Summary
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 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.
