Antigen-presenting cells and T-lymphocytes homing to the thymus shape T cell development.

Hematopoietic precursors entering the thymus undergo a maturation process leading to the generation of a variety of T cell subsets that migrate to the periphery to perform their effector functions. This maturation process is strictly regulated by multiple interactions of developing T cells with thymic stroma cells. Signals received via the T cell receptor for antigen, co-stimulatory molecules and cytokines will determine, through thymic selection and lineage choice, thymocyte-fate. Recently, different populations of peripheral antigen presenting cells and T cells have been reported to enter the thymus. Here we review how these cells migrating from the periphery to the thymus modulate T cell development.