GRAVES IMMUNOGLOBULINS AND CYTOKINES STIMULATE THE EXPRESSION OF INTERCELLULAR-ADHESION MOLECULE-1 (ICAM-1) IN CULTURED GRAVES ORBITAL FIBROBLASTS

Intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) are cell surface adhesion receptors that bind to one another and promote a variety of effector/target cell interactions in tissues affected by inflammatory or immune processes. Local infiltration of the thyroid gland and the retro-ocular space by mononuclear cells is a hallmark of Graves' disease and Graves' ophthalmopathy (GO). Thus, we studied the role of these adhesion receptors in the interaction of inflammatory cells with retro-ocular fibroblasts (OF) derived from patients undergoing transantral decompression for severe GO, and from normal individuals. Confluent OF-monolayers were incubated with various cytokines or protein-A affinity-purified IgGs prepared from sera of patients with severe GO, Hashimoto's thyroiditis (HT), rheumatoid arthritis (RA) and normal individuals. As determined by immunocytochemistry and immunoprecipitation using a monoclonal anti-ICAM-1 antibody, interleukin-1-alpha (IL-1a), tumour necrosis factor-alpha (TNFa) and interferon-gamma (IFNg) strongly enhanced surface expression of ICAM-1 in both GO- and normal OF. By contrast, Graves' IgGs stimulated ICAM-1 expression only in GO-, but not in normal OF. No effect was observed in either cell type with interleukin-2, transforming growth factor-beta, or IgGs from patients with HT, RA and normal individuals. Using phorbol ester-activated, Cr-51-labelled peripheral blood mononuclear cells (PBMCs) in a cell adhesion assay, we demonstrated potent adhesive activity of ICAM-1 in GO-OF pretreated with IL-1a, TNFa, IFNg or Graves' IgGs, while all other compounds did not affect PBMC adhesion to GO-OF. In other studies, PBMCs or GO-OF were pre-incubated (following stimulation with cytokines or Graves' IgGs) with monoclonal antibodies against ICAM-1 or LFA-1-alpha. While PBMC-adherence was only partially inhibited by anti-ICAM-1 antibody, anti-LFA-1-alpha almost completely blocked cell attachment. In conclusion, inflammatory cytokines and Graves' IgGs are potent modulators of ICAM-1/LFA-1-mediated interactions between immunocompetent cells and GO-OF. These mechanisms likely play a role in the localization of the inflammatory infiltrate within the orbit and may affect antigen presentation and maintenance of the chronic immune process in GO.