Interaction between rabbit erythroblast ferritin and normal plasma proteins.

Erythroblast ferritin (EF), isolated from variable in different plasmas. The binding phenylhydrazine-anemic rabbit marrow, activity for rabbit EF is also present in interacts with components of normal heterologous plasma of mouse, guinea plasma and forms a complex separable by pig, and man. The active principles in starch granule electrophoresis and by plasma were identified as two heat-stable dialysis techniques. The binding is facilicomponents which fractionate as immunototed at low ionic strength. The plasma globulins, one as IgG and the other as factors responsible for binding EF are lgM. The results support the hypothesis present in autologous, as well as homolothat natural antiferntin antibodies of low gous, plasma of normal nonimmune robtiter are present in normal plasma. bits, although binding activities are quite A LTHOUGH ORGAN SPECIFICITY of ferritin was demonstrated in 1967,i2 little progress has since been made in elucidating the unique structural properties ofthe ferritin in erythroid cells. Erythroblast ferritin (EF) forms an iron pool which is physicochemically separable and metabolically distinct from that of the reticuloendothelial cells.3 Because of the rapid turnover of its iron, high-specific-activity iron labeling of EF can be readily achieved in vitro.4 Although it appears likely that EF chiefly subserves the iron requirements of heme synthesis, there is little direct experimental evidence about its role in erythropoiesis. Deiss and Cartwright have found in vitro evidence for a catabolic pathway for EF from reticulocyte to plasma to monocyte.5 The present experiments describe plasma factors capable of binding relatively small quantities of EF.