A study of the structure, function and distribution of β5 integrins using novel anti-β5 monoclonal antibodies

Abstract

Here, we have utilized six new anti-human β5 mono-clonal antibodies to perform a detailed investigation of the structure, function and distribution of β5 integrins. Monoclonal anti-β5 specificity was confirmed by reac-tivity with β5-transfected CHO cells, by direct binding to the β5 subunit (immunoblotting), and by immunode-pletion experiments using polyclonal anti-β5 serum. The β5 subunit was predominantly associated with the av subunit, although on some cell lines, the level of β5 exceeded that of αv for unknown reasons. Cell adhesion studies showed that the adhesive function of β5 could be stimulated, inhibited or unaltered by different anti-β5 monoclonal antibodies. The β5 subunit was involved in adhesion to both vitronectin and fibronectin and, at least for K562 cells, fibronectin appeared to be the preferred ligand. Flow-cytometry studies showed that the β5 subunit was expressed at moderate to high levels on all adherent cell lines examined, was absent from all lym-phoid cell lines, and was only weakly expressed on myeloid cell lines. Staining of thymic sections showed the distribution of β5 on blood vessels, Hassal’s corpus-cles, cortical and medullary stromal cells, and basement membranes. Skin sections showed β5 on the basal layer of the epidermis and on some dermal blood vessel walls, and kidney sections showed staining of glomerular regions, juxta glomerular apparatus, proximal convo-luted tubules and collecting tubules, and at least one anti-β5 antibody also stained epithelial cells of proximal tubules.