Dieterich W, Trapp D, Esslinger B, Leidenberger M, Piper J, Hahn E, Schuppan D
Department of Medicine I, University of Erlangen-Nuernberg, Germany.
Gut. 2003 Nov;52(11):1562-6. doi: 10.1136/gut.52.11.1562.
Coeliac disease (CD) is characterised by the presence of autoantibodies against tissue transglutaminase (tTG), the endomysial autoantigen. This study was performed to determine the effect of purified autoantibodies on the enzymatic activity of tTG.
Total IgA and IgG class antibodies and purified anti-tTG autoantibodies were isolated from sera of untreated patients with CD and controls. The inhibitory capacity of the antibodies on tTG activity was checked by a fluorometric assay based on the incorporation of monodansyl cadaverine into casein and by tTG-catalysed cross linking of biotinylated cadaverine to gliadin.
The enriched IgA and IgG fractions of five patients with CD and three controls resulted in no significantly different inhibition of enzymatic activity. In contrast, the use of affinity purified anti-tTG autoantibodies of 12 patients with CD led to a dose dependent reduction of tTG activity, compared to control immunoglobulins (n=6). However, the remaining activity was sufficient for cross linking of cadaverine into gliadin, and enzymatic tTG activity was only blocked completely by high concentrations of a monoclonal antibody, which is directed to the active centre of tTG.
Despite a partial inhibitory effect of isolated anti-tTG autoantibodies from patients with CD, residual enzymatic activity remains sufficiently high to cast doubt on their in vivo relevance.
乳糜泻（CD）的特征是存在针对组织转谷氨酰胺酶（tTG）（一种肌内膜自身抗原）的自身抗体。本研究旨在确定纯化的自身抗体对tTG酶活性的影响。
从未经治疗的CD患者和对照者的血清中分离出总IgA和IgG类抗体以及纯化的抗tTG自身抗体。通过基于单丹磺酰尸胺掺入酪蛋白的荧光测定法以及tTG催化的生物素化尸胺与麦醇溶蛋白的交联来检测抗体对tTG活性的抑制能力。
5例CD患者和3例对照者的富集IgA和IgG组分对酶活性的抑制无显著差异。相比之下，与对照免疫球蛋白（n = 6）相比，使用12例CD患者的亲和纯化抗tTG自身抗体导致tTG活性呈剂量依赖性降低。然而，剩余的活性足以使尸胺与麦醇溶蛋白交联，并且只有高浓度的针对tTG活性中心的单克隆抗体才能完全阻断tTG的酶活性。
尽管从CD患者中分离出的抗tTG自身抗体有部分抑制作用，但残留的酶活性仍然足够高，使其体内相关性受到质疑。
