T, B and K cells in autoimmune thyroid disease

Area of Science:

• Immunology
• Endocrinology
• Cell Biology

Background:

• Autoimmune thyroid diseases (AITD) encompass conditions like Hashimoto thyroiditis and thyrotoxicosis.
• The role of cytotoxic activity in the pathogenesis of AITD is not fully understood.
• Natural killer (NK) cell activity, specifically K-cell mediated cytotoxicity, is a key component of innate immunity.

Purpose of the Study:

• To investigate K-cell cytotoxic activity in patients with various autoimmune thyroid diseases.
• To determine if K-cell activity differs between untreated patients, those in early treatment stages, and those with longer treatment durations.
• To explore correlations between K-cell activity, disease severity markers (goiter size, antibody titers), and lymphocyte subsets in AITD.

Main Methods:

• Peripheral blood lymphoid cells from 104 AITD patients and controls were assessed for K-cell cytotoxic activity using chicken erythrocytes as target cells.
• Patients were categorized by diagnosis (Hashimoto thyroiditis, primary hypothyroidism, thyrotoxicosis) and treatment status (newly diagnosed/untreated, ≤1 year, >1 to ≤5 years).
• Lymphocyte subsets (T and B cells) were quantified using sheep red blood cell rosettes and indirect immunofluorescence; null cell percentages were calculated.

Main Results:

• Significantly elevated K-cell cytotoxic activity was observed in newly diagnosed/untreated patients and those treated for ≤1 year across AITD types.
• Patients treated for >1 to ≤5 years did not show a comparable increase in K-cell activity.
• In untreated thyrotoxicosis, high K-cell activity was linked to smaller goiters and undetectable serum thyroid autoantibodies.
• Circulating T and B lymphocyte numbers and proportions, as well as null cell percentages, did not differ significantly between patients and controls.

Conclusions:

• K-cell cytotoxic activity is enhanced in early stages of autoimmune thyroid disease, particularly in untreated or recently treated individuals.
• The observed correlation between K-cell activity, goiter size, and antibody status in thyrotoxicosis suggests a potential role in disease modulation.
• Peripheral blood lymphocyte subset distribution remains largely unchanged in AITD, indicating that alterations in K-cell activity are not explained by shifts in T and B cell populations.