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 (theta)] 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 (theta) antigens than average normal thymocytes.