Blood Transfusion is Associated with Donor Leukocyte Microchimerism in Trauma Patients

High Frequency of Post-Transfusion Microchimerism Among Multi-Transfused Beta-Thalassemic Patients

Background

Transfusion-associated microchimerism implies the presence of allogeneic hematopoietic cells in an individual, following the transfusion of a blood product. It is a transfusion-related adverse effect/long-term consequence, which has not been well-investigated among regularly transfused patients with thalassemia.

Patients and Methods

We investigated 64 regularly transfused, homozygous β-thalassemic patients and 21 never-transfused healthy volunteer blood donors (controls) for the presence of microchimerism in their sera, using real-time PCR targeting circulating allogeneic, both, Human Leukocyte Antigen-DR isotype (HLA-DR) and non-HLA alleles. The investigation was longitudinally repeated in patient subsets for more than 2 years. Results were correlated with clinical and laboratory parameters, peripheral blood lymphocyte immunophenotype, blood storage time, and donor's gender to identify potential contributing factors for microchimerism generation.

Results

Overall, microchimerism was detected in 52 of the 64 patients (81.2%) and in 6 of the 21 controls (28.5%, p = 0.0001). Forty-four patients (68.7%) exhibited long-term microchimerism (persisted for more than 6 months), confirmed at all time-points investigated. Microchimerism was more frequent among elderly, women, splenectomized and more heavily transfused patients, and among those who exhibit higher serum ferritin levels. In these patients, a distinct descending pattern of CD16^dim+CD56^dim+ natural killer (NK)-cells (p < 0.001) and an ascending pattern of CD4+CD25^brightCD127– regulatory T-cells (p = 0.022) for increasing allelic burden were noticed, suggesting the establishment of recipient immune tolerance against the donor-derived chimeric alleles. Both splenectomized and non-splenectomized thalassemic patients exhibited the same trend. The storage time of transfused blood products and donor/gender mismatch had no impact on the development of microchimerism.

Discussion-Conclusive Remarks

Transfusion-associated microchimerism appears to be a very common complication among multi-transfused thalassemic patients. The potential clinical consequences of this phenomenon remain as yet unclear. Immune tolerance attributed to disease itself and to repeated transfusions might at least in part explain its appearance.

Blood transfusions may adversely affect survival outcomes of patients with lung cancer: a systematic review and meta-analysis

Background

Despite common use in clinical practice, the impact of blood transfusions on prognosis among patients with lung cancer remains unclear. The purpose of the current study is to perform an updated systematic review and meta-analysis to evaluate the influence of blood transfusions on survival outcomes of lung cancer patients.

Methods

We searched PubMed, Embase, Cochrane Library, and Ovid MEDLINE for publications illustrating the association between blood transfusions and prognosis among people with lung cancer from inception to November 2019. Overall survival (OS) and disease-free survival (DFS) were the outcomes of interest. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were computed using the random-effects model. Study heterogeneity was evaluated with the I² test. Publication bias was explored via funnel plot and trim-and-fill analyses.

Results

We included 23 cohort studies with 12,175 patients (3,027 cases and 9,148 controls) for meta-analysis. Among these records, 22 studies investigated the effect of perioperative transfusions, while one examined that of transfusions during chemotherapy. Two studies suggested the possible dose-dependent effect in accordance with the number of transfused units. In pooled analyses, blood transfusions deleteriously influenced both OS (HR=1.35, 95% CI: 1.14–1.61, P<0.001, I²=0%) and DFS (HR=1.46, 95% CI: 1.15–1.86, P=0.001, I²=0%) of people with lung cancer. No evidence of significant publication bias was detected in funnel plot and trim-and-fill analyses (OS: HR=1.26, 95% CI: 1.07–1.49, P=0.006; DFS: HR=1.35, 95% CI: 1.08–1.69, P=0.008).

Conclusions

Blood transfusions were associated with decreased survival of patients with lung cancer.

Murine Myeloid Progenitors Attenuate Immune Dysfunction Induced by Hemorrhagic Shock

Hemorrhagic shock induces an aberrant immune response characterized by simultaneous induction of a proinflammatory state and impaired host defenses. The objective of this study was to evaluate the impact of conditionally immortalized neutrophil progenitors (NPs) on this aberrant immune response. We employed a mouse model of hemorrhagic shock, followed by the adoptive transfer of NPs and subsequent inoculation of Staphylococcus aureus to induce pneumonia. We observed that transplant of NPs decreases the proportion of host neutrophils that express programmed death ligand 1 and intercellular adhesion molecule 1 in the context of prior hemorrhage. Following hemorrhage, NP transplant decreased proinflammatory cytokines in the lungs, increased neutrophil migration into the airspaces, and enhanced bacterial clearance. Further, hemorrhagic shock improved NP engraftment in the bone marrow. These results suggest that NPs hold the potential for use as a cellular therapy in the treatment and prevention of secondary infection following hemorrhagic shock.

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Myeloid progenitors restore a competent inflammatory response to pneumonia

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Progenitor transplantation promotes clearance of secondary S. aureus pneumonia

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Hemorrhagic shock enhances engraftment of transplanted myeloid progenitors

Damage control resuscitation

The United States Navy originally utilized the concept of damage control to describe the process of prioritizing the critical repairs needed to return a ship safely to shore during a maritime emergency. To pursue a completed repair would detract from the goal of saving the ship. This concept of damage control management in crisis is well suited to the care of the critically ill trauma patient, and has evolved into the standard of care. Damage control resuscitation is not one technique, but, rather, a group of strategies which address the lethal triad of coagulopathy, acidosis, and hypothermia. In this article, we describe this approach to trauma resuscitation and the supporting evidence base.

Lack of persistent microchimerism in contemporary transfused trauma patients

BACKGROUND

Following transfusion, donor white blood cells (WBCs) can persist long-term in the recipient, a phenomenon termed transfusion-associated microchimerism (TA-MC). Prior studies suggest TA-MC is limited to transfusion following traumatic injury, and is not prevented by leukoreduction.

STUDY DESIGN AND METHODS

We conducted a prospective cohort study at a major trauma center to evaluate TA-MC following injury. Index samples were collected upon arrival, prior to transfusion. Follow-up samples were collected at intervals up to one year, and beyond for those testing positive for TA-MC. TA-MC was detected by real-time quantitative allele-specific polymerase chain reaction assays at the HLA-DR locus and several polymorphic insertion deletion sites screening for non-recipient alleles.

RESULTS

A total of 378 trauma patients were enrolled (324 transfused cases and 54 non-transfused controls). Mean age was 42 ± 18 years, 74% were male, and 80% were injured by blunt mechanism. Mean Injury Severity Score was 20 ± 12. Among transfused patients, the median (interquartile range) number of red cell units transfused was 6 (3,12), and median time to first transfusion was 9 (0.8,45) hours. Only one case of long-term TA-MC was confirmed in our cohort. We detected short-term TA-MC in 6.5% of transfused subjects and 5.6% on non-transfused controls.

CONCLUSIONS

In contrast to earlier studies, persistent TA-MC was not observed in our cohort of trauma subjects. Short-term TA-MC was detected, but at a lower frequency than previously observed, and rates were not significantly different than what was observed in non-transfused controls. The reduction in TA-MC occurrence may be attributable to changes in leukoreduction or other blood processing methods.

Microchimerism in Ghanaian children recipients of whole blood transfusion for severe anaemia

BACKGROUND AND OBJECTIVES

Transfusion-acquired microchimerism (TA-Mc) has been reported in major trauma but not in young children despite relative immunodeficiency who, in sub-Saharan Africa, often suffer severe anaemia related to haemoglobinopathies or primary malaria infections. We examined the hypothesis that such massive red cell destructions might provide conditions favourable to TA-Mc, particularly when exposed to massive amounts of parasite antigens.

MATERIALS AND METHODS

Twenty-seven female children <5 years transfused with male whole blood for severe anaemia (13 with acute malaria and 14 with other causes) were retrospectively identified, and a blood sample was collected >6 months post-transfusion. Four whole blood samples from paediatric females transfused with blood from female donors and five secondary school female students never pregnant, never transfused were used as negative controls.

RESULTS

Nineteen patients (70%) carried male Mc with four (15%) having high levels of Mc (>100 genome equivalent of male cells/million of host cells) compared to three controls (37·5%). There was no difference in frequency or quantity of male Mc between paediatric patients with severe malaria and paediatric patients with other causes of severe anaemia. TA-Mc was not correlated with patient age, duration of whole blood storage or lymphocyte load transfused. After a median of 7 months post-transfusion, acute malaria did not increase the frequency of TA-Mc. One negative control appeared to carry low-level male cells.

CONCLUSION

Transfusion-acquired microchimerism appears frequent in young children transfused with whole blood for severe anaemia.

Donor white blood cell survival and cytokine profiles following red blood cell transfusion in Australian major trauma patients

BACKGROUND

The potential for the co-existence of genetically disparate cells (microchimerism) and associated cytokine profiles following red blood cell (RBC) transfusion in trauma patients has not been well characterized to date. This study investigated the incidence of surviving donor white blood cells (known as transfused-associated microchimerism (TAM)) and cytokine changes following blood transfusion in trauma patients.

STUDY DESIGN AND METHODS

Trauma patients with an injury severity score (ISS) >12 who had been transfused between 2012-2016 with at least 5 units of RBC units over a 4 h period were recruited. Trauma patients with ISS > 12 who did not require blood transfusion were recruited as controls. The incidence of TAM was determined using a panel of insertion/deletion (InDel) bi-allelic polymorphisms. Selected pro- and anti-inflammatory cytokine profiles were analyzed using cytometric bead array.

RESULTS

The transfused cohort (n = 40) had median ISS of 28 [12-66], received a median of 11 RBC units [4-114] and had median hospital length of stay of 35 days [1-152]. Only 11 (27.5%) patients returned for follow-up blood sampling after discharge. Of these, one patient showed an InDel pattern indicating the presence of TAM. No patients in the control cohort (n = 49) showed TAM. Cytokines IL-10 and IL-6 were found to be elevated in the transfused trauma patients.

CONCLUSION

In this cohort, TAM was found to occur in one patient of the 11 who received a blood transfusion. Elevated IL-6 and IL-10 cytokines were detected in those patients who were transfused. However, the incidence of TAM could not be correlated with the elevated cytokine profiles for this cohort.

Male microchimerism in peripheral blood leukocytes from women with multiple sclerosis

BACKGROUND

Fetal microchimerism (F-MC), the persistence of fetal cells in the mother, is frequently encountered following pregnancy. The high prevalence of F-MC in autoimmune disease prompts consideration of the role for immune tolerance and regulation. This study examines the association between F-MC and multiple sclerosis (MS), an autoimmune disorder, of undetermined etiology.

RESULTS

21 out of 51 MS-positive subjects (41%) were classified as positive for F-MC; 4 of 22 (18%) of MS-negative sibling controls, were also positive for MC (p = 0.066). Unanticipated F-MC in controls lead to re-evaluation using 30 female singleton cord blood units (CBUs) as a biological control. Four CBUs were low-level positive.

STUDY DESIGN AND METHODS

Seventy-three female subjects were assigned to three groups according to disease status and pregnancy history: (1) MS positive (+) women with a history of one male pregnancy before symptom onset (n = 27); (2) MS negative (-) female siblings of MS(+) women with a history of one male pregnancy (n = 22); and (3) MS(+) women that reported never having been pregnant (n = 24). Ten micrograms of genomic DNA obtained from peripheral blood leukocytes of each subject were analyzed for F-MC using allele-specific real-time PCR targeting the SR-Y sequence on the Y-chromosome. MC classification was dichotomous (positive vs. negative) based on PCR results.

CONCLUSION

The association between F-MC and MS warrants further study to define this relationship. F-MC in women self-reporting as nulligravid, supports previous findings that a significant proportion of pregnancies go undetected. This lead to re-validation of a Y-chromosome based assay for F-MC detection.

Engineering Therapeutic T Cells: From Synthetic Biology to Clinical Trials

Engineered T cells are currently in clinical trials to treat patients with cancer, solid organ transplants, and autoimmune diseases. However, the field is still in its infancy. The design, and manufacturing, of T cell therapies is not standardized and is performed mostly in academic settings by competing groups. Reliable methods to define dose and pharmacokinetics of T cell therapies need to be developed. As of mid-2016, there are no US Food and Drug Administration (FDA)-approved T cell therapeutics on the market, and FDA regulations are only slowly adapting to the new technologies. Further development of engineered T cell therapies requires advances in immunology, synthetic biology, manufacturing processes, and government regulation. In this review, we outline some of these challenges and discuss the contributions that pathologists can make to this emerging field.

Leukodepleted blood components do not remove the potential for long-term transfusion-associated microchimerism in Australian major trauma patients

Despite the introduction of leukodepleted blood components, it has been shown that donor leukocyte engraftment (microchimerism) remains a long-term consequence of red blood cell (RBC) transfusion. The incidence of microchimerism may be affected by international disparities in blood processing methods or variations in transfusion practices. This study was conducted to determine the prevalence of microchimerism in Australian trauma patients. A secondary aim was to examine whether any patient complications correlated to the incidence of microchimerism. Australian trauma patients (n = 86) who had been transfused with red blood cell (RBC) units between 2000 and 2012 with an injury severity score (ISS) of greater than 15 were recruited. The prevalence of microchimerism was determined using genetic screening with a panel of insertion/deletion biallelic polymorphisms. The mean storage age of the transfused RBC units was 20 ± 8 days and the mean length of stay (LOS) in hospital was 40 ± 39 days. There were no significant associations in this study sample to bias for patient age, gender, number of transfused RBC units or ISS. Nine of the 55 (16.3%) patients transfused with non-leukodepleted blood components displayed an incidence of microchimerism. Of the 31 patients transfused with leukodepleted RBC units, 3 (9.6%) displayed an incidence of microchimerism. Therefore, despite the universal introduction of leukodepleted blood components in Australia, the prevalence of transfusion-associated microchimerism was found to be unchanged. Furthermore, half of the patients exhibiting microchimerism were recorded to have had splenic injury or required splenectomy at the time of transfusion.

Microchimerism in the transfused obstetric population

Microchimerism (MC), the coexistence of allogeneic populations of cells within a host, is well described in pregnancy and blood transfusion. To date, transfusion-associated MC (TA-MC) appears unique to patients transfused after severe traumatic injury. We sought to determine whether transfusion in the peripartum period results in enduring, high-level TA-MC. We conducted a prospective cohort study of 22 women who were newly transfused within 48 h of delivery. Two subjects showed evidence of transient TA-MC; however, MC was not detected at 6 weeks and 6 months. The negative findings suggest that enduring TA-MC does not occur in this population.

Immunomodulation in transfused trauma patients

PURPOSE OF REVIEW

Traumatic injury is a major human health problem, with many injured people supported by transfusion of allogeneic blood. Although trauma and transfusion have both been known to have immunomodulatory effects for some time, little is known about their combined effects or the scope and kinetics of such responses.

RECENT FINDINGS

Traumatic injury has a profound immunomodulatory effect on the patient, affecting a broad array of immunological components. This can be further complicated by transfusion, though the contribution of transfusion relative to the massive response triggered by trauma is small. The response to trauma involves a strong immunosuppressive component, which, contrary to the systemic inflammatory response syndrome/compensatory anti-inflammatory response syndrome model, occurs at the earliest time points examined and overlaps with proinflammatory and antimicrobial elements. This response is remarkably similar in a wide range of patients with different types and severities of injury.

SUMMARY

The response to trauma and transfusion involves a massive and rapid reorganization of the immune system that can put the patient at increased risk of infection, tissue damage, and organ failure. The scope of the response presents challenges to the development of treatments to control this dysregulation.

Intensive red blood cell transfusions and risk of alloimmunization

BACKGROUND

Exposure to allogenic red blood cells (RBCs) may lead to formation of antibodies against nonself-antigens in transfused patients. While alloimmunization rates are known to increase with the number of transfusions, the transfusion course in patients can vary from receiving multiple units during a single transfusion event or getting them dispersed over a long(er) period. In this study we compared the immunization risk between different transfusion intensities.

STUDY DESIGN AND METHODS

An incident new-user cohort study was conducted among consecutive transfused patients at two university medical centers. All patients who received their first RBC transfusion within the study period from January 2005 to December 2011 were eligible. Intensive transfusions were defined as at least 5, at least 10, and at least 20 RBC units within 48 hours. Alloimmunization hazard ratios (HRs), comparing patients receiving intensive transfusions to patients never receiving intensive transfusions, were estimated.

RESULTS

The study cohort was composed of 5812 patients who had received a median of 7 (interquartile range, 4-12) units. RBC alloantibodies were formed by 156 patients. The adjusted Cox regression HRs for alloimmunization, with number of units as the time covariate and adjusted for patient age, sex, and follow-up time after first transfusion, ranged from 0.8 to 1.2 (95% confidence interval, 0.4-2.6).

CONCLUSION

The occurrence of RBC alloimmunization in patients receiving intensive transfusions did not differ significantly from patients receiving nonintensive transfusions.

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.

Blood ties: chimerism can mask twin discordance in high-throughput sequencing

Twin studies have long provided a means to separate the contributions of genetic and environmental factors. A recent pioneering report by Baranzini et al. presented an analysis of the complete genomes and epigenomes of a monozygotic (MZ) twin pair discordant for multiple sclerosis. This failed to find any difference between the twins, raising doubts regarding the value of whole-genome twin studies for defining disease susceptibility alleles. However, the study was carried out with DNA extracted from blood. In many cases, the hematopoietic lineages of MZ twins are chimeric due to twin-to-twin exchange of hematopoietic stem cells during embryogenesis. We therefore wondered how chimerism might impact the ability to identify genetic differences. We inferred the blood chimerism rates and profiles of more than 30 discordant twin cases from a wide variety of medical conditions. We found that the genotype compositions of the twins were highly similar. We then benchmarked the performance of SNP callers to detect discordant variations using high-throughput sequencing data. Our analysis revealed that chimerism patterns, well within the range normally observed in MZ twins, greatly reduce the sensitivity of SNP calls. This raises questions regarding any conclusions of genomic homogeneity that might be drawn from studies of blood-derived twin DNA.

Transfusion medicine in trauma patients

Injured patients stress the transfusion service with frequent demands for uncrossmatched red cells and plasma, occasional requirements for large amounts of blood products and the need for new and better blood products. Transfusion services stress trauma centers with demands for strict accountability for individual blood component units and adherence to indications in a clinical field where research has been difficult, and guidance opinion-based. New data suggest that the most severely injured patients arrive at the trauma center already coagulopathic and that these patients benefit from prompt, specific, corrective treatment. This research is clarifying trauma system requirements for new blood products and blood-product usage patterns, but the inability to obtain informed consent from severely injured patients remains an obstacle to further research.

Association between length of storage of transfused red blood cells and multiple organ dysfunction syndrome in pediatric intensive care patients

BACKGROUND

The objective was to determine if there is an association between red blood cell (RBC) storage time and development of new or progressive multiple organ dysfunction syndrome (MODS) in critically ill children.

STUDY DESIGN AND METHODS

This was an analytic cohort analysis of patients enrolled in a randomized controlled trial, TRIPICU (Transfusion Requirements in Pediatric Intensive Care Units; ISRCTN37246456), in which stable critically ill children were randomly assigned to a restrictive or liberal strategy. Transfused patients were analyzed using three different sliding time cutoffs (7, 14, and 21 days). Storage time for multiply transfused patients was defined according to the oldest unit transfused.

RESULTS

A total of 455 patients were retained (liberal, 310; restrictive, 145). Multivariate logistic regression was performed to determine independent associations. In the restrictive group, a maximum RBC storage time of more than 21 days was independently associated with new or progressive MODS (adjusted odds ratio [OR], 3.29; 95% confidence interval [CI], 1.21-9.04). The same association was found in the liberal group for a storage time of more than 14 days (adjusted OR, 2.50; 95% CI, 1.12-5.58). When the two groups were combined in a meta-analysis, a storage time of more than 14 days was independently associated with increased MODS (adjusted OR, 2.23; 95% CI, 1.20-4.15) and more than 21 days was associated with increased Pediatric Logistic Organ Dysfunction (PELOD) scores (adjusted mean difference, 4.26; 95% CI, 1.99-6.53) and higher mortality (9.2% vs. 3.8%).

CONCLUSION

Stable critically ill children who receive RBC units with storage times longer than 2 to 3 weeks may be at greater risk of developing new or progressive MODS.

Transfusion associated microchimerism: a heretofore little-recognized complication following transfusion

Potent antiplatelet and antithrombotic agents have significantly reduced mortality in the setting of acute coronary syndromes and percutaneous coronary intervention. However these agents are associated with increased bleeding which is in turn associated with adverse clinical outcomes. In many centers, transfusion is often used to correct for blood loss. Blood transfusion in the setting of acute coronary syndrome has been associated with adverse clinical outcomes including increased mortality. Transfusion associated microchimerism (TA-MC) is a newly recognized complication of blood transfusion. There is engraftment of the donor's hematopoietic stem cells in patients who then develop microchimerism. This article discusses the association of bleeding/blood transfusion with adverse outcomes and the potential role of TA-MC in clinical outcomes.

The TNF (-308A) polymorphism is associated with microchimerism in transfused trauma patients

Microchimerism (MC), defined as the persistence of allogeneic cells at low concentrations, is well documented in transfused trauma patients. We hypothesized that genetic polymorphisms linked to cytokine production could contribute to trauma-induced immune modulation and development of microchimerism after transfusion of trauma patients. We used high-throughput SYBR-green-based genotyping of single nucleotide polymorphisms (SNPs) to characterize 59 transfused trauma patients, with MC (n=30) and without MC (n=29), for 4 functionally significant SNPs: TNF (-308), IL 10 (-1082), IFNG (+874), and TGFB1 (+915). We then compared likelihood for development of MC and the magnitude of immune suppression among subjects with and without these selected immune response SNPs. We identified a significant association between TNF (-308A) SNP and both development of MC and diminished immune responsiveness. Hence predisposing genetic factors may explain, in part, why only a subset of trauma patients develops transfusion-associated microchimerism.

Fetal microchimerism in women with breast cancer

Fetal microchimerism (FMc) describes long-term persistence of small numbers of fetal-derived allogeneic cells in the mother. Although FMc has been implicated as a mechanism of autoimmune disease, it may confer a beneficial effect with immune surveillance of malignant cells. We hypothesized that allogeneic FMc imparts a protective effect against breast cancer. Two observations provided a rationale for the study hypothesis. First, allogeneic cells convey risk reduction for recurrent malignancy in hematopoietic cell transplantation. Second, reduced risk of breast cancer is well recognized among parous compared with nulliparous women. As an initial test of the hypothesis, we investigated 82 women, 35 with breast cancer and 47 who were healthy, for male DNA in peripheral blood, presumed from a prior pregnancy with a male fetus. The prevalence and levels of male DNA were determined by real-time quantitative PCR for the Y chromosome-specific gene DYS14 in DNA extracted from peripheral blood mononuclear cells. FMc was found significantly more often in healthy women than women with breast cancer (43% versus 14%, respectively). Considering the absence of FMc as a risk factor, the odds ratio was 4.4 [95% confidence intervals (95% CI), 1.34-16.99; P = 0.006]. Restricting analysis to women known to had given birth to a son, the odds ratio was 5.9 (95% CI, 1.26-6.69; P = 0.01). Our findings indicate that allogeneic FMc may contribute to reduction in risk of breast cancer. Further studies are indicated and, if confirmed, extended studies to examine whether allogeneic immune surveillance from FMc is deficient in women with breast cancer.

Detection of anti-D in D- recipients transfused with D+ red blood cells

BACKGROUND

The D antigen is highly immunogenic, requiring only a small quantity of transfused red blood cells (RBCs) to cause alloimmunization in D- immunocompetent recipients. The relatively low sensitization rate in oncology patients transfused with D+ platelets is well documented. A study of the alloimmunization rate of primarily nononcology D- recipients transfused with D+ RBCs was undertaken.

STUDY DESIGN AND METHODS

Transfusion service records were examined to identify D- recipients who were not alloimmunized to the D antigen and who had a follow-up antibody screen performed at least 10 days after the initial D+ RBC transfusion(s). The age and sex of the recipients, date and number of D+ RBC transfusion(s) and their leukoreduction status, all subsequent serologic investigations, and the hospital ward where the units were issued were recorded.

RESULTS

There were 98 study-eligible recipients identified who received a total of 445 D+ RBC units. The mean follow-up length was 182 days. Most recipients (87%) had antibody screens performed more than 21 days after the initial D+ RBC transfusion. In total, 24 recipients made 44 new alloantibodies: 22 anti-D (22%), 11 anti-E, 5 anti-C, 2 anti-K, and 1 each of anti-Kp(a), anti-Jk(a), anti-Bg, and anti-Fy(b). The rate of anti-D alloimmunization among recipients of entirely leukoreduced D+ units was 13 percent (1/8). Reexposure to D+ RBCs after the initial bleeding episode did not increase the rate of alloimmunization.

CONCLUSIONS

The 22 percent rate of anti-D alloimmunization in patients requiring urgent RBC transfusion was intermediate between the rates previously reported for D- oncology patients transfused with D+ RBCs and that in immunocompetent volunteer recipients.

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.

Risk of cancer after blood transfusion from donors with subclinical cancer: a retrospective cohort study

BACKGROUND

Although mechanisms for detection of short-term complications after blood transfusions are well developed, complications with delayed onset, notably transmission of chronic diseases such as cancer, have been difficult to assess. Our aim was to investigate the possible risk of cancer transmission from blood donors to recipients through blood transfusion.

METHODS

We did a register-based retrospective cohort study of cancer incidence among patients who received blood from donors deemed to have a subclinical cancer at the time of donation. These precancerous donors were diagnosed with a cancer within 5 years of the donation. Data from all computerised blood bank registers in Sweden and Denmark gathered between 1968 and 2002 were merged into a common database. Demographic and medical data, including mortality and cancer incidence, were ascertained through linkages with nationwide, and essentially complete, population and health-care registers. The risk of cancer in exposed recipients relative to that in recipients who received blood from non-cancerous donors was estimated with multivariate Poisson regression, adjusting for potential confounding factors.

FINDINGS

Of the 354 094 transfusion recipients eligible for this analysis, 12,012 (3%) were exposed to blood products from precancerous donors. There was no excess risk of cancer overall (adjusted relative risk 1.00, 95% CI 0.94-1.07) or in crude anatomical subsites among recipients of blood from precancerous donors compared with recipients of blood from non-cancerous donors.

INTERPRETATION

Our data provide no evidence that blood transfusions from precancerous blood donors are associated with increased risk of cancer among recipients compared with transfusions from non-cancerous donors.

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).

Enhanced ascertainment of microchimerism with real-time quantitative polymerase chain reaction amplification of insertion-deletion polymorphisms

BACKGROUND

The characterization of microchimerism (MC) by gene amplification has been limited by few allogeneic markers, ascertainment bias, and assay analytic performance. To address this, a panel of 12 MC assays based on insertion-deletion (InDel) polymorphisms had been optimized.

STUDY DESIGN AND METHODS

The InDel assays were validated with comprehensive in vitro spiking studies at the stochastic limit of detection. Their ability was also determined to ascertain MC of unknown source genotype with both theoretical and actual donor-recipient pairs, and the assays were applied to a clinical population of 73 trauma patients who received transfusions where MC was previously characterized by HLA-based assays alone.

RESULTS

In the stochastic spiking experiments, all assays were sensitive to a single copy of target DNA, and no false-positive amplification occurred among 1128 samples studied. Among 219 theoretical donor-recipient pairs, informative alleles existed for 99.5 percent with both InDel and HLA compared to 91.3 percent with HLA alone. In the clinical population, 33 cases of MC were detected (9 more cases than by HLA-DR alone) in the nonleukoreduced (non-LR) group and 8 cases (1 more case than by HLA-DR) in the LR group for the short-term follow-up. Among 27 long-term follow-up samples, 8 cases were detected overall (3 more cases than by HLA-DR alone).

CONCLUSION

It is concluded that an InDel-based assay panel has excellent technical performance characteristics while also allowing for ascertainment of some MC cases not detectable with HLA alone. The tandem use of both the InDel and the HLA provides a powerful tool for the enhanced ascertainment of MC.

Leukoreduction of blood transfusions does not diminish transfusion-associated microchimerism in trauma patients

BACKGROUND

Transfusion of trauma patients can result in long-term survival of donor white blood cells (WBCs) or "transfusion-associated microchimerism" (TA-MC). The aim was to determine whether leukoreduction of blood transfusions, advocated to reduce the immunomodulatory effect of transfusion, decreases the likelihood of developing TA-MC.

STUDY DESIGN AND METHODS

A subgroup of trauma patients from a randomized trial was examined, evaluating the risk of infection following leukoreduced versus nonleukoreduced blood transfusion. Patients' blood was sampled at least 1 month after hospital discharge, and TA-MC was assessed with quantitative allele-specific polymerase chain reaction detection of differences at the HLA-DR locus or a panel of insertion-deletion polymorphism loci distributed throughout the chromosomal complement. At the time of blood sampling, a scripted interview was used to ascertain symptoms suggestive of chronic graft-versus host disease (cGVHD).

RESULTS

For 67 patients evaluated, the mean age was 43 +/- 17 years and mean Injury Severity Score was 24 +/- 12. Median time from injury to blood sampling for TA-MC was 240 (interquartile range, 116-360) days. Nine of 32 patients (28%) in the nonleukoreduced transfusion group developed TA-MC compared to 13 of 35 patients (37%) in the leukoreduced group (p = 0.43). Subjects with TA-MC were no more likely than subjects without TA-MC to have at least one symptom suggestive of cGVHD (64% vs. 76%, respectively).

CONCLUSIONS

TA-MC seems to be a prevalent condition among injured patients at the second of two regional trauma centers evaluated, suggesting that it is a common phenomenon after transfusion in the setting of injury. Although leukoreduction removes greater than 99.9 percent of donor WBCs, it fails to prevent or even substantially reduce the likelihood of developing TA-MC. TA-MC does not appear to be strongly associated with symptoms suggestive of cGVHD several months after transfusion.

Soluble Donor DNA Concentrations in Recipient Serum Correlate with Pancreas-Kidney Rejection

Background: There is no reliable serum marker available to monitor incipient pancreas or islet-cell rejection. We tested the hypothesis that quantification of donor-specific genomic DNA in serum (from tissue damage) can serve as a marker of rejection.

Methods: Using a recently developed panel of HLA-specific quantitative PCR assays (Q-PCR), we tested 158 sera from 42 pancreas-kidney transplant recipients. Temporally related biopsies for 65 sera permitted analysis for correlation of donor DNA concentrations with rejection.

Results: Donor DNA concentrations were higher in sera from recipients who had experienced allograft rejection (n = 31) than from those who had not (n = 34). Median concentrations, expressed as the genome-equivalent (gEq) number of donor cells per 106 host cells, were 2613 and 59 gEq/106, respectively (P = 0.03).

Conclusion: Q-PCR for donor-specific genetic polymorphisms merits further investigation as a noninvasive approach to monitor pancreas-kidney as well as other types of allograft rejection.

Massive blood transfusion for trauma

PURPOSE OF REVIEW

Massive blood transfusion saves the lives of thousands of severely injured patients each year, but it does so in the context of the evolving epidemiology of injury, of trauma centers and trauma systems, and of blood safety and new technologies for hemorrhage control. This article reviews recent knowledge and advances that impact on the use and effectiveness of massive transfusion.

RECENT FINDINGS

Injury is rapidly becoming the second leading cause of death in the world. These deaths are highly preventable with social and engineering controls and good trauma care. Massive transfusion is readily available, safe, effective, and cheap in the context of modern trauma center care. However, aged blood products can cause transfusion-related acute lung injury, and better blood storage systems are under development. Recent work has improved understanding of the coagulopathy associated with acidosis and provided guidance for limiting dilutional coagulopathy. Nevertheless, massive transfusion always leads to coagulopathy and so is at best an adjunct to good surgical care. Better drugs and devices for hemorrhage control, such as recombinant activated factor VII and hemostatic bandages, are in development.

SUMMARY

Injury is a major public health and medical system problem. Progress in basic science, clinical care, and the development of better hemorrhage control devices are all improving outcome for massively transfused patients. Investment in trauma care and supporting blood supply systems is highly cost effective.

Microchimerism in transfused trauma patients is associated with diminished donor-specific lymphocyte response

BACKGROUND

Blood transfusion can result in long-term survival of donor leukocyte subpopulations, or microchimerism, in the peripheral blood of injured patients. Neither injury severity nor the number of transfusions is associated with its occurrence. We sought to determine whether changes in general or antigen-specific lymphocyte activation may be associated with the subsequent development of microchimerism.

METHODS

We evaluated 63 transfused trauma patients, which we compared with 10 non-transfused trauma patients and 10 healthy control subjects. Of the 63 transfused patients, 31 were known to have evidence of microchimerism at hospital discharge with real-time quantitative PCR for non-recipient HLA DR alleles. We assessed lymphocyte response to phytohemagglutinin (PHA) using blood sampled upon arrival to the hospital (before transfusion) and at discharge. We performed one-way mixed leukocyte cultures (MLC) with pre-transfusion recipient specimens to assess recipient lymphocyte response to mitomycin-C treated donor cells and vice versa.

RESULTS

Lymphocyte response to PHA in microchimeric transfusion recipients was lower at admission (before transfusion) and discharge than in non-microchimeric recipients. Lymphocytes from microchimeric patients had less response to donor cells than did lymphocytes from non-microchimeric patients. Microchimeric patients also more frequently had diminished lymphocyte response to a single blood donor on MLC.

CONCLUSIONS

Transfusion-associated microchimerism is correlated with diminished response to mitogen challenge as well as to specific alloantigenic challenges. This microchimerism is predated by diminished lymphocyte response to a specific blood donor in many instances. The blood donor associated with this diminished alloantigenic lymphocyte response may be the source of microchimeric cells present in the recipient.

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.

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.