Microchimerism decades after transfusion among combat-injured US veterans from the Vietnam, Korean, and World War II conflicts

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.

Hematopoietic stem and progenitor cells outside the bone marrow: where, when, and why

Bone marrow (BM) is the primary site of adult blood production, hosting the majority of all hematopoietic stem and progenitor cells (HSPCs). Rare HSPCs are also found outside of the BM at steady state. In times of large hematopoietic demand or BM failure, substantial production of mature blood cells from HSPCs can occur in a number of tissues, in a process termed extramedullary hematopoiesis (EMH). Over the past decades, our understanding of BM hematopoiesis has advanced drastically. In contrast there has been very little focus on the study of extramedullary HSPC pools and their contributions to blood production. Here we summarize what is currently known about extramedullary HSPCs and EMH in mice and humans. We describe the evidence of existing extramedullary HSPC pools at steady state, then discuss their role in the hematopoietic stress response. We highlight that although EMH in humans is much less pronounced and likely physiologically distinct to that in mice, it can be informative about premalignant and malignant changes. Finally, we reflect on the open questions in the field and on whether a better understanding of EMH, particularly in humans, may have relevant clinical implications for hematological and nonhematological disorders.

Implications of perioperative allogeneic red blood cell transfusion on the immune-inflammatory response

Background

The allogeneic transfusion-related immunomodulation (TRIM) may be responsible for an increase in survival of renal transplants but in contrast it could increase the rate of bacterial infections or the recurrence rate of tumors post-operatively.

Objective

This review focuses in the implications of perioperative allogeneic transfusions on the immune-inflammatory response of surgical transfused patients.

Results

ABTs modify immune functions in recipients including decrease of the number of lymphocytes; decrease the CD4 cells; decrease the CD4/CD8 T-cell ratio; decrease NK cells; and decrease the lymphocyte response to mitogens. TRIM effects may be mediated by allogeneic white cells present in blood products; soluble peptides present in transfused plasma; and/or biologic mediators released into the supernatant of blood units. A recent systematic review and meta-analysis including 36 clinical observational studies (n = 174,036) concluded that perioperative ABTs not only decreased overall survival and reduced colorectal cancer-specific survival. Furthermore ABTs increased the rate of infectious, cardiac, pulmonary and anastomotic complications in colorectal cancer patients undergoing surgery.

Conclusions

It has been demonstrated by laboratory tests that TRIM is associated with transfusion recipient immune alterations but its influence in colorectal cancer recurrence after resection remains controversial though may exist. Surgical techniques reducing intraoperative blood loss have limited the number of ABTs perioperatively, however increase in mortality continues to be reported in literature after ABT in colorectal cancer surgery. Poor survival associated to TRIM in colorectal cancer might be due to higher number of allogeneic transfused units and/or prolonged length of blood storage.

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.

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.

Monoclonal B-cell lymphocytosis in healthy blood donors: an unexpectedly common finding

Circulating monoclonal B cells may be detected in healthy adults, a condition called monoclonal B-cell lymphocytosis (MBL). MBL has also been identified in donated blood, but no systematic study of blood donors has been reported. Using sensitive and specific laboratory methods, we detected MBL in 149 (7.1%; 95% confidence interval, 6.0% to 8.3%) of 2098 unique donors ages 45 years or older in a Midwestern US regional blood center between 2010 and 2011. Most of the 149 donors had low-count MBL, including 99 chronic lymphocytic leukemia-like (66.4%), 22 atypical (14.8%), and 19 CD5(-) (12.8%) immunophenotypes. However, 5 donors (3.4%) had B-cell clonal counts above 500 cells per µL, including 3 with 1693 to 2887 cells per µL; the clone accounted for nearly all their circulating B cells. Four donors (2.7%) had 2 distinct MBL clones. Of 51 MBL samples in which immunoglobulin heavy chain (IGH)V-D-J genotypes could be determined, 71% and 29% used IGHV3- and IGHV4-family genes, respectively. Sequencing revealed 82% with somatic hypermutation, whereas 18% had >98% germ-line identity, including 5 with entirely germ-line sequences. In conclusion, MBL prevalence is much higher in blood donors than previously reported, and although uncommon, the presence of high-count MBL warrants further investigations to define the biological fate of the transfused cells in recipients.

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 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.

The US military experience with fresh whole blood during the conflicts in Iraq and Afghanistan

Since its introduction in the early part of the last century, fresh whole blood (FWB) has been used by the US military as a battlefield expedient resuscitation method, even after the development of component therapy in the 1960s. In the recent conflicts in Iraq and Afghanistan, FWB was used once more, often collected in the setting of a walking blood bank (WBB). Considerable research and opinion from military circles has cited these experiences and sparked renewed interest in FWB as an effective resuscitation tool in the setting of trauma. Despite efforts by the US military to improve the effectiveness and safety of FWB through a series of widely published guidelines, transfusion transmitted infections (TTI) remain a vexing challenge. These experiences in Iraq and Afghanistan will help inform a larger discussion regarding the reintroduction of FWB in civilian trauma resuscitation.

The FIB-PPH trial: fibrinogen concentrate as initial treatment for postpartum haemorrhage: study protocol for a randomised controlled trial

BACKGROUND

Postpartum haemorrhage (PPH) remains a leading cause of maternal mortality worldwide. In Denmark 2% of parturients receive blood transfusion. During the course of bleeding fibrinogen (coagulation factor I) may be depleted and fall to critically low levels, impairing haemostasis and thus worsening the ongoing bleeding. A plasma level of fibrinogen below 2 g/L in the early phase of postpartum haemorrhage is associated with subsequent development of severe haemorrhage. Use of fibrinogen concentrate allows high-dose substitution without the need for blood type crossmatch. So far no publications of randomised controlled trials involving acutely bleeding patients in the obstetrical setting have been published. This trial aims to investigate if early treatment with fibrinogen concentrate reduces the need for blood transfusion in women suffering severe PPH.

METHODS/DESIGN

In this randomised placebo-controlled double-blind multicentre trial, parturients with primary PPH are eligible following vaginal delivery in case of: manual removal of placenta (blood loss ≥ 500 ml) or manual exploration of the uterus after the birth of placenta (blood loss ≥ 1000 ml). Caesarean sections are also eligible in case of perioperative blood loss ≥ 1000 ml. The exclusion criteria are known inherited haemostatic deficiencies, prepartum treatment with antithrombotics, pre-pregnancy weight <45 kg or refusal to receive blood transfusion. Following informed consent, patients are randomly allocated to either early treatment with 2 g fibrinogen concentrate or 100 ml isotonic saline (placebo). Haemostatic monitoring with standard laboratory coagulation tests and thromboelastography (TEG, functional fibrinogen and Rapid TEG) is performed during the initial 24 hours.Primary outcome is the need for blood transfusion. To investigate a 33% reduction in the need for blood transfusion, a total of 245 patients will be included. Four university-affiliated public tertiary care hospitals will include patients during a two-year period. Adverse events including thrombosis are assessed in accordance with International Conference on Harmonisation (ICH) good clinical practice (GCP).

DISCUSSION

A widespread belief in the benefits of early fibrinogen substitution in cases of PPH has led to increased off-label use. The FIB-PPH trial is investigator-initiated and aims to provide an evidence-based platform for the recommendations of the early use of fibrinogen concentrate in PPH.

TRIAL REGISTRATION

ClincialTrials.gov NCT01359878.

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.

Comparison of platelet transfusion as fresh whole blood versus apheresis platelets for massively transfused combat trauma patients (CME)

BACKGROUND

At major combat hospitals, the military is able to provide blood products to include apheresis platelets (aPLT), but also has extensive experience using fresh whole blood (FWB). In massively transfused trauma patients, we compared outcomes of patients receiving FWB to those receiving aPLT.

STUDY DESIGN AND METHODS

This study was a retrospective review of casualties at the military hospital in Baghdad, Iraq, between January 2004 and December 2006. Patients requiring massive transfusion (≥10 units in 24 hr) were divided into two groups: those receiving FWB (n = 85) or aPLT (n = 284) during their resuscitation. Admission characteristics, resuscitation, and survival were compared between groups. Multivariate regression analyses were performed comparing survival of patients at 24 hours and at 30 days. Secondary outcomes including adverse events and causes of death were analyzed.

RESULTS

Unadjusted survival between groups receiving aPLT and FWB was similar at 24 hours (84% vs. 81%, respectively; p = 0.52) and at 30 days (60% versus 57%, respectively; p = 0.72). Multivariate regression failed to identify differences in survival between patients receiving PLT transfusions either as FWB or as aPLT at 24 hours or at 30 days.

CONCLUSIONS

Survival for massively transfused trauma patients receiving FWB appears to be similar to patients resuscitated with aPLT. Prospective trials will be necessary before consideration of FWB in the routine management of civilian trauma. However, in austere environments where standard blood products are unavailable, FWB is a feasible alternative.