ANALYSIS OF IL-2 AND IL-6 BINDING TO PERIPHERAL-BLOOD LYMPHOCYTES IN GRAVES-DISEASE - RELATIONSHIP WITH DISEASE-ACTIVITY

Growing evidence points to the possible involvement of cytokines in th e pathogenesis of some autoimmune diseases. To investigate the possibl e role of interleukin 2 (IL-2) and interleukin 6 (IL-6) on the pathoge nesis of Graves disease (GD), the binding of both exogenous IL-2 and I L-6 and the expression of the IL-2 receptor subunit p55 (CD25) were ev aluated by flow cytometry in peripheral blood T and B cells from 70 GD patients, in different states of the disease, and from 19 age- and se x-matched healthy volunteers. Serum levels of total T3 and T4, of free T4, and of anti-TSH receptor antibodies were also simultaneously dete rmined, All GD patients displayed significantly increased numbers of B cells bound to IL-2. Hyperthyroid untreated GD patients had significa ntly higher numbers of T and B cells expressing the IL-2 receptor subu nit p55 as compared to euthyroid patients in long-term remission. In a ddition, serum anti-TSH receptor antibody levels were directly correla ted with the absolute numbers of T cells hound to IL-2 (r = 0.565, P < 0.05) and to IL-6 (r = 0.653, P = 0.02) in the hyperthyroid untreated patients, but not in long-term remission euthyroid GD patients or in patients treated with methimazole. The serum levels of total T3 and fr ee T4 were significantly correlated with the absolute numbers of circu lating T cells binding IL-2 (r = 0.720, P < 0.01 and r = 0.783, P < 0. 002, respectively) as well as with the absolute numbers of circulating T cells binding IL-6 (r = 0.671, P < 0.02 and r = 0.626, P < 0.02, re spectively). The serum levels of total T3 were also correlated with bo th the absolute numbers of B cells binding to IL-2 (r = 0.586, P < 0.0 5) and to IL-6 (r = 0.757, P < 0.001). These findings suggest that IL- 2 and IL-6 may play a role in the pathogenesis of GD. (C) 1997 Wiley L iss, Inc.