BINDING AND SUPPRESSIVE ACTIVITY OF HUMAN RECOMBINANT FERRITINS ON ERYTHROID-CELLS

We studied the relation between ferritin cellular binding and suppress ive activity of recombinant H- and L-ferritin on human erythroid cells at different proliferation/differentiation phases. L-ferritin failed to show any suppressive activity or detectable binding to erythroblast s at any stage of maturation. In contrast, H-ferritin demonstrated bin ding to erythroblasts derived from peripheral BFU-E cells which increa sed steadily between 7-14 days of culture up to 15,000 molecules per c ell. Reticulocytes and erythrocytes failed to bind either L- or H-ferr itin. H-ferritin suppressed BFU-E colony formation and reduced K562 ce ll proliferation at nanomolar concentrations. This suggests that the e xpression of H-ferritin binding sites is modulated by cellular prolife ration and differentiation, that cells expressing H-ferritin binding s ites are sensitive to ferritin suppressive activity and that a causal relation exists between ferritin cellular binding and suppressive acti vity.