Structure and function of a variation of sialyl Lewis X carbohydrate chains on glycoproteins.

本研究的目的是阐明白细胞膜上唾液酸化Lewis X(SLeX)碳水化合物链的变化及其在选择素依赖的细胞黏附和白细胞活化中的作用。(1)抗SLeX碳水化合物链的单抗诱导人血单核细胞产生肿瘤坏死因子(TNF)。几种不同类别和结合特异性的抗体在单核细胞激活中具有不同的效力。此外，P-选择素-L(P-选择素糖蛋白配体-L)抗体可部分抑制单核细胞的这种诱导作用。(2)P-选择素依赖的白细胞黏附与其细胞表面SLeX糖链的总表达水平无关，而与PSGL-1结合的SLeX抗原的量有关。(3)人血中性粒细胞与固定化P-选择素孵育后产生超氧阴离子。在荧光显微镜下观察SLeX表位的分布，发现它们在细胞附着部位形成一簇。这些结果表明，依赖于选择素的白细胞的黏附和功能激活基本上是由SLeX碳水化合物链与选择素的相互作用介导的，并受到碳水化合物配体的变化、糖载体分子的性质及其在细胞膜上的定位的影响。

The purpose of this research project was the elucidation of a variation of sialyl Lewis X (sLeX) carbhohydrate chains on leukocyte membranes and their roles in the selectin-dependent cell adhesion and leukocyte activation.(1) The production of tumor necrosis factor (TNF) in human blood monocytes was induced by monoclonal antibodies against sLeX carbohydrate chains. Several antibodies with different classes and binding specificities examined had distinct potency in the monocyte activation. In addition, the induction was partially inhibited by the pretreatment of monocytes with an anti-PSGL-l (P-selectin glycoprotein ligand-l) antibody.(2) P-selectin-dependent adhesion of leukocytes was not necessarily correlated with the total expression levels of sLeX carbohydrate chains on their cell surface, but correlated with the amounts of sLeX antigen linked to PSGL- 1.(3) Human blood neutrophils produced superoxide anion when they were incubated with immobilized P-selectin. The distribution sLeX epitopes was examined by fluorescent microscopy, and they were found to form a cluster at the cell attachment site.These results suggest that the selectin-dependent leukocyte adhesion and functional activation were basically mediated by the interaction of sLeX carbohydrate chains with selectins and were influenced by a variation of the carbohydrate ligands, the nature of the carbohydrate-carrier molecules and their localization on cell membranes.