RETROBULBAR ADIPOCYTES AND HUMORAL IMMUNITY IN GRAVES OPHTHALMOPATHY

As CT and MR-imaging revealed an enlargement of retrobulbar fat tissue in patients with Graves' ophthalmopathy, the role of the retrobulbar adipocytes in the pathogenesis of this disorder remains to be elucidat ed. To evaluate the in vitro influence of humoral immunity on retrobul bar adipose tissue, the effects of IgG and sera from 56 euthyroid opht halmopathy patients and 53 controls on both porcine and human (patient s' and controls') retrobulbar adipocytes were measured by means of sev eral assays: An enzyme-linked immunosorbent assay was employed to reve al specific binding of antibodies to the adipocytes. Metabolic activit y was determined by means of a colorimetric dimethyl thiazolium-diphen yl-tetrazolium bromide test which quantifies the activity of mitochond rial dehydrogenases; cell proliferation was measured by incorporation of [H-3]-thymidine in 24h, and activities of adipocyte specific enzyme s, such as membrane-bound lipoprotein lipase and 1-glycerol-3-phosphat e-dehydrogenase were determined. By means of these specific enzyme tes ts no distinctions could be made between patients and controls. Furthe rmore, a significant difference between patients' (untreated and treat ed) and controls' IgG to bind to, to activate or to stimulate the prol iferation of porcine or human (patients' and controls') retrobulbar ad ipocytes could not be detected under the employed experimental conditi ons. The effects of patients' heat-inactivated and non-inactivated ser a were indistinguishable from those of the controls. Incubation with a utologous sera, however, led to an activation of the retrobulbar adipo cytes which was higher than the median caused by the patients' group a nd that engendered by incubation with autologous IgG. Yet, a significa nt role that humoral immunity might play directly on retrobulbar adipo cyte tissue could not be detected.