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

Abstract

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 discussed 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.

Expression of Very Late Antigen-4 and Lymphocyte Function-Associated Antigen-1 on Peripheral Blood Lymphocytes from Patients with Graves Disease

“…Futhermore, these authors underlined the potential role of serum autoantibodies directed against LFA-1 and lymphokines for down-regulation of these glycoproteins and revealed that the defect in membranous LFA-1 synthesis was due to the incorporation of a viral genome in the lymphocytes in GD patients. Hovewer, increased percentages of LFA-1␣-and VLA-4␣-positive T cells were observed in the thyroid gland and retroocular tissues in newly diagnosed patients with GD compared with peripheral blood T lymphocytes from the same patients (21,22). The results of our study imply that the decreased integrin expression in peripheral blood lymphocytes could probably be associated with the increased migration of CD11a ϩ and CD49d ϩ cells to the thyroid gland.…”

Lymphocyte traffic and homing in autoimmune thyroid disorders

“…Not only thyroid infiltrating cells but also mononuclear cells infiltrating the orbit express LFA-1 (30). With regard to PBLs, untreated GD patients have significantly less LFA-1 (31, 32), CD18 and CD29 (32) expression than controls.…”

“…Vascular endothelium in retro-ocular tissues in Graves' ophthalmopathy has also revealed a strong immunoreactivity for ICAM-1, LFA-3, E-selectin and VCAM-1, not present in normal retro-ocular tissues (22). In addition, ICAM-1 expression has been induced after in vitro exposure to several cytokines of retro-ocular fibroblasts of GD patients (30). All these findings together suggest that the LFA-1/ICAM-1, VLA-4/VCAM-1, and selectin adhesion pathways are probably predominant in leukocyte adherence to and migration through the endothelium of both the thyroid and the orbit in AITD (19, 21, 22).…”

Clinical implications of somatostatin-receptor scintigraphy in ophthalmic Graves' disease

“…Several cytokines, such as interferon-g, tumour necrosis factor-a, interleukin-1 and transforming growth factor-b, as well as growth factors, such as insulin-like growth factor-I (IGF-I) and platelet-derived growth factor, have been detected within the orbital tissues (5±8). All these substances are probably produced both by infiltrating immunocompetent cells and by residential fibroblasts, adipocytes, myocytes and microvascular endothelial cells (9). Cytokines and growth factors stimulate cell proliferation, glycosaminoglycan synthesis and expression of immunomodulatory molecules in orbital fibroblasts and microvascular endothelial cells (Table 2).…”