Aire suppresses CTLA-4 expression from the thymic stroma to control autoimmunity

Area of Science:

• Immunology
• Autoimmunity
• Cell Biology

Background:

• Aire-dependent autoimmunity is linked to impaired thymic regulatory T cell (Treg) production.
• Treg development requires T cell receptor (TCR) stimulation by self-antigens presented by medullary thymic epithelial cells (mTECs).
• Reduced self-antigen expression in mTECs was previously thought to cause lower Treg production in Aire deficiency.

Purpose of the Study:

• To investigate the role of CTLA-4 expression in mTECs in Aire-deficient mice.
• To elucidate the mechanism by which Aire deficiency leads to impaired Treg production and autoimmunity.
• To determine if targeting mTEC CTLA-4 can restore Treg production and prevent autoimmunity.

Main Methods:

• Analysis of CTLA-4 expression in mTECs from Aire-deficient mice.
• Investigating the interaction between mTECs and thymic dendritic cells (DCs) using co-culture systems.
• Assessing Treg production and autoimmunity in Aire-deficient mice with and without mTEC-specific CTLA-4 depletion.

Main Results:

• Aire-deficient mTECs abnormally express CTLA-4.
• Ectopic mTEC CTLA-4 binds and removes CD80/CD86 ligands from DCs, impairing DC co-stimulation and self-antigen presentation.
• Depletion of CTLA-4 from mTECs rescued Treg production and prevented organ-specific autoimmunity in Aire-deficient mice.

Conclusions:

• Aire deficiency disrupts thymic tolerance by inducing aberrant mTEC CTLA-4 expression.
• This mechanism impairs DC function, leading to insufficient Treg development and autoimmunity.
• Targeting mTEC CTLA-4 represents a potential therapeutic strategy for Aire-dependent autoimmune diseases.