Thyroid cell survival in coculture with autologous peripheral or intrathyroidal lymphocytes

Abstract

Objective. We have studied lymphocyte induced cytotoxicity and the production of interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α) during coculture of thyrocytes and autologous lymphocytes from patients with Graves' disease and from normal subjects. Patients. Thyroid tissues and lymphocytes were obtained from 28 patients with Graves' disease and from 9 control subjects. Measurements. Lymphocyte induced cytotoxicity was evaluated on autologous thyrocytes using 5 metabolic tests: the MTT assay, the neutral red uptake, lactate dehydrogenase measurement and glutathione assay. IFN-γ and TNF-α measurements were performed after 1, 5 or 7 days' coculture. Results. The lymphocytes isolated from peripheral blood (PB lymphocytes) altered the morphology and the metabolism of autologous thyrocytes. The intrathyroidal lymphocytes isolated after Dispase digestion were not toxic whereas mechanically isolated lymphocytes exerted a little toxicity. No difference was seen between Graves' disease and normal cells. The supernatants from cocultures had higher IFN-γ levels than those from lymphocyte cultures. In coculture, PB lymphocytes secreted more IFN-γ and TNF-α than intrathyroidal lymphocytes. The PR lymphocyte induced cytotoxicity was not due to IFN-γ and TNF-α alone. Conclusion. Peripheral blood lymphocytes are cytotoxic in vitro to autologous thyrocytes whereas intrathyroidal lymphocytes exert little or no cytotoxicity according to their Isolation method. The mechanisms of lymphocyte induced toxicity remain to be explained.