Compensatory splenic hemopoiesis in beta-thalassemic mice.

beta-Thalassemic mice, homozygous for the deletion of the beta major-globin gene, were investigated for compensatory hemopoiesis in bone marrow and spleen. Apart from characteristic severe anemia, these mice have a marked granulocytosis, monocytosis and lymphocytosis. A large compensatory expansion of late (CFU-E) erythroid progenitor cells was demonstrated, predominantly in the spleen. Immature hemopoietic cells (CFU-S) were also expanded, as were early progenitor cells of erythroid (BFU-E), as well as granulocyte/macrophage (GM-CFU) and megakaryocytic (CFU-Meg) lineages. It is concluded that the persistent erythropoietic stress results in a selective expansion of immature hemopoietic cells and inappropriate production of nonerythroid blood cells from excess production of progenitor cells.