The Role of the Thymus in the Immune Response.

The thymus is a primary lymphoid organ essential for the development of T lymphocytes, which orchestrate adaptive immune responses. T-cell development in the thymus is spatially regulated; key checkpoints in T-cell maturation and selection occur in cortical and medullary regions to eliminate self-reactive T cells, establish central tolerance, and export naïve T cells to the periphery with the potential to recognize diverse pathogens. Thymic output is also temporally regulated due to age-related involution of the thymus accompanied by loss of epithelial cells. This review discusses the structural and age-related control of thymus function in humans.