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J. Exp. Med.,
Volume 189, Number 1, January 4, 1999 145-158
B in Promoting
Double Positive Thymocyte Apoptosis
By


From the * Departments of Medicine and Pathology, University of Chicago, Chicago, Illinois 60637;
and the To examine the role of nuclear factor (NF)-
Department of Pharmacology, University of California San Diego, San Diego,
California 92093
B in T cell development and activation in vivo,
we produced transgenic mice that express a superinhibitory mutant form of inhibitor
B-
(I
B-
A32/36) under the control of the T cell-specific CD2 promoter and enhancer (mutant
[m]I
B-
mice). Thymocyte development proceeded normally in the mI
B-
mice. However, the numbers of peripheral CD8+ T cells were significantly reduced in these animals. The
mI
B-
thymocytes displayed a marked proliferative defect and significant reductions in interleukin (IL)-2, IL-3, and granulocyte/macrophage colony-stimulating factor production after
cross-linking of the T cell antigen receptor. Perhaps more unexpectedly, double positive (CD4+CD8+; DP) thymocytes from the mI
B-
mice were resistant to
-CD3-mediated apoptosis in vivo. In contrast, they remained sensitive to apoptosis induced by
-irradiation. Apoptosis of wild-type DP thymocytes after in vivo administration of
-CD3 mAb was preceded
by a significant reduction in the level of expression of the antiapoptotic gene, bcl-xL. In contrast, the DP mI
B-
thymocytes maintained high level expression of bcl-xL after
-CD3 treatment. Taken together, these results demonstrated important roles for NF-
B in both inducible cytokine expression and T cell proliferation after TCR engagement. In addition, NF-
B is required for the
-CD3-mediated apoptosis of DP thymocytes through a pathway that involves
the regulation of the antiapoptotic gene, bcl-xL.
B;
inhibitor
B-
A32/36;
thymocytes;
apoptosis;
bcl-xL
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