A role for accessibility to self-peptide-self-MHC complexes in intrathymic negative selection

Area of Science:

• Immunology
• Cell Biology
• Developmental Biology

Background:

• The anatomical sites of intrathymic T cell selection are debated.
• Understanding T cell selection is crucial for autoimmune disease research.

Purpose of the Study:

• To investigate in vivo T cell negative selection by self-peptide-MHC complexes with differential tissue expression.
• To determine if anatomical location influences T cell negative selection.

Main Methods:

• Utilized Y-Ae mAb and 1H3.1 TCR specific for E alpha 52-68 peptide bound to I-A(b).
• Generated 1H3.1 TCR-transgenic mice bred to mice with I-E alpha transgenes under various tissue-specific promoters.
• Analyzed thymic cellularity, T cell populations (V beta 6(+)CD4(+) cells), and in vitro responses.

Main Results:

• All double-transgenic mice showed diminished thymic cellularity and depletion of V beta 6(+)CD4(+) lymph node cells.
• CD4(+)CD8(+) thymocyte numbers were significantly reduced, indicating effective in vivo negative selection in the thymic cortex.
• Both cortical epithelial cells and dendritic cells supported negative selection, though with differing efficiencies.

Conclusions:

• Negative selection of autoreactive T cells can occur effectively in the thymic cortex in vivo.
• Accessibility to self-peptide-MHC complexes, not just anatomical site, determines negative selection efficiency.
• This finding supports a model where T cell selection is influenced by peptide-MHC availability.