EFFECT OF LYMPHOCYTES ON HORMONAL SECRETION BY AUTOLOGOUS THYROCYTES CULTURED IN MONOLAYERS

We studied the lymphocyte-induced alterations in hormonal metabolism a nd the production of tumour necrosis factor alpha (TNF-alpha) during c oculture of thyrocytes and autologous lymphocytes from 20 patients wit h Graves' disease and from five normal subjects. Thyroglobulin (Tg) mR NA was assessed by slot-blot analysis under TSH stimulation. Tg, tri-i odothyronine (T-3) and cAMP secretion in the presence of TSH were meas ured by RIA after 3 or 5 days of coculture. TNF-alpha levels produced after 5 days incubation were also assayed in lymphocyte culture and co culture media. Lymphocytes isolated from peripheral blood (PBLs) alter ed the production of Tg, T-3 and cAMP in autologous thyrocytes. Intrat hyroidal lymphocytes (ITLs) decreased Tg and cAMP secretion but had no effect on T-3 secretion. The reductions in Tg and cAMP levels obtaine d with mechanically isolated ITLs (M-ITLs) were generally higher than those obtained with ITLs isolated by dispase (D-ITLs). No difference w as seen between Graves' disease and normal cocultures. PBLs secreted l arge concentrations of TNF-alpha, larger than those obtained with M-IT Ls whereas D-ITLs produced low amounts of this cytokine. In coculture, TNF-alpha levels were lower than those observed in lymphocyte culture . Significant correlations were obtained between TNF-alpha levels and the decrease in Tg, T-3 and cAMP concentrations. The percentage of T l ymphocytes was higher in PBLs and D-ITLs than in M-ITLs. B lymphocytes levels were higher in ITLs, especially M-ITLs, than in PBLs. TNF-alph a production by B lymphocytes was maximal in M-ITLs. In conclusion, ly mphocytes induced a decrease in hormonal thyroid metabolism when cocul tured with autologous thyrocytes. These perturbations may be attribute d, at least partly, to TNF-alpha secreted by lymphocytes. TNF-alpha in teracts via the adenylate cyclase pathway of TSH signal transduction.