Extramedullary eosinophilopoiesis in the liver of Schistosoma japonicum-infected mice, with reference to hemopoietic stem cells.

Extramedullary hemopoiesis recognized as hemopoietic foci increased in the liver of Schistosoma japonicum-infected mice in parallel with kinetic changes in periovular granuloma formation. At the peak of the response, about 65% of the hepatic hemopoietic foci were of eosinophil lineage. When S. japonicum-infected mice were irradiated, hepatic hemopoietic foci rapidly disappeared within 3 days, whereas inflammatory cells in the periovular granulomas slowly reduced in number. When the number of hemopoietic stem cells in the liver were examined by spleen-colony assay, kinetic changes in the number of hemopoietic stem cells in hepatic nonparenchymal cells paralleled those of hepatic hemopoietic foci. Hemopoietic stem cells were rare in the granuloma cells. These results indicate that in response to the increased demand for eosinophils and other inflammatory cells, the liver acts as an extramedullary hemopoietic organ in which inflammatory cells are generated from hemopoietic stem cells.