Antigen challenge inhibits thymic emigration.

T cell development in the thymus involves a series of TCR-mediated control points including TCR-beta selection and positive and negative selection. Approximately half of the thymic sojourn is spent in the medulla, where thymocytes undergo final maturation before emigrating to the periphery. Although it is acknowledged that thymic emigration is an active process, relatively little is known about how this is regulated, why it takes so long, and whether TCR-mediated signaling can influence this step.

Activation of thymic regeneration in mice and humans following androgen blockade.

The thymus undergoes age-related atrophy, coincident with increased circulating sex steroids from puberty. The impact of thymic atrophy is most profound in clinical conditions that cause a severe loss in peripheral T cells with the ability to regenerate adequate numbers of naive CD4+ T cells indirectly correlating with patient age. The present study demonstrates that androgen ablation results in the complete regeneration of the aged male mouse thymus, restoration of peripheral T cell phenotype and function and enhanced thymus regeneration following bone marrow transplantation.

Role for CCR7 ligands in the emigration of newly generated T lymphocytes from the neonatal thymus.

Most T lymphocytes are generated within the thymus. It is unclear, however, how newly generated T cells relocate out of the thymus to the circulation. The present study shows that a CC chemokine CCL19 attracts mature T cells out of the fetal thymus organ culture.