Ianelli C J, Edson C M, Thorley-Lawson D A
Department of Pathology, Tufts University School of Medicine, Boston, MA 02111, USA.
J Immunol. 1997 Oct 15;159(8):3910-20.
CD48 is a member of the Ig superfamily with a high degree of sequence homology to CD58 (LFA-3). In rodents, CD48 is the ligand for CD2 whereas in humans, CD58 is the ligand for CD2. Despite intensive efforts, no ligand for human CD48 has been convincingly demonstrated. We now show that a ligand for human CD48 is present on epithelial cells. The ligand was detected based on the ability of epithelial cells to bind both a decameric, soluble CD48 IgM fusion protein and monomeric CD48 immobilized on plastic dishes. mAbs raised to the ligand completely block binding of CD48 to all epithelial cells tested. We further show that the cell surface proteoglycan CD44 plays an auxiliary role in the binding of epithelial cells to CD48 and that this interaction involves the glycosaminoglycan binding site of CD44. No interaction of human CD48 with CD2 was detected. This is the first clear demonstration that human CD48 can function as an adhesion molecule and suggests a role for CD48 in lymphocyte epithelial cell interactions.
CD48是免疫球蛋白超家族的成员，与CD58（淋巴细胞功能相关抗原-3）具有高度的序列同源性。在啮齿动物中，CD48是CD2的配体，而在人类中，CD58是CD2的配体。尽管进行了大量研究，但尚未令人信服地证明人类CD48的配体。我们现在表明，人类CD48的配体存在于上皮细胞上。基于上皮细胞结合十聚体可溶性CD48 IgM融合蛋白和固定在塑料培养皿上的单体CD48的能力，检测到了该配体。针对该配体产生的单克隆抗体完全阻断了CD48与所有测试上皮细胞的结合。我们进一步表明，细胞表面蛋白聚糖CD44在上皮细胞与CD48的结合中起辅助作用，并且这种相互作用涉及CD44的糖胺聚糖结合位点。未检测到人类CD48与CD2的相互作用。这是首次明确证明人类CD48可作为黏附分子，并提示CD48在淋巴细胞与上皮细胞相互作用中发挥作用。
