This study maps where different thymosin peptides are made inside the human thymus and shows that the amount of some, especially thymosin fraction 6, is highest in very young infants and in adults up to their early 30s, hinting that production drops as we age. It doesn’t test taking thymosin‑alpha‑1 as a supplement, so there’s no direct dosing advice.

The specific compartmentalization of intrathymic lymphoid cells in different steps of T-cell maturation and the involvement of thymosin components in these steps prompted us to evaluate the localization of epithelial cells synthesizing various thymosin components. Thymosin fractions 5 and 6 were found in epithelial cells throughout the thymus cortex and medulla. Thymosin alpha 1 and beta 4 were observed in subcapsular and perivascular epithelial cells, and thymosin alpha 1 was observed in the medullary epithelium. Thymosin alpha 7 was exclusively found in Hassall's corpuscles and adjacent epithelial cells. We conclude that the organ localization of epithelium synthesizing different thymosin components is associated with the organ localization of intrathymic T-cell maturation steps. The involution of the human thymus, starting during the third decade of life, has been related to the age-dependency of thymus humoral factors in the circulation. However, quantitative data on humoral factor synthesizing epithelial cells are lacking. We found a strong intensity of thymosin fraction 6 expression by epithelium in thymus tissue from donors in the early postnatal period (2-4 months of age) and from all four donors aged 20-30 years. This phenomenon was paralleled by a high number of thymosin fraction 6 positive cells per unit area.