Early T Cell Receptor β Gene Expression Is Regulated by the Pre-T Cell Receptor–CD3 Complex

We have examined the question of whether there is an additional checkpoint in T cell development that regulates T cell receptor (TCR)-β expression in CD25⁺44⁻ thymocytes by mechanisms that are independent of the pre-TCR. Our analysis in various mutant mice indicates that all changes in cytoplasmic TCR-β expression can be accounted for by pre-TCR–dependent signal mediation, putting into question the function of a putative pro-TCR.