SPLEEN FOCUS IN FRIEND'S DISEASE: AN ELECTRON MICROSCOPIC STUDY

The spleen foci of Friend's disease, which were proved to be early splenic lesions of Friend's disease, were produced in male DDD mice and in female hybrid, F1 (C3H/DDD) mice by the inoculation of the diluted virus solution, and were examined by electron microscopy. The major part of the spleen foci in early stages was occupied by tumor cells, which resembled the proerythroblasts or basophilic erythroblasts. The most complex cells, which might be interpreted as immature reticulum cells and considered identical to Friend cells that former researchers had described, showed gradual transition to the proerythroblastic tumor cells. Viral particles were more frequently observed in and around the spleen foci than in other areas, and their budding was seen in all kinds of tumor cells. Even the small, morphologically normal basophilic erythroblasts were observed budding the viral particles. Megakaryocytes near the spleen foci showed irregularly shaped viral particles, suggesting active proliferation of the virus in such early stages.