Steady-state dendritic cells continuously inactivate T cells that escape thymic negative selection

Area of Science:

• Immunology
• Autoimmunity
• T cell tolerance

Background:

• Peripheral tolerance is vital for preventing autoimmune diseases caused by self-reactive T cells escaping thymic deletion.
• The precise roles of thymic versus peripheral tolerance in managing self-specific T cell repertoires remain unclear.

Purpose of the Study:

• To investigate the relative contributions of thymic and peripheral tolerance induction in inactivating self-reactive T cells.
• To assess the role of peripheral dendritic cells (DCs) in maintaining tolerance to self-antigens.

Main Methods:

• Utilized 11c.OVA mice with ovalbumin (OVA) expression targeted to DCs and Vbeta5 TCR transgenic mice with diverse OVA-specific T cells.
• Examined the frequency of OVA-specific CD8 single-positive thymocytes and peripheral T cells.
• Assessed the impact of adult thymectomy on peripheral OVA-specific T cells.

Main Results:

• OVA expression in thymic DCs reduced the frequency of OVA-specific CD8 thymocytes, but some escaped negative selection.
• Functional OVA-specific T cells were detected in the periphery after escaping thymic deletion.
• Peripheral T cells specific for OVA declined after adult thymectomy, indicating susceptibility to peripheral inactivation.

Conclusions:

• Peripheral tolerance induction by steady-state dendritic cells is essential for inactivating self-reactive T cells that escape thymic negative selection.
• Resting peripheral DCs play a critical role in maintaining immune homeostasis when thymic deletion is insufficient.