Streicher J, Fabian B, Herkner K, Pointner H, Bayer P M
Department of Anatomy, University of Vienna, Austria.
J Clin Lab Anal. 1998;12(1):54-9. doi: 10.1002/(sici)1098-2825(1998)12:1<54::aid-jcla9>3.0.co;2-j.
Antibodies to neutrophil cytoplasmic antigens (ANCA) targeted toward granule enzymes have been recognized as a valuable diagnostic tool in the detection of Wegener's granulomatosis and systemic vasculitides. However, the most commonly used method of detection, the indirect immunofluorescence assay, is prone to false-positive results due to antibodies of different pathological significance either targeted to, or cross-reacting with, similarly distributed epitopes. Using double immunofluorescence, the present study demonstrates that anticytokeratin antibodies are able to produce false-positive C-ANCA immunofluorescence assays. In addition, a case of natural appearance of cytokeratin-reactive antibodies causing a false-positive "pseudo-ANCA" staining pattern in a patient presenting with sepsis is reported. Since the expression of cytokeratins is almost exclusively confined to epithelial cells, the most plausible explanation for both phenomena is a crossreaction of anticytokeratin antibodies with granule associated epitopes. Due to the natural appearance of anticytokeratin antibodies in association with a variety of other pathologic entities, it is of crucial importance for the diagnostic significance of the C-ANCA immunofluorescence assay to exclude anticytokeratin caused false-positive results. It is shown that supplementary indirect immunofluorescence tests performed on cultured human epithelial cells readily distinguish anticytokeratin caused "pseudo-ANCA" from true C-ANCA.
针对颗粒酶的抗中性粒细胞胞浆抗原（ANCA）抗体已被公认为是检测韦格纳肉芽肿和系统性血管炎的一种有价值的诊断工具。然而，最常用的检测方法——间接免疫荧光法，由于具有不同病理意义的抗体靶向或交叉反应于分布相似的表位，容易出现假阳性结果。本研究通过双重免疫荧光法证明，抗细胞角蛋白抗体能够产生假阳性的C-ANCA免疫荧光检测结果。此外，还报告了1例在脓毒症患者中自然出现的细胞角蛋白反应性抗体导致假阳性“假ANCA”染色模式的病例。由于细胞角蛋白的表达几乎仅局限于上皮细胞，对这两种现象最合理的解释是抗细胞角蛋白抗体与颗粒相关表位发生了交叉反应。由于抗细胞角蛋白抗体与多种其他病理实体相关的自然出现，排除抗细胞角蛋白引起的假阳性结果对于C-ANCA免疫荧光检测的诊断意义至关重要。结果表明，对培养的人上皮细胞进行补充间接免疫荧光试验，可轻易区分抗细胞角蛋白引起的“假ANCA”与真正的C-ANCA。
