This study clearly demonstrates that DHTR can occur in the absence of detectable antibody. In these cases, a mechanism of excessive eryptosis is proposed.

Pulmonary pressures increase during severe acute chest syndrome, and pulmonary hypertension is associated with cardiac biomarker elevation and a higher risk of death.

BackgroundAbnormal interactions between red blood cells, leukocytes and endothelial cells play a critical role in the occurrence of the painful vaso-occlusive crises associated with sickle cell disease. We investigated the interaction between circulating leukocytes and red blood cells which could lead to aggregate formation, enhancing the incidence of vaso-occlusive crises. Design and MethodsBlood samples from patients with sickle cell disease (n=25) and healthy subjects (n=5) were analyzed by imaging and classical flow cytometry after density gradient separation. The identity of the cells in the peripheral blood mononuclear cell layer was determined using antibodies directed specifically against white (anti-CD45) or red (anti-glycophorin A) blood cells. ResultsAggregates between red blood cells and peripheral blood mononuclear cells were visualized in whole blood from patients with sickle cell disease. The aggregation rate was 10-fold higher in these patients than in control subjects. Both mature red blood cells and reticulocytes were involved in these aggregates through their interaction with mononuclear cells, mainly with monocytes. The size of the aggregates was variable, with one mononuclear cell binding to one, two or several red blood cells. Erythroid Lu/basal cell adhesion molecule and α4β1 integrin were involved in aggregate formation. The aggregation rate was lower in patients treated with hydroxycarbamide than in untreated patients. ConclusionsOur study gives visual evidence of the existence of circulating red blood cell-peripheral blood mononuclear cell aggregates in patients with sickle cell disease and shows that these aggregates are decreased during hydroxycarbamide treatment. Our results strongly suggest that erythroid Lu/basal cell adhesion molecule proteins are implicated in these aggregates through their interaction with α4β1 integrin on peripheral blood mononuclear cells.Key words: α4β1, Lu/BCAM, sickle cell disease, aggregates. disease. Haematologica 2010;95(11):1841-1848. doi:10.3324/haematol.2010 This is an open-access paper. Citation: Chaar V, Picot J, Renaud O, Bartolucci P, Nzouakou R, Bachir D, Galactéros F, Colin Y, Le Van Kim C, and El Nemer W. Aggregation of mononuclear and red blood cells through an α4β1-Lu/basal cell adhesion molecule interaction in sickle cellAggregation of mononuclear and red blood cells through an α4β1-Lu/basal cell adhesion molecule interaction in sickle cell disease

Hydroxyurea (HU) is useful for treating sickle cell anemia because of its ability to reduce some of the severe clinical events such as painful crises and acute chest syndrome. It may also reduce the need for blood transfusions and frequent hospitalizations and reduce mortality. Nevertheless, no consistent recommendations regarding its therapeutic schedule are defined. Our aim was to improve and validate a high performance liquid chromatography (HPLC) technique to measure HU and to study HU levels in serum and urine of sickle cell anemia patients and relate this to treatment efficacy and compliance. Thirty-seven patients received 1,128 +/- 333 mg of HU per day (8.0 to 28.0 mg/kg/day). Plasma and/or urine were sampled and HU was measured using an HPLC method coupled with UV detection. We validated a specific, sensitive assay with good reproducibility and linearity, and showed a positive relationship between plasma HU concentrations and time elapsed between oral HU intake and sampling. We observed plasma HU concentrations were positively correlated with change in mean corpuscular volume (MCV) before and during the treatment. No correlation was obtained between HU concentration and Hb F level.

Strokes are one of the most severe complications of sickle-cell disease. Most studies have been restricted to children with sickle-cell disease. To better understand the characteristics and follow-up of strokes occurring from childhood to adulthood, we undertook a retrospective cohort study of 69 stroke patients among the 2,875 patients consulting at the French Adult Sickle-Cell Disease Referral Center. Between 1970 and 2008, they had experienced 104 strokes: 80 ischemic, 22 hemorrhagic, and 2 intracranial sinus thromboses. Coma and/or fatal outcomes underscored the severity of strokes in sickle-cell disease patients. Hemorrhagic strokes occurred mostly in adults and carried a higher risk of death than ischemic stroke. The mechanisms underlying sickle-cell disease associated strokes were reevaluated and etiologies were determined for first stroke and recurrences, in childhood and adulthood. Sickle-cell disease vasculopathy concerned only SS patients and remains their most frequent stroke etiology. Cardioembolism, vaso-occlusive crisis and triggering factors were other etiologies identified in adults. Recurrences occurred in 19 SS patients only after a first ischemic stroke. SC patients' strokes occurred in adulthood and were associated with cardiovascular risk factors. Our findings provide novel information about cerebrovascular pathologies throughout the lives of sickle-cell disease patients and suggest the need for different diagnostic and therapeutic management approaches in those different settings.