Circulating autoantibody to type II alveolar pneumocytes in patients with idiopathic interstial pneumonia

本文报道隐源性纤维性肺泡炎患者存在肺蛋白自身抗体。为了评价这种自身抗体的作用，我们在29例特发性间质性肺炎（IIP）患者中检测了这种自身抗体，并比较了有或无这种自身抗体的患者的临床特征。用亲和层析法从患者血浆中纯化血清IqG。用丙酮固定人A549 II型肺泡细胞的Cytospin制备物，并用蛋白A和正常人血清封闭。用纯化的病人IgG孵育，洗涤后，用蛋白A-碱性磷酸酶偶联物孵育，用Vector Red显色。29例患者中有10例（34 g）血浆呈阳性染色。自身抗体阳性组血清IgG、IgE水平显著高于阴性组，支气管肺泡灌洗液中嗜酸性粒细胞计数显著低于阴性组，年龄、性别、肺功能等实验室指标无显著性差异。免疫组化染色显示，共聚焦激光扫描显微镜下，抗体定位于肺泡Ⅱ型细胞的胞浆内。抗体阳性组患者血清IgG经Dott印迹法检测，A549细胞胞浆部分也呈阳性。结果提示，约1/3的IIP患者体内可检测到抗Ⅱ型肺泡细胞自身抗体，并定位于肺泡Ⅱ型细胞胞浆内，这些患者可能存在不同的肺部炎症模式。

The existence of circulating autoantibody to lung proteins in patients with cryptogenic fibrosing alveolitis was reported. To evaluate the role of this autoantibody, we attemted to detect this in 29 patients with idiopathic interstitial pneumonia (IIP), and compared the clinical characteristics between the patients with or without this autoantibody. Serum IqG was purified from plasma of the patients by affinity chromatoqraphy. Cytospin preparations of human A549 type II alveolar cells were fixed by acetone and blocked with protein A and normal human serum. They were incubated with purified patient's IgG.After washing, they were incubated with protein A-alkalinephosphatase conjugate, and visualized by Vector Red. plasma from 10 of 29 patients (34g) gave positive staining. Serm IgG and IgE levels were significantly higher in patients with autoantibody than those without it. Number of eosinophils in bronchoalveolar lavage fiuids were significantly lower in patients with autoantibody than those without it. There were no significant differences in age, sex, pulmonary functions and other laboratory data. Immunohistochemical staining of lung tissues revealed the localization of the autoantibody in cytoplasm of type II alveolar pneumocyte by using confocal laser scanning microscope. Dott blotting with purified serum IgG from patients with positive antibody group also showed positive staning in cytosol fraction of A549 cells. These results suggest that circulating autoantibody to type II alveolar cells could be detected in about 1/3 of the patients with IIP,which localized to cytosol of type II alveolar pneumocyte, and these patients may have different mode of pulmonary inflammation.