Deletional tolerance mediated by extrathymic Aire-expressing cells

Area of Science:

• Immunology
• Autoimmunity research
• T cell biology

Background:

• Autoimmunity arises from self-reactive T cells, necessitating their elimination during development.
• The thymus, through the autoimmune regulator (Aire) gene, expresses self-antigens to eliminate these T cells.
• A potential gap exists for T cells escaping thymic selection.

Purpose of the Study:

• To identify novel cellular mechanisms involved in preventing autoimmunity.
• To investigate the role of extrathymic cells in T cell tolerance.
• To understand how immune tolerance is maintained beyond the thymus.

Main Methods:

• Identification and characterization of extrathymic Aire-expressing cells (eTACs).
• Analysis of self-antigen expression by eTACs.
• In vivo two-photon microscopy to observe T cell-eTAC interactions.
• Assessment of eTACs' capacity to delete autoreactive T cells.

Main Results:

• Extrathymic Aire-expressing cells (eTACs) were identified in secondary lymphoid organs.
• eTACs express a diverse repertoire of self-antigens.
• Stable, antigen-specific interactions between eTACs and autoreactive T cells were observed.
• eTACs demonstrated the ability to delete autoreactive T cells.

Conclusions:

• A secondary network of extrathymic stromal cells contributes to immune tolerance.
• eTACs play a crucial role in eliminating autoreactive T cells that escape thymic negative selection.
• This extrathymic mechanism reinforces self-tolerance and prevents autoimmunity.