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Updated: Aug 10, 2026

Examination of Thymic Positive and Negative Selection by Flow Cytometry
Published on: October 8, 2012
Clonal deletion and clonal anergy in the thymus induced by cellular elements with different radiation sensitivities
J L Roberts1, S O Sharrow, A Singer
1Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Abstract:
The present study demonstrates that immune tolerance can be achieved in the thymus both by clonal deletion and by clonal inactivation, but that the two tolerant states are induced by cellular elements with different radiation sensitivities. TCR engagement of self antigens on bone marrow-derived, radiation-sensitive (presumably dendritic) cells induces clonal deletion of developing thymocytes, whereas TCR engagement of self antigens on radiation-resistant cellular elements, such as thymic epithelium, induces clonal anergy. The nondeleted, anergic thymocytes can express IL-2-Rs but are unable to proliferate in response to either specific antigen or anti-TCR antibodies, and do develop into phenotypically mature cells that emigrate out of the thymus and into the periphery.
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