T-CELLS AND ORBITAL CONNECTIVE-TISSUE IN ENDOCRINE ORBITOPATHY

In order to analyse the immunological changes in patients with endocri ne orbitopathy (EO) the antigenic character of orbital connective tiss ue was studied. Counterstimulation assays of patients' lymphocytes wit h autologous retrobulbar fibroblasts resulted in a markedly increased lymphocyte proliferation in comparison to incu bation with retrobulbar control fibroblasts. Proliferation tests of retrobulbar T cell lines showed significant responses to autologous retro-orbital connective ti ssue proteins, with molecular weights of 6-10 kD and 19-26 kD. Phenoty pic analysis of orbital T cell lines indicates that they consisted pre dominantly of CD4(+) cells. Hyaluronic acid production of orbital fibr o blasts following co-cultivation with lymphocytes of EO patients or c ontrols revealed a threefold increased synthesis in patients with EO. Furthermore, distribution pattern of orbital extracellular matrix glyc osaminoglycans (GAG) differs in EO patients in comparison to controls. The results suggest the presence of autoreactive T cells directed aga inst antigens of orbital fibroblasts, whose stimulation results in an augmented GAG synthesis in patients with EO.