Mapping the two distinct proliferative bursts early in T-cell development.

T-cell development occurs in the thymus and is tightly regulated to produce a diverse enough repertoire of mature T cells that can recognize any potential pathogen. The development of T cells is dependent on small numbers of uncommitted precursors that continually seed the thymus from the bone marrow. As they progress along the developmental pathway, there is a massive expansion in cell number to generate the necessary diversity in T-cell receptor chain usage.