T Cells Off

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Science  18 Dec 1998:
Vol. 282, Issue 5397, pp. 2149
DOI: 10.1126/science.282.5397.2149m

T cells not only can be activated, but also must be turned off or the organism runs the risk of rampant autoimmunity, as is the case in mice genetically deficient in the protein CTLA-4. Lee et al. (p. 2263) determined the stage of the activation process that is affected by CTLA-4. CTLA-4 complexes with a phosphatase, SHP-2, and was found to bind to and dephosphorylate the ξ chain of the T cell antigen receptor. This direct action at the “source” of the activation signal implies that the TCR signal may be thwarted before the cell is committed to proliferate.

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