The effect of isoferritins on granulopoiesis.

The evidence for a regulatory role of acidic isoferritins on hemopoiesis is not entirely consistent with our knowledge of ferritin biochemistry, and no clear picture of this phenomeonon has emerged. In the present study, we have been unable to confirm a consistent effect of purified heart (acidic), spleen (basic), or serum (glycosylated) isoferritins on CFU-GM colony formation in vitro. Inhibition of colony formation by cell extracts or conditioned media does not relate to the presence of acidic isoferritins, nor is this effect neutralized by a monoclonal antibody to acidic isoferritins. The composition of ferritin preparations previously described as inhibitory to CFU-GM colony growth could not be confirmed, and they were not found to be predominantly acidic in nature. Our data do not support a role for acidic isoferritins as inhibitors of granulopoiesis.