Characterization of adhesion receptors on cultured microvascular endothelial cells derived from the retroorbital connective tissue of patients with Graves' ophthalmopathy

T lymphocytes have been demonstrated recently to play an important role in the pathogenesis and propagation of Graves' ophthalmopathy (GO). Recruitment of T cells to the retroorbital tissue in GO involves the activation of certain adhesion molecules both in the vascular endothelium and in the extravascular connective tissue within the retroorbital space. To characterize the interactions between orbital endothelial cells (OECs) and circulating T cells in vitro, we designed a two-step immunopurification procedure with bead-immobilized Ulex europaeus I lectin and anti-human endothelial cell antigen (CD31) monoclonal antibody for rapid and reproducible isolation of highly pure microvascular endothelial cell populations from small quantities of retroorbital connective tissue. Endothelial origin of the resulting cell populations was confirmed by positive immunoreactivity for von Willebrand factor, CD31 and thrombomodulin. Under baseline conditions, GO-OECs, but not normal OECs, expressed intercellular adhesion molecule 1 (ICAM-1) and CD44 immunoreactivity but no immunoreactivity for endothelial leukocyte adhesion molecule 1 (ELAM-1) and vascular cell adhesion molecule 1 (VCAM-1) was detected. Exposure of GO-OEC and normal OEC monolayers to interferon gamma, interleukin 1 alpha and tumor necrosis factor alpha resulted in marked up-regulation of immunoreactivity for ICAM-1 and in induction of ELAM-1 and VCAM-1. Blocking experiments using monoclonal antibodies directed against various adhesion molecules demonstrated that interactions between matched activated T lymphocytes and OECs were mediated by integrin-dependent (ICAM-1/leukocyte function-associated antigen 1 (LFA-1); VCAM-1/very late antigen 4 (VLA-4)) and integrin-independent (CD44) pathways, and revealed marked differences when comparing GO-OECs and normal OECs, In conclusion. the availability of OECs from affected retroorbital tissue of patients with GO provides a valuable tool for studying further the mechanisms responsible for orbit-specific lymphocyte recruitment in GO.