Donor WBCs can persist and transiently mediate immunologic function in a murine transfusion model: effects of irradiation, storage, and histocompatibility

Transfusion-associated microchimerism: the hybrid within

Microchimerism, the coexistence of genetically disparate populations of cells in a receptive host, is well described in both clinical and physiological settings, including transplantation and pregnancy. Microchimerism can also occur after allogeneic blood transfusion in traumatically injured patients, where donor cells have been observed decades after transfusion. To date, transfusion-associated microchimerism (TA-MC) appears confined to this clinical subset, most likely due to the immune perturbations that occur after severe trauma that allow foreign donor cells to survive. Transfusion-associated microchimerism appears to be unaffected by leukoreduction and has been documented after transfusion with an array of blood products. The only significant predictor of TA-MC to date is the age of red cells, with fresher units associated with higher risk. Thus far, no adverse clinical effect has been observed in limited studies of TA-MC. There are, however, hypothesized links to transfusion-associated graft vs host disease that may be unrecognized and consequently underreported. Microchimerism in other settings has gained increasing attention owing to a plausible link to autoimmune diseases, as well as its diagnostic and therapeutic potential vis-a-vis antenatal testing and adoptive immunotherapy, respectively. Furthermore, microchimerism provides a tool to further our understanding of immune tolerance and regulation.

Understanding loss of donor white blood cell immunogenicity after pathogen reduction: mechanisms of action in ultraviolet illumination and riboflavin treatment

BACKGROUND

Donor white blood cells (WBCs) present in transfusion products can lead to immune sequelae such as production of HLA antibodies or graft-versus-host disease in susceptible transfusion recipients. Eliminating the immunogenicity of blood products may prove to be of clinical benefit, particularly in patients requiring multiple transfusions in whom allosensitization is common. This study examines a method of pathogen reduction based on ultraviolet light illumination in the presence of riboflavin. In addition to pathogens, WBCs treated with this system are affected and fail to stimulate proliferation of allogeneic peripheral blood mononuclear cells (PBMNCs) in vitro.

STUDY DESIGN AND METHODS

This study sought to determine the mechanisms regulating this loss of immunogenicity. Treated cells were examined for surface expression of a number of molecules involved in activation and adhesion, viability, cell-cell conjugation, and ability to stimulate immune responses in allogeneic PBMNCs.

RESULTS

Compared with untreated controls, ultraviolet (UV)-irradiated antigen-presenting cells showed slightly reduced surface expression of HLA Class II and costimulatory molecules and had more significant reductions in surface expression of a number of adhesion molecules. Furthermore, treated cells had a severe defect in cell-cell conjugation. The observed loss of immunogenicity was nearly complete, with UV-irradiated cells stimulating barely measurable interferon-gamma production and no detectable STAT-3, STAT-5, or CD3-epsilon phosphorylation in allospecific primed T cells.

CONCLUSION

These results suggest that defective cell-cell adhesion prevents UV-irradiated cells from inducing T-cell activation.

Transfusion-associated microchimerism

Blood transfusion is a newly recognized cause of microchimerism, the stable persistence of a minor population of allogeneic cells. Relatively recent advances in polymerase chain reaction technology have spawned new information about the frequency and aetiology of transfusion-associated microchimerism (TA-MC). Although conceptually related to fetal-maternal microchimerism, TA-MC is a distinct and separate entity. Evidence of TA-MC has been strongest among patients with severe traumatic injuries who receive relatively fresh blood products shortly after an episode of massive haemorrhage. The presence of a focal deficit in the cellular immunologic repertoire prior to transfusion that happens to match a blood donor's human leucocyte antigen type also appears to be an important predisposing factor. TA-MC seems to be common (affecting approximately 10% of transfused injured patients), enduring (lasting years to decades) and pronounced (involving up to 5% of circulating leucocytes and multiple immunophenotypic lineages suggestive of haematopoietic engraftment). Further study of this topic may reveal important information regarding potential clinical consequences of TA-MC, as well as basic haematologic and immunologic processes.

Transfusion-associated microchimerism: a new complication of blood transfusions in severely injured patients

Microchimerism, the stable persistence of an allogeneic cell population, can result from allogeneic exposures including blood transfusion. Transfusion-associated microchimerism (TA-MC) appears to be a common but newly recognized complication of blood transfusion. Thus far TA-MC has been detected when severely injured patients are transfused. Injury induces an immunosuppressive and inflammatory milieu in which fresh blood products with replication-competent leukocytes can sometimes cause TA-MC. TA-MC is present in approximately half of transfused severely injured patients at hospital discharge and is not affected by leukoreduction. In approximately 10% of patients, the chimerism from a single blood donor may increase in magnitude over months to years, reaching as much as 2% to 5% of all circulating leukocytes. In this review, we discuss recent studies of TA-MC in the civilian trauma population and the potential for study of TA-MC in the military population, where the severity of injury and freshness of blood products suggest that TA-MC may be even more prominent. We also discuss the need for future studies to address the immunology of TA-MC, its stem cell biology, and its clinical manifestations that have the potential to be either pathologic (autoimmunity, graft-versus-host disease) or therapeutic (tolerance induction, various cell and gene therapies).

High-level long-term white blood cell microchimerism after transfusion of leukoreduced blood components to patients resuscitated after severe traumatic injury

BACKGROUND

Long-term white blood cell (WBC) microchimerism (MC), of at least 2 years, has been reported in trauma patients receiving fresh nonleukoreduced (non-LR) blood. It is unknown, however, whether this occurs with LR blood products that are nearly devoid of WBCs. Twenty-seven patients transfused with LR and non-LR blood products were studied after severe traumatic injury. A secondary aim was to explore donor-recipient mixed lymphocyte reactivity in vitro.

STUDY DESIGN AND METHODS

To quantify MC, allele-specific real-time polymerase chain reaction assays were developed targeting HLA Class II sequence polymorphisms. Extensive validation showed that these assays reliably detect a single copy of target sequence in a complex allogeneic background without false positivity.

RESULTS

At a median follow-up of 26 months (range, 24-39 months), long-term MC was observed in 3 of 20 patients (15%) who received non-LR blood products and 2 of 7 (29%) who received LR blood products. The maximum MC ranged from 0.40 to 4.90 percent of circulating WBCs and appeared, by Class II genotype analysis, to be attributable to a single donor.

CONCLUSION

It is concluded that robust levels of long-term MC, apparently traceable to a single donor, occur at similar frequency despite leukoreduction of transfused blood products. Exploratory analysis of donor-recipient mixed lymphocyte reactivity suggests that long-term MC may require a state of bidirectional tolerance before transfusion.

Quantitative analysis of survival of transplanted smooth muscle cells with real-time polymerase chain reaction

BACKGROUND

Cell transplantation improves heart function after myocardial infarction. This study investigated the survival of implanted cells in normal and infarcted myocardium.

METHODS

Male rat aortic smooth muscle cells were cultured. For the in vitro study, male smooth muscle cells mixed with female smooth muscle cells or male smooth muscle cells injected into a piece of female rat myocardium were used to evaluate the accuracy of quantitative real-time polymerase chain reaction to measure Y chromosomes. For the in vivo study, 2 million live or dead male smooth muscle cells were injected into normal or infarcted female myocardium. At 1 hour and 1 and 4 weeks after transplantation, hearts, lungs, and kidneys were harvested for measurement of Y chromosomes.

RESULTS

In vitro, the accuracy of polymerase chain reaction measurement was excellent in cultured cells (r2 = 0.996) and the myocardium (r2 = 0.786). In vivo, 1 hour after 2 x 10(6) cell implantation, live cell numbers decreased to 1.0 +/- 0.2 x 10 6 and 1.1 +/- 0.3 x 10(6) , and dead cell numbers decreased to 0.9 +/- 0.2 x 10(6) and 0.8 +/- 0.2 x 10(6) in the normal and infarcted myocardium, respectively (P < .01 for all groups). Lungs and kidneys contained 8.5% and 1.5% of the implanted cells, but no cells were detected at 1 week. At 1 week, no dead smooth muscle cells were detected in the normal or infarcted myocardium. The numbers of live cells at 1 and 4 weeks were 0.48 +/- 0.06 x 10(6) and 0.27 +/- 0.07 x 10(6) in normal myocardium and 0.29 +/- 0.08 x 10(6) and 0.18 +/- 0.05 x 10(6) in infarcted myocardium.

CONCLUSIONS

One hour after implantation, only 50% of smooth muscle cells remained in the implanted area. Some implanted cells deposited in other tissue. Implanted cell survival progressively decreased during the 4-week study.

Minimum conditions of major histocompatibility complex compatibility and recipient immune compromise required to establish donor white blood cell persistence in a murine transfusion model

BACKGROUND

In some patients multiply transfused to treat severe trauma, white blood cells (WBCs) from a single blood donor can persist for years, constituting up to 5 percent of all circulating WBCs. The immunologic mechanisms responsible for this are not known but, if understood, might allow manipulation of the human immune system to induce microchimerism for a variety of therapeutic purposes. To better characterize these mechanisms, a murine transfusion model was developed with a panel of immunologic knockouts as transfusion recipients. By conducting a systematic series of transfusion experiments, the purpose was to determine which recipient immune cell population, when abrogated, could lead to prolonged survival of donor cells (microchimerism).

STUDY DESIGN AND METHODS

Blood was transfused from normal donors to knockout recipients in syngeneic, allogeneic, and xenogeneic settings. Donor WBC survival was evaluated by quantitative polymerase chain reaction, and recipient lymphocyte subsets by fluorescence-activated cell sorting.

RESULTS

In the syngeneic setting, donor WBCs persisted in C2ta, RAG-1, and TCR knockout recipients. Allogeneic donor WBCs persisted in RAG-2 and RAG-2/Common gamma knockout recipients. Xenogeneic donor WBCs required RAG-2/Common gamma and RAG-2/Pfp double knockouts to persist.

CONCLUSION

It is concluded that donor-recipient major histocompatibility complex (MHC) concordance alone is not sufficient to achieve microchimerism. Further, the degree of recipient immune compromise necessary to achieve persistent microchimerism is directly proportional to the degree of donor-recipient MHC disparity.

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.

One-step concentration of malarial parasite-infected red blood cells and removal of contaminating white blood cells

Background

Isolation of a concentrated, living preparation of malarial parasite-infected red blood cells (PRBCs) that have low contamination of white blood cells (WBCs) facilitates research on the molecular, biochemical and immunological aspects of malarial parasites. This is currently carried out by a two-step method, including the concentration of PRBCs using density gradient centrifugation through Percoll or Nycodenz, followed by the removal of host WBCs using a cellulose powder column or a commercially available filtration unit. These two-step methods can help isolate sufficient PRBCs, but they are laborious. In this study, a simplified one-step procedure that takes advantage of the difference between diamagnetic low-spin oxyhaemoglobin and paramagnetic haemozoin (haem polymer) was described. The paramagnetic polymer is deposited in the food vacuoles of the parasite, allowing the use of magnetic separation to efficiently and rapidly concentrate PRBCs while removing contaminating host WBCs.

Methods

The magnetic removal of WBCs using a commercial LD column (MACS) was evaluated as a new method for concentrating and purifying PRBCs. To compare this method with the two density gradient centrifugation methods using Percoll or Nycodenz, we analysed the quantities of enriched PRBCs and contaminating host WBCs as well as the viability of malarial parasites in the final preparations.

Results

The quantity of PRBCs and the viability of malarial parasites in the isolated PRBCs were similar between magnetic and centrifugation methods. However, 90–99% of the contaminating WBCs were removed from the starting material using a magnetic column, whereas WBC content did not change using the Percoll or Nycodenz methods.

Conclusion

The use of a commercially available magnetic LD column is effective, safe and easy for the one-step purification of PRBCs. This simple method does not affect the viability of malarial parasites.

Targeted bone marrow radioablation with 153Samarium-lexidronam promotes allogeneic hematopoietic chimerism and donor-specific immunologic hyporesponsiveness

BACKGROUND

Transplantation tolerance, defined as acceptance of a graft by an otherwise fully immunocompetent host, has been an elusive goal. Although robust tolerance has been achieved by the induction of stable hematopoietic chimerism after bone marrow transplantation, lethal or sublethal radiation conditioning used to induce long-term chimerism precludes its clinical use. We studied whether targeted delivery of radiation to bone marrow could allow for bone marrow cell (BMC) engraftment, chimerism, and donor-specific tolerance in the absence of the side effects associated with external irradiation.

METHODS

We administered a radioactive bone-seeking compound (Samarium-Lexidronam, Quadramet, Berlex Laboratories, Wayne, NJ) together with transient T-cell costimulatory blockade to recipient mice. Allogeneic BMCs were given 7 or 14 days after preconditioning. Costimulatory blockade was obtained by the use of an anti-CD154 antibody for 4 weeks. Chimerism was assessed by flow cytometry. Mice then received donor-specific and third-party skin grafts. Graft survival was analyzed with mechanisms of donor-specific hyporesponsiveness.

RESULTS

High levels of stable chimerism across an allogeneic barrier were achieved in mice by a single administration of Samarium-Lexidronam, transient T-cell costimulatory blockade, and BMC transplantation. A large percentage of chimeric animals retained donor-derived skin grafts for more than 120 days without requiring additional immunosuppression, suggesting that harsh cytotoxic preconditioning is not necessary to achieve stable chimerism and donor specific hyporesponsiveness. Analysis of the T-cell repertoire in chimeras indicates T-cell deletional mechanisms.

CONCLUSIONS

These data broaden the potential use of BMC transplantation for tolerance induction and argue for its potential in treating autoimmune diseases.

Foreign cells in polymyositis: Could stem cell transplantation and pregnancy-derived chimerism lead to the same disease?

A growing number of hematopoietic stem cell transplantation centers have reported that patients with chronic graft versus host disease (GVHD) can develop polymyositis (PM). GVHD-PM is similar to idiopathic PM in signs, symptoms, laboratory values, electromyography, radiography, and histology, suggesting that the two conditions may share a similar mechanism in pathogenesis. In chronic GVHD-PM, interactions between allogeneic donor cells and host cells lead to chronic inflammation. In idiopathic PM, the foreign cells could be partially human leukocyte antigen-matched maternal or fetal cells acquired during pregnancy. Thus, PM can be added to the list of potentially allo-autoimmune diseases in which pregnancy-derived microchimerism may play a role.

Cardiopulmonary resuscitation in the mouse

We sought to develop a model of cardiac arrest and resuscitation on mice that would be comparable to that of large mammals and would allow for more fundamental investigations on cardiopulmonary arrest and cardiac resuscitation. A model of cardiopulmonary resuscitation previously developed by our group on rats was adapted to anesthetized, mechanically ventilated adult male Institute of Cancer Research mice that weighed 46 +/- 3 g. The trachea was intubated through the mouth, and end-tidal PCO(2) (PET(CO(2))) was measured with a microcapnometer. Catheters were advanced into the aorta and into the right atrium, and coronary perfusion pressure (CPP) was computed. A 1.5-mA alternating current was delivered to the right ventricular endocardium, which produced ventricular fibrillation or a pulseless rhythm. Precordial compression was begun 4 min later. Ten sequential studies were performed, during which five animals were successfully resuscitated and five failed resuscitation efforts. Successful resuscitation was contingent on the restoration of threshold levels of CPP and PET(CO(2)) during chest compression. As in rats, swine, and human patients, threshold levels of mean aortic pressure, CPP, and PET(CO(2)) were critical determinates of resuscitability in this murine model of threshold level of cardiac arrest and resuscitation.