Murine thymic selection quantified using a unique method to capture deleted T cells

• Published in: Proceedings of the National Academy of Sciences - PNAS 2013-03, Vol.110 (12), p.4679-4684
• Main Authors: Stritesky, Gretta L., Xing, Yan, Erickson, Jami R., Kalekar, Lokesh A., Wang, Xiaodan, Mueller, Daniel L., Jameson, Stephen C., Hogquist, Kristin A.
• Format: Article
• Language: English
• Subjects: Animals; Antigen presenting cells; Antigens; Apoptosis; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - immunology; Bcl-2-Like Protein 11; Biological Sciences; Clonal deletion; Clonal Deletion - physiology; Cloning; Cytometry; Genotype & phenotype; Histocompatibility Antigens - immunology; Membrane Proteins - genetics; Membrane Proteins - immunology; Mice; Mice, Knockout; Models, Immunological; Negative selection; Nuclear Receptor Subfamily 4, Group A, Member 1 - genetics; Nuclear Receptor Subfamily 4, Group A, Member 1 - immunology; Positive selection; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - immunology; Rodents; T cell antigen receptors; T cell receptors; T lymphocytes; T-Lymphocytes, Regulatory - immunology; Thymocytes; Thymus Gland - immunology; Tissues
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1217532110

Thymic positive and negative selection events generate a T-cell repertoire that is MHC restricted and self-tolerant. The number of T cells undergoing positive and negative selection in normal mice has never been firmly established. We generated mice that lack the proapoptotic molecule Bim (bcl2l11) together with a Nur77 ᴳFᴾ transgene, which allowed the identification and enumeration of T cells that would normally undergo clonal deletion. Using this method, we report the striking observation that six times more cells undergo negative selection than complete positive selection. Seventy-five percent of the negatively selected cells are deleted at the double positive stage in the thymic cortex, compared with 25% at the single positive stage in the medulla. The fact that more thymocytes are highly reactive to MHC than are weakly reactive is inconsistent with a random model of recognition and suggests that T-cell recognition is MHC biased. Furthermore, Bim ⁻/⁻ mice had an increased number of GFP ʰⁱ cells in the peripheral lymphoid tissue and a corresponding increase in antigen experienced or anergic cell phenotype. Our data also show that the CD4+ T cells that are clonally deleted experienced only slightly stronger T-cell receptor signaling than those that developed into regulatory T cells.