Biological Variation in the Heterogeneous Distribution of Haemoglobin F among Erythrocytes

S ummary . The development of highly specific fluorescent labelled antibodies against haemoglobin F presented an opportunity to investigate variables which might influence distribution of this haemoglobin among individual erythrocytes. Earlier investigations revealed heterogeneous distribution within healthy individuals and in individuals with sickle cell disease and other haemoglobinopathies. The current study demonstrates quantitatively that there are normal biological determinants of variability in the frequency of F‐containing erythrocytes in individuals who have a haemoglobin A electrophoretic phenotype. It also is shown that the frequency of F‐containing erythrocytes during the early recovery phase of sickle cell crisis is significantly higher than when there is no recent history of crisis. The mean quantity of haemoglobin F per F‐containing erythrocyte appears to be lower after a crisis than in individuals without recent history of crisis. This suggests that following a crisis there may either be biochemical constraints on haemoglobin F synthesis per erythrocyte precursor cell or else there is limited opportunity for selective removal of low F‐containing erythrocytes from the circulation.