Regulation of early chicken thymocyte proliferation by transforming growth factor-β from thymic stromal cells and thymocytes

We examined expression of TGF-βs in chicken thymic stromal cells and thymocytes and roles of TGF-βs in thymocyte development within the thymus. Thymic stromal cells expressed TGF-β 2 and 3 genes but not TGF-β 4 gene. Thymocytes showed expressions of TGF-β 2, 3 and 4 genes and each TGF-β gene was expressed more strongly in CD3− than CD3+ thymocytes. When anti-TGF-β antibody was added with supernatants of stromal cells into thymocyte culture, only proliferative activity of CD3− thymocytes was enhanced and the cell in S and G2/M compartments of cell cycle increased. These results suggest that TGF-β which is expressed in the thymus may regulate the ability of immature thymocytes to progress through the cells cycle and to differentiate to CD3+ thymocytes.