Beta-1 integrins in the normal human glomerular capillary wall: an immunoelectron microscopy study.

The localization of the alpha 2, alpha 3 and alpha 6 subunits of the beta 1 integrin family on different cells of the glomerular capillary wall and on juxta-capillary mesangium was investigated using an immunoelectron microscopic technique on freshly harvested normal human glomeruli. Alpha 2 beta 1, alpha 3 beta 1 and alpha 6 beta 1 were weakly expressed on both luminal and abluminal surfaces of glomerular endothelial cells; alpha 2 beta 1 and alpha 3 beta 1 were also found on the mesangium of the juxta-capillary areas. Alpha 3 beta 1 was regularly present in great density on the basal and lateral surface of podocyte foot processes, confirming alpha 3 beta 1 as the unique beta 1 integrin on glomerular epithelial cells. None of these integrins was strictly polarized along the glomerular basement membrane, thus suggesting, in agreement with recent literature, that these molecules perform other biological functions in addition to adhesivity.