Update on leucocyte depletion of blood components by filtration

Design and introduction of a rational mechanical eluting system for leukocyte recovery from leukoreduction filters: A cell differential approach

OBJECTIVES

The use of leukoreduction filters has been highly increased in Iranian Blood Transfusion Centers within the last decade to provide sufficient leukoreduced blood products from healthy repeated donors for alloimmunized or sensitive recipients. Leucoflex LCR5, the dominant brand which procured by the Iranian Blood Transfusion Organization, is the most updated generation of the filters used around the world.

MATERIAL AND METHODS

In this study, we recovered trapped leukocytes from these filters using different buffer solutions and optimized elution method. The count of recovered cells assessed by cell counter, and cell viability was detected using trypan blue staining. The percent of leukocyte subpopulations was evaluated using a panel of monoclonal antibodies and flow cytometric analysis.

RESULTS

It illustrated that a buffer solution consistent with PBS in pH 7.2 containing 2mM EDTA and 4% (w/w) Dextran 40 was the best buffer for LCR5 filter backflushing. The white cell counted as 4.56×10⁸ Granulocytes, 3.34×10⁸ Lymphocytes, and 0.64×10⁸ Monocytes according to analysis with auto hemoanalysis and flow cytometric methods.

CONCLUSION

The study guides and assists blood management systems in arranging a national blood profile database for future cell therapy strategies. Also, the recovered cells could be of significance in stem cell research, cellular interaction studies as well as novel molecular developments in drug discovery.

Metabolic effects occurring in irradiated and non-irradiated red blood cellular components for clinical transfusion practice: An in vitro comparison

Background

Storage lesions occur in red blood cell products when potassium ions, haemoglobin and lactate dehydrogenase are released into the extracellular plasma due to post-irradiation storage or cellular degeneration. The South African blood transfusion establishments do not comply with the universal leucocyte-reduction policy due to cost and the current HIV pandemic. Various studies regarding storage lesions have been completed in well-developed countries but not in Cape Town, South Africa.

Objective

This study aimed to determine cellular degeneration occurring in non-irradiated and irradiated red blood cells (RBC) by comparing the measured biochemical and haematological indices during storage of up to 42 days.

Method

Eighty whole blood units were collected from voluntary, non-remunerated donors. Blood components tested weekly until expiry were whole blood, RBC concentrate, leucocyte-reduced RBC concentrate (pre-storage) and paediatric RBC concentrate (n = 20). Ten units per product were irradiated and 10 were not. Evaluations included potassium, sodium, glucose, lactate dehydrogenase, phosphate, haemoglobin, haematocrit, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentrate, mean cell volume and plasma haemoglobin. Plasma haemolysis levels were calculated using an approved formula.

Results

The haemolysis levels evaluated on Day 35 and Day 42 were higher than the recommended 0.8%, whereas results for the non-irradiated components up to expiry were all below 0.8%.

Conclusion

This study confirms that gamma irradiation aggravates the RBC storage lesions. The products tested yielded similar results to other studies in developed countries, however the South Africa transfusion medicine policy should remain unchanged.

A robust mass spectrometry method for rapid profiling of erythrocyte ghost membrane proteomes

Background

Red blood cell (RBC) physiology is directly linked to many human disorders associated with low tissue oxygen levels or anemia including chronic obstructive pulmonary disease, congenital heart disease, sleep apnea and sickle cell anemia. Parasites such as Plasmodium spp. and phylum Apicomplexa directly target RBCs, and surface molecules within the RBC membrane are critical for pathogen interactions. Proteomics of RBC membrane ‘ghost’ fractions has therefore been of considerable interest, but protocols described to date are either suboptimal or too extensive to be applicable to a larger set of clinical cohorts.

Methods

Here, we describe an optimised erythrocyte isolation protocol from blood, tested for various storage conditions and explored using different fractionation conditions for isolating ghost RBC membranes. Liquid chromatography mass spectrometry (LC–MS) analysis on a Q-Exactive Orbitrap instrument was used to profile proteins isolated from the comparative conditions. Data analysis was run on the MASCOT and MaxQuant platforms to assess their scope and diversity.

Results

The results obtained demonstrate a robust method for membrane enrichment enabling consistent MS based characterisation of > 900 RBC membrane proteins in single LC–MS/MS analyses. Non-detergent based membrane solubilisation methods using the tissue and supernatant fractions of isolated ghost membranes are shown to offer effective haemoglobin removal as well as diverse recovery including erythrocyte membrane proteins of high and low abundance.

Conclusions

The methods described in this manuscript propose a medium to high throughput framework for membrane proteome profiling by LC–MS of potential applicability to larger clinical cohorts in a variety of disease contexts.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9190-4) contains supplementary material, which is available to authorized users.

Interleukin-6 and C-reactive protein load in pre-storage and post-storage white blood cell-filtered red blood cell transfusions in premature infants

OBJECTIVE

Leukocyte contamination during blood transfusion can cause many adverse effects. Filtration can be performed either at bedside during the transfusion or as pre-storage filtration. Pre-storage filtration is superior to bedside filtration because leukocytes are removed prior to storage, thus preventing further adverse effects associated with the storage of these cells.

METHODS AND MATERIALS

One hundred and six infants were randomised into two groups: pre-storage filtration (group 1, n = 53) and bedside filtration (group 2, n = 53). C-reactive protein (CRP) and interleukin-6 (IL-6) levels were analysed within 24 h prior to the transfusion and 24 h after completion of the transfusion.

RESULTS

In group 1, pre-transfusion median CRP and IL-6 levels were 2·95 (0·73-10·25) mg L(-1) and 8·59 (3·45-20·55) pg L(-1) , respectively, and post-transfusion median CRP and IL-6 levels were 2·28 (0·44-12·87) mg L(-1) and 6·62 (2·18-27·87) pg L(-1) , respectively. In group 2, pre-transfusion median CRP and IL-6 levels were 1·30 (0·40-7·84) mg L(-1) and 4·40 (2-17·12) pg L(-1) , respectively, and post-transfusion median CRP and IL-6 levels were 3·50 (0·50-7·85) mg L(-1) and 8·30 (3·48-23·75) pg L(-1) , respectively. There were no differences between pre-storage and post-storage leukoreduction average IL-6 and CRP levels in either group (P > 0·05 for both). Packed red blood cell (PRBC)-related necrotizing enterocolitis was detected in one infant in group 2.

CONCLUSIONS

Because leukocytes in PRBC transfusions can be associated with many undesirable effects, leukoreduction is the best choice to prevent those effects. However, this method is still controversial. We demonstrated that using pre-storage and post-storage leukoreduction methods in erythrocyte transfusions did not change CRP or IL-6 levels, which are indicators of acute-phase response.

Biochemical storage lesions occurring in nonirradiated and irradiated red blood cells: a brief review

Red blood cells undergo a series of biochemical fluctuations during 35-42-day storage period at 1°C to 6°C. The sodium/potassium pump is immobilised causing a decrease in intracellular potassium with an increase in cytoplasmic sodium levels, glucose levels decline, and acidosis occurs as a result of low pH levels. The frailty of stored erythrocytes triggers the formation of haemoglobin-containing microparticles and the release of cell-free haemoglobin which may add to transfusion difficulties. Lipid peroxidation, oxidative stress to band 3 structures, and other morphological and structural molecular changes also occur leading to spheroechinocytes and osmotic fragility. These changes that transpire in the red cells during the storage period are referred to as "storage lesions." It is well documented that gamma irradiation exacerbates storage lesions and the reports of increased potassium levels leading to adverse reactions observed in neonates and infants have been of particular concern. There are, however, remarkably few systematic studies comparing the in vitro storage lesions of irradiated and nonirradiated red cell concentrates and it has been suggested that the impact of storage lesions on leucocyte reduced red blood cell concentrate (RBCC) is incomplete. The review examines storage lesions in red blood cells and their adverse effects in reference to blood transfusion.

Intraoperative blood salvage during liver transplantation in patients with hepatocellular carcinoma: efficiency of leukocyte depletion filters in the removal of tumor cells

BACKGROUND

Intraoperative blood salvage (IBS) reduces homologous transfusion in orthotopic liver transplantation (OLT), but may carry with it the risk of reinfusing tumor cells in patients with hepatocellular carcinoma (HCC). The use of leukocyte depletion filters (LDFs) for the removal of tumor cells is rarely reported in clinical OLT. The aims of this study were to evaluate the frequency of tumor cell contamination in surgical field during OLT for HCC recipients and to investigate the efficiency of additional LDFs for eliminating tumor cells from IBS.

METHODS

Thirty-two HCC patients with preoperatively elevated serum alpha-fetoprotein (AFP) underwent OLT. The blood from the surgical field was collected and processed by an autotransfusion device (Cell Saver 5), followed by 2 consecutive LDF filtrations. The HCC cells in IBS samples and filtered samples were determined using a nested RT-PCR technique to detect the AFP mRNA.

RESULTS

The shed blood samples from 20 (62.5%) of the 32 HCC patients were contaminated with HCC cells and 15 of them remained positive after Cell Saver processing. Patients within the Milan or UCSF criteria were less likely to have HCC cell contamination and the contaminated HCC cells were more likely to be removed by the Cell Saver in these patients as compared to other patients (P<0.01). After filtration through an additional LDF, most cases (13/15) became negative except for those with ruptured tumors (P<0.05).

CONCLUSIONS

Our results suggest that blood filtration with the LDF can efficiently remove tumor cells and the use of an additional LDF after use of the Cell Saver could markedly reduce the risk of tumor cell reintroduction during the OLT in HCC recipients with nonruptured tumors.

Leukoreduction filtration of whole-blood units from sickle trait donors: effects of a metered citrate anticoagulant system

BACKGROUND

Polymerization of hemoglobin (Hb) S is exacerbated by acidic and hyperosmotic citrate anticoagulant solutions and often results in occlusion of leukoreduction filters by red blood cells (RBCs) from sickle cell trait (Hb AS) donors. This study evaluates a blood collection instrument that adds citrate anticoagulant in a metered fashion, thus mitigating adverse citrate effects.

STUDY DESIGN AND METHODS

Collection of whole blood by a metered anticoagulant system was compared to traditional phlebotomy in 12 Hb AS and 12 non-sickle trait (Hb AA) donors. Each donated twice; on one occasion, units were filtered after 4-hour storage at 20 to 24 degrees C, and on the other, units were stored at 1 to 6 degrees C for 24 hours before filtration.

RESULTS

Filtration times, RBC recoveries, and residual white blood cell (WBC) counts met defined criteria more often in Hb AS units collected by a metered anticoagulant system (9 of 12, 8 of 12, and 4 of 12, respectively) compared to traditional phlebotomy (1 of 12, 2 of 12, and 0 of 12, respectively). Overall, Hb AS units filtered better after storage at 1 to 6 degrees C for 24 hours, with units collected by a metered anticoagulant system undergoing filtration most effectively (5 of 6 had >85% RBC recovery, 3 of 6 had <5 x 10(6) residual WBC). Units exhibited similar changes in RBC storage parameters.

CONCLUSION

Use of a metered anticoagulation instrument demonstrates potential for successful leukoreduction and acceptable storage of Hb AS units; however, the system needs further modifications and improvements before it can be utilized to collect and leukoreduce Hb AS blood.

Characterization of blood components prepared from whole-blood donations after a 24-hour hold with the platelet-rich plasma method

BACKGROUND

The preparation of platelet (PLT) concentrates (PCs) from PLT-rich plasma (PRP) requires that whole blood (WB) be processed within 8 hours of collection. Increasing WB storage time to 24 hours would be logistically attractive. This study compares the in vitro quality of blood components prepared from WB stored for 8 and 24 hours at room temperature before processing with the PRP method.

STUDY DESIGN AND METHODS

WB units were collected from ABO-matched blood donors. To reduce individual variations, paired donations were drawn in parallel, pooled, and split back in the collection bag. One unit was held for 6 to 8 hours and the other for 22 to 24 hours at 20 to 24 degrees C. Prestorage leukoreduced components were prepared with the PRP as intermediate product and analyzed during storage.

RESULTS

RBC units prepared after an 8- or 24-hour hold were comparable in terms of hemolysis, sodium, pH, and ATP levels. RBC 2,3- diphosphoglycerate (2,3-DPG) was significantly lower in RBCs prepared from 24-hour hold donations immediately after processing but not after 20 days of storage. Residual white blood cells were approximately fivefold higher (p < 0.05) in 24-hour RBC units. For PCs, measurements for glucose, ATP, lactate, pH, extent of shape change, hypotonic shock response, and CD62p activation were similar. No differences were observed in the von Willebrand factor, factor (F)V, FVIII, and fibrinogen content of fresh-frozen plasma.

CONCLUSIONS

The decrease in FVIII and RBC 2,3-DPG can be acceptable as a compromise to improve blood component logistics, but leukoreduction efficiency must be improved before considering the adoption of an overnight storage of WB before PRP processing.

Detection and clinical evaluation of antineutrophil antibodies in neonates who had a blood transfusion or exchange transfusion

BACKGROUND

The aim of this study was to detect and investigate the clinical effects of antineutrophil antibodies in neonates who had received a blood transfusion or exchange transfusion.

METHODS

Venous blood samples were drawn from 34 neonates at pretransfusion (sample 0), immediately after transfusion (sample 1), 2-3 weeks (sample 2) and 8-12 weeks (sample 3) after transfusion. Ten healthy neonates were in the control group. Antineutrophil antibodies were detected using flow cytometric assay.

RESULTS

Antineutrophil antibody was detected in the sera of 20 (58.8%) neonates in the study group. Of these 20 neonates, nine had antineutrophil antibodies in serum samples 0, 1 and 2, which were probably due to the passive transfer of maternal antibodies. Nine neonates had antineutrophil antibodies in serum samples 1 and 2, which were probably due to neutrophil antibodies being present in the donor's blood. In two neonates, antineutrophil antibodies were not detected in samples 0 and 1, but appeared in sample 2, which were probably actively produced by the neonates. All of the antineutrophil antibodies disappeared in the serum samples, except in one neonate. Only one preterm newborn developed neutropenia, which resolved spontaneously in a week. The presence of antineutrophil antibody in transfused neonates was significantly higher than in non-transfused neonates.

CONCLUSIONS

The presence of neutrophil specific antibodies in transfused neonates is not rare and antineutrophil antibodies may be found more often in transfused neonates compared to non-transfused neonates. The clinical significance of those antibodies needs to be assessed since they are transient and their clinical effects are not evident.

Increasing hemoglobin oxygen saturation levels in sickle trait donor whole blood prevents hemoglobin S polymerization and allows effective white blood cell reduction by filtration

BACKGROUND Red blood cell (RBC) components from donors with sickle cell trait (Hb AS) often occlude white blood cell (WBC) reduction filters. Techniques were investigated to successfully filter Hb AS donor blood by increasing the Hb oxygen saturation with storage bags and conditions suitable for transfusion products.

STUDY DESIGN AND METHODS

Oxygenation kinetics were measured over 3 days in whole-blood units stored in standard-sized 600-mL polyvinylchloride (PVC) bags and whole-blood units divided into three equal parts and stored in standard-sized blood bags made from PVC, tri-2-(ethylhexyl)trimellitate (CLX) plastic, or Teflon. The filterability of Hb AS blood stored for 3 days was tested with whole-blood filters.

RESULTS

Oxygen saturation levels did not increase in full whole-blood units from donors without sickle cell trait during 3 days of storage in 600-mL PVC bags. In divided Hb AS whole-blood units stored for 3 days, oxygen saturation levels increased from baseline levels of 45 to 56, 66, and 94 percent after storage in 600-mL PVC, CLX, and Teflon bags, respectively (n = 5, p < 0.02), and all components filtered completely. When full Hb AS whole-blood units from eight donors were stored for 3 days in 1.5-L CLX bags, all units filtered completely, but one had a high residual WBC count.

CONCLUSION

Storage of Hb AS whole blood in large-capacity oxygen-permeable bags increases oxygen tension and allows more effective WBC reduction by filtration.

Feasibility of Veno-Venous Bypass Surgery Using Leukocyte Adhesion Filters during Abdominal Surgery in a Porcine Model

During oncologic surgery, manipulation of tumour tissue is almost unpreventable; liver resection even carries a higher risk of tumour cell dissemination into venous blood. Under in vitro conditions, a tumour cell reducing effect of some leukocyte adhesion filter systems has been shown. In a preclinical porcine model, these filters were used as integrated parts of a veno-venous bypass system used for liver surgery, run by a biopump. Practicability, handling and safety aspects of the filter system were analysed; the system was easy and safe to handle, and treated animals survived without any complications. For the future, effectiveness of the tumour cell depletion has to be examined in further experimental and clinical studies.

WBC reduction in cryopreserved RBC units

BACKGROUND

WBC reduction of blood components by filtration is widely practiced to decrease the incidence of alloimmunization. Freezing RBCs reduces the WBC load but is insufficient to achieve the currently recommended US limit of 5 x 10(6) cells per unit.

STUDY DESIGN AND METHODS

Blood units were WBC reduced by filtration or by buffy-coat (BC) removal and then frozen in the presence of a high-glycerol concentration. The count of residual WBCs was determined by flow cytometry after deglycerolization.

RESULTS

Without WBC reduction, the total number of WBCs present after freezing and thawing was 11.5 +/- 9.2 x 10(6) WBCs per unit (n = 18). Particulate residues from monocytes and neutrophils that were detected in the remaining cell populations were positive for CD66b, CD3, CD14, and CD41. Removal of 40 mL of BC at the time of blood collection lowered the number of WBCs after freezing and deglycerolization to 1.9 +/- 1.20 x 10(6) per unit (n = 11). Similar results were obtained when only 20 mL of BC was removed using a modified blood-bag design. Unfiltered RBC units that were stored for 15 days at 4 degrees C after BC removal contained fewer than 5 x 10(6) WBCs after deglycerolization. Units WBC reduced by filtration before freezing had no detectable WBCs after thawing and washing (n = 14) and did not contain particulate residues. Filtration after deglycerolization was effective in reducing the WBC count below 10(6), although some debris was still present.

CONCLUSION

RBC freezing alone will not reduce residual counts to recommended levels. However, initial removal of BC can provide an economical alternative to WBC filtration for cryopreserved units. Units that were not WBC reduced before freezing can be filtered after deglycerolization when needed.

Sickle Hb polymerization in RBC components from donors with sickle cell trait prevents effective WBC reduction by filtration

BACKGROUND

RBC components collected from donors with sickle cell trait frequently occlude WBC-reduction filters. In vitro, sickle trait RBCs have the potential for sickle Hb (Hb S) polymerization at low oxygen saturations and high Hb concentrations.

STUDY DESIGN AND METHOD

To determine if the low pH and high osmolarity of the CP2D used in the collection contributed to filter failures, the filterability of sickle trait donor RBCs collected in CP2D was compared with RBCs from the same donors collected in heparin.

RESULTS

Five of six sickle trait components collected in CP2D did not complete filtration, but all six RBC components collected in heparin filtered completely. RBC components collected in CP2D from four other sickle trait donors were divided in two, and one-half was treated with carbon monoxide to convert Hb S to its liganded form to prevent Hb S polymerization. All four carbon monoxide-treated components filtered within 9 minutes, but only one untreated component filtered completely. RBC components collected by apheresis contained less CP2D, and five of seven sickle trait apheresis components filtered completely; four of the five filtered rapidly (<15 min) and one filtered in 100 minutes. Hb oxygen saturation was greater in the four rapidly filtering apheresis RBC components (68 +/- 9%) than in the three that filtered slowly or incompletely (37 +/- 5%, p = 0.03).

CONCLUSIONS

Hb S polymerization appears responsible for RBC WBC-reduction filter failures. Citrate anticoagulant and low oxygen saturation are responsible in part for Hb S polymerization in this setting.

Removal of T and B lymphocytes by in-line filtration: evaluation of the efficiency of a polyester filter type (Pall WBF-2) by flow cytometric counting

BACKGROUND AND OBJECTIVES

The aim of this study was to investigate whether in-line filtration, using a polyester filter for the preparation of red cell concentrates (RCC) and plasma (PL), leads to an altered proportion of T and B lymphocytes in the fraction of residual white blood cells (WBC).

MATERIALS AND METHODS

The capacity of Pall WBF-2 in-line filters to reduce the numbers of T and B lymphocytes from red blood cell concentrates (RCC) and plasma (PL) of 22 donations was investigated by three-colour flow cytometry (FC) using the Tritest-Trucount kit. T and B lymphocytes were identified using monoclonal antibodies (mAbs) against CD3, CD19 and CD45, conjugated with fluorescein isothiocyanate, phycoerythrin or peridinin chlorophyll protein-A, respectively. As the number of B cells was below the detection limit of the FC method, WBC of the respective blood components of healthy donors were concentrated 25-fold by Percoll density-gradient centrifugation. In this fraction the absolute numbers of T and B cells, as well as their ratio, were determined using the Attractor software, which provides a discrimination of rare cell counts from FC in relation to debris.

RESULTS

The mean numbers, as well as minima and maxima of T and B lymphocytes per unit, were as follows. T cells in RCC: 4.51 x 10(3) (1.68 x 10(2)-4.09 x 10(4)) and in PL: 1.35 x 10(3) (2.21-1.78 x 10(4)); B cells in RCC: 2.33 x 10(3) (7.10 x 10(1)-9.15 x 10(3)) and in PL: 2.33 x 102 (7.5 x 10(2)-2.8 x 10(3)). T cells were retained, on average, at a higher level than B cells: 3.01 times higher in RCC and 1.01 times higher in PL.

CONCLUSION

After filtration, the ratio of T and B lymphocytes changed in RCC (1.95 : 1) compared with unfiltered blood, where it was 5.83 : 1. In PL the ratio did not change notably compared to unfiltered blood. The results of this research show that cell concentration (using gradient centrifugation) in combination with an appropriate FC acquisition and analysis procedure, allows both residual T and B lymphocytes (being under the detection limit without cell concentration) to be determined.

Reduction of Yersinia enterocolitica load in deliberately inoculated blood: the effects of blood prestorage temperature and WBC filtration

BACKGROUND

Yersinia enterocolitica is known to cause severe infections in patients who receive transfusions.

STUDY DESIGN AND METHODS

The aim of the study was to define the best strategy for reducing the bacterial load in blood that was deliberately contaminated with Y. enterocolitica by combining prestorage temperature and WBC filtration with conditions of blood processing close to those applied in blood banks.

RESULTS

The effects of three prestorage temperatures (4 degrees C, 20 degrees C, 37 degrees C) were evaluated at various times after infection. The best reduction of bacterial load was achieved after 3 hours at 20 degrees C. In further experiments, conducted according to the former specifications, filtration of whole blood from eight and six donors with an inoculum of 100 and 500 to 1000 CFUs per mL, respectively, resulted in a total inhibition of bacterial growth up to 42 days after infection. After fractionation of blood components, in contrast to plasma and RBCs, filtration was shown to reduce dramatically the bacterial growth in buffy coats, demonstrating that the antibacterial effect of filtration was supported by the removal of infected WBCs from blood samples.

CONCLUSION

These results provide support for the systematic use of blood filtration in the preparation of blood components to prevent Y. enterocolitica infection of patients receiving transfusions.

Improved storage of erythrocytes by prior leukodepletion: flow cytometric evaluation of stored erythrocytes

In vivo phagocytosis of senescent red blood cells (RBCs) by macrophages occurs 120 days after their release into the circulation. It depends on two sequential signals that trigger phagocytosis: (1) desialylation of membrane glycoconjugates with the exposure of the penultimate beta-galactosyl residues and (2) exposure of phosphatidylserine in the membrane outer leaflet. Leukodepleted and nonleukodepleted RBCs were compared using flow cytometric procedures to determine whether the in vitro deterioration of RBCs during storage might be attributable to an identical mechanism of desialylation induced by leukocyte neuraminidases, resulting in exposure of beta-galactosyl and subsequently phosphatidylserine residues - signals of senescent RBCs. Without prior leukodepletion, stored RBCs showed an increased population of senescent RBCs (using light scatter measurements), extensive desialylation with the exposure of beta-galactosyl residues (using specific fluorescein isothiocyanate [FITC]-lectins), significant exposure of phosphatidylserine in the outer leaflet of the RBC membrane (using FITC-annexin V), and extensive in vitro phagocytosis (using PKH-26-labeled RBCs). There were minimal changes observed with the leukodepleted RBCs. These results lead to the conclusion that leukocyte enzymes, including neuraminidases, are definitive contributers to the desialylation of RBCs during storage and to the exposure of phosphatidylserine residues. These deleterious effects resulting from highly active leukocyte enzymes are preventable by prior leukodepletion of the stored RBCs. Previously developed flow cytometric procedures to detect in vivo "RBC senescence" have been applied and proved to be reliable criteria to monitor the viability of stored RBCs.

Timing of leukocyte filtration during cardiopulmonary bypass

The effects of leukocyte filtration on the outcome of cardiac surgery with cardiopulmonary bypass (CPB) have been shown by numerous investigators. In the majority of cases a leukocyte filter is placed in the arterial line instead of a standard arterial line filter and used throughout CPB. However, protocols to optimize onset and duration of leukocyte filtration have not been sufficiently evaluated to date. In this paper, current efforts to improve such protocols are demonstrated and discussed. These efforts are based on studies of leukocyte pathogenicity during cardiac surgery. A first study (double-blind randomized) was performed in routine coronary artery bypass graft (CABG) patients to evaluate whether short-term leukocyte filtration during reperfusion by release of the aortic crossclamp would reduce reperfusion-associated myocardial damage. Further data compare the efficacy of three different filtration concepts to reduce CPB- and/or reperfusion-associated leukocyte pathogenicity. Clinical endpoints, standard laboratory variables and functional in vitro assays are provided and discussed.

Filtration of malignant cells: tumour cell depletion in an ex vivo model using a leukocyte adhesion filter

The clinical use of leukocyte adhesion filters is based on differentiated depletion of blood cells, although most of the mechanisms of filtration are still unclear. There is also evidence that leukocyte adhesion filters can remove disseminated tumour cells from patients' blood. The following proves this observation and consists of three parts: in the first part we analysed the depletion capacity of the LeucotrapWB filter medium (Pall) in an employed small-scale model for the cell line HT29 (colorectal origin) in phosphate-buffered saline (PBS) solution. A depletion rate of more than 99.6% for HT29 cells was seen. In the second part of the study, samples of whole blood were spiked with HT29 cells in a similar setting, showing comparable results. In the last part, defined cell suspensions of various human primary tumours were admixed to whole blood samples and afterwards filtrated in a scale-up model. Again, a nearly complete tumour cell reduction was seen after filtration. Results show a significant tumour cell reduction and, for most cases, a complete depletion of tumour cells independently from quality and origin of the tumour tissue. These experiments and further investigation are supposed to help to reduce the risk of dissemination of tumour cells in patients undergoing oncological surgery.

Irreversible loss of donor blood leucocyte activation may explain a paucity of transfusion-associated graft-versus-host disease from stored blood

Transfusion-associated graft-versus-host disease (TA-GVHD) is usually a fatal outcome of blood transfusion therapy, caused by viable leucocytes contained in the donor blood. Most cases of TA-GVHD occur when less than 4-d-old blood is transfused. We therefore examined the molecular changes that occur during storage that may account for the paucity of TA-GVHD following infusion of older blood. Leucocyte number and viability were essentially unchanged from freshly obtained blood, but the expression of cell-surface lymphocyte activation antigens (CD3, CD4, CD28, CD2, CD45) decreased rapidly within the first 24 h and continued to fall to less than 20% of original levels by d 9 of storage at 4 degrees C. The decrease in CD antigen expression directly correlated with a decreasing ability to induce activation of the T-lymphocyte cellular signal transduction pathway. As a result, cells became less responsive in a mixed lymphocyte culture (MLC) by d 3, with abrogation of the MLC responsiveness by d 5. Donor leucocytes stored for 4 d or less at 4 degrees C were able to partially re-express CD antigens and reconstitute their signalling pathway when placed at 37 degrees C. whereas those stored for more than 4 d were not. These irreversible changes result from a permanent downregulation of donor cell protein synthesis. These findings provide a mechanism to explain the paucity of TA-GVHD following transfusion of blood that is more than 4 d-old. Further study may show that aged blood provides additional assurances for the prevention of TA-GVHD; however, use of aged blood should not replace current protocols using irradiation.