Role of neuropeptides, hormones, and growth factors in regulating thymopoiesis in middle to old age

The deterioration in adaptive immunity and T-lymphocyte output and the narrowing of the T cell receptor repertoire with age are largely attributable to thymic involution. The loss of thymic function with age may be due to diminished numbers of early thymic progenitors and epithelial cells, and the loss of critical tropic factors within the thymic microenvironment. Here we review some of the recent literature demonstrating a role for neuropeptides, hormones, and growth factors that can influence thymopoiesis associated with stress and aging.