CELLULAR-IMMUNITY AND RETROBULBAR FIBROBLASTS IN GRAVES OPHTHALMOPATHY

In Graves' ophthalmopathy (GO), retrobulbar connective tissue is infil trated by T cells whose role in the pathogenesis of the disease was in vestigated in the present work. The aims included firstly to character ize subsets of blood lymphocytes and of sessile lymphocytes cloned fro m a retroorbital tissue specimen. Second, in counterstimulation assays , the ability of patients' T cells to influence cultivated retrobulbar fibroblasts and in turn the enhancement of lymphocyte proliferation b y retrobulbar fibroblasts was investigated. Blood lymphocytes of 16 GO patients and 12 controls isolated by density gradient centrifugation and retrobulbar fibroblasts obtained from orbital decompression were a lternately exposed to irradiation of 4000 rad (to suppress proliferati on of either cell type), then cocultivated for 48 h. Subsequently, the cells (250,000 lymphocytes, 5000 retrobulbar fibroblasts) were incuba ted with [H-3]thymidine for 24 h. A stimulation index representing the degree of proliferation in comparison with a control was determined. Screening of 62 retrobullar lymphocyte clones by cell-ELISA revealed a CD4/CD8 ratio of 8.2, contrasting with a normal ratio of 2.1 in perip heral lymphocytes (as obtained by FACS analysis). Incubation of patien t's lymphocytes with autologous retrobulbar fibroblasts resulted in a markedly elevated stimulation index (9.7) compared to incubation of ly mphocytes with retrobulbar fibroblasts from controls (2.5). In another assay, the degree of stimulation amounted to 2.2 vs. -0.8. Retrobulba r fibroblasts were stimulated twice as much by lymphocytes of the same patient compared to retrobulbar fibroblasts from controls. The autolo gous reactions demonstrated suggest the presence of autoreactive T lym phocytes in GO patients directed against retrobulbar fibroblasts, whic h, in addition, are stimulated by these lymphocytes.