Gabriele Stiegler

Differential induction of P-selectin expression on platelets by two cell separators during plateletpheresis and the effect of gender on the release of soluble P-selectin

BACKGROUND: Though a number of studies have elegantly characterized platelet activation during storage, less attention has been paid to the initial activation caused by different collection procedures. STUDY DESIGN AND METHODS: The effects of two blood cell separators on the initial activation of platelets were measured by flow cytometric analysis of P‐selectin expression in 13 male donors on one cell separator (CS 3000 Plus) and 11 men and 9 women on the other (MCS 3P). In addition, the storage and release of soluble P‐selectin (circulating P‐selectin [cP‐selectin]) by platelets were quantified, to determine whether the change in cP‐selectin is a more sensitive marker for initial platelet activation, and the influence of gender on measured endpoints was evaluated. RESULTS: The CS 3000 Plus increased the percentage of P‐selectin‐positive platelets from a median of 3.4 percent before apheresis to 7.6 percent (p = 0.006) in platelet concentrates (PCs), whereas the MCS 3P did not (p = 0.002 between the two cell separators). When preapheresis cP‐selectin levels were compared to those in apheresis PCs, cP‐selectin increased from 51 to 101 ng per mL in plasma of CS 3000 Plus PCs, whereas cP‐selectin levels increased from 53 to 78 ng per mL in MCS 3P PCs (men) and from 48 to 99 ng per mL in MSC 3P PCs (women) (p<0.005 for all). The relative increase in cP‐selectin was higher in women than in men in MCS 3P PCs (p = 0.013). Concomitantly, the amount of P‐selectin stored in platelets before apheresis decreased (p<0.025 for all). When donors undergoing apheresis on the MCS 3P were compared, the amount of P‐ selectin stored in the platelets of PCs was higher in men than women (p = 0.026). CONCLUSION: This trial shows 1) that initial activation of platelets obtained with the MCS 3P is less than that of platelets obtained with the CS 3000 Plus; 2) that the increase in cP‐selectin is a more sensitive marker for initial platelet activation than the expression of P‐selectin on the surface; and 3) that the relative amount of cP‐selectin is higher in women than in men given the same stimulus. Differences in platelet activation by various cell separators and the sex of the donor may contribute to variability of PC quality.

Red cell antibodies in frequently transfused patients with myelodysplastic syndrome

Abstract. Therapy for myelodysplastic syndrome (MDS) is often restricted to lifelong support with red blood cell units (RBCU). A variety of immune phenomena associated with antibody production have been reported in MDS patients. Therefore, we hypothesized that red cell antibodies are more frequent in patients with MDS compared to other regularly transfused patients. Red cell antibodies were determined in 42 MDS patients, in 28 patients with other hematological disorders, and in a historical group of 129 patients with end-stage renal failure. All of these patients received frequent red cell substitution therapy, at least two RBCU in biweekly intervals. Red cell antibodies were detected in 9 of 42 patients with MDS, in 3 of 28 patients with other hematological disorders, and in 4 of 129 patients with end-stage renal failure. Evidence of red cell antibodies was displayed by 6 of 27 MDS patients treated with prestorage leukocyte-depleted RBCU and 3 of 15 MDS patients transfused with bedside leukocyte-filtered RBCU. Red cell antibodies are frequent in patients with hematological disorders who require repetitive red cell transfusions. The formation of alloantibodies to red cell antigens is as frequent in MDS patients as in other patients with hematological disorders.

Safety issues of plateletpheresis: comparison of the effects of two cell separators on the activation of coagulation, fibrinolysis, and neutrophils and on the formation of neutrophil-platelet aggregates.

BACKGROUND: Although many donors undergo repeated plateletpheresis, data on the consequences of plateletpheresis for the donors health remain scarce. Thus, the effect of plateletpheresis on the activation of coagulation, fibrinolysis, and neutrophils was investigated.

Elevated numbers of reticulated platelets in hyperthyroidism: direct evidence for an increase of thrombopoiesis

We studied thrombopoietic activity in hyperthyroidism by determination of reticulated platelet counts. At the time of hyperthyroidism 14/15 patients had higher reticulated platelets than after achievement of euthyroidism (P < 0.001). There was no difference in peripheral platelet counts and mean platelet volumes at the time of hyperthyroidism when compared to euthyroidism. Three patients had pan‐ and auto‐reactive platelet antibodies during hyperthyroidism. These antibodies were directed against GPIIb/IIIa in two patients and against GPIb/IX in one patient. Our findings provide direct evidence that hyperthyroidism is associated with increased platelet production, as reflected by an increase in reticulated platelets.

The rise of reticulated platelets after intensive chemotherapy for AML reduces the need for platelet transfusions.

Abstract We assumed that a recovery of thrombopoiesis after intensive chemotherapy for acute myelogenous leukemia (AML) could reduce the need for prophylactic platelet transfusions. We therefore assessed the start of platelet production by means of daily determination of reticulated platelets (RP). The increase in RP occurred on day 20 (median) after the start of chemotherapy and was followed by a rise of peripheral platelet counts 2–3 days thereafter. Consequently, a rise of RP during the period of recovery can be regarded as representing the reconstitution of the peripheral platelet count and may reduce or eliminate the need for prophylactic platelet transfusions.

P-selectin mRNA is maintained in platelet concentrates stored at 4°C

BACKGROUND: Platelets (PLTs) contain mRNA and synthesize proteins in response to activation. Most guidelines for PLT concentrates (PCs) recommend ambient temperature for storage but the impact of the storage temperature on PLT mRNA content has not yet been investigated.

The influence of human platelet antigen match on the success of allogeneic peripheral blood progenitor cell transplantation following a reduced-intensity conditioning regimen

BACKGROUND:  Allogeneic transplantation in elderly patients requires a dose‐reduced conditioning regimen. Owing to reduced‐intensity conditioning, host‐ and donor‐type immune responses may affect the early posttransplant period, whereas only later on donor‐derived reactions may ensue. Mismatches in the HLA system are known to be detrimental for the outcome of transplantation. Mismatches between donor and recipient for human platelet antigens (HPAs) may also affect the success of transplantation owing to serving as minor histocompatibility antigens and therefore rendering recipients at risk for graft‐versus‐host disease (GVHD) or graft rejection and inhibition of thrombopoiesis attributed to platelet (PLT) antibodies.

Response to vWF‐coated beads and soluble p‐selectin to characterize apheresis platelets: a comparison of three cell separators

BACKGROUND: Plateletpheresis technologies differ among various cell separators. Differences in centrifugation force, centrifugation time, and platelet concentration in the platelet concentrate may affect platelet activation and function.

The proportion of reticulated platelets is higher in bone marrow than in peripheral blood in haematological patients

Abstract: Since the detection that platelets originate from megakaryocytes (MK), the site of megakaryocyte fragmentation has been disputed. Some authors have even postulated that platelets are solely produced in the lungs. Thus, we have directly measured platelet generation in the bone marrow (BM) by comparing the relative number of young RNA‐containing, so‐called reticulated platelets (%RP) in the BM and in the peripheral blood (PB). Two separate prospective, cross sectional trials have been conducted in patients routinely undergoing BM biopsies for diagnostic purposes. In the first part of the study 30 patients with stem cell or bone marrow transplantation were examined. The second part of the study was performed in 62 haematological patients visiting the outpatients clinic. Median %RP were higher in BM than in PB (p < 0.001). In the second part of the study the difference averaged 133% (interquartile range: 30–383%). There was a moderate correlation between %RP in BM and in PB (r = 0.67; p < 0.001). The absolute number of RP in PB correlated weakly with the number of megakaryocytes (0.42; p = 0.001), which was due to a correlation between the platelet counts and the megakaryocyte counts (r = 0.55; p < 0.001 in biopsies). Two patients with autoimmune antibodies against GPIIb/IIIa exhibited 10% and 16% RP in PB, and had 29% and 59% RP in BM, respectively. It is concluded that the relative number of RP is significantly higher in BM than in blood. This supports the notion that platelets are at least in part released from MK in the bone marrow, particularly in patients suffering from immune thrombocytopenia.