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Background: Post‐transfusion survival of donor red blood cells (RBCs) is important for effective chronic transfusion therapy in conditions including sickle cell disease (SCD). Biotin labeling RBCs allows direct in vivo measurement of multiple donor RBC units simultaneously post‐transfusion. Study Design and Methods: In an observational trial of patients with SCD receiving monthly chronic transfusion therapy, aliquots of RBCs from one transfusion episode were biotin‐labeled and infused along with the unlabeled RBC units. Serial blood samples were obtained to measure RBC survival. Donor units were tested for RBC indices, hemoglobin fractionation, and glucose‐6‐phosphate dehydrogenase (G6PD) enzyme activity. For microcytic donor RBCs (MCV < 70 fL), HBA1 and HBA2 genetic testing was performed on whole blood. Results: We present one recipient, a pediatric patient with SCD and splenectomy who received two RBC units with aliquots from each unit labeled at distinct biotin densities (2 and 18 μg/mL biotin). One donor unit was identified to have microcytosis (MCV 68.5 fL after biotinylation); whole blood sample obtained at a subsequent donation showed 2‐gene deletion alpha‐thalassemia trait (ɑ–3.7kb/ɑ–3.7kb) and normal serum ferritin. G6PD activity was >60% of normal mean for both. The RBCs with alpha‐thalassemia RBC had accelerated clearance and increased surface phosphatidylserine post‐transfusion, as compared with the normocytic RBC (half life 65 vs. 86 days, respectively). Discussion: Post‐transfusion RBC survival may be lower for units from donors with alpha‐thalassemia trait, although the impact of thalassemia trait donors on transfusion efficacy requires further study. [ABSTRACT FROM AUTHOR]

Background: Red blood cell (RBC) antibodies are common in multiply transfused patients with sickle cell disease (SCD). Unlike RBC alloantibodies, the potential of autoantibodies to cause post‐transfusion hemolysis may be uncertain. Biotin‐labeling provides a direct measurement of red cell survival (RCS) over time, thus can be used to assess the clinical significance of RBC antibodies. Antibodies to biotinylated RBC (B‐RBC) occasionally are detected after exposure, which may impact B‐RBC survival in subsequent RCS studies. Study Design and Methods: Pediatric patients with SCD receiving monthly chronic transfusions underwent RCS studies, receiving aliquots of allogeneic RBC labeled at distinct densities of biotin (2–18 μg/mL). B‐RBC survival was followed for 4 months post‐transfusion, and B‐RBC antibody screening for 6 months. Patients with warm autoantibodies (WAA) or B‐RBC antibodies are reported here. Results: RBC antibodies were detected during RCS in four patients: one with WAA, one with WAA followed by B‐RBC‐specific antibodies, and two with transient B‐RBC antibodies within the first 5 weeks of exposure. B‐RBC half‐lives (T50) ranged 37.6–61.7 days (mean 47.8 days). There was no evidence of increased hemolysis or accelerated B‐RBC clearance in the presence of WAA or B‐RBC antibodies. Discussion: Biotinylation of allogenic RBC can be used to assess the possible effects of RBC antibodies on transfusion survival in individual cases, particularly when it is uncertain if the detected antibodies may result in hemolysis. In the cases presented here, neither WAA nor B‐RBC antibodies were associated with significant shortening of B‐RBC survival in individuals with SCD. [ABSTRACT FROM AUTHOR]

Sickling in oxygenated red blood cells (SS RBC) was studied using the fluorescent cholesterol analogue dehydroergosterol. The changes in the membrane structure and sterol exchange between SS RBC and unilammelar vesicles were examined by measuring the fluorescence intensity of the cholesterol analogue dehydroergosterol and by direct analysis of RBC using high-performance liquid chromatography.

Patients with sickle cell anemia experience cellular dehydration and cation depletion. A study of the net cation movements show that in the presence of external Ca2+, deoxygenation-induced Na+ influx and K+ efflux are unbalanced and this pathway mediates cation loss and contributes directly to cellular dehydration in low-density sickle red blood cells. The deoxygenation-induced Na+ influx was affected more than K+ efflux, leading to a Ca2+-dependent net cation loss. This occurred under conditions in which there was no activation of Ca2+-dependent K+ channels.

The molecular sterol transfer mechanism, involving anionic phospholipids and liver sterol carrier protein-2 (SCP2), induces sterol domain structural modifications and variations in the sterol desorption rate via protein-membrane surface interactions. SCP2 is independent of the protein's ability to facilitate sterol transfer during sterol binding.

The structural domains and regulation of cholesterol in erythrocyte membranes are determined by studying the kinetics of sterol exchange in erythrocyte ghost membranes. The kinetics are studied using dehydroergosterol fluorescence polarization. Three kinetic cholesterol domains characterize the sterol exchange between small, unilamellar cholesterols (SUV). The SUV in several cases was replaced by erythrocyte ghosts.

The enhanced permeability of Na, K, and Ca to membranes and the causes for the reduction of cellular cations are revealed by deoxygenating sickle cells. Monovalent cations reveal actions which are stimulated by deoxygenation and controlled by a pathway whose physiological characteristics are examined. Saturation is not seen in external Rb concentration which shows Rb influx stimulated by deoxygenation to be a linear mechanism of the Rb concentration. Alkaline pH supports the activation of the pathway, which is stimulated by deoxygenation. The activated pathway reveals the ion movement where the cells are incubated in media in which Cl is substituted for NO3 to remove KCl cotransport.

Erythrocyte dehydration resulting from sickle cell anemia may be brought about by three cation transport pathways. The first is the potassium efflux andcalcium and sodium influx resulting from deoxygenation. The second is a cotransport pathway between potassium and chloride and the third is a potassiumentry through a calcium-dependent channel. Recent findings suggest a link amongthese three pathways. The interaction among these pathways may be further modified by extraneous factors as suggested by the heterogeneity in the dehydration rate.