Identification of Annexin 1 as a Novel Autoantigen in Acute Exacerbation of Idiopathic Pulmonary Fibrosis

根据肺上皮细胞凋亡是特发性肺间质纤维化(IPF)急性加重的关键这一假说，我们采用重组表达克隆(SEREX)技术，以II型肺泡癌(A549)细胞株为研究对象，对IPF急性加重相关抗体进行了血清学鉴定。通过对SEREX分析鉴定的重组自身抗原组抗体的调查，5种抗体被鉴定为IPE急性加重的新候选抗体。我们的研究表明，在IPE急性加重期患者的血清和BAL材料中，分别有47%和53%的患者检测到膜联蛋白1抗体。10例IPF急性加重期患者在1~3个月的序贯资料中均发现了一些相同的T细胞受体(TCR)Vbeta基因，提示部分浸润性的CD4阳性T细胞在疾病扩展过程中通过抗原驱动的刺激而共享有限的表位。从3例IPF急性加重期患者的序列资料中发现，相同的TCR Vbeta基因的每1/3互补决定区与TEPITOPE分析预测的人类白细胞抗原DR配体表位中包含的Annexin 1的N端部分高度同源。通过Western blotting分析和支气管肺泡灌洗液(BAL)中的CD4阳性T细胞反应，在这3例患者中，Annexin 1的N端部分被切割，并诱导了显著的CD4阳性T细胞的增殖反应。我们的研究表明，膜联蛋白1作为一种自身抗原，可以提高IPF急性加重期患者的抗体产生和T细胞反应，并且膜联蛋白I的N末端部分在IPF急性加重期的发病机制中可能有一定的作用。

Consistent with hypothesis that pulmonary epithelium apoptosis would be the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we carried out serological identification of antigens by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify antibodies related to acute exacerbation of IPF patients. By a survey of antibodies to the panel of recombinant autoantigens identified by SEREX analysis, five antibodies were identified as a novel candidate in acute exacerbation of IPE. Our study shows that antibody to annexin 1 was detected in 47% and 53% of the sera and BAL materials from patients with acute exacerbation of IPE. Some identical T cell receptor (TCR) Vbeta genes were identified in sequential materials during 1 to 3 months in all 10 acute exacerbation of IPF cases, suggesting that some infiltrating CD4-positive T cells shared limited epitopes expand by antigen-driven stimulation during disease extension. The each third complementarity determining region of identical TCR Vbeta genes identified in sequential materials from three acute exacerbation of IPF cases showed high homology with the N-terminal portion of annexin 1, included in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and CD4-positive T cells responses of bronchoalveolar lavage (BAL) samples, the N-terminal portion of annexin 1 was cleaved and induced marked proliferative responses of CD4-positive T cells in those three patients. Our study demonstrated that annexin 1 as an autoantigen that raises both antibody production and T cell response in patients with acute exacerbation of IPF and that N terminal portion of annexin I would have some role in the pathogenesis of acute exacerbation of IPF patients.