Parkkinen J
Department of Gynecology & Obstetrics, University Central Hospital, Helsinki, Finland.
Clin Chem. 1989 Aug;35(8):1638-43.
Structural studies of oligosaccharide chains of immunoglobulin G (IgG) in serum have revealed a specific galactosylation deficiency associated with rheumatoid arthritis (RA). Using a two-site lectin-immunofluorometric assay, I studied the interaction of IgG with immobilized lectins. Compared with control IgG, IgG purified from RA patients' sera bound up to 40-fold more strongly to immobilized Bandeiraea simplicifolia agglutinin II, a lectin that specifically binds agalacto forms of other glycoproteins. However, inhibition studies and treatment of IgG with glycosidase suggested that only a minor part of this binding was mediated by agalacto oligosaccharides of IgG. Furthermore, these IgG samples bound even more intensively to some other immobilized lectins, including Ricinus communis agglutinin (RCA). The binding to RCA was not inhibited by lactose, a hapten sugar of RCA, whereas other lectin species in solution effectively inhibited it. Compared with intact RA IgG, isolated F(ab')2 fragments displayed only low RCA-binding activity. These results indicate the existence of a carbohydrate-nondependent interaction between RA IgG and different plant lectins. With use of immobilized RCA, the lectin-immunofluorometric assay was rapid and reproducible for measuring the aberrant lectin-binding activity of IgG directly in diluted serum samples.
血清中免疫球蛋白G（IgG）寡糖链的结构研究显示，类风湿关节炎（RA）患者存在特定的半乳糖基化缺陷。我使用双位点凝集素免疫荧光测定法研究了IgG与固定化凝集素的相互作用。与对照IgG相比，从RA患者血清中纯化的IgG与固定化的巴西豆凝集素II（一种能特异性结合其他糖蛋白的无半乳糖形式的凝集素）的结合力强40倍之多。然而，抑制研究以及用糖苷酶处理IgG的结果表明，这种结合中只有一小部分是由IgG的无半乳糖寡糖介导的。此外，这些IgG样本与其他一些固定化凝集素，包括蓖麻凝集素（RCA）的结合更为强烈。RCA的半抗原糖乳糖并不能抑制与RCA的结合，而溶液中的其他凝集素则能有效抑制这种结合。与完整的RA IgG相比，分离出的F(ab')2片段仅表现出较低的RCA结合活性。这些结果表明，RA IgG与不同植物凝集素之间存在一种不依赖碳水化合物的相互作用。利用固定化的RCA，凝集素免疫荧光测定法可快速且可重复地直接测量稀释血清样本中IgG异常的凝集素结合活性。
