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An electron microscopic study of hepatic erythropoiesis in adult mice with Friend virus disease.

A polycythemia-inducing strain of Friend virus was injected into adult mice. Animals were sacrificed on days 2, 5, 9, 11, and 14, and specimens of liver were fixed and embedded for light and electron microscopy. From some mice, samples of bone marrow and spleen were also processed for microscopy. Hepatic erythropoiesis was established as early as 2 to 5 days after inoculation. Often, red cell maturation occurred in typical islands. These included a central macrophage which in many instances appeared to be a Kupffer cell. The number and size of red cell foci increased through day 14. Extensive ineffective erythropoiesis involving erythroblast death occurred within these foci. This premature cell death may be related to large inclusions, thought to be autophagosomes, in the cytoplasm of erythroblasts. A few undifferentiated cells, presumed to be the reticulum cells of Friend virus disease, were observed in the liver at 9 to 14 days after infection. The morphology of these cells resembled that of primitive hemopoietic elements. These studies indicate that the liver, along with the spleen, contributes to the polycythemia in the early phase of Friend virus disease.