Electron Microscopic Study of Lymphatic Tissues of Mice Inoculated with a Leukemogenic Extract from Radiation-induced Tumors

Macroscopic, histological, and ultrastructural changes in lymphatic tissues, particularly that of the spleen, were studied in C57BL mice inoculated i.p. with a cell-free extract (Passage D from Dr. Duplan) of lymphatic tissues from mice in which leukemia was originally radiation induced. Splenomegaly was observed macroscopically, followed by hypertrophy of lymph nodes. But no change of the thymus was apparent throughout the course of this infection. The histological appearance of the spleen showed hyperplasia of the germinal centers within the lymphatic nodules. The lymphoid cells were replaced progressively by proliferation of the reticular cells and, to a lesser extent, by cells of the plasmocytic line. Typical type C particles were found in the splenic white pulp. During the early stages of this disease, the particles were concentrated in the extracellular spaces within the germinal centers. The infected cells were predominantly immunoblasts, plasmoblasts, plasmocytes, and to a lesser extent lymphoblasts, lymphocytes, and reticular cells. Viral particles could not be detected within megakaryo-cytes or erythrocytic precursor cells. A few intracisternal type A particles were observed in both plasmocytes and reticular cells. The characteristics of this leukemia are discussed in relation to those described by Kaplan and Rauscher.