Walsh G M, Symon F A, Lazarovils A L, Wardlaw A J
Department of Respiratory Medicine University of Leicester Medical School, Glenfield General Hospital, UK.
Immunology. 1996 Sep;89(1):112-9. doi: 10.1046/j.1365-2567.1996.d01-713.x.
We have investigated the contribution of integrin alpha 4 beta 7 to human peripheral blood eosinophil adhesive interactions. Immunofluorescence and flow cytometry demonstrated constitutive expression of alpha 4 beta 7 by eosinophils. Expression of alpha 4 beta 7 or alpha 4 beta 7 was not enhanced by eosinophil activation with platelet-activating factor (PAF). Expression of alpha 4 beta 7 was confirmed by immuno-precipitation of 125I-labeled lysates analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE). Approximately 20% of unstimulated eosinophils were adherent to L1-2 cells transfected with vascular cell adhesion molecule-1 (VCAM-1) cDNA, while very few resting eosinophils adhered to mouse mucosal adressin cell adhesion molecule-1 (MAdCAM-1) transfectants. Binding of unstimulated eosinophils to VCAM-1 transfectant was inhibited by HPI 2 (an antibody that blocks both alpha 4 beta 1 and alpha 4 beta 7 functions), but not Act-1, and alpha 4 beta 1 monoclonal antibody (mAb). PAF stimulation resulted in increased binding of eosinophils to MAdCAM-1 transfectants, which was inhibited by both HPI 2 and Act-1. In contrast, PAF did not enhance binding to VCAM 1 transfectants, although binding of PAE-stimulated eosinophils to VCAM-1 could be partially inhibited by Act-1. Stimulation of eosinophils with the beta 7-activating mAb TS2 16 resulted in enhanced binding of eosinophils to both VCAM-1 and MAdCAM-1 transfectants. The increased binding was largely alpha 4 beta 7-dependent. Unstimulated eosinophils bound to soluble recombinant human (rh) VCAM-1 and fibronectin (Fn), coated on 96-well plates in dose-dependent manner. Binding was inhibited by HPI-2 and 4b4, an anti-beta 1 mAb, but not by Act-1. TS2 16 treatment increased adherent cell numbers and this enhanced binding was inhibited by Act-1. We have therefore confirmed that alpha 4 beta 7 is functionally active on unstimulated eosinophils. In contrast, PAF-induced enhancement of eosinophils binding to VCAM-1 or MAdCAM-1 was alpha 4 beta 7-dependent. In addition treatment with TS2 16 resulted in a alpha 4 beta 7-dependent enhancement of eosinophil binding to VCAM-1, MAdCAM-1 and Fn. We therefore hypothesize that alpha 4 beta 7 may have an important role in eosinophil localization in diseases such as asthma and inflammatory bowel disease.
我们研究了整合素α4β7在人外周血嗜酸性粒细胞黏附相互作用中的作用。免疫荧光和流式细胞术显示嗜酸性粒细胞组成性表达α4β7。用血小板活化因子（PAF）激活嗜酸性粒细胞不会增强α4β7或α4β7的表达。通过十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）分析125I标记的裂解物的免疫沉淀法证实了α4β7的表达。约20%未受刺激的嗜酸性粒细胞黏附于转染了血管细胞黏附分子-1（VCAM-1）cDNA的L1-2细胞，而极少有静息嗜酸性粒细胞黏附于转染了小鼠黏膜地址素细胞黏附分子-1（MAdCAM-1）的细胞。未受刺激的嗜酸性粒细胞与VCAM-1转染细胞的结合被HPI 2（一种阻断α4β1和α4β7功能的抗体）抑制，但不受Act-1和α4β1单克隆抗体（mAb）抑制。PAF刺激导致嗜酸性粒细胞与MAdCAM-1转染细胞的结合增加，这被HPI 2和Act-1均抑制。相反，PAF未增强与VCAM-1转染细胞的结合，尽管PAF刺激的嗜酸性粒细胞与VCAM-1的结合可被Act-1部分抑制。用β7激活单克隆抗体TS2 16刺激嗜酸性粒细胞导致嗜酸性粒细胞与VCAM-1和MAdCAM-1转染细胞的结合增强。增加的结合在很大程度上依赖于α4β7。未受刺激的嗜酸性粒细胞以剂量依赖性方式与包被在96孔板上的可溶性重组人（rh）VCAM-1和纤连蛋白（Fn）结合。结合被HPI-2和抗β1单克隆抗体4b4抑制，但不受Act-1抑制。TS2 16处理增加了黏附细胞数量，且这种增强的结合被Act-1抑制。因此，我们证实了α4β7在未受刺激的嗜酸性粒细胞上具有功能活性。相反，PAF诱导的嗜酸性粒细胞与VCAM-1或MAdCAM-1结合的增强依赖于α4β7。此外，用TS2 16处理导致嗜酸性粒细胞与VCAM-1、MAdCAM-1和Fn的结合以α4β7依赖的方式增强。因此，我们推测α4β7可能在哮喘和炎症性肠病等疾病的嗜酸性粒细胞定位中起重要作用。
