Central tolerance to self-antigen expressed by cortical epithelial cells

Area of Science:

• Immunology
• T cell development
• Self-tolerance

Background:

• Developing thymocytes exposed to high-affinity self-antigens (self-Ag) induce T cell tolerance.
• Mechanisms include clonal deletion, receptor editing, anergy, and regulatory T cell selection.
• The signals determining these distinct tolerance pathways remain unclear.

Purpose of the Study:

• To investigate whether specific instructions from cortical epithelial cells (cEC) presenting self-antigen lead to receptor editing.
• To determine if the antigen-presenting cell (APC) subset influences thymic tolerance mechanisms.
• To explore intrinsic differences in T cell receptor (TCR) engagement with self-antigens.

Main Methods:

• Generated transgenic mice expressing specific self-antigens (2C and HY ligands) under the keratin 14 promoter, specifically in cEC.
• Utilized OT-I mice where antigen was presented by all thymic APCs.
• Analyzed the tolerance mechanisms (clonal deletion vs. receptor editing) in developing T cells.

Main Results:

• Contrary to the hypothesis, the APC subset did not influence the tolerance mechanism.
• Clonal deletion was observed in 2C and HY models even when antigen was presented solely by cEC.
• Receptor editing occurred in OT-I mice irrespective of whether antigen was presented by all thymic APCs.

Conclusions:

• Thymic tolerance mechanisms are not dictated by the APC subset presenting the antigen.
• Different TCRs exhibit intrinsic variations that determine their specific thymic tolerance pathway.
• Self-antigen presentation by cEC alone can lead to clonal deletion, while broader presentation does not preclude receptor editing.