THYROGLOBULIN-REACTIVE T-LYMPHOCYTES IN THYROIDITIS-PRONE BB WOR RATS/

Autoimmune lymphocytic thyroiditis (LT) is a common cause of primary h ypothyroidism. Autoreactive T lymphocytes are clearly associated with this disorder, but their pathogenic role in spontaneously occurring LT remains to be established, In the present study, thyroglobulin-reacti ve T lymphocytes were cultured from young, unprimed LT-prone BB/Wor ra ts before the age of spontaneously-occurring LT, Although similar inve stigations have been conducted in animal models for experimental autoi mmune thyroiditis (EAT), this study is unique because it examines a ma mmalian model for spontaneous LT. Splenic T lymphocytes were isolated from unprimed 30 to 45-day-old Fisher and LT-prone BB/Wor rats before the onset of LT, then tested for activation by normal (NL), iodine-poo r (LI), and iodine-rich (HI) rat thyroglobulin (Tg) in bulk proliferat ion assay. BB/Worrat lymphocytes were activated by all three Tg prepar ations, but Fisher lymphocytes were unresponsive (BB/Wor vs Fisher; p< 0.0001, Student's t-test). There was no difference between BB/Wor rat responses to the three preparations (p>0.05, ANOVA), Based on these re sults, we conclude that Tg-responsive T lymphocytes can be cultured fr om young, unprimed LT-prone BB/Wor rats. Isolating such lymphocytes be fore the onset of histologically demonstrable LT strengthens the argum ent that antigen-specific T cells have a pathogenic role in the develo pment of spontaneous autoimmune thyroid disease, The fact that these l ymphocytes recognized normal, iodine-rich and iodine poor preparations of rat Tg equally well suggest that unlike the EAT model, spontaneous ly-occurring Tg-reactive T cells are not influenced by thyroglobulin's iodine content.