Endocrine Abstracts

Objective: The Fas/Fas ligand (FasL) apoptotic pathway is activated in patients with autoimmune thyroid disease (AITD). It is believed that Fas and FasL expression in intrathyroidal T lymphocytes and thyrocytes is regulated in a manner resulting in thyroid cell apoptosis in Hashimoto’s thyroiditis (HT) or lymphocyte apoptosis in Graves’ disease (GD). The hypothesis that Fas and FasL may be differentially expressed on peripheral lymphocytes in patients with HT and GD was investigated in the present study.

Methods: A total of 45 patients with untreated HT, 30 with subclinical hypothyroidism (mean age 34.9±14.9 years) and 15 with clinical hypothyroidism (mean age 37.0±18.4 years) as well as 13 hyperthyroid patients with untreated GD (mean age 35.8±14 years) were studied and compared with 20 healthy controls (mean age 37.4±15.3 years. Fas and FasL expression on CD4⁺ and CD8⁺ peripheral T lymphocytes were evaluated using two- and three-color flow cytometry on FACScan and the appropriate software (CELL Quest, Becton Dickinson).

Results: The proportion of CD4⁺ T cells expressing Fas was increased in both GD (64.1%±14.2, P<0.05) and HT patients (61.1%±15.1 in those with clinical and 61.4%±13.0 in those with subclinical hypothyroidism, compared to controls (49.9%±7.7, P<0.05). The proportion of CD8+T cells expressing Fas was also increased in patients with HT (77.4%±16.6 in those with clinical and 74.4%±14.4 in those with sublclinical hypothyroidism, P<0.05) while no significant increase was observed in patients with GD (67.2%±10.7) compared to controls (59.8%±14.0). FasL expression on peripheral CD4⁺, CD8⁺ lymphocytes was below 3%.

Conclusion: Fas expression is upregulated in peripheral CD4⁺ and CD8⁺ T lymphocytes in patients with untreated AITD with no significant differences between patients with HT and those with GD. This may reflect the activation of the Fas mediated apoptotic pathway in AITD.