VASCULAR ADHESION MOLECULES IN ACUTE AND CHRONIC LIVER INFLAMMATION

Adhesion to and penetration through the sinusoidal vascular endothelium is a mandatory step for leukocyte migration and accumulation at sites of liver inflammation. This leukocyte trafficking is controlled by interactions between adhesion molecules on leukocytes and corresponding ligands on endothelial cells. We have analyzed the in situ distribution of two recently described vascular adhesion molecules (i.e., endothelial leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1) and of the lymphocyte "homing" receptor cluster of differentiation antigen-44 in normal and inflamed liver biopsy specimens. Endothelial leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 were absent from normal liver tissue, but they were strongly expressed on sinusoidal lining cells in inflammatory liver diseases. Endothelial leukocyte adhesion molecule-1 expression predominated diffusely throughout the liver parenchyma in acute hepatitis; in contrast, vascular cell adhesion molecule-1 was mainly expressed in areas of periportal and intralobular inflammation in chronic active and persistent hepatitis. The "homing" receptor cluster of differentiation antigen-44 was weakly expressed on scattered mononuclear cells and on sinusoidal lining cells in normal liver tissue, but it was strongly up-regulated on mononuclear inflammatory cells and sinusoidal lining cells in acute and chronic hepatitis. In addition, reactivity for the cluster of differentiation antigen-44 was found on the membranes of variously sized clusters of hepatocytes in biopsy specimens with acute hepatitis. De novo or up-regulated expression of these adhesion molecules on sinusoidal lining cells in inflamed liver biopsy specimens indicates that these cells actively modulate their phenotype in response to environmental factors, thus playing a key role in the recruitment of leukocytes in acute and chronic liver inflammation.