Induction of T-Cell Differentiation In Vitro by Thymin, a Purified Polypeptide Hormone of the Thymus

Thymin, a purified polypeptide isolated from bovine thymus, was shown to induce the expression of differentiation antigens characteristic of thymocytes [TL and Thy-1 (θ)] when incubated in vitro with mouse bone marrow or spleen cells. This induction occurred in 5-10% of the cells from bone marrow after a 2-hr incubation with subnanogram concentrations of thymin. The induced cells expressed more TL and Thy-1 (θ) antigens than average normal thymocytes.