Apoptosis, transforming growth factor-beta, and the immunosuppressive effect of transfusion

Transforming growth factor-β released by apoptotic white blood cells during red blood cell storage promotes transfusion-induced alloimmunomodulation

BACKGROUND

Red blood cell (RBC) alloimmunization is a major immunologic risk of transfusion. However, RBC storage facilitates white blood cell (WBC) apoptosis and apoptotic cells have immunomodulatory properties. We investigated the behavior of WBCs, and apoptosis in particular, in RBC units during storage and then studied the impact of WBC apoptosis on the modulation of posttransfusion alloimmunization in RBC products stored short term.

STUDY DESIGN AND METHODS

We used a mouse model of alloimmunization to transfused HEL-ovalbumin-Duffy (HOD) surface antigen expressed specifically on RBCs. The presence of circulating anti-HOD immunoglobulin G detected by flow cytometry confirmed immunization to HOD+ RBCs. WBC apoptosis and factors released by apoptotic WBCs during storage were determined and in particular the role of transforming growth factor (TGF)-β was assessed on RBC alloimmunization.

RESULTS

In blood stored 72 hours, 30% of WBCs were apoptotic, and transfusion of short-term-stored blood resulted in lesser immunization than did fresh blood or stored leukoreduced (LR) RBCs. WBCs undergoing apoptosis released during short-term storage factors modulating RBC alloimmunization. Indeed apoptotic cell-released factors modulate alloimmunization whereas exogenous apoptotic cells directly transfused with LR RBCs did not. While microparticles released during RBC storage had no immunomodulatory role, TGF-β found in the supernatant of stored blood demonstrated the capacity to favor Treg polarization of naïve CD4+CD25- T cells in vitro and limited RBC alloimmunization in vivo. Indeed, addition of recombinant TGF-β to stored LR RBC transfusion strongly limited posttransfusion RBC alloimmunization.

CONCLUSION

Our findings show that short-term storage of non-LR blood facilitates WBC apoptosis therefore releasing TGF-β that modulates posttransfusion RBC alloimmunization.

Impact of intraoperatively salvaged and washed blood on stimulated cytokine release in vitro

BACKGROUND

Intraoperative blood salvage and processing it with commercially available devices is a widespread standard procedure to reduce allogeneic blood transfusion in patients undergoing major orthopedic surgery. The aim of this study was to investigate the impact of such processed blood on the immune system by measuring pro- and anti-inflammatory cytokines.

STUDY DESIGN AND METHODS

Salvaged blood from 20 patients undergoing hip arthroplasty was processed with a continuous autotransfusion system. One part of the processed blood was left without further treatment, one part was additionally leukoreduced, one part was irradiated, and one part was separated into its cellular and soluble fraction by centrifugation. Specimens from each part were mixed in vitro with venous blood from the patient in ratios of 3:1, 1:1, and 1:3 and incubated with endotoxin for 24 hours. Tumor necrosis factor (TNF)-α and interleukin (IL)-10 were measured in cell culture supernatants by enzyme-linked immunosorbent assay.

RESULTS

All parts of the salvaged blood were without a significant influence on TNF-α release. In contrast, IL-10 was significantly increased, independently of the admixtured salvaged blood being plain, additionally irradiated, or additionally leukoreduced. This IL-10 increase was also found with the cellular fraction of the plain salvaged blood, whereas the soluble fraction had no influence on IL-10 release.

CONCLUSION

Intraoperative salvaged blood is not immunologically inert. We observed a significant increase in the anti-inflammatory IL-10 response without affecting the proinflammatory TNF-α release. Neither leukofiltration nor gamma irradiation eliminated this effect that was limited only to the cellular fraction of the salvaged blood, suggesting red blood cells to be responsible for the observed immunomodulation.

Intravenous delivery of the plasma fraction of stored packed erythrocytes promotes pancreatic cancer growth in immunocompetent mice

BACKGROUND

Perioperative blood transfusion in pancreatic cancer patients has been linked to decreased survival; however, a causal mechanism has not been determined. During the processing and storage of packed erythrocytes, biologically active molecules accumulated in the acellular plasma fraction; therefore, the authors hypothesized that the plasma fraction of stored packed erythrocytes promoted tumor progression.

METHODS

Proliferation and migration of murine pancreatic cancer and control cells were determined in vitro in response to the plasma fraction from leukocyte and nonleukocyte-reduced fresh versus stored packed erythrocytes. Last, an immunocompetent murine model was used to assess the effect of the plasma fraction of stored and processed packed erythrocytes on pancreatic cancer progression.

RESULTS

Incubation of pancreatic cancer cells with the plasma fraction of packed erythrocytes increased proliferation and migration. Intravenous delivery of the acellular plasma fraction to mice with pancreatic cancer significantly increased the tumor weight in both leukocyte-reduced and nonleukocyte-reduced packed-erythrocyte groups (P<.01), although tumor growth and morbidity were greatest in the nonleukocyte-reduced group.

CONCLUSIONS

The plasma fraction of stored packed erythrocytes promoted murine pancreatic cancer proliferation and migration in vitro and when administered intravenously, significantly augmented pancreatic cancer growth in immunocompetent mice.

In situ-targeting of dendritic cells with donor-derived apoptotic cells restrains indirect allorecognition and ameliorates allograft vasculopathy

Chronic allograft vasculopathy (CAV) is an atheromatous-like lesion that affects vessels of transplanted organs. It is a component of chronic rejection that conventional immuno-suppression fails to prevent, and is a major cause of graft loss. Indirect allo-recognition through T cells and allo-Abs are critical during CAV pathogenesis. We tested whether the indirect allo-response and its impact on CAV is down-regulated by in situ-delivery of donor Ags to recipient's dendritic cells (DCs) in lymphoid organs in a pro-tolerogenic fashion, through administration of donor splenocytes undergoing early apoptosis. Following systemic injection, donor apoptotic cells were internalized by splenic CD11c^hi CD8α⁺ and CD8⁻ DCs, but not by CD11c^int plasmacytoid DCs. Those DCs that phagocytosed apoptotic cells in vivo remained quiescent, resisted ex vivo-maturation, and presented allo-Ag for up to 3 days. Administration of donor apoptotic splenocytes, unlike cells alive, (i) promoted deletion, FoxP3 expression and IL-10 secretion, and decreased IFN-γ-release in indirect pathway CD4 T cells; and (ii) reduced cross-priming of anti-donor CD8 T cells in vivo. Targeting recipient's DCs with donor apoptotic cells reduced significantly CAV in a fully-mismatched aortic allograft model. The effect was donor specific, dependent on the physical characteristics of the apoptotic cells, and was associated to down-regulation of the indirect type-1 T cell allo-response and secretion of allo-Abs, when compared to recipients treated with donor cells alive or necrotic. Down-regulation of indirect allo-recognition through in situ-delivery of donor-Ag to recipient's quiescent DCs constitutes a promising strategy to prevent/ameliorate indirect allorecognition and CAV.

Transfusion of apoptotic beta-cells induces immune tolerance to beta-cell antigens and prevents type 1 diabetes in NOD mice

In vivo induction of beta-cell apoptosis has been demonstrated to be effective in preventing type 1 diabetes in NOD mice. Based on the notion that steady-state cell apoptosis is associated with self-tolerance and the need for developing a more practical approach using apoptotic beta-cells to prevent type 1 diabetes, the current study was designed to investigate apoptotic beta-cells induced ex vivo in preventing type 1 diabetes. The NIT-1 cell line serves as a source of beta-cells. Apoptotic NIT-1 cells were prepared by ultraviolet B (UVB) irradiation. Three weekly transfusions of UVB-irradiated NIT-1 cells (1 x 10(5)/mouse) or PBS were used to determine whether transfusions of UVB-irradiated NIT-1 cells induce immune tolerance to beta-cell antigens in vivo and prevent type 1 diabetes. The suppression of anti-beta-cell antibodies, polarization of T-helper (Th) cells, and induction of regulatory T-cells by UVB-irradiated NIT-1 cell treatment were investigated. The transfusions of apoptotic NIT-1 cells suppress anti-beta-cell antibody development and induce Th2 responses and interleukin-10-producing regulatory type 1 cells. Importantly, this treatment significantly delays and prevents the onset of diabetes when 10-week-old NOD mice are treated. Adoptive transfer of splenocytes from UVB-irradiated NIT-1 cell-treated mice prevents diabetes caused by simultaneously injected diabetogenic splenocytes in NOD-Rag(-/-) mice. Moreover, the proliferation of adoptively transferred carboxyfluorescein diacetate succinimidyl ester-labeled beta-cell antigen-specific T-cell receptor-transgenic T-cells in UVB-irradiated NIT-1-cell treated mice is markedly suppressed. The transfusion of apoptotic beta-cells effectively protects against type 1 diabetes in NOD mice by inducing immune tolerance to beta-cell antigens. This approach has great potential for immune intervention for human type 1 diabetes.

Release of PMN elastase, TGF-β1 and neopterin during blood storage; unfiltered versus filtered blood

Release of inflammatory mediators from blood cells during prestorage leukocyte filtration may result in recipient immune suppression. To investigate the effects of prestorage leukocyte filtration on the quality of blood components, twenty-four blood units were collected from healthy donors and randomised into 3 groups. Eight units were stored as whole blood, eight units were separated into plasma, red blood cells (RBC) and buffy coat and eight units were collected and filtered through the ASAHI RZ 2000 leukocyte filter and separated into plasma and RBC. The units were stored for 35 days. Samples were collected weekly for analyses of polymorphonuclear elastase (PMN elastase), transforming growth factor-beta1 (TGF-beta1) and neopterin. PMN elastase and neopterin increased during storage of whole blood and RBC. From the beginning and throughout storage, PMN elastase was increased in filtered plasma as compared with unfiltered plasma. Filtration per se did not influence the neopterin concentration in plasma or RBC. TGF-beta1 increased in plasma and RBC during storage. In filtered plasma, an elevation of the TGF-beta1 concentration was observed from the start of storage. The TGF-beta1 levels were higher in filtered plasma compared with unfiltered plasma. Prestorage leukocyte filtration increased the release of PMN elastase and TGF-beta1 in plasma and RBC.

Blood Cell Apoptosis/Necrosis: Some Clinical and Laboratory Aspects

Exposure of phosphatidyl-serine on blood cell membrane surface and microvesiculation as the hallmarks of apoptosis/necrosis were investigated. The effect of leukofiltration on the retention/generation of microvesicules, leukocyte subsets and major biological response modifiers were evaluated in a like study. It is concluded that apoptotic cells potentially contribute to transfusion reactions in donor/recipient-specific ways.

What’s happening? The expanding role of apheresis platelet support in neonatal alloimmune thrombocytopenia: Current status and future trends

Despite some unresolved problems that may be associated with platelet transfusion, such as alloimmunisation, refractoriness, bacterial contamination, and the potential side effects related to the development of some biological response modifiers during storage, platelet therapy remains the most effective treatment for the management and prevention of severe thrombocytopenia and hemorrhage [Seghatchian J, Snyder EL, Krailadsiri P, editors. Platelet therapy: current status and future trends. Amsterdam, The Netherlands: Elsevier; 2000]. This appears to be particularly the case in neonatal alloimmune thrombocytopenia (NAIT), which arises due to an incompatibility of the platelet specific antigens between the pregnant mother and her baby. Over 80% of severe NAIT cases in the Caucasian population occur when the mother and baby differ in their HPA-1 epitope (HPA-1a negative and positive respectively) leading, in 10% of cases, to the production of anti-HPA-1a which can cross the placenta and cause NAIT in utero or post-partum. Anti-HPA-5b is the second most cause of NAIT, although severe cases occur only after the first pregnancy. Clinical manifestations of NAIT vary from mild (petechia and bruises) to severe (intracranial haemorrhage with possible death or life long morbidity). A recent study in Scotland indicated that the cost per case of severe NAIT detected during screening of pregnant women, where anti-HPA-1a is detected for the first time, would amount to $98,771 [Turner M, Bessos H, et al. Prospective epidemiological study of the outcome and cost effectiveness of antenatal screening to detect neonatal alloimmune thrombocytopenia (NAIT) due to anti-HPA-1a. Transfusion, in press. Yet, unlike the case with Rhesus hemolytic disease of the new born, the cost-effectiveness of HPA-1 screening in NAIT remains unresolved, as does the most optimal mode of treatment. Therefore, in the absence of a consensus on the screening and optimal management of NAIT, the availability and provision of HPA-1a/5b negative apheresis platelets based on current practice (transfusionguidelines.org.uk) appear to be a clinically effective treatment in NAIT. In that vein, an increasing number of blood transfusion centres are screening blood donors in order to secure panels of donors for the prompt provision of HPA-1a/5b negative apheresis platelets. However, evidence is also accumulating that while platelets derived from various apheresis technologies currently in use may be equivalent in terms of cellular contents (thus meeting specifications), they may differ in terms of the platelet storage lesion, microvesiculation and the development of platelet-derived cytokines and some other biological response modifiers [Seghatchian J. Platelet storage lesion: the influence of various leukoreduction procedures on generation/retention of some biological response modifiers, microvesiculation, distribution of membrane-bound/soluble Prion and the rate of HLA-CLASS1 release. Trans Apher Sci, in press. This manuscript summarises strategy and progress both in the improvement of apheresis platelet quality and provision in NAIT.

The application of a new quantitative assay for the monitoring of integrin-associated protein CD47 on red blood cells during storage and comparison with the expression of CD47 and phosphatidylserine with flow cytometry

BACKGROUND

After the introduction of universal leukoreduction, the role of factors other than white blood cells in red cell (RBC) storage lesion is attracting increasing attention. These include changes in the levels of CD47 and phosphatidylserine (PS) markers on RBCs during storage. The aim of this study was to monitor these changes with both flow cytometry (FACS) and a newly developed quantitative enzyme-linked immunosorbent assay (ELISA).

STUDY DESIGN AND METHODS

A new quantitative ELISA (monoclonal antibody immobilization of RBC antigens [MAIRA]) was developed. The assay yielded consistent linear curves that enabled the measurement of CD47 expression on RBCs. In addition, FACS was used to measure both CD47 expression and PS on RBCs (n = 3 units) during storage (Days 4, 10, 24, and 31).

RESULTS

A significant reduction in CD47 expression was observed both by MAIRA assay and by FACS by Days 24 and 31 (p < 0.01), and the correlation between the two assays was significant (p < 0.01). In addition, a significant increase in PS was observed by the same storage days with FACS (p < 0.01).

CONCLUSION

The MAIRA assay appears to be suitable for the quantitative measurement of RBC markers during storage. Significant changes in CD47 and PS levels were observed during storage, which may have detrimental immunomodulatory and hemostatic effects on the transfused RBCs.

Transforming growth factor-beta1, Th1 responses, and autoimmune liver disease

Transforming growth factor-beta1 (TGF-beta1) is released during the storage of blood components, particularly platelet concentrates, and transfusion recipients are exposed to high levels of TGF-beta1. Because TGF-beta1 is one of the most potent immunosuppressive cytokines known, understanding the immunobiologic functions of TGF-beta1 may be relevant for understanding the immunobiologic effects of transfusion. Our laboratory studies the biologic effects of TGF-beta1 in the immune system. Mice deficient in TGF-beta1 spontaneously develop autoimmunity, confirming the important role of this cytokinean an immune regulator. A few years ago, my laboratory made the observation that genetic background strongly affects the phenotype of TGF-beta1-/- mice. TGF-beta1-/- mice on the BALB/c background rapidly develop an aggressive T-cell-mediated hepatitis, whereas TGF-beta1-/- mice on the 129/CF-1 background do not. In this review, I summarize findings published or in press from our laboratory on disease pathogenesis in TGF-beta1-/- mice and then discuss some of the exciting (as-yet-unpublished) directions our laboratory is currently taking.

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.

Red cell storage lesion: The potential impact of storage-induced CD47 decline on immunomodulation and the survival of leucofiltered red 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.

Expression of Fas and Fas ligand on spleen T cells of experimental animals after unmodified or leukoreduced allogeneic blood transfusions

BACKGROUND

The clonal deletion seen in recipients of allogeneic blood transfusion (ABT) refers to the removal of lymphocytes that promote the clearance of transfused alloantigens. Interactions between Fas (CD95) and FasL (CD95L) are involved in the clonal deletion of T cells and in the down regulation of the cytotoxic T-cell activity.

STUDY DESIGN AND METHODS

The expression of CD95/95 L on spleen T cells of C57Bl/6 mice infused with unmodified ABT, prestorage leukoreduced ABT (LR-ABT), or saline was investigated by flow cytometry. The numbers of apoptotic spleen cells were evaluated after transfusion using the acridine orange and ethidium bromide uptake technique.

RESULTS

Compared with untransfused animals, mice transfused with ABT showed higher expression of CD95 (MFI = 94.4 +/- 8.6 vs. 73.1 +/- 7.9, p = 0.02) and CD95L (23.5 +/- 6.9 vs. 8.1 +/- 2.0, p = 0.008) on CD4+ spleen cells. Expression of CD95 (92.2 +/- 7.5 vs. 64.9 +/- 7.5, p = 0.007) and CD95L (17.7 +/- 3.6 vs. 8.2 +/- 2.2, p = 0.02) was also increased on CD8+ cells of these animals. CD8+ spleen cells from mice transfused with ABT showed higher expression of CD95 (92.2 +/- 7.5 vs. 76.9 +/- 4.0, p = 0.03) and CD95L (17.7 +/- 3.6 vs. 8.3 +/- 1.5, p = 0.03) than cells from mice transfused with LR-ABT. The number of apoptotic spleen cells from mice transfused with ABT was greater than that from mice infused with LR-ABT (10.9 +/- 1.3 vs. 6.6 +/- 1.8, p = 0.01) or saline (10.9 +/- 1.3 vs. 6.5 +/- 0.7, p = 0.001).

CONCLUSIONS

The data suggest that ABT up-regulates the expression of Fas/FasL on spleen T cells of mice and may promote their apoptosis. These ABT-associated immunologic alterations can be partially prevented by the leukoreduction of the transfused blood.

Accumulation of interleukin-1 receptor antagonist in blood products and the effect of pre-storage leukocyte reduction

Interleukin-1 receptor antagonist (IL-1 ra) is one of the anti-inflammatory cytokines and its concentration is reported to increase in a time-dependent manner in the blood products. We have checked the effects of pre-storage leukocyte reduction on the accumulation of IL-1 ra. Although IL-1 ra concentration exhibited a major increase in non-filtered blood, it remains quite stable in blood filtered before storage. As the increase in IL-1 ra may have an immunosuppressive effect on recipients, universal pre-storage leukocyte reduction appears to be advisable even for autologous blood donation.

Anemia in acute renal failure: role for erythropoiesis-stimulating proteins?

The use of recombinant human erythropoietin (rHuEpo) has revolutionized anemia management of early and late stages of chronic kidney disease. Darbopoietin is also now available for the treatment of anemia of chronic kidney disease. In addition, rHuEpo has been used for the treatment of anemia observed in critical illness. Unfortunately, the existing clinical studies of anemia in critically ill patients do not distinguish between those with and without acute renal failure (ARF). This review summarizes the existing experimental and clinical studies supporting the use of rHuEpo in ARF due to ischemic/nephrotoxic injury and conclusions are drawn on the rationale for further research into the use of this drug in ARF.