T cell interaction with ICAM-1-deficient endothelium in vitro: transendothelial migration of different T cell populations is mediated by endothelial ICAM-1 and ICAM-2.

The trafficking of T lymphocytes is carefully regulated by adhesive interactions with the vascular endothelium. Depending on their maturation and activation stage, T lymphocytes exhibit distinctive patterns of homing and recirculation, which is at least partly due to the selective expression of cell adhesion molecules (CAM) on the T cell surface. In order to define whether the differential usage of CAM during the steps of transendothelial migration is involved in organ-specific recirculation of different T cell subsets we compared the interaction of three different T cell populations with mouse endothelioma cell lines in vitro. Using a novel approach, where we directly compared T cell interaction with ICAM-1-deficient endothelium to wild-type endothelium, we recently demonstrated that endothelial ICAM-1 and ICAM-2 play a key role in mediating the transendothelial migration of CD4(+) memory T cells. Here we show that endothelial ICAM-1 and ICAM-2 are equally required for the transendothelial migration of other T cell populations such as thymocytes and T lymphoma cells, which differ from CD4(+) memory T cells in their maturation and activation stage, as well as in their surface expression of adhesion molecules. Our data therefore demonstrate that transendothelial migration of different T cell populations is mediated by the same endothelial CAM, i.e. ICAM-1 and ICAM-2, and thus subset-specific interaction of T cells with endothelial cells must be regulated prior to transendothelial migration.