Kato M, Abraham R T, Okada S, Kita H
Department of Immunology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA.
Am J Respir Cell Mol Biol. 1998 May;18(5):675-86. doi: 10.1165/ajrcmb.18.5.2885.
Evidence suggests that cellular adhesion is critical for eosinophil effector functions. Here, we tested the hypothesis that an adhesion molecule, specifically beta2 integrin, participates in intracellular signaling events of eosinophils. Eosinophils stimulated with interleukin (IL)-5 and adherent to protein-coated tissue culture plates via beta2 integrin (CD18) showed tyrosine phosphorylation of a number of proteins. Among these proteins, tyrosine phosphorylation of the 105 kD and 115 kD proteins and the product of the c-cbl protooncogene, Cbl, was specifically inhibited using soluble anti-CD18 monoclonal antibody (mAb) to block eosinophil cell adhesion. Furthermore, phosphoinositide turnover of IL-5-stimulated adherent eosinophils was also inhibited by anti-CD18 mAb, suggesting that cellular adhesion plays important roles in eosinophil signal transduction. alphaM beta2 (Mac-1, CD11b/18) was one of the beta2 integrins involved in eosinophil adhesion to protein-coated plates. We found that direct ligation of eosinophil alphaM beta2 with anti-CD11b mAb coupled to polystyrene microbeads induced tyrosine phosphorylation of a 115 kD protein and Cbl. Furthermore, anti-CD11b mAb microbeads induced increases in both phosphoinositide hydrolysis and the eosinophil degranulation response. Control antibodies, such as mouse myeloma IgG1 and anti-HLA class I antigen mAb, did not induce these cellular responses. These results suggest that engagement of beta2 integrin either by cell adhesion or by anti-CD11b mAb triggers activation of an intracellular signaling cascade, including protein tyrosine phosphorylation and phosphoinositide turnover, and subsequent cellular degranulation in human eosinophils. Tyrosine phosphorylation of a 115 kD protein and Cbl may play important roles in adhesion-dependent cellular functions of eosinophils.
有证据表明细胞黏附对于嗜酸性粒细胞的效应功能至关重要。在此，我们检验了一种假说，即一种黏附分子，具体而言是β2整合素，参与嗜酸性粒细胞的细胞内信号传导事件。用白细胞介素（IL）-5刺激并通过β2整合素（CD18）黏附于蛋白包被的组织培养板上的嗜酸性粒细胞显示出多种蛋白质的酪氨酸磷酸化。在这些蛋白质中，使用可溶性抗CD18单克隆抗体（mAb）阻断嗜酸性粒细胞的细胞黏附可特异性抑制105 kD和115 kD蛋白质以及原癌基因c-cbl的产物Cbl的酪氨酸磷酸化。此外，抗CD18 mAb也抑制了IL-5刺激的黏附嗜酸性粒细胞的磷酸肌醇代谢，提示细胞黏附在嗜酸性粒细胞信号转导中起重要作用。αMβ2（巨噬细胞-1，CD11b/18）是参与嗜酸性粒细胞黏附于蛋白包被板的β2整合素之一。我们发现用偶联于聚苯乙烯微珠的抗CD11b mAb直接连接嗜酸性粒细胞αMβ2可诱导115 kD蛋白质和Cbl的酪氨酸磷酸化。此外，抗CD11b mAb微珠可诱导磷酸肌醇水解和嗜酸性粒细胞脱颗粒反应增加。对照抗体，如小鼠骨髓瘤IgG1和抗HLA I类抗原mAb，未诱导这些细胞反应。这些结果提示，通过细胞黏附或抗CD11b mAb使β2整合素结合可触发细胞内信号级联反应的激活，包括蛋白质酪氨酸磷酸化和磷酸肌醇代谢，以及随后人类嗜酸性粒细胞的细胞脱颗粒。115 kD蛋白质和Cbl的酪氨酸磷酸化可能在嗜酸性粒细胞的黏附依赖性细胞功能中起重要作用。
