INFILTRATION OF BOTH T-CELLS AND NEUTROPHILS IN THE SKIN IS ACCOMPANIED BY THE EXPRESSION OF ENDOTHELIAL LEUKOCYTE ADHESION MOLECULE-1 (ELAM-1) - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Various inducible adhesion molecules on human endothelial cells like the endothelial leukocyte adhesion molecule-1 (ELAM-1) seem to be the basis of mechanisms that allow peripheral blood leukocytes to enter precisely areas of inflamed tissue. Because in vitro data had shown that ELAM-1 plays a central role in neutrophil as well as memory T-cell endothelium interactions, we analyzed in vivo at the light and electron microscopic level its expression in various benign and malignant skin diseases, which differ in the composition of the cellular infiltrates. The expression of ELAM-1 on endothelial cells at different anatomical sites could be demonstrated independently from the cell type (neutrophils/memory T cells) infiltrating the surrounding tissue. On the ultrastructural level we demonstrate that the expression of ELAM-1 is restricted to certain segments of post-capillary venules exhibiting distinctive morphologic features. The ELAM-1-positive endothelia are identical to those vessels that are currently described to be the preferred sites of lymphocyte trafficking in diseased skin.