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

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.

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.

Involvement of blood mononuclear cells in the infertility, age-associated diseases and cancer treatment

Blood mononuclear cells consist of T cells and monocyte derived cells. Beside immunity, the blood mononuclear cells belong to the complex tissue control system (TCS), where they exhibit morphostatic function by stimulating proliferation of tissue stem cells followed by cellular differentiation, that is stopped after attaining the proper functional stage, which differs among various tissue types. Therefore, the term immune and morphostatic system (IMS) should be implied. The TCS-mediated morphostasis also consists of vascular pericytes controlled by autonomic innervation, which is regulating the quantity of distinct tissues in vivo. Lack of proper differentiation of tissue cells by TCS causes either tissue underdevelopment, e.g., muscular dystrophy, or degenerative functional failures, e.g., type 1 diabetes and age-associated diseases. With the gradual IMS regression after 35 years of age the gonadal infertility develops, followed by a growing incidence of age-associated diseases and cancers. Without restoring an altered TCS function in a degenerative disease, the implantation of tissue-specific stem cells alone by regenerative medicine can not be successful. Transfused young blood could temporarily restore fertility to enable parenthood. The young blood could also temporarily alleviate aging diseases, and this can be extended by substances inducing IMS regeneration, like the honey bee propolis. The local and/or systemic use of honey bee propolis stopped hair and teeth loss, regressed varicose veins, improved altered hearing, and lowered high blood pressure and sugar levels. Complete regression of stage IV ovarian cancer with liver metastases after a simple elaborated immunotherapy is also reported.

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.

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.

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.

Chimerism in women with end stage renal diseases: Who's who?

Many sources of foreign or semi foreign cells, known as microchimerism (Mc), can be found in healthy individuals. We have recently shown in women with end stage renal disease (ESRD) that Mc frequencies and levels are exacerbated prior to kidney transplantation. Is Mc arising from pregnancy a protective factor for renal diseases explaining lower incidence in women? Is Mc helpful in slowing down disease progression? However, natural Mc is not the only actor as post blood transfusion Mc is also found at high levels in women with ESRD. The difficulty is therefore to distinguish the different types of Mc and this is made even more complicated when the recipient receives a potentially chimeric organ. What part does each source of chimerism play in disease and transplant fate, and can one decipher each role knowing that one chimerism may hide another?

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.

Naturally acquired tolerance and sensitization to minor histocompatibility antigens in healthy family members

Bidirectional cell transfer during pregnancy frequently leads to postpartum persistence of allogeneic cells and alloimmune responses in both the mother and in her offspring. The life-long consequences of naturally acquired alloimmune reactivity are probably of importance for the outcome of allogeneic stem cell transplantation. We investigated the presence of CD8(pos) minor histocompatibility (H) antigen-specific cytotoxic T lymphocytes (T(CTL)) and CD8(pos) minor H antigen-specific T regulator cells (T(REG)) in peripheral blood cells obtained from 17 minor H antigen-disparate mother-offspring pairs. Absence of minor H antigen-specific T(REG), as marked by the feasibility to expand T(CTL) from isolated tetramer(pos) populations, was observed in 6 mothers and 1 son. The presence of minor H alloantigen-specific T(REG) was observed in 4 mothers and 5 sons. These T(REG) were detected within isolated tetramer(dim) staining fractions and functioned in a CTLA-4-dependent fashion. Our study indicates that both T(CTL) and T(REG) mediated alloimmunity against minor H antigens may be present in healthy female and male hematopoietic stem cell donors, potentially influencing graft-versus-host reactivity in different ways.

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.

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-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).

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.

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.