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Negative selection of T cells occurs throughout thymic development.
K K Baldwin1, B P Trenchak, J D Altman
1Program in Immunology, Department of Microbiology and Immunology, Howard Hughes Medical Institute, Stanford University, CA 94305, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|July 8, 1999
Summary
Thymic selection processes, including positive and negative selection, shape T cell development. This study reveals negative selection occurs independently and prior to positive selection, ensuring self-tolerance without sequential dependency.
Area of Science:
- Immunology
- T cell development
- Thymic selection
Background:
- T cell repertoire development relies on thymic positive and negative selections to ensure self-MHC reactivity and self-tolerance.
- The sequential or independent nature of these selection processes remains a subject of debate in immunology.
Purpose of the Study:
- To investigate the relationship between positive and negative selection during T cell development.
- To determine if thymic selection processes occur independently or sequentially.
Main Methods:
- Utilized tetrameric peptide-MHC complexes for fluorescent labeling and monitoring of thymocyte populations.
- Focused on thymocytes specific for moth cytochrome c (MCC)/I-Ek in TCR beta mice.
- Analyzed thymocyte deletion and T cell receptor (TCR) expression levels.
Main Results:
- Tetramer-positive thymocytes were detected even in the earliest TCR-expressing immature cells.
- Strongly binding thymocytes specific for MCC/I-Ek were deleted earlier and more extensively than weakly binding cells.
- Negative selection occurred continuously throughout development and preceded any observable positive selection.
Conclusions:
- Positive and negative selection are independent processes in T cell development.
- These selection events do not require a specific sequential order for T cell repertoire maturation.
- Findings clarify the distinct mechanisms governing self-MHC reactivity and self-tolerance in developing T cells.