SIGNALING CHECKPOINTS DURING THE DEVELOPMENT OF T-LYMPHOCYTES

Two major lineage decisions face immature T cells as they develop in t he thymus. At an early stage in their development, they must first com mit to either the gamma delta or alpha beta lineages. If they opt for the alpha beta lineage, then at a later stage they must also choose be tween a CD4(+) or CD8(+) fate before they can pass through the thymic medulla and exit to the periphery. Thymocyte survival at key developme ntal checkpoints is determined by signaling from cytokine receptors an d the T-cell receptor. Recent advances have been made in contemporary understanding of the signals that regulate thymocyte survival. prolife ration and lineage decisions.