T-cell subset relationships in thymocyte development.

During the past couple of years there has been significant progress in our understanding of the development of different lineages of T cells within the thymus. Pathways, subpopulations and cellular dynamics are all becoming clearer. Signal transduction through primary and accessory receptors is also beginning to be understood. However, the exact nature of the events that lead uncommitted cells to choose a particular lineage (either alpha beta/gamma delta or CD4+/CD8+) has still not been determined.