它们在网状内皮系统外沉积以及狼疮性肾炎和狼疮相关皮肤病等表现。与颧骨皮疹相关的 mCRP 水平降低。由于两种亚型之间的相互关系似乎（a）区分静止和活动 SLE 和（b）SLE 和 AAV 之间的差异，我们的数据表明两种 CRP 亚型可以发挥对比免疫学作用和/或反映不同的环境。鉴于 mCRP 的生物学效应，改变的水平可能表明免疫复合物和凋亡碎片的调理作用增加，从而防止它们在网状内皮系统外沉积以及狼疮性肾炎和狼疮相关皮肤病等表现。我们的数据表明，这两种 CRP 亚型可以发挥不同的免疫效应和/或反映不同的环境。鉴于 mCRP 的生物学效应，改变的水平可能表明免疫复合物和凋亡碎片的调理作用增加，从而防止它们在网状内皮系统外沉积以及狼疮肾炎和狼疮相关皮肤病等表现。我们的数据表明，这两种 CRP 亚型可以发挥不同的免疫效应和/或反映不同的环境。鉴于 mCRP 的生物学效应，改变的水平可能表明免疫复合物和凋亡碎片的调理作用增加，从而防止它们在网状内皮系统外沉积以及狼疮肾炎和狼疮相关皮肤病等表现。