Adhesion to fibronectin primes eosinophils via alpha 4 beta 1 (VLA-4).
Human peripheral blood eosinophils adhered specifically to microtitre plates coated with plasma fibronectin (Fn) in a dose- and time-dependent fashion. Adhesion was optimal at 60 min at a concentration of 100 micrograms/ml. Adherence to Fn was up-regulated by platelet-activating factor (PAF; optimum concentration of 10(-6) M) and was significantly inhibited by a polyclonal anti-Fn antibody (P < 0.05). The following evidence suggested that eosinophil adhesion to Fn was mediated by alpha 4 beta 1: (1) eosinophil adherence to Fn was not inhibited by an Arg-Gly-Asp-Ser (RGDS) synthetic peptide; (2) there was a dose-dependent adherence of eosinophils to microtitre plates coated with the 40,000 MW proteolytic fragment of Fn that contains the CS-1 alpha 4 beta 1 binding region, whereas adherence to the 120,000 MW chymotryptic fragment of Fn, which contains the RGD-dependent binding site, was weak and only observed at high concentrations (> 250 micrograms/ml); (3) significant inhibition of eosinophil adherence to Fn was achieved by monoclonal antibodies (mAb) against the alpha chain of VLA-4 but not by a mAb against CD45 or a mouse myeloma antibody as negative controls. After adhesion to Fn, eosinophils were investigated for their capacity to release leukotriene C4 in response to stimulation with a suboptimal concentration of calcium ionophore (2 x 10(-6) M). Significant enhancement of release was detected with Fn-coated plates but not with the control bovine serum albumin (BSA) (P < 0.01). Furthermore, this enhancement was significantly inhibited by the alpha 4 beta 1 mAb HP2/1 (P < 0.05) but not by an anti-CD45 mAb. From these studies we conclude that (1) alpha 4 beta 1 (VLA-4) integrin is a major receptor for Fn on human eosinophils and (2) adhesion to Fn may prime eosinophils for mediator release during allergic inflammation.
Anwar
A R
AR
Department of Allergy and Clinical Immunology, National Heart & Lung Institute, London.
Walsh
G M
GM
Cromwell
O
O
Kay
A B
AB
Wardlaw
A J
AJ
D000906:Antibodies / Q000276:immunology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D004804:Eosinophils / Q000276:immunology / Q000378:metabolism*; D005353:Fibronectins / Q000097:blood* / Q000276:immunology; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000276:immunology*; D007700:Kinetics; D017997:Leukotriene C4 / Q000097:blood; D009842:Oligopeptides / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
D000906:Antibodies; D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D009842:Oligopeptides; D010972:Platelet Activating Factor; D017997:Leukotriene C4; C046617:arginyl-glycyl-aspartyl-serine