Fetal Hb Production during Acute Erythroid Expansion: I. OBSERVATIONS IN PATIENTS WITH TRANSIENT ERYTHROBLASTOPENIA AND POST‐PHLEBOTOMY

Abstract

To study fetal Hb production during acute erythroid expansion, sequential measurements were done of Hb F-containing erythrocytes (F-cells) and of relevant hematological parameters in 10 subjects recovering from erythroid aplasia, Fe deficiency anemia or following phlebotomy. Increased production of F-cells was consistently observed during the acute marrow expansion, but there were significant differences in maximum F-cell response among individuals. These differences could not be explained by differences in degree of anemia alone, nor could they be correlated with the level of peak reticulocytosis. Two patients who reached the highest F-cell numbers were probably carriers of heterocellular hereditary persistence of Hb F, suggesting that this gene may play a role in determining the magnitude of F-cell production in anemic patients. The main reason for the consistently observed increase in F-cell production during acute marrow expansion is apparently the premature terminal differentiation of earlier erythroid precursors (burst forming units; BFUe). This proposition is in accord with observations in vitro which suggest that Hb F is expressed in erythroid clones derived from BFUe. Differences in degree of BFUe recruitment may underly the disparities in Hb F response among individuals subjected to similar anemic stimuli.