Expression of major histocompatibility complex class II antigen in NOD mouse thyroid

Area of Science:

• Immunology
• Endocrinology
• Autoimmunity

Background:

• Non-obese diabetic (NOD) mice spontaneously develop autoimmune thyroiditis alongside diabetes.
• Thyroid infiltration by mononuclear cells is an early event in NOD mice.
• The role of major histocompatibility complex (MHC) class II (Ia) antigen expression in thyroid autoimmunity is unclear.

Purpose of the Study:

• To investigate the expression of MHC class II (Ia) antigens in the thyroids of NOD mice at different ages and disease stages.
• To determine if Ia antigen expression precedes or follows immune cell infiltration in the development of thyroiditis.

Main Methods:

• Immunohistochemical analysis of thyroid tissues from NOD mice of varying ages (18-33 days, 51-73 days, >89 days) with and without thyroiditis.
• Assessment of MHC class II (Ia) antigen expression on thyroid epithelial cells (TEC) and interstitial cells, including macrophages.
• Comparison with age-matched non-autoimmune BALB/c mice as controls.

Main Results:

• MHC class II antigen expression was minimal in young NOD mice (18-33 days) with infiltrated thyroids, suggesting it is secondary to infiltration.
• Ia antigen expression significantly increased in both infiltrated and uninfiltrated thyroids of older NOD mice (51-73 days and >89 days).
• Ia-expressing cells included TEC and macrophages; macrophages were present in NOD mice from early ages, with increased prevalence in older mice.

Conclusions:

• MHC class II antigen expression in NOD mouse thyroids appears to be a consequence, not the initiator, of the autoimmune process.
• Ia-positive cells, including TEC and macrophages, can present thyroid-specific antigens to T cells, potentially perpetuating autoimmune thyroid destruction.
• The findings highlight the dynamic role of antigen-presenting cells in the pathogenesis of autoimmune thyroiditis in NOD mice.