The Autoimmune Infiltrate of Basedow's Disease: Analysis at Clonal Level and Comparison with Hashimoto's Thyroiditis

The availability of high efficiency T-cell cloning techniques recently allowed the identification and characterization of clones derived from the thyroid infiltrate of patients with autoimmune thyroid diseases. Phenotypical and functional analysis of T-cell clones obtained from thyroid infiltrates of patients with Hashimoto's thyroiditis show that most of them are progenies of CD8+ cytolytic T cells with natural killer activity. This phenomenon, of potential importance in tissue damage, is markedly less pronounced in Basedow's disease glands. In both Hashimoto's thyroiditis and Basedow's disease only a minority of clones appear to be specific for autologous thyroid cells and most of them are potent interferon-gamma producers, while increased secretion of tumor necrosis factor-alpha is observed only in Hashimoto's thyroiditis. In contrast with normal lymphoid tissue, only very few T cell clones derived from both BD and HT infiltrates were able to produce detectable amounts of IL-4, suggesting that most of the thyroid-infiltrating T cells represent quite homogeneous populations of Th1-type "inflammatory" T cells. This peculiar potential of lymphokine secretion could play a role in the expression and/or maintenance of thyroid autoimmunity and thyroid functional damage.