TCR and Notch signaling in CD4 and CD8 T-cell development.

The generation of CD4 and CD8 alphabeta T-cell lineages from CD4+ CD8+ double-positive (DP) thymocyte precursors is a complex process initiated by engagement of major histocompatibility complex (MHC) by T-cell receptor (TCR) and coreceptor. Quantitative differences in TCR signaling induced by this interaction impose an instructional bias on CD4/CD8 lineage commitment that must be reinforced by MHC recognition and TCR signaling over subsequent selection steps in order for the thymocyte to progress and mature in the adopted lineage. Our studies show that the transmembrane receptor Notch plays a role in this process by modifying TCR signal transduction in DP thymocytes. In this review, we consider the functional relationship of TCR and Notch signaling pathways in the selection and specification of CD4 and CD8 T-cell lineages.