Ultrastructure of the involuting thymus in mice.

The study was intended to research the changes in the fine structure of thymus in old mice. The research were made in 3 strains of mice (Swiss, Porton and C 57 BL). In the stroma of the senile thymus takes place--full disappearance of mesenchymal reticular cells, as well as the considerable reduction of thymocytes, which were digested by macrophages. In the involuted thymus a large number of plasma cells and lymphoblasts were present. The author suggest the hypothesis that involution has an immunologic character.