THYROGLOBULIN-SPECIFIC T-CELL LINE FROM A HEALTHY INDIVIDUAL DOES NOTPRODUCE PROINFLAMMATORY CYTOKINES ON ANTIGENIC-STIMULATION - AN IMPLICATION FOR POSSIBLE FAIL-SAFE MECHANISM TO AVOID AUTOIMMUNITY

In order to investigate the regulation of autoimmune response to thyro globulin (Tg), one of the thyroid autoantigens, we established a Tg-sp ecific T cell line by stimulation of peripheral blood mononuclear cell s from a healthy volunteer with Tg and characterized its cytokine prod uction pattern. The Tg-specific T cell line, designated DH5D1, obtaine d from a limiting dilution culture bore alphabeta T cell receptor and was CD4 and CD45RO positive. Upon stimulation with Tg, DH5D1 secreted little or no titers of IL-2, TNF-alpha, and IFN-gamma, whereas activat ion with combination of phorbor myristate acetate and calcium ionophor e produced measurable levels of these cytokines. These results indicat e that the Tg-specific T cell line is not defective in its capacity to produce proinflammatory cytokines and suggest that the inability of c ytokine production by autoreactive T cells of healthy individuals is o ne fail-safe mechanism for preventing aggression of harmful autoimmune response.