A cell surface amine oxidase directly controls lymphocyte migration

Lymphocytes leave the blood using a sequential adhesion cascade. Vascular a dhesion molecule-1 (VAP-1) is a surface-expressed endothelial glycoprotein, which belongs to a distinct subgroup of monoamine oxidases. We show here t hat catalytic activity of VAP-1 on primary endothelial cells directly regul ates lymphocyte rolling under defined laminar shear. VAP-1 seems to bind to a primary amino group presented on the lymphocyte surface and oxidatively deaminate it in a reaction, which results in the formation of a transient c ovalent bond between the two cell types. Instead, soluble reaction products (aldehydes and hydrogen peroxide) are not needed for the VAP-1-dependent r olling. Enzymatic regulation of lymphocyte adhesion to endothelium provides a previously unrecognized rapid way of controlling the extravasation proce ss.