The kinetics of haemopoietic differentiation assessed by in vitro bone marrow culture in endotoxin-treated and in anaemic calves.

Marrow aspirates from calves injected with Pseudomonas aeruginosa endotoxin showed an increased number of granulocyte/macrophage progenitor cells, and a reduced number of erythroid progenitor cells. On the other hand, marrow aspirates from calves made anaemic by repeated phlebotomy showed an increased number of erythroid progenitor cells, and a reduced number of granulocyte/macrophage progenitor cells. These observations were interpreted as evidence of stem cell erythroid-granuloid directional competition occurring in response to the need for a particular cell type.