Boldt D H, Armstrong J P
J Clin Invest. 1976 Apr;57(4):1068-78. doi: 10.1172/JCI108349.
Rosette formation with unsensitized sheep erythrocytes is a characteristic of human thymus dependent lymphocytes. Release of glycopeptides from the sheep erythrocyte by trypsin reduces rosette formation. These tryptic glycopeptides inhibit rosette formation by untrypsinized sheep erythrocytes; this suggests that rosetting is mediated by erythrocyte surface glycopeptides. To investigate the molecular nature of this interaction, we examined the abilities of various model compounds to act as haptenic inhibitors of rosette formation. Inhibition is given by glycopeptides bearing oligosaccharide units rich in sialic acid, galactose, N-acetylglucosamine, and mannose linked to asparagine residues through glycosylamine bonds. Among compounds tested, fetuin glycopeptide is most effective, but human transferrin glycopeptide and human erythrocyte glycopeptide I also inhibit rosette formation. Other compounds including human erythrocyte glycopeptide II, human IgG glycopeptide, lacto-N-neotetraose, 3'- and 6'-sialyllactose show no significant inhibition. Neither sialic acid, galactose, manose, nor N-acetyl-glucosamine alone inhibits rosette formation. Stepwise degradation of fetuin glycopeptide established the galactose residues as important determinants of inhibitory activity. Fetuin glycopeptide blocks rosette formation when added to a suspension of human lymphocytes and sheep erythrocytes or when preincubated with human lymphocytes, but not when preincubated with sheep erythrocytes. Studies of the binding of [3H] fetuin glycopeptide to normal lymphocytes demonstrate 7.5 x 10(6) saturable binding sites per cell. No saturable binding of this compound to sheep erythrocyte membranes is observed. Compared to normals, lymphocytes from patients with chronic lymphatic leukemia demonstrate decreased fetuin glycopeptide binding with a mean of 0.9 x 10(6) sites per cell. This decreased binding correlates with the impaired ability of these cells to form rosettes. The data suggest that fetuin glycopeptide inhibits rosette formation by binding to the thymus-dependent cell where competition occurs with sheep erythrocytes for specific lymphocyte surface receptors.
与未致敏绵羊红细胞形成玫瑰花结是人类胸腺依赖性淋巴细胞的一个特征。胰蛋白酶从绵羊红细胞中释放糖肽会减少玫瑰花结的形成。这些胰蛋白酶处理过的糖肽会抑制未用胰蛋白酶处理的绵羊红细胞形成玫瑰花结；这表明玫瑰花结形成是由红细胞表面糖肽介导的。为了研究这种相互作用的分子本质，我们检测了各种模型化合物作为玫瑰花结形成的半抗原抑制剂的能力。富含唾液酸、半乳糖、N-乙酰葡糖胺和甘露糖的寡糖单元通过糖胺键与天冬酰胺残基相连的糖肽具有抑制作用。在所测试的化合物中，胎球蛋白糖肽最有效，但人转铁蛋白糖肽和人红细胞糖肽I也能抑制玫瑰花结的形成。其他化合物，包括人红细胞糖肽II、人IgG糖肽、乳糖-N-新四糖、3'-和6'-唾液酸乳糖均无明显抑制作用。单独的唾液酸、半乳糖、甘露糖或N-乙酰葡糖胺均不抑制玫瑰花结的形成。胎球蛋白糖肽的逐步降解确定半乳糖残基是抑制活性的重要决定因素。当将胎球蛋白糖肽添加到人淋巴细胞和绵羊红细胞的悬液中或将其与人淋巴细胞预孵育时，它会阻断玫瑰花结的形成，但与绵羊红细胞预孵育时则不会。对[3H]胎球蛋白糖肽与正常淋巴细胞结合的研究表明，每个细胞有7.5×10(6)个可饱和结合位点。未观察到该化合物与绵羊红细胞膜的可饱和结合。与正常人相比，慢性淋巴细胞白血病患者的淋巴细胞显示胎球蛋白糖肽结合减少，平均每个细胞有0.9×10(6)个位点。这种结合减少与这些细胞形成玫瑰花结的能力受损相关。数据表明，胎球蛋白糖肽通过与胸腺依赖性细胞结合来抑制玫瑰花结的形成，在该细胞中它与绵羊红细胞竞争特异性淋巴细胞表面受体。
