IL-10 expression in thyroid glands: protective or harmful role against thyroid autoimmunity?

Area of Science:

• Immunology
• Endocrinology
• Molecular Biology

Background:

• Interleukin-10 (IL-10) is a cytokine with known immunomodulatory functions, including suppression of cellular immunity and stimulation of humoral responses.
• In animal models, IL-10 has demonstrated protective effects against autoimmune conditions.
• The specific role of IL-10 in human autoimmune thyroid disease remains to be fully elucidated.

Purpose of the Study:

• To investigate the presence and role of IL-10 in human autoimmune thyroid disease.
• To determine if IL-10 levels correlate with disease activity and histological features.
• To explore the in vitro effects of IL-10 on thyrocyte HLA class II expression.

Main Methods:

• Total RNA extraction from thyroid tissue samples (normal, multinodular, Graves', Hashimoto's).
• Semiquantitative polymerase chain reaction (PCR) to measure IL-10 mRNA levels.
• In situ hybridization and immunohistochemistry to localize IL-10 expression.
• Assessment of HLA class II expression on thyrocytes and in vitro functional assays with IL-10 and anti-IL-10 antibodies.

Main Results:

• Significantly higher IL-10 levels were detected in autoimmune thyroid glands compared to non-autoimmune glands.
• IL-10 mRNA was localized to infiltrating lymphomononuclear cells within the thyroid tissue.
• Higher IL-10 levels correlated with increased B and T cell infiltration and spontaneous HLA class II expression on thyrocytes.
• In vitro, IL-10 did not regulate spontaneous or induced HLA class II expression on thyrocytes.

Conclusions:

• Active autoimmune thyroiditis involves the simultaneous production of both Th1 and Th2 cytokines, including IL-10.
• The role of IL-10 in autoimmune thyroiditis may be primarily to stimulate B cell proliferation and antibody production.
• IL-10 does not appear to suppress proinflammatory cytokine release or directly regulate thyrocyte HLA class II expression in this context.