Sickle red blood cells (RBCs) become depleted of potassium, leading to dehy
dration and abnormally elevated cellular density. The increased sickling th
at results is important for both hemolysis and vasocclusion. In this study,
sickle cells were subjected to high-speed centrifugation, and the bottom 1
5% were isolated. This procedure removed light cells and to a variable degr
ee enriched cells that were denser than normal to produce a high-density-en
riched (HDE) population of sickle cells. Autologous HDE cells from 3 subjec
ts were labeled with biotin and re-infused. The following determinations we
re performed:(1) the survival and density changes of HDE:cells; (2) the amo
unt of fetal hemoglobin (HbF) in labeled cells after magnetic isolation; (3
) the percentage of labeled F cells; (4) the percentage of labeled cells di
splaying external phosphatidylserine (PS). For patients with 3.5%, 4,5%, an
d 24% HbF in the HDE RBCs, the circulation half-time was 40, 80, and 180 ho
urs, respectively. The percentage of HbF (measured in all 3 subjects) and o
f F cells (measured in 2 subjects) in labeled RBCs increased with time afte
r re-infusion, indicating that HDE F cells have longer in vivo survival tha
n HDE non-F cells. The percentage of PS+, biotin-labeled HDE cells showed n
o consistent increase or decrease with time after re-infusion. These data p
rovide evidence that HDE sickle cells, especially those that do not contain
HbF, have a very short in vivo survival, and that the percentage of PS+ ce
lls in a re-infused HDE population does not change in a consistent manner a
s these cells age in the circulation. (C) 2000 by The American Society of H
ematology.