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刘易斯X（sLeX）碳水化合物链的变化及其在选择素依赖的细胞粘附和白细胞活化中的作用。(1)用抗sLeX糖链单克隆抗体诱导人血单核细胞产生肿瘤坏死因子（TNF）。检查的具有不同类别和结合特异性的几种抗体在单核细胞活化中具有不同的效力。此外，通过用抗PSGL-1（P-选择素糖蛋白配体-1）抗体预处理单核细胞部分抑制诱导。(2)白细胞的P-选择素依赖性粘附不一定与其细胞表面sLeX糖链的总表达水平相关，但与PSGL- 1连接的sLeX抗原的量相关。(3)人血中性粒细胞产生超氧阴离子时，他们与固定的P-选择素孵育。荧光显微镜观察sLeX表位的分布，发现它们在细胞粘附位点形成簇，提示选择素依赖的白细胞粘附和功能激活基本上是由sLeX糖链与选择素的相互作用介导的，并受糖配体的变化影响，碳水化合物载体分子的性质及其在细胞膜上的定位。

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.