Effect of Corynebacterium parvum on hemopoietic stem-cell kinetics.

The intravenous administration of 548 microgram of killed Corynebacterium parvum (C. parvum) into C57BL mice leads to a significant decrease in the number of bone-marrow colony-forming-units in spleen (CFUs) as early as 12 h after the injection of the bacterium. This decrease persisted in varying degrees for 3 weeks. After an initial fall at 24 h, the splenic CFUs exhibited a rapid expansion and reached values 10 times higher than the control range on the ninth day. A significant rise in the number of circulating CFUs, reaching a first peak at 2 h and a second one on the fifth day, was also observed. The proliferative status of femoral CFUs was increased at 48 and 72 h, while that of splenic CFUs presented a significant increase only 48 h after the injection of C. parvum. The sequence of events which were observed in these experiments indicates that an accelerated migration of hemopoietic stem cells from bone marrow to spleen via the blood circulation has to take place.