van der Merwe P A, McPherson D C, Brown M H, Barclay A N, Cyster J G, Williams A F, Davis S J
MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, GB.
Eur J Immunol. 1993 Jun;23(6):1373-7. doi: 10.1002/eji.1830230628.
CD2, CD48 and CD58 are structurally similar cell adhesion-molecules forming a subset of the immunoglobulin superfamily (IgSF). In humans CD58 is a ligand for CD2 while in mice CD2 binds CD48. We constructed a soluble chimeric molecule comprising the extracellular portion of rat CD48 and domains 3 and 4 of rat CD4 (sCD48-CD4) and used it to examine whether CD2 is a ligand for CD48 in rats. sCD48-CD4-coated polystyrene Dynabeads formed rosettes on rat CD2-transfected COS-7 cells, and this rosetting was blocked by anti-CD2 (OX34) and anti-CD48 (OX45) monoclonal antibodies. We used sucrose-gradient ultracentrifugation to show that sCD48-CD4 binds, in solution, to soluble forms of rat CD2 including the single NH2-terminal IgSF domain of rat CD2 expressed in bacteria. The upper limit of the affinity of the rat CD48-CD2 interaction is 4 x 10(5) M-1, lower than the published affinity of human CD2 for CD58. These results show that rat CD48 binds CD2 on its NH2-terminal IgSF domain with a low affinity and that binding is independent of glycosylation.
CD2、CD48和CD58是结构相似的细胞粘附分子，构成免疫球蛋白超家族（IgSF）的一个亚群。在人类中，CD58是CD2的配体，而在小鼠中，CD2结合CD48。我们构建了一种可溶性嵌合分子，其包含大鼠CD48的胞外部分和大鼠CD4的结构域3和4（sCD48-CD4），并用它来检测在大鼠中CD2是否是CD48的配体。用sCD48-CD4包被的聚苯乙烯磁珠在转染了大鼠CD2的COS-7细胞上形成玫瑰花结，并且这种玫瑰花结形成被抗CD2（OX34）和抗CD48（OX45）单克隆抗体阻断。我们使用蔗糖梯度超速离心来表明sCD48-CD4在溶液中与大鼠CD2的可溶性形式结合，包括在细菌中表达的大鼠CD2的单个NH2末端IgSF结构域。大鼠CD48与CD2相互作用的亲和力上限为4×10⁵ M⁻¹，低于已发表的人类CD2对CD58的亲和力。这些结果表明大鼠CD48以低亲和力结合其NH2末端IgSF结构域上的CD2，并且这种结合不依赖于糖基化。
