Survival of transfused donor white blood cells in HIV-infected recipients

Transfusion-associated graft-versus-host disease (TA-GVHD) and graft-versus-host disease (GVHD): Pathophysiology and management (contrasted and compared)

Transfusion of blood products is a common lifesaving medical procedure in clinical practice. However, it poses the risk of potential adverse reactions for the recipient. Transfusion-associated graft-versus-host-disease (TA-GVHD) is a rare adverse event, fatal in >90% of cases. TA-GVHD pathophysiology is not completely understood involving two factors: (i) underlying immunosuppression and (ii) human leukocyte antigen compatibility between blood donor and recipient. Clinical presentation is not specific, and the difficulty in correlating the clinical syndrome to the transfusion renders diagnosis challenging. As no effective treatment exists to date, irradiation of blood products remains the cornerstone of TA-GVHD prevention. Distinct differences emerge in comparing TA-GVHD to GVHD, a common event of the bone marrow graft to the recipient after allogeneic hematopoietic stem cell transplantation; thus, GVHD may be a helpful disease model used to better understand TA-GVHD. This is a review of TA-GVHD in comparison with GVHD.

Automatic recognition of white blood cell images with memory efficient superpixel metric GNN: SMGNN

An automatic recognizing system of white blood cells can assist hematologists in the diagnosis of many diseases, where accuracy and efficiency are paramount for computer-based systems. In this paper, we presented a new image processing system to recognize the five types of white blood cells in peripheral blood with marked improvement in efficiency when juxtaposed against mainstream methods. The prevailing deep learning segmentation solutions often utilize millions of parameters to extract high-level image features and neglect the incorporation of prior domain knowledge, which consequently consumes substantial computational resources and increases the risk of overfitting, especially when limited medical image samples are available for training. To address these challenges, we proposed a novel memory-efficient strategy that exploits graph structures derived from the images. Specifically, we introduced a lightweight superpixel-based graph neural network (GNN) and broke new ground by introducing superpixel metric learning to segment nucleus and cytoplasm. Remarkably, our proposed segmentation model superpixel metric graph neural network (SMGNN) achieved state of the art segmentation performance while utilizing at most 10000$ \times $ less than the parameters compared to existing approaches. The subsequent segmentation-based cell type classification processes showed satisfactory results that such automatic recognizing algorithms are accurate and efficient to execeute in hematological laboratories. Our code is publicly available at https://github.com/jyh6681/SPXL-GNN.

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.

Novel non-neutral mitochondrial DNA mutations found in childhood acute lymphoblastic leukemia

Mitochondria produce adenosine triphosphate (ATP) for energy requirements via the mitochondrial oxidative phosphorylation (OXPHOS) system. One of the hallmarks of cancer is the energy shift toward glycolysis. Low OXPHOS activity and increased glycolysis are associated with aggressive types of cancer. Mitochondria have their own genome (mitochondrial DNA [mtDNA]) encoding for 13 essential subunits of the OXPHOS enzyme complexes. We studied mtDNA in childhood acute lymphoblastic leukemia (ALL) to detect potential pathogenic mutations in OXPHOS complexes. The whole mtDNA from blood and bone marrow samples at diagnosis and follow-up from 36 ALL patients were analyzed. Novel or previously described pathogenic mtDNA mutations were identified in 8 out of 36 patients. Six out of these 8 patients had died from ALL. Five out of 36 patients had an identified poor prognosis genetic marker, and 4 of these patients had mtDNA mutations. Missense or nonsense mtDNA mutations were detected in the genes encoding subunits of OXPHOS complexes, as follows: MT-ND1, MT-ND2, MT-ND4L and MT-ND6 of complex I; MT-CO3 of complex IV; and MT-ATP6 and MT-ATP8 of complex V. We discovered mtDNA mutations in childhood ALL supporting the hypothesis that non-neutral variants in mtDNA affecting the OXPHOS function may be related to leukemic clones.

A case of maternal-foetal chimerism identified during routine histocompatibility testing for hematopoietic stem cell transplantation

This report describes a case of maternal-foetal chimerism identified in a boy diagnosed with SCID, who underwent HLA testing in preparation for HSCT. The first analysis was carried out on DNA from peripheral blood and included HLA-A, HLA-B, HLA-DRB1 typing using PCR-SSO. The patient's HLA-B typing results were noninterpretable. All samples were re-typed for HLA-B using PCR-SSP, again resulting in noninterpretable typing of patient's HLA-B. In both cases, several weak positive probes/reactions interfered with the interpretation when using commercial software. Next round of HLA typing, using PCR-SSP and PCR-SSO methods, included the patient's bone marrow sample and HLA-C locus, but interpretation was again not possible. The PCR-STR analysis performed on both peripheral blood and bone marrow samples revealed seven STRs for which two maternal and one paternal allele were detected. Retrospective manual interpretation of HLA-B and HLA-C typing revealed that weak positive reactions were indeed owed to paternal HLA-B and HLA-C alleles and that the patient had both maternal and one paternal allele. Retyping of HLA-B and HLA-C loci and STR analysis on the patient's buccal cells sample revealed the expected one maternal/one paternal allele pattern. In summary, the combination of several different typing methods and manual interpretation were necessary to obtain the patient's HLA typing results.

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.

Transfusion-Associated Graft Versus Host Disease in the Immunocompetent Patient

Transfusion associated-graft versus host disease (TA-GVHD) is a rare complication of blood transfusion. It carries a very high mortality rate. Although the phenomenon has been well described in immunocompromised patients, this review focuses on the immunocompetent host. Cases of TA-GVHD continue to be reported following a variety of surgical procedures, especially cardiac procedures requiring cardiopulmonary bypass. Additional risk factors for TA-GVHD include blood component transfusion in populations with limited genetic diversity, the use of directed donations from family members, and the transfusion of fresh blood. As there is no effective treatment, the focus is on prevention.

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.

Absence of transfusion-associated microchimerism in pediatric and adult recipients of leukoreduced and gamma-irradiated blood components

BACKGROUND

Transfusion-associated microchimerism (TA-MC), the persistence of significant levels of donor white blood cells (WBCs) in blood recipients for prolonged periods, has been demonstrated after nonleukoreduced and leukoreduced transfusion to patients with severe traumatic injury. Development of TA-MC has not been rigorously studied in settings that do not involve massive trauma where the blood is leukoreduced and irradiated.

STUDY DESIGN AND METHODS

A cohort of 409 prospectively followed medical and surgical adult and pediatric female recipients of leukoreduced and mostly irradiated allogeneic red blood cell and platelet transfusions were evaluated to determine development of TA-MC. Four- and 8-weeks-posttransfusion samples were analyzed using quantitative real-time polymerase chain reaction for Y-chromosome sequences in WBC DNA, the marker for microchimeric cells in female blood recipients. Repeat testing was performed on Y-chromosome-positive samples to confirm microchimerism (MC), and subsequent posttransfusion samples were tested to investigate persistence of MC.

RESULTS

On initial testing, 40 of 207 (19%) adult and 44 of 202 (22%) pediatric female blood recipients demonstrated low-level MC. On repeat testing of these and additional specimens, 12 (3%) recipients demonstrated low-level transient MC, but none had persistent TA-MC similar to that seen in transfused trauma patients.

CONCLUSION

Persistence of MC was not demonstrated in adult and pediatric recipients of leukoreduced and mostly irradiated blood components. The risk of TA-MC appears to be dependent on the clinical setting and is rare other than in patients sustaining severe traumatic injury.

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.

Chimerism occurs in thyroid, lung, skin and lymph nodes of women with sons

Chimerism indicates the presence of cells from one individual in another. Pregnancy and blood transfusions are considered the main sources for chimerism. Chimeric cells have been attributed a pathogenic role in various autoimmune diseases. However, data on the occurrence of chimeric cells in normal organs are scarce. In order to gain insight into the possible pathogenic potential of chimeric cells in autoimmune disease, it is necessary to determine the prevalence of chimeric cells in organs not affected by autoimmune disease. In situ hybridization for the Y-chromosome was performed on organs obtained at autopsy of 51 women. We investigated 44 thyroid, 38 lung, 21 skin and 7 lymph node samples. All women had sons, and data from their blood transfusion histories were retrieved for at least 10 years before death. Slides were scored semi-quantitatively for chimerism as low (1-3 Y-chromosome-positive cells per slide), moderate (4-10 positive cells per slide) or high (more than 10 positive cells per slide). Y-chromosome-positive cells were found in 8 thyroid, 10 lung, 3 skin and 1 lymph node samples of 18 women. There was no association between the presence of chimeric cells and blood transfusion history. Most organs in which chimerism was present contained a small to moderate level. Thus, chimerism can occur in normal organs of women without autoimmune disease. Our results indicate that chimerism is not necessarily associated with disease.

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.

Immune modulation and microchimerism after unmodified versus leukoreduced allogeneic red blood cell transfusion in cancer patients: results of a randomized study

BACKGROUND

Transfusion of red blood cells (RBCs) has been associated with immunomodulatory effects. Persistence of donor cells in the recipient may be contributive.

STUDY DESIGN AND METHODS

A randomized single-center trial was conducted to compare microchimerism and immune responses in 35 patients undergoing cancer surgery and transfused perioperatively with either unmodified RBCs (UN-RBCs, n = 18) or leukoreduced RBCs (LR-RBCs, n = 17). Biologic parameters included microchimerism assessment peripheral blood mononuclear cell (PBMNC) phenotyping, cytokine production by stimulated PBMNCs, FoxP3 gene expression, and T-cell repertoire (TCR) analysis.

RESULTS

Microchimerism was documented in 8 of 18 patients after UN-RBC transfusion while absent after LR-RBC transfusion (0/17; p = 0.001). After UN-RBC transfusion, microchimerism was associated with increased interleukin (IL)-10 production (p = 0.02), reduced TCR alteration (p = 0.04), and reduced CD56+ cell counts (p = 0.02) when compared to recipients without evidence for microchimerism. FoxP3 gene expression did not differ significantly between both treatment groups nor with the presence or absence of microchimerism in the UN-RBC group. Finally, after an initial early decrease after surgery and transfusion, IL-12 production increased and more significantly so after UN-RBC transfusion versus LR-RBC transfusion (p = 0.05).

CONCLUSION

UN-RBC-induced microchimerism is associated with specific immunomodulatory effects in cancer patients who received transfusions during surgery.

Transfusion-related immunomodulation (TRIM): an update

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

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).

Kinetics and organ distribution of allogeneic natural killer lymphocytes transfused into patients suffering from renal cell carcinoma

The transfusion of natural killer (NK) lymphocytes into patients suffering from malignant diseases is an approach of current interest in the field of immunotherapy. Little is known about the organ distribution, survival, and clearance of donor immune effector cells in cellular therapy, and no reports exist on these important parameters considering NK cells in particular or any other type of allogeneic lymphocytes in humans. In the context of a clinical Phase I/II study we examined the distribution of transfused allogeneic NK cells in patients suffering from renal cell carcinoma. The NK cells were ex vivo cultivated and activated before transfusion. To assess the circulation of the transfused cells in the peripheral blood, we used a nested PCR technique to detect HLA DRB1 alleles of the NK cell donors. Post-transfusion, all patients showed evidence of circulating donor cells for up to 3 days. After 7 days, all donor cells were cleared from the blood to undetectable levels. To assess organ distribution, (111)In-labeled NK cells were injected and monitored by whole-body scintiscans. A distribution to the whole body, with preference for liver, spleen, and bone marrow, was observed after a short initial uptake in the lungs. No activity was observed in lymphatic nodes. A total of 2/4 evaluable metastases showed a clear accumulation of transfused NK cells. The half-life corrected activity in all body compartments remained almost constant over the 6-day observation period in concordance with the absence of any excretion of radioactivity. This may indicate an extended survival of the transfused cells, despite their foreign nature, in the host organism.

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.

Microchimerism in immune competent patients related to the leukocyte content of transfused red blood cell concentrates

BACKGROUND

Microchimerism may play a part in transfusion complications. The aim of this study was to examine whether establishment of post-transfusion microchimerism was related to leukocyte content.

METHODS

Twenty non-pregnant female patients, without known malignant or immunological diseases, mean age 68 years, receiving 2-4 units of red blood cell concentrates during elective surgery, were included. One or two of the units were from male donors. Ten patients received buffy-coat depleted red blood cell concentrates, leukocyte count 108-109 per unit, and 10 patients received red blood cells leukoreduced by prestorage leukocyte filtration, with a leukocyte count of <106 per unit. EDTA samples were collected in vacuum tubes before and after 1 week and 6 months after transfusion. The tubes were frozen and stored at -400 degrees C. Genomic DNA was isolated and PCR performed using four primer sets amplifying markers on the Y-chromosome.

RESULTS

Microchimerism was detected in a total of eight out of the 20 patients. In three patients microchimerism was detected only before transfusion. These patients had given birth to one or two boys each, and had no history of previous transfusion. Two patients receiving buffy-coat depleted red blood cell concentrates and two patients receiving leukoreduced red blood cell concentrates had detectable microchimerism 1 week after transfusion. The age of the transfused red blood cell concentrates was 6, 24, 8 and 7 days, respectively. One patient receiving leukoreduced red blood cell concentrates had detectable microchimerism after 6 months. The age of this concentrate was 22 days.

DISCUSSION

This study demonstrates that microchimerism after transfusion does not seem to be dose dependent, and can be induced even by a >3 week old leukoreduced red blood cell concentrate with a very low leukocyte content.

Blood Transfusion is Associated with Donor Leukocyte Microchimerism in Trauma Patients

INTRODUCTION

Blood transfusion can result in survival of donor leukocyte subpopulations in the recipient. Persistence of donor leukocytes in the transfusion recipient is termed microchimerism. Microchimerism likely reflects engraftment of the recipient with donor hematopoietic stem cells and is very uncommon with transfusion for elective surgery, sickle cell anemia, thalassemia, and HIV. We have found, however, that microchimerism may be more common in trauma patients.

OBJECTIVE

To determine how frequently transfusion after trauma is associated with microchimerism.

METHODS

We prospectively enrolled 45 trauma patients who were transfused > or =2 units of PRBCs. We sampled blood before hospital discharge and determined microchimerism by polymerase chain reaction (PCR) analysis of specimens using quantitative allele-specific HLA DR assays to detect non-recipient alleles. Data are expressed as median with interquartile range.

RESULTS

Patients had a median age of 38 (interquartile range 25, 58) years, ISS of 19 (13, 29), and mortality of 7%. Seventy-eight percent were men, and 84% had blunt trauma. Patients received a median of 6 (4, 16) (range 2, 87) units of PRBCs. Of the 45 patients, 24 (53%) had evidence of microchimerism. Compared with patients without evidence of microchimerism, these patients had no difference in mean age, gender, ISS, units of PRBCs transfused, time from transfusion to blood sampling, or proportion that underwent splenectomy. Twenty-one of the 24 patients with microchimerism had only 1 or 2 non-recipient DR alleles identified by PCR.

CONCLUSIONS

Transfusion after trauma is associated with over half of recipients having evidence of microchimerism. Age, sex, ISS, and splenectomy of the recipient and the number of transfused units did not correlate with microchimerism. Because the median time from transfusion to sampling for PCR analysis was not longer in the group without microchimerism, it is unlikely microchimerism is due merely to failure of the recipient to clear transfused donor leukocytes.

Genotyping patients with recent blood transfusions

BACKGROUND

Many studies have used polymerase chain reaction amplification (PCR) to genotype for common polymorphisms in intensive-care units (ICUs) where blood transfusions are common. Evidence that donor leukocytes in transfused blood can be detected by PCR of the recipient blood suggests that this minor population of donor white cells (microchimerism) can interfere with genotyping of allelic polymorphisms in critically ill transfused patients. To investigate this possibility, we assayed DNA extracted from the blood and buccal cells of ICU patients for 2 common polymorphisms in the TNF-beta gene and the surfactant protein-B (SP-B) gene.

METHODS

Study subjects were ICU patients from the Massachusetts General Hospital (Boston, MA) enrolled into a study on the molecular epidemiology of acute respiratory distress syndrome between January 1999 and October 2000. Blood and buccal cells were collected and DNA was extracted from 145 patients. Genotyping was performed by enzyme digestion and pyrosequencing.

RESULTS

The Kappa statistics comparing the genotype results from blood and buccal cells were 0.98 (95% confidence interval [CI] = 0.94-1.01) for TNFB and 0.95 (CI = 0.87-1.02) for SP-B. When the analysis was restricted only to the 107 patients who were transfused, the Kappa statistic remained high at 0.97 (CI = 0.93-1.01) for TNFB and 0.93 (CI = 0.84-1.03) for SP-B.

CONCLUSION

We conclude that microchimerism from allogeneic blood transfusion is unlikely to have major effects on the genotype results of common polymorphisms in large molecular epidemiology studies conducted in the critical care setting if DNA is collected within a day after transfusions.

Post-transplant Kaposi sarcoma originates from the seeding of donor-derived progenitors

Kaposi sarcoma (KS) is a vascular tumor that can develop in recipients of solid tissue transplants as a result of either primary infection or reactivation of a gammaherpesvirus, the KS- associated herpesvirus, also known as human herpesvirus-8 (HHV-8). We studied whether HHV-8 and the elusive KS progenitor cells could be transmitted from the donor through the grafts. We used a variety of molecular, cytogenetic, immunohistochemical and immunofluorescence methods to show that the HHV-8-infected neoplastic cells in post-transplant KS from five of eight renal transplant patients harbored either genetic or antigenic markers of their matched donors. These data suggest the use of donor-derived HHV-8-specific T cells for the control of post-transplant KS.

Meta-analysis of randomized controlled trials comparing the risk of postoperative infection between recipients of allogeneic and autologous blood transfusion

BACKGROUND AND OBJECTIVES

A previous meta-analysis of randomized controlled trials (RCTs), comparing the risk of postoperative infection between recipients of allogeneic blood or autologous blood obtained by preoperative autologous blood donation (PABD), did not detect an immunomodulatory (TRIM) effect of allogeneic blood transfusion (ABT). If such a TRIM effect was mediated by white blood cell (WBC)-derived soluble mediators accumulating during storage, however, stored autologous blood obtained by PABD would not prevent the TRIM effect, whereas unstored autologous blood obtained by acute normovolemic haemodilution (ANH), intraoperative blood recovery (IBR), or postoperative blood recovery (PBR), would abrogate the TRIM effect.

MATERIALS AND METHODS

RCTs reported through January 2002 were retrieved, and five studies met the criteria for meta-analysis. Summary odds ratios (ORs) of postoperative infection in recipients of allogeneic vs. autologous blood were calculated across studies.

RESULTS

No difference in the risk of infection between the comparison arms was detected across all five RCTs [summary OR = 1.22, 95% confidence interval (95% CI): 0.75-1.98], or when the results of studies using PABD or ANH/IBR/PBR were integrated separately (summary OR = 1.35; 95% CI: 0.45-4.08; and summary OR = 1.49; 95% CI: 0.69-3.22, respectively).

CONCLUSIONS

The finding of no TRIM effect of ABT across RCTs using ANH/IBR/PBR to obtain autologous blood does not support the hypothesis that a TRIM effect of ABT is mediated by WBC-derived soluble mediators accumulating during storage. The null finding of the overall meta-analysis also does not support a TRIM effect of ABT mediated by other blood constituents.