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Elucidating the precise mechanisms of cumulative red cell damages during storage and the potential harmful consequences after transfusion are achievable by exacting laboratory science and well-defined clinical studies in progress. Accordingly, for larger magnitude blood transfusions (i.e. 8-12 U in 24 hours), the quality of the stored blood and its characterisation are of special academic and clinical importance. Our main objectives in this review are to illuminate facets of the red cell storage lesion for prolonged storage (0-42 days) by concentrating on various hallmarks of the disorder: 1) identifying and characterising serial markers of the progressive lesion with respect to red cell dysmorphology, deformability, haemolytic fragility and dysfunction both in storage and the microcirculation; and 2) relevant biochemical findings of redox status correlated to oxidative stress of erythrocyte proteins. This is accomplished in part by reliance on advanced metabolomic and proteomic technologies using various sophisticated tools such as high pressure liquid chromatography in combination with mass spectrometry of proteins and small molecule metabolites. It is anticipated that these sophisticated methodologies and the experimental results therein shall lead to further advances in the quality improvement of red cell storage.

Red blood cells (RBCs) units are the most requested transfusion product worldwide. Indications for transfusion include symptomatic anaemia, acute sickle cell crisis, and acute blood loss of more than 30% of the blood volume, with the aim of restoring tissue oxygen delivery. However, stored RBCs from donors are not a qualitative equal product, and, in many ways, this is a matter of concern in the transfusion practice. Besides donor-to-donor variation, the storage time influences the RBC unit at the qualitative level, as RBCs age in the storage bag and are exposed to the so-called storage lesion. Several studies have shown that the storage lesion leads to post-transfusion enhanced clearance, plasma transferrin saturation, nitric oxide scavenging and/or immunomodulation with potential unwanted transfusion-related clinical outcomes, such as acute lung injury or higher mortality rate. While, to date, several studies have claimed the risk or deleterious effects of "old" vs "young" RBC transfusion regimes, it is still a matter of debate, and consideration should be taken of the clinical context. Transfusion-dependent patients may benefit from transfusion with "young" RBC units, as it assures longer inter-transfusion periods, while transfusion with "old" RBC units is not itself harmful. Unbiased Omics approaches are being applied to the characterisation of RBC through storage, to better understand the (patho)physiological role of microparticles (MPs) that are found naturally, and also on stored RBC units. Perhaps RBC storage time is not an accurate surrogate for RBC quality and there is a need to establish which parameters do indeed reflect optimal efficacy and safety. A better Omics characterisation of components of "young" and "old" RBC units, including MPs, donor and recipient, might lead to the development of new therapies, including the use of engineered RBCs or MPs as cell-based drug delivering tools, or cost-effective personalised transfusion strategies.

Red blood cell storage in the blood bank makes millions of units of available for transfusion to civilian and military recipients every year. From glass bottles to plastic bags, from anticoagulants to complex additives, from whole blood to leukocyte filtered packed red blood cells: huge strides have been made in the field of blood component processing and storage in the blood bank during the last century. Still, refrigerated preservation of packed red blood cells under blood bank conditions results in the progressive accumulation of a wide series of biochemical and morphological changes to the stored erythrocytes, collectively referred to as the storage lesion(s). Approximately ten years ago, retrospective clinical evidence had suggested that such lesion(s) may be clinically relevant and mediate some of the untoward transfusion-related effects observed especially in some categories of recipients at risk (e.g. massively or chronically transfused recipients). Since then, randomized clinical trials have failed to prospectively detect any signal related to red cell storage duration and increased morbidity and mortality in several categories of recipients, at the limits of the statistical power of these studies. While a good part of the transfusion community has immediately adopted the take-home message "if it isn't broken, don't fix it" (i.e. no change to the standard of practice should be pursued), decision makers have been further questioning whether there may be room for further improvements in this field. Provocatively, we argue that consensus has yet to be unanimously reached on what makes a good quality marker of the red cell storage lesion and transfusion safety/efficacy. In other words, if it is true that "you can't manage what you can't measure", then future advancements in the field of transfusion medicine will necessarily rely on state of the art analytical omics technologies of well-defined quality parameters. Heavily borrowing from Douglas Adam's imaginary repertoire from the world famous "Hitchhiker's guide to the galaxy", we briefly summarize how some of the principles for intergalactic hitchhikers may indeed apply to inform navigation through the complex universe of red cell storage quality, safety and efficacy., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Extracellular vesicles (EVs), including microvesicles and exosomes, are small phospholipid vesicles (≤1μm in diameter) that are present in blood products, accumulate during storage, and have a potential transfusion-related immunomodulatory role. Knowledge of EVs in stored blood products is limited due to the challenges and difficulties in detecting these heterogeneous submicron-sized vesicles. The aim of this study was to assess the impact of different approaches to characterize EVs in stored RBC products. Quantification and size-profiling of EVs in leukoreduced red cell concentrates (RCCs) were examined on day 3, 7, 21, and 42 of storage using tunable resistive plus sensing (TRPS), flow cytometer (FC), and dynamic light scatting (DLS) methods. Using the TRPS method, the concentration of EVs<200nm significantly increased throughout storage (p<0.05). This change in exosome concentration was not detectable with FC or DLS due to limitations in their ability to resolve particles <200nm and/or accurately determine EV concentration. Both the TRPS and FC demonstrate that the concentration of EVs≥200nm significantly increases in RCCs by day 42/43 compared to EVs present on day 3 (p<0.001). As the DLS measures the average size of particles in suspension, only an increase in the zeta-average size was observed during storage. EV size and concentration in RBC products is significantly influenced by the length of storage. Overall, this study shows that combining technologies may be important to improve the characterization and study of EVs in stored RCCs., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Red blood cell (RBC) transfusion is a life-saving treatment for several pathologies. RBCs for transfusion are stored refrigerated in a preservative solution, which extends their shelf-life for up to 42 days. During storage, the RBCs endure abundant physicochemical changes, named RBC storage lesions, which affect the overall quality standard, the functional integrity and in vivo survival of the transfused RBCs. Some of the changes occurring in the early stages of the storage period (for approximately two weeks) are reversible but become irreversible later on as the storage is extended. In this review, we aim to decipher the duration of RBC storage and inflammatory marker generation. This phenomenon is included as one of the causes of transfusion-related immunomodulation (TRIM), an emerging concept developed to potentially elucidate numerous clinical observations that suggest that RBC transfusion is associated with increased inflammatory events or effects with clinical consequence.

What is following the impressive progress that has been made? During the last couple of years several tremors have shaken the field of Transfusion Medicine. The epicentres of those tremors were located on novel insights into the RBC storage lesion, on emerging connections between storage lesion and post-transfusion performance and effects, and on acknowledging that storage time is only one (rather than the most prominent) of the parameters which contribute to the progression of storage lesion in any given unit of blood. The optimisation of bio-preservation conditions emerged at the same time with all-new scientific knowledge gained by advances in research tools, implementation of technological innovations, and application of elegant in vitro and in vivo models of transfusion. Simultaneously, one after another, all the reported randomised clinical trials concluded, with spectacular consensus, that there is no significant difference in the rate of adverse clinical events (including death) among patients who underwent transfusion with fresh (and presumably good) or standard of care (and presumably bad) blood. The comparative analysis and comprehension of the aforementioned data would set the context for the next generation of research in blood transfusion science, since the need for safer and more efficient transfusions remains.

Red blood cell storage lesion (RSL) is a multifaceted biological phenomenon. It refers to deterioration in RBC quality that is characterized by lethal and sub-lethal, reversible and irreversible defects. RSL is influenced by prestorage variables and it might be associated with variable clinical outcomes. Optimal biopreservation conditions are expected to offer maximum levels of RBC survival and acceptable functionality and bioreactivity in-bag and in vivo; consequently, full appraisal of RSL requires understanding of how RSL changes interact with each other and with the recipient. Recent technological innovation in MS-based omics, imaging, cytometry, small particle and systems biology has offered better understanding of RSL contributing factors and effects. A number of elegant in vivo and in vitro studies have paved the way for the identification of quality control biomarkers useful to predict RSL profile and posttransfusion performance. Moreover, screening tools for the early detection of good or poor "storers" and donors have been developed. In the light of new perspectives, storage time is not the touchstone to rule on the quality of a packed RBC unit. At least by a biochemical standpoint, the metabolic aging pattern during storage may not correspond to the currently fresh/old distinction of stored RBCs. Finally, although each unit of RBCs is probably unique, a metabolic signature of RSL across storage variables might exist. Moving forward from traditional hematologic measures to integrated information on structure, composition, biochemistry and interactions collected in bag and in vivo will allow identification of points for intervention in a transfusion meaningful context., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Release of vesicles from cells is a universal biological system, an adaptive cellular response to endogenous or external physiological or stressful stimuli and a genius means for intercellular, inter-organ and even inter-organism communication. These secreted vesicles that are collectively designated extracellular vesicles (EVs) have increasingly attracted the interest of cell biologists due to their imaginable interactions with every piece of the known biological systems in both health and disease states. Although EVs isolation and characterization are challenges, owing to their particular physicochemical features and complex biology, recent technological innovation has offered better understanding and inevitably, driven the revision of previously established theories on them. However, a crucial question remains unsolved: the physiological relevance of EVs in vivo. Since membrane vesiculation is an integral part of red blood cell (RBC) aging and homeostatic machinery and a prominent feature of RBC storage lesion, the characterization of storage EVs and their probable clinical relevance with the therapeutic or adverse effects of transfusions are extremely important targets in the research fields of transfusion biology and medicine. The scientists involved should transfer nascent knowledge and state-of-the-art technological tools in the packed RBC unit in order to: (i) update the inventory of biochemical and biophysical features of storage EVs; (ii) gain insight into the molecular pathways/signals underlying their generation; and (iii) clarify their dependence on blood donor, storage strategies and analytical variations, in order to step forward on understanding their interactions with stored or recipient target cells., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Blood cells generate heterogeneous populations of vesicles that are delivered, as small-specialized packages of highly active cell fragments in blood circulation, having almost similar functional activities, as the mother cells. These so called extracellular vesicles are the essential part of an energy-dependent natural apoptotic process; hence their beneficial and harmful biological functions cannot be ignored. Evidence is accumulating, that cellular derived vesicles, originate from all viable cells including: megakaryocytes, platelets, red blood cells, white blood cells and endothelial cells, the highest in proportions from platelets. Shedding can also be triggered by pathological activation of inflammatory processes and activation of coagulation or complement pathways, or even by shear stress in the circulation. Structurally, so called MV/EV appear to be, sometimes inside-out and sometimes outside-in cell fragments having a bilayered phospholipid structure exposing coagulant-active phosphatidylserine, expressing various membrane receptors, and they serve as cell-to-cell shuttles for bioactive molecules such as lipids, growth factors, microRNAs, and mitochondria. Ex vivo processing of blood into its components, embodying centrifugation, processing by various apheresis procedures, leukoreduction, pathogen reduction, and finally storage in different media and different types of blood bags, also have major impacts on the generation and retention of MV content. These artificially generated small, but highly liable packages, together with the original pool of MVs collected from the donor, do exhibit differing biological activities, and are not inert elements and should be considered as a parameter of blood safety in haemovigilance programmes. Harmonization and consensus in sampling protocols, sample handling, processing, and assessment methods, in particular converting to full automation, are needed to achieve consensual interpretations. This review focuses on some of our past personal studies on the role of MV/EV focusing on characterization of platelet storage lesion and platelet therapy that shows the highest transfusion hazards [up to 25%], and loss of 25% platelet efficacy after various leukoreduction and validated platelet pathogen reduction treatments. The planned paths for the future of EV/MV involvement in immunological and viral/ non-viral transfusion hazards are also discussed. Whilst considerable advances made on the characterization of EV/MV, but disparity still exists between various surrogate markers, showing some subtle differences in the levels of MV/ EV & BRMs in platelet preparations, and the clinical outcome showing platelets derived by all current technologies are equivalents in vivo. One possible reason for such a disparity may be relatedto the fact that MVs, being the end products of apoptotic cells, have little specificity and clear rapidly from circulation [<6 h in thrombocytopoenia]. This makes their clinical usefulness rather short lived. The recent findings that pegylating smaller subsets of EV increases its circulatory life from <15 minutes to approximately about one hour is highly promising, in particular, for drug delivery on specific sides. Hence a promising clinical utility of EV/MV continues, as a journey without end, indeed. This manuscript is based mainly on the selected key readings listed below., (Copyright © 2016. Published by Elsevier Ltd.)

Blood cells and tissues generate heterogeneous populations of cell-derived vesicles, ranging from approximately 50 nm to 1 µm in diameter. Under normal physiological conditions and as an essential part of an energy-dependent natural process, microparticles (MPs) are continuously shed into the circulation from membranes of all viable cells such as megakaryocytes, platelets, red blood cells, white blood cells and endothelial cells. MP shedding can also be triggered by pathological activation of inflammatory processes and activation of coagulation or complement systems, or even by shear stress in the circulation. Structurally, MPs have a bilayered phospholipid structure exposing coagulant-active phosphatidylserine and expressing various membrane receptors, and they serve as cell-to-cell shuttles for bioactive molecules such as lipids, growth factors, microRNAs, and mitochondria. It was established that ex vivo processing of blood into its components, involving centrifugation, processing by various apheresis procedures, leucoreduction, pathogen reduction, and finally storage in different media and different types of blood bags, can impact MP generation and content. This is mostly due to exposure of the collected blood to anticoagulant/storage media and due to shear stresses or activation, contact with artificial surfaces, or exposure to various leucocyte-removal filters and pathogen-reduction treatments. Such artificially generated MPs, which are added to the original pool of MPs collected from the donor, may exhibit specific functional characteristics, as MPs are not an inert element of blood components. Not surprisingly, MPs' roles and functionality are therefore increasingly seen to be fully relevant to the field of transfusion medicine, and as a parameter of blood safety that must be considered in haemovigilance programmes. Continual advancements in assessment methods of MPs and storage lesions are gradually leading to a better understanding of the impacts of blood collection on MP generation, while clinical research should clarify links of MPs with transfusion reactions and certain clinical disorders. Harmonization and consensus in sampling protocols, sample handling and processing, and assessment methods are needed to achieve consensual interpretations. This review focuses on the role of MPs as an essential laboratory tool and as a most effective player in transfusion science and medicine and in health and disease., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Microvesicles (MVs), or microparticles, are a complex, dynamic and functional part of cells. Red blood cell (RBC)-derived MVs are naturally produced in vivo (during normal aging processes or in several diseases) as well as ex vivo during cold storage of RBCs, or in vitro by ATP depletion or treatment with Ca(2+) and calcium ionophore. All these MVs are equivalently classified according to their size and/or surface markers. Nevertheless, their content in proteins can differ and a few differences in terms of lipid raft proteins, notably stomatin and flotillin-2, have been reported. Based on two-dimensional gel electrophoreses, the present study highlights the differences between MVs induced during storage of RBCs (storage-MVs) and MVs stimulated by Ca(2+) entry (Ca-MVs). Upon treatment, Ca-MVs are formed following a clear recruitment of Ca(2+)-binding proteins (sorcin, grancalcin, PDCD6) and particularly annexins (4 and 5). Therefore, it emerges that different molecular pathways are available to produce similar MVs by disturbing the membrane/cytoskeleton interactions. Interestingly, these differences provide non-negligible pieces of information on the parent cells, and the mechanisms and modes of actions involved in the formation of MVs. In addition to biophysical characterization, protein analysis is important to classify these cellular corpuscles and evaluate their potential impacts in diseases or transfusion medicine., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Platelet concentrates can be cryopreserved in dimethylsulphoxide (DMSO) and stored at -80 °C, which increases the shelf-life from 5 days to up to 4 years. Cryopreserved platelets have been shown to contain a high number of microparticles that have in vitro haemostatic activity. Further, when transfused, cryopreserved platelets have been shown to be at least as haemostatically active, as liquid-stored platelets, if not more so. Given that microparticles are traditionally considered to be pro-coagulant, it is likely that their presence in the cryopreserved component contributes to this haemostatic effect. However, as microparticles are known to mediate many physiological and pathological processes, including in thrombosis and cancer development and progression, further work is warranted to fully understand the functional scope of the microparticles in cryopreserved platelets., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The storage and handling conditions of cellular blood components and plasma are often rigorous, which is causing extensive discard of components that may be of acceptable quality as the rules for “out of optimal storage conditions” seem to be based more on tradition than scientific investigations. This short review summarizes some of the key papers indicating that it should be time for reconsideration of these rules, and some new suggestions are carefully indicated. Red cell concentrates, platelet concentrates and FFP are considered;lyophilized plasma and never-frozen liquid plasma are not included in this paper.

Bacterial contamination of blood and its cellular components remains the most common microbiological cause of transfusion associated morbidity and mortality, even in developed countries. This yet unresolved complication is seen more often in platelet transfusions, as platelet concentrates are stored at room temperature, in gas permeable containers with constant agitation, which support bacterial proliferation from relatively low undetectable levels, at the beginning of storage time, to relatively high virulent bacteria titers and endotoxin generation, at the end of shelf life. Accordingly, several combined strategies are introduced and implemented to at least reduce the potential risk of bacterial contaminated products for transfusion. These embody: improved donors arms cleaning; bacterial avoidance by diversion of the first portion of collection; reducing bacterial growth through development of newer storage media for longer platelet shelf life; bacterial load reduction by leucoreduction/viral inactivation, in some countries and eliminating the use potentially contaminated units through screening, through current available testing procedures, though none are not yet fully secure. We have not seen the same reduction in bacterial associated transfusion infections as we have observed for the sharp drop in transfusion associated transmission rates of HIV and hepatitis B and C. This great viral reduction is not only caused by the introduction of newer and more sensitive and specific detection methods for different viruses, but also the identification of donor risk groups through questionnaires and personal interviews. While search for more efficient methods for identifying potential blood donors with asymptomatic bacteremia, as well as a better way for detecting bacteria in stored blood components will be continuing, it is necessary to establish more standardized guidelines for the recognition the adverse reactions in recipients of potentially contaminated units. Efforts also should be also directed to identify blood donors with significant risk of bacteremia, at the time of donation in the first place as a high priority. The goal of this review is to highlights strategies for identifying both the sources of bacterial contamination of blood components in Norway and identifying donors with a higher risk of bacteremia at the time of donation. The key to achieving this goal is initiating continual revising and upgrading the Norwegian transfusion guidelines, based on the transfusion legislation and by introducing a relevant specialized donor bacterial questionnaire., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Multilayer preventative strategies have been instituted to enhance transfusion safety for patients in need of critical blood components. Presently blood safety is at its highest levels, with the implementation of precautionary/preventative measures against vCJD, bacterial and viral contamination of the blood supply. The implementation of these strategies together with advances in automation and computerization led to significant improvements in standardisation for transfusion practices. These include validation, verification, adherence to GLP and GMP and other regulatory requirements. In most European countries, universal prestorage leukodepletion is routine practice. In France proactive pathogen inactivation treatments [PITs] have been implemented emphasizing patient safety. This at least conceptually reduces the risk of transfusing viable WBCs, emerging bacteria and viruses, all with potential transfusion complications. In the UK, prion removal filters for red cell products are used selectively for special groups of patients. Some research establishments are exploring the potential impact of pathogen inactivation of whole blood or red cell components, using the new generation of S-303 PIT and the prion removal filters in combination. It needs to be determined whether such a combined strategy, applied synergistically, enhances red cell transfusion safety without compromising the overall criteria of acceptability. It is necessary to critically examine the impact of a new generation of PIT technologies, which may exacerbate the red cell storage lesion and cause the development of undesirable antibodies in the recipient. The development of innovative laboratory tools is vital to study impacts of these measures on the quality of stored blood and their clinical outcome. The ultimate aim of red cell transfusion is to provide oxygen enriched red blood cells to the microcirculations and tissues. Definitive studies are needed to establish the potential unforeseen negative long term toxicity, overall efficacy/quality and the clinical outcome of treated stored blood., (Copyright © 2013. Published by Elsevier Ltd.)

In most countries whole blood transfusions have been replaced by component therapy. This has allowed for both better usage of the blood donations and better quality during storage. While this strategy was initially motivated by the commercial need for plasma the plasma reduction also reduced the levels of low grade proteases and sialidase, hence minimizing the cellular storage lesion/microvesiculation during prolonged storage. Plasma reduction also reduces transfusion reactions associated with plasma. During special military conditions, however, blood transfusion is urgently needed without corresponding access to blood components, in particular platelets. Accordingly, new focus on whole blood has aroused and added a new challenge to the blood transfusion services. This special issue of "what is happening" highlights the planed efforts by Swedish and Norwegian groups in the developments of military walking blood bank, which is applicable to civil blood services., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A primary function of blood transfusion services is to ensure the safety of the community's blood supply. Multilayer strategies of safety need to be incorporated into the processing of blood components in order to minimize untoward transfusion events related to infections or the blood storage lesion. While there have been considerable technical advances over the past few decades to advance blood component safety, there is a need for continued improvement. One significant problem area is transfusion transmitted bacterial infections. In infectious disease, blood borne bacteria are the major cause of morbidity in transfusion medicine. Proactive implementation of pathogen inactivation technologies, PIT can help to eliminate bacterial contamination of blood. This is accomplished by inactivation of various known and emerging bacterial pathogens, which have been identified through their nucleic acid sequences. The current PIT has additional positive impacts on transfusion safety by reducing adverse clinical events associated with viable residual leukocytes in the blood. Given the valuable benefits of pathogen inactivation, there is a practicable need to advance this technology. In order for a particular pathogen inactivation strategy to gain widespread acceptance, it must satisfy a number of important criteria. The technology shall be: (1) Effective to eliminate pathogens. (2) Uncomplicated and cost-effective to implement in the preparation of blood components. (3) Minimally toxic while maintaining the quality of blood storage products for transfusion purposes. (4) Safe. Currently, PIT is not suitable for all blood components. Future advances in PIT for whole blood and red cell components should expand the application of this technology across a broader range of blood products. Based on available laboratory and clinical data, current pathogen inactivation procedures appear to leave the cell components sufficiently viable to achieve an effective transfusion. Novel technologies continue to evolve for the inactivation of pathogens in the blood supply. We need to ensure these procedures do not worsen the storage lesion causing potential harm to patients. Quality research and development supporting multi-centre clinical trials are necessary. One purpose of such trials is to determine whether this new generation of procedures for processing blood yields bioequivalency regarding the quality of the products. Validated haematological assays should be utilized to test the extent of the blood storage lesion. Post-marketing surveillance involving active haemovigilance is necessary regarding possible adverse outcomes of transfusion., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Platelets derived from whole blood and diverse apheresis procedures come in contact with various artificial surfaces and undergo contact activation, sheer stress-induced shape changes, aggregation and microvesiculation during collection, processing and storage. These dynamic changes are qualitatively reflected in the log-normal platelet size distribution patterns seen, when using modern automated cell counters and can be measured quantitatively by counting the paired samples, without and with added EDTA, and calculating the differences (d) in platelet cellular indices (dPLT/dMPV/dPDW). Reporting the differences instead of the absolute values of cellular indices makes the measurements independent of basic principles used for cell counting (i.e. aperture-impedance or flow-optic). The measurements can be performed either in blood centres, hospital blood banks or nearby patient clinics equipped with a validated cell counter. At least three useful quality indices could be derived simultaneously from this procedure (accurate estimation of platelet yields using the value of the EDTA-containing sample); quantitative assessment of the % of reversible platelet aggregates, an age/pH/temperature-dependent degree of microvesiculation/apoptosis/PS exposure, based on the response to EDTA. This new set of indices correlate significantly with other conventional tests for platelet quality; hence, provide additional supportive evidence for confirming the low pH values and the subjective poor swirling data occasionally seen with stored PC. In the following study, the Sysmex SE 9000 was successfully employed for estimation of platelet cellular indices comparing the platelet storage lesion index of three types of leukoreduced platelet concentrates in current practice. The relationship between this in vitro response to clinical outcome remains to be established.

Platelets are known to undergo shape change, activation, a release reaction and apoptosis/necrosis during processing and storage, all of which are collectively known as the platelet storage lesion. Any additional processing may have some deleterious impact on platelet activability and functional integrity, which need to be investigated. This preliminary investigation was undertaken to establish the combined effects of standard platelet storage media and the intercept pathogen reduction technology on platelet activation and activability during 7 day storage, using buffy-coat derived platelets in standard storage media containing 35% plasma (N=24). P-selectin (CD62p) expression, a classical marker of platelet activation, and phosphatidylserine (PS) exposure on the platelet surface membrane, a hallmark of cellular necrosis/apoptosis, were both measured by flow cytometry. The results reveal significant increases in activation, from an average of 22.7% on day 1 before treatment to 31.6% on day 2 after treatment and 58.7% at the end of storage. Concomitantly, the basal expression of PS was slightly increased from 1.9% to 2.8% at day 2 after treatment and 7.3% at the end of storage. However, the functional reserve of platelets during storage, which reflects their capability to undergo activation and the release reaction when platelets were challenged with either calcium ionophore or thrombin, was relatively well maintained. These preliminary data confirm the earlier data on the use of intercept, and for the first time, based on the assessment of platelet functional integrity, suggest that platelet functional reserve is relatively well maintained, with little change in the formation of apoptotic cells.

Red blood cells undergo major biochemical and biomechanical changes during storage that could effect their post transfusion performance. Biochemical effects include changes in 2,3-diphosphoglycerate (2,3-DPG), ATP, and calcium levels, as well as metabolic modulation and release of Annexin V, a cytosolic component of blood cells, as a global marker of cellular injury and fragmentation. Biomechanical changes include alterations in cellular membrane, shape changes, phospholipid content, phospholipid asymmetry, and antigenic markers. Although the extent of these changes under various storage conditions has been well documented, their clinical effects remain unclear. In the current era of universal leucodepletion, the immunomodulatory effects of some essential markers such as CD47 and phosphatidyl serine become the focus of interest as highlighted in this manuscript.

Platelets derived from platelet rich plasma, buffy coat and Apheresis technologies differ in terms of in vitro functional activity, aggregation states and storage characteristics, as measured by automated cell counters, and pH assessment. This may be related to either differences in the subpopulation of platelets and leucocytes recovered or the processing/storage induced cellular damage. Some types of methodologies, such as BC derived-PC, appear to have a higher rate of bacterial contamination.

The conventional and a new marker of global cellular lesion (Annexin V) are used to assess the processing/storage-induced changes in four types of RBC and filtered blood at 4 degrees and 22 degrees C, stored for a period of 35 days, in multi-satellite packs. It appears that mechanical trauma and presence of leucocytes and residual platelets have potential to increase levels of all markers of storage lesion, but to a variable extend. We have also provided new evidence that multi-satellite packs can be safely used for up to 35 days for small volume transfusion to sick premature infants, in a well-managed system by administering several transfusions from the same donation, hence reducing donor exposure.