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Proc Natl Acad Sci U S A. 2011 Aug 30;108(35):14602-7. doi: 10.1073/pnas.1109806108. Epub 2011 Aug 22.

Quantitative impact of thymic selection on Foxp3+ and Foxp3- subsets of self-peptide/MHC class II-specific CD4+ T cells.

Author information

  • 1Department of Microbiology and Center for Immunology, University of Minnesota Medical School, Minneapolis, MN 55455, USA. jjmoon@mgh.harvard.edu

Abstract

It is currently thought that T cells with specificity for self-peptide/MHC (pMHC) ligands are deleted during thymic development, thereby preventing autoimmunity. In the case of CD4(+) T cells, what is unclear is the extent to which self-peptide/MHC class II (pMHCII)-specific T cells are deleted or become Foxp3(+) regulatory T cells. We addressed this issue by characterizing a natural polyclonal pMHCII-specific CD4(+) T-cell population in mice that either lacked or expressed the relevant antigen in a ubiquitous pattern. Mice expressing the antigen contained one-third the number of pMHCII-specific T cells as mice lacking the antigen, and the remaining cells exhibited low TCR avidity. In mice lacking the antigen, the pMHCII-specific T-cell population was dominated by phenotypically naive Foxp3(-) cells, but also contained a subset of Foxp3(+) regulatory cells. Both Foxp3(-) and Foxp3(+) pMHCII-specific T-cell numbers were reduced in mice expressing the antigen, but the Foxp3(+) subset was more resistant to changes in number and TCR repertoire. Therefore, thymic selection of self-pMHCII-specific CD4(+) T cells results in incomplete deletion within the normal polyclonal repertoire, especially among regulatory T cells.

PMID:
21873213
[PubMed - indexed for MEDLINE]
PMCID:
PMC3167500
Free PMC Article

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