Alpha 4 integrin-dependent leukocyte recruitment does not require VCAM-1 in a chronic model of inflammation.
Rats immunized with Mycobacterium butyricum in Freund's adjuvant develop a chronic vasculitis, with large increases in leukocyte rolling and adhesion in mesenteric postcapillary venules that are significantly inhibited with an alpha 4 integrin Ab. Using intravital microscopy to visualize chronically inflamed microvessels, we demonstrated that alpha 4 integrin-dependent leukocyte rolling and adhesion was inhibited with a beta 1 integrin, but not a beta 7 integrin Ab. To date, VCAM-1 has been presumed to be the primary ligand for alpha 4 beta 1 integrin in the vasculature. However, alpha 4 beta 1 integrin-dependent interactions were not reduced by monoclonal or polyclonal VCAM-1 Abs or a VCAM-1 antisense oligonucleotide despite increased VCAM-1 expression in the mesenteric vasculature. To ensure that the VCAM-1 Abs were functional and used at saturating concentrations, blood from Ab-treated rats was perfused over monolayers of CHO cells transfected with rat VCAM-1. Sufficient alpha 4 integrin or VCAM-1 Ab was present to inhibit leukocyte interactions with rat VCAM-1 by 95-100%. Under in vitro flow conditions, only mononuclear leukocytes were recruited from blood of control rats onto purified VCAM-1. However, neutrophils were also recruited onto VCAM-1 from whole blood of adjuvant-immunized animals via alpha 4 integrin. Another ligand for alpha 4 beta 1 integrin is the connecting segment-1 (CS-1) region of fibronectin. An Ab to the CS-1 portion of fibronectin, which did not reduce rolling and adhesion in adjuvant arthritis animals, completely inhibited leukocyte adhesion to CS-1 under static conditions. These findings provide the first evidence that alpha 4 beta 1 integrin-dependent leukocyte rolling and adhesion can occur in vivo via a mechanism other than VCAM-1.
Johnston
B
B
Immunology Research Group, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada.
Chee
A
A
Issekutz
T B
TB
Ugarova
T
T
Fox-Robichaud
A
A
Hickey
M J
MJ
Kubes
P
P
D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D015703:Antigens, CD / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D001169:Arthritis, Experimental / Q000276:immunology* / Q000473:pathology; D002465:Cell Movement / Q000276:immunology*; D002908:Chronic Disease; D006224:Cricetinae; D005353:Fibronectins / Q000276:immunology / Q000378:metabolism; D007275:Injections, Intravenous; D039441:Integrin alpha4; D039041:Integrin alpha4beta1; D016023:Integrins / Q000502:physiology*; D007962:Leukocytes / Q000276:immunology* / Q000473:pathology; D008024:Ligands; D008297:Male; D008833:Microcirculation / Q000276:immunology / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016201:Receptors, Lymphocyte Homing / Q000502:physiology; D019010:Vascular Cell Adhesion Molecule-1 / Q000502:physiology*
D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D008024:Ligands; D010446:Peptide Fragments; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; D039441:Integrin alpha4