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Updated: Sep 26, 2026

Examination of Thymic Positive and Negative Selection by Flow Cytometry
Published on: October 8, 2012
A role for the B7-1/B7-2:CD28/CTLA-4 pathway during negative selection
Janet E Buhlmann1, Sheryl Krevsky Elkin, Arlene H Sharpe
1Department of Pathology, Immunology Research Division, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
Abstract:
Although costimulation plays an important role in activating naive T cells, its role in negative selection is controversial. By following thymocyte deletion induced by endogenous superantigens in mice lacking B7-1 and/or B7-2, we have identified a role for both B7-1 and B7-2 in negative selection. Studies using CD28-deficient and CD28/CTLA-4-double-deficient mice have revealed that either CD28 or another as yet undefined coreceptor can mediate these B7-dependent signals that promote negative selection. Finally, CTLA-4 delivers signals that inhibit selection, suggesting that CTLA-4 and CD28 have opposing functions in thymic development. Combined, the data demonstrate that B7-1/B7-2-dependent signals help shape the T cell repertoire.
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