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tiation, thereby temporarily exhausting the supply of antigen-reactive cells.11 The activity of autoaggressive T cells may also be suppressed by veto cells,12 antigen-specific regulatory T cells,13 or nutrient deprivation in specialized sites such as the maternal-fetal interface.14 What follows is a review of a novel form of tolerance induction by which mature, peripheral CD4+ T cells reinitiate rearrangement of TCR loci to transform a self reactive TCR into one that is self tolerant. This tolerance mechanism, termed TCR revision, rescues self reactive lymphocytes and generates from them a diverse population of functional, self tolerant CD4+ T cells. However TCR revision is a risky form of tolerance induction, as it entails potential illegitimate DNA rearrangement events and generation of TCRs outside the selective thymic microenvironment.

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