Blood transfusion and immunomodulation: a possible mechanism

Post-COVID-19 Lymphocytopenia and Opportunistic Pathogens Infection in a Thalassemia Major Patient

Transfusion-dependent thalassemia patients undergo transfusion immunomodulating effects, which result in a general immune response depression and, consequently, an increase in the frequency of infectious episodes and neoplastic events due to a reduction in phagocytic function. Altered natural killer functions and IL-2-mediated lymphocytic response, defects in antigen presentation due to monocyte–macrophage cells, and decreases in bone marrow precursors and HLA II+ cells all play key roles in immunodepression in thalassemia major. SARS-CoV-2 infection presents marked lymphopenia, occurring in 96.1% of severe cases. COVID-19-related lymphopenia is due to various mechanisms, which lead to an increase in lymphocytic apoptosis. Post-COVID-19 lymphocytic quantitative and functional disorders may compromise immune response and promote the onset of infections via opportunistic pathogens. Herein, we report a case of a thalassemia major patient who developed severe post-COVID-19 lymphocytopenia, which may have facilitated the onset of a severe Klebsiella Pneumoniae infection.

Blood transfusion and the risk for infections in kidney transplant patients

BACKGROUND

Receipt of a red blood cell transfusion (RBCT) post-kidney transplantation may alter immunity which could predispose to subsequent infection.

METHODS

We carried out a single-center, retrospective cohort study of 1,258 adult kidney transplant recipients from 2002 to 2018 (mean age 52, 64% male). The receipt of RBCT post-transplant (468 participants transfused, total 2,373 RBCT) was analyzed as a time-varying, cumulative exposure. Adjusted cox proportional hazards models were used to calculate hazard ratios (HR) for outcomes of bacterial or viral (BK or CMV) infection.

RESULTS

Over a median follow-up of 3.8 years, bacterial infection occurred in 34% of participants at a median of 409 days post-transplant and viral infection occurred in 25% at a median of 154 days post-transplant. Transfusion was associated with a step-wise higher risk of bacterial infection (HR 1.35, 95%CI 0.95-1.91; HR 1.29, 95%CI 0.92-1.82; HR 2.63, 95%CI 1.94-3.56; HR 3.38, 95%CI 2.30-4.95, for 1, 2, 3-5 and >5 RBCT respectively), but not viral infection. These findings were consistent in multiple additional analyses, including accounting for reverse causality.

CONCLUSION

Blood transfusion after kidney transplant is associated with a higher risk for bacterial infection, emphasizing the need to use transfusions judiciously in this population already at risk for infections.

Effect of storage period of red blood cell suspensions on helper T-cell subpopulations

BACKGROUND

The aim of this study was to investigate the immunological alterations that occur during the storage of erythrocyte suspensions which may lead to transfusion-related immunomodulation following allogeneic blood transfusion.

MATERIALS AND METHODS

One part of the erythrocyte suspensions obtained from donors was leucoreduced while the other part was not. The leucoreduced (LR) and non-leucoreduced (NL) erythrocyte suspensions were then further divided into three equal amounts which were stored for 0, 21 or 42 days prior to measurements, by enzyme-linked immunosorbent assays, of cytokine levels in their supernatants. T-helper (Th) lymphocyte subgroups and gene expression were analysed in the NL erythrocyte suspensions by flow cytometry and real-time polymerase chain reaction, respectively. Results were compared to those of storage day 0.

RESULTS

By day 21, the number of Th2 cells had increased significantly and the numbers of Th1, Th22 and Treg cells had decreased significantly in the NL erythrocyte suspensions. On day 42 the numbers of Th2 and Treg cells in the NL suspensions were significantly increased while the number of Th1 cells was significantly decreased. The levels of transcription factors (TBX21, GATA3, and SPI.1) were significantly decreased on days 21 and 42, and AHR, FOXP3 and RORC2 levels were significantly increased on day 42 in NL erythrocyte suspensions. The decrease in interleukin-22 and increase in transforming growth factor-β levels found in NL erythrocyte suspensions on day 21 were statistically significant. Elevated levels of interleukin-17A were found in both LR and NL erythrocyte suspensions on day 42.

DISCUSSION

Our results suggest that allogeneic leucocytes and cytokines may play significant roles in the development of transfusion-related immunomodulation.

Anemia and Transfusion in Critical Care

Objective:

The objective of this report is to review the physiology and management of anemia in critical care. Selected publications on physiology and transfusion related to anemia and critical care, including the modern randomized trials of conservative versus liberal transfusion policy, were used. Anemia is compensated and tolerated in most critically ill patients as long as oxygen delivery is at least twice oxygen consumption. There are risks to blood transfusion which can be minimized by blood banking practice. The availability of cultured red cells may allow correction of anemia without significant risk. The benefit of transfusion in anemia must be weighted against the risk in any specific patient.

Conclusion and Recommendation:

In a criticially ill patient, anemia should be managed to avoid oxygen supply dependency (oxygen delivery less than twice comsumption) and to maintain moderate oxygen delivery reserve (DO2/VO2 > 3).

Association of perioperative allogeneic blood transfusions and prognosis of patients with gastric cancer after curative gastrectomy

BACKGROUND

The relationship between perioperative allogeneic blood transfusions (PABTs) and prognosis in patients with gastric cancer remains controversial.

METHODS

Six hundred five consecutive patients with gastric cancer who underwent curative gastrectomy from a single center were enrolled in this retrospective study. Clinical and pathologic variables were prospectively collected. The effect of PABT on the long-term survival of patients with gastric cancer after curative gastrectomy was evaluated by univariate and multivariate analyses.

RESULTS

The overall 5-year survival rate was 65.0%. On univariate analyses, PABT had a statistically significant negative impact on 3-year and 5-year survival rates (66.3% vs 80.5% [P = .005] and 38.7% vs 76.4% [P < .001], respectively). However, multivariate analyses revealed that duration of operation (P = .009), tumor size (P = .001), and tumor stage (P < .001), instead of PABT, were independent prognostic factors.

CONCLUSIONS

Our study indicates that PABT is not an independent prognostic factor for long-term survival in patients with gastric cancer after curative gastrectomy.

Transfusion-associated immunomodulation: Quantitative changes in cytokines as a measure of immune responsiveness after one time blood transfusion in neurosurgery patients

Very few studies in humans have investigated the laboratory evidences suggestive of transfusion-associated immunologic changes. In this prospective study, we examined the effects of perioperative blood transfusion on immune response, by measuring various cytokines production, namely, interferon-gamma (IFN-γ), interleukin-10 (IL-10), and Fas Ligand (FasL). A total of 40 patients undergoing neurosurgery were randomly allocated into four groups: (a) no transfusion, (b) allogeneic non-leukofiltered transfusion, (c) prestorage leukofiltered transfusion, (d) autologous transfusion. Samples were collected before operation (day 0) and postoperative days (post-op) 1, 7, and 14. IFN-γ and IL-10 production capacity was measured in supernatant after whole blood culture and serum FasL levels in patients’ sera using commercially available ELISA kits. Change in ratios (cytokine value after PHA stimulation/control value) of IFN-γ and IL-10 and percentage change from baseline for serum FasL levels across different transfusion groups during the sampling period were calculated. There was an increase in IL-10 production in patients receiving allogeneic non-leukofiltered transfusion on days 1 and 7 (mean ratio 2.22 (± 2.16), 4.12 (± 1.71), 4.46 (± 1.97) on days 0, 1, and 7, respectively). Similarly there was a significant (P<0.05) decrease in IFN-γ production in patients who received allogeneic non-leukofiltered red cell transfusion on post-op days 1, 7, and 14 (mean ratio 6.88 (± 4.56), 2.53 (± 0.95), 3.04 (± 1.38) and 2.58 (± 1.48) on day 0, 1, 7, and 14, respectively). Serum FasL production was increased across all patients till 7th day except for ‘no transfusion’ group and this increase was most significant in the non-leukofiltered group. We conclude that one time transfusion leads to quantitative changes in levels of these cytokines largely through interplay of Th2/Th1 pathways in allogeneic nonleukofiltered blood transfusion; however, soluble mediators like FasL which are also present in autologous and leukofiltered blood products may contribute toward minor immunologic effect in these settings.

Platelet transfusions from D+ donors to D- patients: a 10-year follow-up study of 1014 patients

BACKGROUND

Current guidelines recommend that platelets (PLTs) from D- donors should be given to D- patients. However, such evidence comes from studies with a limited number of included patients that reported an incidence of anti-D alloimmunization to be up to 19%. We thus decided to extend these findings by examining anti-D alloimmunization at our institution, where PLT transfusions from D+ donors are transfused to D- patients because of logistic constraints.

STUDY DESIGN AND METHODS

From April 1999 to December 2009, we retrospectively reviewed the clinical and transfusion records of all D- patients who received PLT transfusions from D+ donors at our hospital. PLT concentrates (PCs) were obtained from apheresis and from whole blood donations. RhIG was not administered after the transfusion of PCs from D+ donors. The antibody screen test to detect anti-D was performed by low-ionic-strength solution indirect antiglobulin test using the gel test.

RESULTS

Our series comprises 1014 D- patients who received 5128 PLT transfusions from D+ donors (89% were pooled PCs). We had 315 (31.1%) patients who had a blood sample to analyze the presence of anti-D 4 or more weeks after the first D+ PLT transfusion with a median follow-up of 29 weeks (range, 4-718 weeks). Anti-D developed in 12 (3.8%) of these 315 patients.

CONCLUSIONS

The frequency of anti-D alloimmunization of D- patients after receiving pooled PCs from D+ donors is low. The transfusion of D-incompatible pooled PCs without immunoprophylaxis to D- men or D- women without childbearing potential seems a reasonable and safe alternative.

Transfusion-related immunomodulation (TRIM): an update

Allogeneic blood transfusion (ABT)-related immunomodulation (TRIM) encompasses the laboratory immune aberrations that occur after ABT and their established or purported clinical effects. TRIM is a real biologic phenomenon resulting in at least one established beneficial clinical effect in humans, but the existence of deleterious clinical TRIM effects has not yet been confirmed. Initially, TRIM encompassed effects attributable to ABT by immunomodulatory mechanisms (e.g., cancer recurrence, postoperative infection, or virus activation). More recently, TRIM has also included effects attributable to ABT by pro-inflammatory mechanisms (e.g., multiple-organ failure or mortality). TRIM effects may be mediated by: (1) allogeneic mononuclear cells; (2) white-blood-cell (WBC)-derived soluble mediators; and/or (3) soluble HLA peptides circulating in allogeneic plasma. This review categorizes the available randomized controlled trials based on the inference(s) that they permit about possible mediator(s) of TRIM, and examines the strength of the evidence available for relying on WBC reduction or autologous transfusion to prevent TRIM effects.

Why have meta-analyses of randomized controlled trials of the association between non-white-blood-cell-reduced allogeneic blood transfusion and postoperative infection produced discordant results?

Intention-to-treat analyses of randomized controlled trials (RCTs) of the association between non-white-blood-cell (WBC)-reduced allogeneic blood transfusion (ABT) and postoperative infection were reported as the reason why meta-analyses of RCTs of this association have produced discordant results. We examined three possible reasons for disagreements between meta-analyses: (i) sources of medical heterogeneity and integration of RCTs despite extreme heterogeneity; (ii) reliance on as-treated (vs. intention-to-treat) comparisons; and (iii) inclusion (or not) of the three most recent RCTs. When nine RCTs reported up to 2002 were combined despite extreme heterogeneity, both intention-to-treat and as-treated comparisons found an association between non-WBC-reduced ABT and postoperative infection [summary odds ratio (OR) = 1.38, 95% confidence interval (CI) 1.03-1.85, P < 0.05; and summary OR = 1.56, 95% CI 1.06-2.31, P < 0.05, respectively]. When 12 RCTs reported up to 2005 were integrated despite extreme heterogeneity, both intention-to-treat and as-treated comparisons found no association of non-WBC-reduced ABT with postoperative infection (summary OR = 1.24, 95% CI 0.98-1.56, P > 0.05; and summary OR = 1.31, 95% CI 0.98-1.75, P > 0.05, respectively). In both analyses, the separate integration of four RCTs transfusing red blood cells (RBCs) or whole blood filtered after storage showed an association between non-WBC-reduced ABT and postoperative infection, whereas the separate integration of six (or nine) RCTs, reported through 2002 or 2005, and transfusing prestorage-filtered RBCs showed no association, whether intention-to-treat or as-treated comparisons were used. Thus, the published meta-analyses have produced discordant results because they did (or did not) investigate medical sources of heterogeneity and did (or did not) include the most recent RCTs. Intention-to-treat and as-treated comparisons produced concordant results.

Ventilator associated pneumonia and transfusion, is there really an association? (the NAVTRA study)

Background

Anemic syndrome is a frequent problem in intensive care units. The most probable etiology is the suppression of the erythropoietin response due to the direct effects of cytokines, as well as frequent blood sampling.

Transfusions are not free of complications, therefore transfusion reactions are estimated to occur in 2% of the total packed red blood cells (pRBCs) transfused.

In the past several years, several trials had tried to compare the restrictive with the more liberal use of transfusions, and they were found to be equally effective.

Nosocomial pneumonia is the most common nosocomial infection in intensive care units; the prevalence is 47% with an attributive mortality of 33%.

There are multiple risk factors for the development of nosocomial pneumonia. Colonization of the upper airways is the most important pathophysiological factor but there are other factors implicated like, sedation techniques, inappropriate use of antibiotics and recumbent positioning.

A secondary analysis of the CRIT study describes transfusion therapy and its practices in the United States. They found that transfusion practice is an independent risk factor for the development of nosocomial pneumonia.

Methods

This is a multicenter, prospective cohort study in different intensive care units in Colombia. A total of 474 patients were selected who had more than 48 hours of mechanical ventilation.

The primary objective is to try to demonstrate the hypothetical relationship between the use of transfusions and nosocomial pneumonia.

Secondly, we will try to determine which other factors are implicated in the development of pneumonia in intensive care units and describe the incidence of pneumonia and transfusion practices.

Discussion

Ventilator associated pneumonia is a primary problem in the intensive care unit, multiple factors have been associated with its presence in this study we try to explore the possible association between pneumonia and transfusion, describe all other factors associated with this, and the possible association with other nosocomial infections.

The Effects of Perioperative Blood Transfusion on Morbidity and Mortality After Esophagectomy

The effect of blood transfusion on outcomes in esophageal surgery remains controversial. The contrasting conclusions drawn from a number of retrospective analyses with different methodologies create a landscape that is difficult to interpret. Because of the scope of esophageal resection, the need for blood transfusion cannot be eliminated. What recommendations then, if any, can be made for the practicing surgeon? First, surgeons and anesthesiologists need to reevaluate their transfusion thresholds. The age-old practice of keeping the hemoglobin above 10 g/dL has very little evidence-based support. A multicenter, randomized, controlled clinical trial in Canada demonstrated that a restrictive strategy of blood transfusion, in which patients were transfused only for a hemoglobin level of less than 7 g/dL, was at least as effective as and possibly was superior to a liberal transfusion strategy in critically ill patients. It has also been estimated that more than 25% of patients undergoing colorectal resections may receive at least one unit of unnecessary blood. Further, the immediate reduction in the hemoglobin concentration caused by the normovolemic hemodilution associated with surgery and crystalloid fluid replacement is not associated with any increased morbidity or mortality. If these data are examined in the context of the results of Langley and Tachibana indicating that a threshold amount of blood needs to be transfused to impact outcomes, it becomes even more important to limit transfusion to only the amount that is essential. Thus, surgeons and anesthesiologists should adopt a more stringent set of requirements for blood transfusion. Second, with the proven feasibility and reduction in infectious complications associated with autologous blood-donation programs, any patient who meets the criteria discussed here should be encouraged to participate in such a program. Although the effect of autologous blood on cancer outcomes remains unclear, the other advantages certainly make such a program worthy of consideration. This discussion leads to a final point, namely that patients should be encouraged, whenever possible, to participate in clinical trial research. The only way that the community of surgeons treating patients who have esophageal cancer can hope to address properly the question of how blood transfusion affects outcomes is with well-designed clinical trials. A large, multicenter, randomized trial (level I) would be ideal. Short of such a trial, inclusion criteria and study methodology should be discussed among various institutions to avoid the differences in studies that make direct comparisons of results among different investigators difficult and potentially meaningless. This measure would at least allow different level II to IV data to be compared directly with some validity.

Blood Transfusions Decrease the Incidence of Acute Rejection in Cardiac Allograft Recipients

BACKGROUND

Cardiac transplant recipients frequently receive a large number of transfusions. The objective of this study was to determine whether there is an association between total number of blood transfusions and cardiac allograft rejection.

METHODS

A retrospective analysis of all cardiac transplants between October 1, 1997, and December 31, 2001, was performed. Total number of transfusions, total number of rejection episodes Grade 3A or more, rejection-free survival, and overall survival were analyzed. Comparisons between patients bridged to transplantation with a Novacor left ventricular assist device (LVAD) and the primary transplant group were also made.

RESULTS

Eighty-two patients were transplanted. Fifteen were bridged to transplantation, and 67 underwent primary heart transplantation. Age and sex were similar for the LVAD group and the primary transplant group (45 +/- 11 vs 47 +/- 15 years and 67% vs 58% male sex, respectively). Mean follow-up was 658 +/- 486 days for the LVAD group and 708 +/- 548 days for the primary transplant group. Transfusions received were 50 +/- 34 U of packed red blood cells for the LVAD group and 7 +/- 12 for the primary transplant group (p < 0.001). There were no differences in donor characteristics between the 2 groups. The incidence of acute rejection within 1 year was 27% for the LVAD group and 39% for the primary transplant group (p = .28). Freedom from rejection was 71% at 1 year in the LVAD group compared with 59% for the primary transplant group (p = 0.39). In all 82 patients, the total number of transfusions was inversely correlated with the development of acute rejection (p = 0.011). Survival was 80% and 62% for the LVAD group at 1 and 3 years after transplantation and 88% and 85%, respectively, for the primary transplant group (p = 0.045).

CONCLUSIONS

The number of blood transfusions received by heart transplant recipients is inversely related with the number of acute rejection episodes.

Blood Transfers Infectious Immunologic Tolerance in MHC-Incompatible Heart Transplantation in Rats

"Infectious tolerance" or inducing immunologic tolerance of infection in allografts is still poorly understood. We investigated whether transfusing blood from LEW.1A rats tolerant of LEW.1W hearts could transmit tolerance to naive LEW.1A rats. In 4 of 6 cases, transfusing blood from tolerant animals was followed by immunologic tolerance of heart transplants from LEW.1W donor rats in LEW.1A recipient animals, whereas transplanting heart grafts that were tolerated in previous transplantations across MHC barriers did not transfer tolerance in major histocompatibility complex (MHC)-incompatible animals. We conclude that in rat heart transplantation, the transfer of immunologic tolerance can be enhanced by transfusing blood from tolerant animals to naive animals before transplantation across MHC barriers.

Anemia, allogenic blood transfusion, and immunomodulation in the critically ill

Anemia and allogenic RBC transfusions are exceedingly common among critically ill patients. Multiple pathologic mechanisms contribute to the genesis of anemia in these patients. Emerging risks associated with allogenic RBC transfusions including the transmission of newer infectious agents and immune modulation predisposing the patient to infections requires reevaluation of current transfusion strategies. Recent data have suggested that a restrictive transfusion practice is associated with reduced morbidity and mortality during critical illness, with the possible exception of acute coronary syndromes. In this article, we review the immune-modulatory role of allogenic RBC transfusions in critically ill patients.

Pretransplant blood transfusions revisited: a role for CD(4+) regulatory T cells?

Pretransplant blood transfusions have been shown to improve organ allograft survival. However, the immunologic mechanism leading to this beneficial effect of blood transfusions is still unknown. The observation that transfusions sharing at least one HLA-DR antigen (human leukocyte antigen) with the recipient are more effective than HLA-mismatched transfusions has led to the hypothesis that CD(4+) regulatory T cells are induced that recognize allopeptides of the blood transfusion donor in the context of the self-HLA-DR molecule on the donor cells. In vitro studies showed that CD(4+) T cells recognizing an allopeptide in the context of self-HLA-DR are indeed able to decrease the alloimmune response of autologous T cells by affecting the activated T cells directly or indirectly by their modulatory effect on dendritic cells. The first studies in a patient with a well-functioning kidney graft after receiving an HLA-DR-matched pretransplant blood transfusion showed that the low organ donor-specific cytotoxic T-lymphocyte response after transplantation was indeed attributable to the activity of regulatory CD(4+) T cells.

Immunological aspects of blood transfusions

Almost all identified acute and/or severe immunological reactions towards blood transfusions, reported by surveillance systems such as SHOT (Severe Hazards of Transfusion) in the UK are mediated by allo-antibodies. In contrast, the clinical effects of transfusion-induced cellular immunity are virtually unknown. Although alterations in lymphocyte responses and natural killer cell functions after blood transfusion has been reported in many publications, the relevance of these in vitro assays for in vivo immunity are lacking. Even for clinically obvious immunomodulatory effect of blood transfusions, such as the mitigation of renal graft rejection, no uniform in vitro explanation has been identified. In the laboratory animal it has been shown that when two antigenic stimuli are given simultaneously, the response to one of these antigens is often decreased. Blood transfusions introduce a multitude of foreign antigens. Indeed, immunostimulation and suppression by blood transfusions have both been found. Systematic studies on immunological side-effects of blood transfusions are hardly available. Since the UK and France introduced a transfusion vigilance system, severe immunological side-effects such as haemolytic reactions, TRALI (acute lung injury), PTP (post-transfusion purpura) and graft vs. host disease are registrated in these countries and their incidence can be estimated based on the national number of transfusions. However, every blood transfusion interferes with the immune system of the recipient. The available evidence of harm from immune responses not leading to severe transfusion reactions will be discussed.

Signs and symptoms associated with the transfusion of WBC-reduced RBCs and non-WBC-reduced RBCs in patients with anemia and HIV infection: results from the Viral Activation Transfusion Study

BACKGROUND

RBC transfusion is associated with fever and other reactions in some patients. The Viral Activation Transfusion Study randomly assigned patients to receive either unmodified or WBC-reduced RBCs and thus offered an opportunity to assess the effect of WBC-reduced RBCs on the incidence of transfusion reactions prospectively.

STUDY DESIGN AND METHODS

This prospective, randomized, double-blind, multicenter study compared prestorage WBC-reduced RBCs to unmodified RBCs in HIV-infected, CMV-seropositive, and transfusion-naive persons who required transfusions for anemia. Primary endpoints were survival and change in the plasma HIV RNA level at 7 days after transfusion. The incidence of transfusion reactions was prospectively evaluated.

RESULTS

The two groups had similar baseline characteristics and study endpoints; 3864 RBC units (median storage age, 9 days) were administered to 531 patients during 1745 transfusions. The most frequent signs reported were elevated temperature and hypotension. Subjects who reported fever within the week prior to transfusion were more likely to have an elevation in temperature associated with transfusion. The administration of RBCs that were less than 10 days old was associated with a marginal increase in the incidence of transfusion-associated temperature elevation among recipients of unmodified RBCs, but not among recipients of WBC-reduced RBCs. Caregivers reported fewer instances of both elevated temperature and hypotension than were identified by review of transfusion records.

CONCLUSIONS

The incidence of elevated temperature and hypotension associated with transfusion in this population was unexpectedly high. Use of WBC-reduced RBCs had no effect on the overall rates of elevated temperature or hypotension associated with transfusion of RBCs. The occurrence of a pre-existing fever was associated with a higher frequency of transfusion-associated elevated temperature.

The influence of homologous blood transfusion on immunity and clinical outcome in aortic surgery

OBJECTIVES

To evaluate the influence of homologous blood transfusion on immune responses and post-operative morbidity in aortic surgery.

DESIGN

Analysis of the effects of homologous blood transfusion in 128 patients in a prospective randomised trial evaluating homologous and autologous blood transfusion in aortic surgery.

MATERIALS AND METHODS

Blood sampled before and at five times after surgery was assayed for C-reactive protein (CRP), neutrophil elastase, TNF-alpha and IL-6. Transfusions, morbidity and mortality were recorded; factors associated with poor outcome were identified by logistic regression.

RESULTS

homologous transfusion during surgery was required in 32 patients and precipitated an increase in neutrophil elastase (p=0.008) and TNF-alpha (p=0.015) but not IL-6 and CRP. Elastase peaked early in transfused patients at 41.27 (13.92-52.11) Deltang/ml by 2 h compared to a peak of 21.51 (10.64-31.13) Deltang/ml by 24 h in those who were not transfused. TNF-alpha peaked at 1.2 (0-4.33) Deltapg/ml by wound closure in transfused patients and at -0.1 (-2.05-2.52) Deltapg/ml by 2 h without transfusion. Intra-operative homologous transfusion was associated with increased mortality (p=0.01) and prolonged intensive care stay (p=0.03). Mortality increased with age (p=0.003) and was inversely related to the CRP peak (p=0.007). Prolonged surgery predicted post-operative complications (p=0.025).

CONCLUSION

Homologous transfusion increased the inflammatory response to aortic surgery and was associated with mortality.

Modulation of the alloimmune response by blood transfusions

Blood transfusions can induce both immune activation and immunosuppression. The former is expressed by the induction of HLA alloantibodies and T cell activation, while the latter is accompanied by enhanced graft survival in transfused versus non-transfused recipients. The immunological mechanism leading to downregulation of the alloimmune response has not yet been elucidated. Possible explanations include the induction of a Th2 response by non-professional antigen presentation by the transfused blood cells and blockage of alloreactive T cell reactivity by soluble HLA and soluble FasL in the supernatant of blood components. These mechanisms, however, do not explain the observations which have shown that the degree of HLA compatibility between the transfusion donor and patient is a determining factor. Transfusions in which the donor blood shares at least one HLA-DR antigen with the recipient induce tolerance, while fully HLA-DR mismatched transfusions lead to immunization. The importance of HLA-DR sharing suggests a central role for CD4+ regulatory T cells. In this case, indirect recognition of an allopeptide in the context of self-HLA-DR on the transfusion donor by CD4+ T cells of the recipient might be the clue to the induction of tolerance. Recent data from our laboratory in fact show that CD4+ T cells specific for an allopeptide in the context of self HLA-DR are able to downregulate the alloimmune response of autologous T cells. As these regulatory T cells produce IL-10, they may also be involved in the extension of tolerance via their modulatory effect on dendritic cells. It remains to be established whether these regulatory T cells are indeed responsible for the 'blood transfusion effect' in organ transplantation.

Immunological aspects of blood transfusions

Donor selection based on blood group phenotypes, and blood processing such as leukocyte-depletion, gamma-irradiation or washing to remove plasma, are approaches for therapeutic or preventive use to manage the immunological complications of transfusion. Indications for specific components are prescribed in guidelines provided by (inter)national Transfusion Societies. Although the use of guidelines and protocols is in line with modern medicine, these can create a state of tension with the political sense of values to improve the viral safety of blood products and with the commercial exploitation of pooled plasma-products.A century of blood transfusion therapy has facilitated cancer treatment and advanced surgical interventions. The transfusion product has improved progressively, although mostly in response to disasters such as wars and AIDS. Every blood transfusion interacts with the immune system of the recipient. There are, however, very few quantitative figures to estimate the consequences. This review is based on the available literature on the clinical consequences of transfusion induced immunization and modulation. To a large degree the clinical consequences of transfusion induced immune effects are still a mystery.A blood transfusion is a medical intervention, which in many cases remains experimental with respect to the benefit/risk ratio. Ideally, this uncertainty should be communicated to patients and every transfusion included in a study. Such studies preferentially should be randomized because the perceived need for transfusion is associated with clinical conditions with a worse prognosis than those that do not receive transfusion. This difference may mask the interpretation of the transfusion effect. Since the blood supply services in almost all Western countries have been reorganized and nationalized, or at least operate to national quality standards, the measurement of risk: benefit of transfusion, whether political or evidence-based, needs to be reconsidered. Differences in emphasis and responsibilities between transfusion providers and transfusion prescribers will drive the providers to political and liability criteria - ever safer products - that will increase hospital costs with undetermined clinical benefits.

The importance of H2 haplotype sharing in the induction of specific unresponsiveness by pretransplant blood transfusions

BACKGROUND

The beneficial effect on graft survival achieved by pretransplant blood transfusions is well established. Previous studies have shown that the degree of major histocompatibility complex (MHC) (mis)-match between the transfusion donor and the recipient plays a determining role. However, other factors are also involved. In this study, we explored the hypothesis that, in addition to sharing of MHC antigens between the transfusion donor and the recipient, the MHC type of the organ donor is also of importance.

METHODS

To mimic the human situation, F1 mice, rather than inbred strains, were pretreated with haplotype-shared allogeneic whole blood transfusions and transplanted with hearts of organ donors with different matched or mismatched H2 haplotypes.

RESULTS

When a heart was transplanted 1 week after donor-specific transfusion (DST; blood transfusion donor=organ donor), an excellent prolongation of graft survival was obtained (median survival time: 77 days vs. 9 days in untreated mice). However, this was only the case when a haplotype was shared with the recipient; a DST given with no match between organ donor (=BT donor) and recipient did not induce any prolongation. Furthermore, in order to obtain the optimal beneficial effect of a haplotype-shared blood transfusion, the other haplotype of the transfusion donor had to be mismatched with the recipient. The immunogenetic studies showed that haplotype-shared blood transfusions in combinations where the H2 type of the organ donor differed from that of the transfusion donor are less efficient in inducing prolongation of graft survival.

CONCLUSIONS

These results demonstrate that haplotype-shared blood transfusions can induce a significantly prolonged survival of cardiac allografts in F1 mice. The immunogenetic studies suggest that presentation of alloantigen-derived peptides in the context of self MHC (the indirect pathway of allorecognition) is essential for the beneficial effect of haplotype-shared blood transfusions.

Increased anticoagulant osmolality improves separation of leukocytes from red blood cells (RBC)

BACKGROUND

The bottom-and-top (BAT) procedure separates the buffy coat (BC) from plasma and red blood cells (RBC). The contents of mononuclear cells (MNC) remaining in the RBC are about 1 x 10(6) cells/unit, whereas the granulocytes are removed less effectively, 500-800 x 10(6) or more remaining in the RBC unit. The aim was to improve the separation efficacy by collecting the blood in an hyperosmolar anticoagulant, followed by BAT separation. It was expected that the red cells would shrink, thereby increasing their density, while the granulocytes would not change volume and density.

STUDY DESIGN AND METHODS

18 donors were included in the study, 12 in the test group and 6 in the control group. CPD-SAGM bags were used, with a modification of the anticoagulant by removal of 20-ml CPD from all units and addition of 20-ml mannitol (test group) or 20 ml of isotonic saline (control group). The collected blood units were cooled on butanediol plates for 2-4 h, then centrifuged and separated into components. The levels of leukocytes in the whole blood, the BC and the RBC were determined by flow cytometry gated for intact CD45+ cells. A number of other tests were performed during 42-day storage.

RESULTS

The plasma yield was slightly higher in the test group than in the control group (ns). The contents of leukocytes (CD 45+ intact cells) in the RBC units were 32 +/- 20 x 10(6) in the test group and 573 +/- 241 x 10(6) in the control group. The numbers of MNC were 1.2 +/- 0.6 x 10(6) and 2.6 +/- 1.8 x 10(6), respectively. The RBC 2,3-DPG concentration was slightly better maintained in the test group at day 7 of refrigerated storage (p = 0.0027), but most other tested parameters showed no difference during 42-day storage. It was possible to prepare platelet concentrates with good yield using the pooled-BC method.

CONCLUSION

This study indicates that considerable improvement in the BAT procedure can be obtained if the anticoagulant is made hypertonic by the addition of mannitol. This is achieved without altering the already low levels of MNC and keeping the same quality.

Storage of blood components

Recent studies have shown that a restrictive transfusion policy results in lower mortality in patients undergoing surgery. The negative effects of red cell transfusion are associated with the presence of contaminating leukocytes, leukocyte products, and probably also with effects of nonviable and poorly functioning red cells. By relatively simple means it is possible to improve the quality of red cells in these respects. The removal of leukocytes from platelet concentrates (PCs) is even more important because of high immunogenicity and capacity to produce cytokines under the storage conditions applied. Prestorage leukocyte removal has clear advantages. Bacterial contamination of PCs is common, but fatal bacterial complications are rare because most contaminating microorganisms grow slowly and do not produce toxins, which are frequent causes of death. Suitable methods for routine bacterial culture of PCs are available and used in some countries.

Changes in donor leukocytes during blood storage. Implications on post-transfusion immunomodulation and transfusion-associated GVHD

Freshly drawn peripheral blood granulocytes, monocytes and NK cells express Fas-L following activation. Fully functional soluble Fas-L (sFas-L) is released and found in fresh plasma samples from healthy volunteers coupled to a Fas-L binding factor (PFBF). In the absence of plasma leukocytes undergo rapid apoptosis with 15% of the granulocytes and 25% of the monocytes showing signs of apoptosis immediately following separation. Apoptosis progresses during refrigerated storage even in the presence of plasma and all granulocytes disintegrate by day 15 of storage. The absence of plasma increases the rate of apoptosis. The resulting increased expression of PS on apoptosing leukocytes enhances blood procoagulant activity. Whereas transfusions of fresh blood lead to alloimmunization, the functional impairment and death of antigen-presenting cells during storage eliminates their ability to stimulate cytotoxic immune responses. Additionally, loss of function and death of donor T cells during storage preclude the possibility for development of post-transfusion GVHD. Continued storage leads to the secondary necrosis of apoptosed leukocytes and the release of soluble antigens. Depending on dose, transfusion of such products may lead to immunosuppression due to a T2 bias of the immune response.

Stored blood--an effective immunosuppressive method for transplantation of kidneys from unrelated donors. An 11-year follow-up

Thirty-seven patients were submitted to kidney transplantation after transfusion at 2-week intervals with 4-week stored blood from their potential donors. All patients and donors were typed for HLA-A-B and DR antigens. The patients were also tested for cytotoxic antibodies against donor antigens before each transfusion. The percentage of panel reactive antibodies (PRA) was determined against a selected panel of 30 cell donors before and after the transfusions. The patients were immunosuppressed with azathioprine and prednisone. Rejection crises were treated with methylprednisolone. The control group consisted of 23 patients who received grafts from an unrelated donor but who did not receive donor-specific pretransplant blood transfusion. The incidence and reversibility of rejection episodes, allograft loss caused by rejection, and patient and graft survival rates were determined for both groups. Non-parametric methods (chi-square and Fisher tests) were used for statistical analysis, with the level of significance set at P < 0.05. The incidence and reversibility of rejection crises during the first 60 post-transplant days did not differ significantly between groups. The actuarial graft and patient survival rates at five years were 56% and 77%, respectively, for the treated group and 39.8% and 57.5% for the control group. Graft loss due to rejection was significantly higher in the untreated group (P = 0.0026) which also required more intense immunosuppression (P = 0.0001). We conclude that transfusions using stored blood have the immunosuppressive effect of fresh blood transfusions without the risk of provoking a widespread formation of antibodies. In addition, this method permits a reduction of the immunosuppressive drugs during the process without impairing the adequate functioning of the renal graft.

Blood transfusion, blood storage and immunomodulation

Allogeneic blood transfusion is the most frequent allotransplantation procedure performed on a routine basis with no prior HLA-typing. Roughly 50% of the recipients of unprocessed red cells and platelets become alloimmunized. Evidence also exists for some degree of transfusion-induced immunosuppression. Prior transfusion has been shown to enhance kidney transplant survival and evidence of an increase in tumor recurrence and of infectious complications has also been presented. The presence of donor antigen-presenting cells appears to be a prerequisite for alloimmunization and they must be both viable and capable of presenting a costimulatory signal in order to induce IL-2 secretion and proliferation of responding CD4 T cells. APCs presenting antigen but no costimulatory signal can induce non-responsiveness in CD4 T cells, a possible mechanism of transfusion-induced immunosuppression. APCs in refrigerated blood continue to present antigen but progressively lose their ability to provide costimulation. By day 14 costimulatory capacity is absent and transfusion of such blood should not alloimmunize but could induce some degree of immunosuppression. Further refrigerated storage in excess of 2 to 3 weeks leads to induction of apoptosis in contaminating leukocytes. We have found that alloantigens-expressed on such cells do not appear to be recognized by responder T cells and transfusion of blood stored in excess of 3 weeks should neither alloimmunize nor immunosuppress.