Functions of TCR and pre-TCR subunits: lessons from gene ablation

Recent gene-targeting experiments have highlighted the existence of checkpoints that ensure that αβ T cells do not complete intrathymic differentiation if they have not attained certain landmark events. These ‘proofreading’ mechanisms operate by way of the pre-TCR and TCR complexes, which are sequentially expressed during T-cell development. These complexes are likely to signal via their associated CD3 subunits. By activating intracellular effectors, the CD3 subunits probably modulate gene expression profiles and drive the maturing αβ T cells through a precise developmental sequence.