The survival characteristics of dense sickle cells

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.