Galazka M W, Keil L B, Kohles J, Petersheim M, DeBari V A
Department of Chemistry, Seton Hall University, South Orange, NJ 07079, USA.
Ann Clin Lab Sci. 1998 May-Jun;28(3):153-9.
beta 2glycoprotein I (beta 2GPI) is a phospholipid-binding protein of the coagulation system. In patients with the antiphospholipid syndrome (APS), antibodies to beta 2GPI contribute to the population of "antiphospholipid antibodies" measured in the anticardiolipin antibody (aCL) assay. In fact, both IgG and IgM antibodies from patients with APS bind beta 2GPI in the absence of anionic phospholipids if the antigen is bound to a suitable surface, i.e., one which exposes the epitope. The binding of IgA was studied from patients with APS, using an enzyme-linked immunosorbent assay (ELISA), and significantly higher binding of IgA was observed from 39 patients compared to a control group of 50 healthy individuals (p < 0.0001). Moreover, 15 out of 39 APS subjects (38 percent) exhibited binding greater than 5 standard deviations (SD) above the mean of the control group. All 39 APS patients had elevated IgG anti-beta 2GPI; however, depletion of IgG from two APS sera diminished, rather than enhanced, binding of IgA. Pre-incubation with purified IgG from a subject with APS led to inhibition of IgA binding at inhibitor levels > 125 micrograms IgG/well. These data demonstrate that patients with APS have IgA anti-beta 2GPI autoantibodies and that the epitope(s) which are recognized by these antibodies can be presented in the absence of cardiolipin or other anionic phospholipids.
β2糖蛋白I（β2GPI）是凝血系统中的一种磷脂结合蛋白。在抗磷脂综合征（APS）患者中，抗β2GPI抗体是抗心磷脂抗体（aCL）检测中所测定的“抗磷脂抗体”的组成部分。事实上，如果抗原结合到合适的表面，即暴露表位的表面，APS患者的IgG和IgM抗体在无阴离子磷脂的情况下均可结合β2GPI。采用酶联免疫吸附测定（ELISA）研究了APS患者的IgA结合情况，结果显示，与50名健康个体组成的对照组相比，39例患者的IgA结合显著更高（p < 0.0001）。此外，39例APS受试者中有15例（38%）的结合水平高于对照组平均值5个标准差（SD）以上。所有39例APS患者的IgG抗β2GPI均升高；然而，去除两份APS血清中的IgG后，IgA的结合减少而非增强。用APS受试者的纯化IgG预孵育导致在抑制剂水平> 125微克IgG/孔时抑制IgA结合。这些数据表明，APS患者存在IgA抗β2GPI自身抗体，且这些抗体识别的表位在无心磷脂或其他阴离子磷脂的情况下也可呈现。
