Integrin alpha 4 beta 7 mediates human eosinophil interaction with MAdCAM-1, VCAM-1 and fibronectin.
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.
Walsh
G M
GM
Department of Respiratory Medicine University of Leicester Medical School, Glenfield General Hospital, UK.
Symon
F A
FA
Lazarovils
A L
AL
Wardlaw
A J
AJ
D002448:Cell Adhesion; D015815:Cell Adhesion Molecules; D004804:Eosinophils / Q000187:drug effects / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism*; D009088:Mucoproteins / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D011233:Precipitin Tests; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D005353:Fibronectins; D007136:Immunoglobulins; D039041:Integrin alpha4beta1; D016023:Integrins; C504265:MADCAM1 protein, human; C489082:Madcam1 protein, mouse; D009088:Mucoproteins; D010972:Platelet Activating Factor; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; C071777:integrin alpha4beta7