[The relationship between thymus involution and diseases in childhood]

70 thymuses obtained at autopsy from children who died of various diseases were studied with histological, immunohistochemical and ultrastructural methods. In the immunohistochemical study, antibodies against 8 lymphocyte differentiation antigens, including CD4, CD8, CD3, CD1, CD2, CD25, CD22 and T9 as well as those against keration and S-100 protein were used. The findings suggest that thymus involution can occur in different diseases. The differentiation process of thymocytes and the distribution of different sub-populations of T cells in the thymus are not changed by thymus involution. Among the major changes of thymus involution, the decrease in number of dendritic cells and the degeneration of epithelial cells are more important than the decrease in the number of thymocytes. Phagocytosis of macrophages seems to be the secondary way to dispose of the degenerated and dead thymocytes.