Heufelder, Armin E.

Although the autoantigen involved in Graves’ hyperthyroidism is known to be the TSH receptor (TSHr), whether this antigen plays a primary role in the pathogenesis of Graves’ ophthalmopathy (GO) is unclear. We sought to determine whether fibroblasts derived from orbital adipose/connective tissue are capable of differentiating into adipocytes that bear immunoreactive and functional TSHr. In addition, we assessed relative levels of TSHr gene expression in normal and GO orbital adipose/connective tissue specimens.GO and normal orbital preadipocyte fibroblasts, cultured under conditions known to stimulate adipocyte differentiation, showed evidence of adipogenesis and positive immunostaining for TSHr protein. In addition, significantly more cAMP was produced in response to TSH stimulation in the differentiated cultures than in undifferentiated cultures derived from the same individuals’ cells. Other studies demonstrated relatively greater TSHr gene expression in GO than in normal orbital tissue specimens.These results indicate that orbital preadipocyte fibroblasts increase their TSHr expression with differentiation and suggest that these cells play an important role in the pathogenesis of GO. Furthermore, our studies support the concept that TSHr may be an important target antigen in this condition. Factors that stimulate adipocyte differentiation and TSHr expression in the orbit in GO have yet to be defined.

SUMMARYActivation of certain adhesion molecules within vascular endothelium and the surrounding extravascular space is a critical event in the recruitment and targeting of an inflammatory response or autoimmune attack to a particular tissue site. We have recently demonstrated that the adhesion of lymphocytes to cultured retroocular fibroblasts obtained from patients with Graves’ ophthalmopathy (GO) is mediated predominantly by the interaction of lymphocyte function-associated antigen-1 (LFA-1), expressed on lymphocytes, with intercellular adhesion molecule-1 (ICAM-I), expressed by these cells following exposure to interferon-gamma (IFN-γ), tumour necrosis factor-alpha (TNF-α), IL-lα or purified thyroid-stimulating immunoglobulins. We now report the expression and localization in situ of several adhesion molecules. ICAM-1, endothelial leucocyte adhesion molccule-l (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), and LFA-3 in retroocular tissues derived from patients with severe GO (n=4) and normal individuals (n = 3). Serial cryostat sections of tissue specimens were processed for immunoperoxidase staining using various MoAbs against ICAM-1, ELAM-1, VCAM-1 and LFA-3. In addition, consecutive sections were stained with MoAbs against LFA-1, CD45RO (UCHL-1)DR-human leucocyte antigen (HLA-DR), CD11b/CD18 (Mac-1), and CD11c/CD18 (p150,95). In GO-retroocular tissues, strong immunoreactivity for ICAM-1 and LFA-3 was detected in blood vessels (>90%), in perimysial fibroblasts surrounding extraocular muscle fibres, and in connective tissue distinct from extraocular muscle. No ICAM-1 or LFA-3 immunoreactivity was present in extraocular muscle cells themselves. ICAM-1 and LFA-3 immunoreactivity in normal tissues was minimal or absent both in connective and muscle tissues. Vascular endothelium was strongly positive for ELAM-1 and VCAM-1 in GO-retroocular tissues, while VCAM-1 immunoreactivily was minimal (<5% of blood vessels) and ELAM-1 immunoreactivity was generally absent in normal retroocular tissue. LFA-1-expressing, activated mononuclear cells and memory T lymphocytes (CD3+/CD45RO+) were only detected in GO-retrocular tissues, and were mainly localized around blood vessels and in areas of ICAM-1-expressing connective and perimysial tissue. HLA-DR expression was restricted to GO-tissue specimens, with strong immunoreactivity detected in blood vessels, macrophages and connective tissue and perimysial fibroblasts. No HLA-DR was detectable in extraocular muscle cells. In conclusion, infiltration of the orbit in GO by mononuclear cells, and their targeting within the orbit, may depend upon the coordinate expression of certain adhesion and MHC molecules. Activation of appropriate adhesion molecules in mononuclear cells, endothelial cells and fibroblasts in response to various cytokines and inflammatory mediators may be involved in the evolution and perpetuance of GO.

SUMMARYIntercellular adhesion molecule, a ligand for the leucocyte integrins CDlla/CD18 (LFA-1) and CD11b/CD18 (Mac-1), that plays an important role in a variety of inflammatory and immune-mediated mechanisms, is strongly expressed in rctroocular connective tissue from patients with Graves' ophthalmopathy (GO) and involved in lymphocyte attachment to cultured retroocular fibroblasts via the ICAM-1/LFA-1-mediated pathway. Here, we report the detection and functional activity of a soluble form of the ICAM-1 molecule (sICAM-1) in sera from patients with GO and other thyroid diseases. Serum concentrations for sICAM-1 were determined using a highly sensitive ELISA. Compared with normal controls, patients with hyperthyroid or euthyroid GO and patients with Riedcl's invasive fibrous thyroiditis revealed markedly elevated sICAM-1 serum concentrations (all P 0·0001). In patients with Graves’ disease (GD) without clinical GO and in patients with Hashimoto's thyroiditis (HT), sICAM-1 levels were elevated to a lesser degree (both P < 0·001). sICAVI-l serum levels in patients with non-autoimmune hyperthyroidism due to a toxic adenoma were not significantly different from normal controls. In a separate group of 12 patients with severe inflammatory GO, sICAM-1 serum levels markedly declined (P < 0·0001) within 3 months of glucocorticoid therapy in nine patients who responded to this form of treatment with a decrease in periorbital inflammation. In contrast, sICAM-1 serum levels remained unchanged in three patients with poor response to steroids and persistent inflammatory periorbital disease. When tested in a cell adhesion assay, GO sera containing elevated concentrations of sICAM-1 were found to enhance the attachment of peripheral blood mononuclear cells (PBMC) to interferon-gamma (IFN-γ)-treated retroocular fibroblasts in a dose-dependent manner, up to a maximal stimulation of approximately 5×5-fold (P 0·001). This effect was abolished by preabsorption of sera with a MoAb against ICAM-1 and inhibited, in a dose-dependent manner, by coincubation with increasing concentrations of purified sICAM-1. In conclusion, sICAM-1 concentrations are markedly elevated in sera from patients with GO, and changes in sICAM-1 serum levels during glucocorticoid therapy closely parallel changes in the degree of inflammation. Given the capacity of sICAM-l to modulate the adhesion of lymphocytes to retroocular fibroblasts in vitro, sICAM-1 may play a role in the ongoing immune process within the connective tissue in GO.