Comparing alloimmunization in preterm infants after transfusion of fresh unmodified versus stored leukocyte-reduced red blood cells

Transfusion-Related Alloimmunization to Red Blood Cell Antigens in Japanese Pediatric Recipients

Red blood cell (RBC) transfusion to neonates is thought to rarely provoke an immune response. Neonatal testing guidelines suggest that antibody screening is not necessary when the mother has no antibodies. Alternatively, maternal blood samples can be used for antibody screening and cross-matching. However, the guidelines are based on small-scale studies of white-dominant populations. Furthermore, transfusion-related alloimmunization is less well established among children and adolescents as a whole among Japanese and East Asians. To elucidate the incidence of transfusion-related alloimmunization among neonates, children, and adolescents, and whether current guidelines are applicable to Japanese populations, a nationwide retrospective multicenter cohort survey was conducted in 50 tertiary-care hospitals in Japan. Between 2001 and 2015 inclusive, recipients of at least 1 allogeneic RBC transfusion were categorized into groups A-F according to their age at the time of transfusion: (A) neonates <1 month; (B) infants 1 to <12 months; (C) children 1 to <5 years; (D) prepubescents 5 to <10 years; (E) young pubescents 10 to <15 years; and (F) adolescents/young adults 15 to <20 years. Excluding maternally derived antibodies and naturally occurring, cold-reactive, and/or nonspecific antibodies, 69 (0.61%) of 11350 RBC recipients <20 years old formed at least 1 clinically significant alloantibody. The alloimmunization rate differed significantly (P < .0001) by age: none (0%) of 3407 in group A; 11 (0.46%) of 2410 in group B; 18 (0.76%) of 2361 in group C; 9 (0.80%) of 1119 in group D; 12 (1.15%) of 1043 in group E; and 19 (1.88%) of 1010 in group F. Clearly different incidences of alloimmunization emerged in group A compared to B, C, D, E, or F, as confirmed by logistic regression analysis adjusted by numbers of donor exposure. Alloimmunization did not occur from RBC transfusions within the first month of life and rarely occurred (0.46%-0.80%) after transfusion within the first decade of life. Alloimmunization occurred in 1.15%-1.88% of young pubescents and adolescents/young adults. These findings support the use of guidelines developed in Europe and the United States for East Asian pediatric recipients.

Are single-donor red blood cell transfusions still relevant for preterm infants?

OBJECTIVE

To explore the worth of a single-donor program for preterm infants through the recipient profile and the impact on donor exposure, red blood cell (RBC) pack waste, storage duration, and transfusion performance.

STUDY DESIGN

Patients and transfusion characteristics were collected for 3 years (2015-2017) in preterm infants according to single-donor program prescription in a unit not practicing placental transfusion or erythropoietin supplementation.

RESULTS

Among 1048 eligible preterm infants, 161 met the inclusion criteria, and 51 received single-donor packs. Our single-donor program induced a donor number reduction (34% less than the transfusion number) and an extension of storage duration (median: 9 versus 7 days, p < 0.0001) without altering the transfusion performance. However, 41% of small packs were not used.

CONCLUSION

A single-donor program partially reduced donor exposure but led to drastic RBC pack waste. Optimization of transfusion alternatives may increase this phenomenon, calling into question the rationale of this practice.

[Blood transfusion in neonatology: Study of practical aspects in 2016 in France, excluding acute bleeding or surgical care]

BACKGROUND

Blood transfusion is common in neonatology, especially in preterm or low birth weight infants. Recommendations were proposed by the French National Authority of Health (HAS) in 2014 and 2015 for red blood cells and platelet transfusion respectively, but an heterogeneity of practical attitudes persist. The objective of this survey is to evaluate transfusion practices in neonatal intensive care units.

METHODS

Investigation of practice of neonatal transfusion was organized among 68 neonatal intensive care unit (level 3) between September 2016 and May 2017, by mailing survey focused on systematic training of nurses, patient identification, immunohematology, information and technical aspects of blood components administration.

RESULTS

Twenty-three neonatal intensive care units among the 68s answered the questionnaire. One thousand five hundred sixty seven neonates were transfused and 3382 blood products were administered. The results highlight a consensual attitude concerning the procedures of patient identification, immunohematology tests and blood products administration. However, heterogeneity remains concerning information of the parents or the person with parental authority, immediate and delayed follow-up and devices used for the transfusion. However HAS guidelines (2014 and 2015) appear to be well applied by clinicians for blood products, specifications and calcul of transfused volume based on gestational age and weight.

Adverse effects of red blood cell transfusions in neonates: a systematic review and meta-analysis

BACKGROUND

Controversy exists regarding the contribution of blood transfusions to a range of adverse clinical outcomes in neonates. The aim of our systematic review was to identify the broader literature on harmful effects and associations potentially attributable to red blood cell (RBC) transfusions.

STUDY DESIGN AND METHODS

A comprehensive search of MEDLINE (PubMed) and EMBASE was undertaken. Eligible studies included both randomized controlled trials (RCTs) and nonrandomized studies examining the effects of small volume (10-20 mL/kg) RBC transfusions on neonates. Primary outcomes of interest were mortality, chronic lung disease, retinopathy of prematurity, necrotizing enterocolitis, and intraventricular hemorrhage. Two independent authors conducted a review of abstracts and then of full-text article reviews as well as data extraction and quality assessments.

RESULTS

Sixty-one studies were eligible for inclusion, including 16 (26%) randomized studies. The majority of studies were nonrandomized (n = 45; 74%), which included 32 observational studies with and 13 studies without a comparator group. There was no evidence that rates of mortality differed between restrictive and liberal strategies for transfusion (eight RCTs: risk ratio, 1.24; 95% confidence interval, 0.89-1.672, heterogeneity = 0%) or for necrotizing enterocolitis (five RCTs: risk ratio, 1.45; 95% confidence interval, 0.91-2.33; heterogeneity = 0%). A liberal strategy also was not superior to restrictive transfusion practice in the pooled randomized studies for rates of retinopathy of prematurity, chronic lung disease, or intraventricular hemorrhage.

CONCLUSIONS

Statistically significant differences in a range of harmful outcomes between neonates exposed to restrictive and liberal RBC transfusion practice were not found. However, the risks of bias identified in many studies and the lack of consistent reporting and definitions of events limits our conclusions.

Prolonged storage of packed red blood cells for blood transfusion

BACKGROUND

A blood transfusion is an acute intervention, used to address life- and health-threatening conditions on a short-term basis. Packed red blood cells are most often used for blood transfusion. Sometimes blood is transfused after prolonged storage but there is continuing debate as to whether transfusion of 'older' blood is as beneficial as transfusion of 'fresher' blood.

OBJECTIVES

To assess the clinical benefits and harms of prolonged storage of packed red blood cells, in comparison with fresh, on recipients of blood transfusion.

SEARCH METHODS

We ran the search on 1st May 2014. We searched the Cochrane Injuries Group Specialized Register, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE (OvidSP), Embase (OvidSP), CINAHL (EBSCO Host) and two other databases. We also searched clinical trials registers and screened reference lists of the retrieved publications and reviews. We updated this search in June 2015 but these results have not yet been incorporated.

SELECTION CRITERIA

Randomised clinical trials including participants assessed as requiring red blood cell transfusion were eligible for inclusion. Prolonged storage was defined as red blood cells stored for ≥ 21 days in a blood bank. We did not apply limits regarding the duration of follow-up, or country where the study took place. We excluded trials where patients received a combination of short- and long-stored blood products, and also trials without a clear definition of prolonged storage.

DATA COLLECTION AND ANALYSIS

We independently performed study selection, risk of bias assessment and data extraction by at least two review authors. The major outcomes were death from any cause, transfusion-related acute lung injury, and adverse events. We estimated relative risk for dichotomous outcomes. We measured statistical heterogeneity using I(2). We used a random-effects model to synthesise the findings.

MAIN RESULTS

We identified three randomised clinical trials, involving a total of 120 participants, comparing packed red blood cells with ≥ 21 days storage ('prolonged' or 'older') versus packed red blood cells with < 21 days storage ('fresh'). We pooled data to assess the effect of prolonged storage on death from any cause. The confidence in the results from these trials was very low, due to the bias in their design and their limited sample sizes.The estimated effect of packed red blood cells with ≥ 21 days storage versus packed red blood cells with < 21 days storage for the outcome death from any cause was imprecise (5/45 [11.11%] versus 2/46 [4.34%]; RR 2.36; 95% CI 0.65 to 8.52; I(2): 0%, P = 0.26, very low quality of evidence). Trial sequential analysis, with only two trials, shows that we do not yet have convincing evidence that older packed red blood cells induce a 20% relative risk reduction of death from any cause compared with fresher packed red blood cells. No trial included other outcomes of interest specified in this review, namely transfusion-related acute lung injury, postoperative infections, and adverse events. The safety profile is unknown.

AUTHORS' CONCLUSIONS

Recognising the limitations of the review, relating to the size and nature of the included trials, this Cochrane Review provides no evidence to support or reject the use of packed red blood cells for blood transfusion which have been stored for ≥ 21 days ('prolonged' or 'older') compared with those stored for < 21 days ('fresh'). These results are based on three small single centre trials with high risks of bias. There is insufficient evidence to determine the effects of fresh or older packed red blood cells for blood transfusion. Therefore, we urge readers to interpret the trial results with caution. The results from four large ongoing trials will help to inform future updates of this review.

Factors Influencing RBC Alloimmunization: Lessons Learned from Murine Models

Red blood cell (RBC) alloimmunization may occur following transfusion or pregnancy/delivery. Although observational human studies have described the immunogenicity of RBC antigens and the clinical significance of RBC alloantibodies, studies of factors influencing RBC alloimmunization in humans are inherently limited by the large number of independent variables involved. This manuscript reviews data generated in murine models that utilize transgenic donor mice, which express RBC-specific model or authentic human blood group antigens. Transfusion of RBCs from such donors into nontransgenic but otherwise genetically identical recipient mice allows for the investigation of individual donor or recipient-specific variables that may impact RBC alloimmunization. Potential donor-related variables include methods of blood product collection, processing and storage, donor-specific characteristics, RBC antigen-specific factors, and others. Potential recipient-related variables include genetic factors (MHC/HLA type and polymorphisms of immunoregulatory genes), immune activation status, phenotype of regulatory immune cell subsets, immune cell functional characteristics, prior antigen exposures, and others. Although murine models are not perfect surrogates for human biology, these models generate phenomenological and mechanistic hypotheses of RBC alloimmunization and lay the groundwork for follow-up human studies. Long-term goals include improving transfusion safety and minimizing the morbidity/mortality associated with RBC alloimmunization.

Responder individuality in red blood cell alloimmunization

Many different factors influence the propensity of transfusion recipients and pregnant women to form red blood cell alloantibodies (RBCA). RBCA may cause hemolytic transfusion reactions, hemolytic disease of the fetus and newborn and may be a complication in transplantation medicine. Antigenic differences between responder and foreign erythrocytes may lead to such an immune answer, in part with suspected specific HLA class II associations. Biochemical and conformational characteristics of red blood cell (RBC) antigens, their dose (number of transfusions and pregnancies, absolute number of antigens per RBC) and the mode of exposure impact on RBCA rates. In addition, individual circumstances determine the risk to form RBCA. Responder individuality in terms of age, sex, severity of underlying disease, disease- or therapy-induced immunosuppression and inflammation are discussed with respect to influencing RBC alloimmunization. For particular high-risk patients, extended phenotype matching of transfusion and recipient efficiently decreases RBCA induction and associated clinical risks.

Red blood cell alloimmunization mitigation strategies

Hemolytic transfusion reactions due to red blood cell (RBC) alloantibodies are a leading cause of transfusion-associated death. In addition to reported deaths, RBC alloantibodies also cause significant morbidity in the form of delayed hemolytic transfusion reactions. These alloantibodies may also cause morbidity in the form of anemia, with compatible RBC units at times being unable to be located for highly alloimmunized patients, or in the form of hemolytic disease of the newborn. Thus, preventing RBC alloantibodies from developing in the first place, or mitigating the dangers of existing RBC alloantibodies, would decrease transfusion-associated morbidity and mortality. A number of human studies have evaluated the impact on RBC alloimmunization rates of providing partially phenotypically or genotypically matched RBCs for transfusion, and a number of animal studies have evaluated the impact of single variables on RBC alloimmunization. The goal of this review is to take a comprehensive look at existing human and animal data on RBC alloimmunization, focusing on strategies that may mitigate this serious hazard of transfusion. Potential factors that impact initial RBC alloimmunization, on both the donor and recipient sides, will be discussed. These factors include, but are not limited to, exposure to the antigen and an ability of the recipient's immune system to present that antigen. Beyond these basic factors, coexisting "danger signals," which may come from the donor unit itself or which may be present in the recipient, also likely play a role in determining which transfusion recipients may become alloimmunized after RBC antigen exposure. In addition, to better understanding factors that influence the development of RBC alloantibodies, this review will also briefly discuss strategies to decrease the dangers of existing RBC alloantibodies.

The safety and efficacy of red cell transfusions in neonates: a systematic review of randomized controlled trials

Premature neonates commonly receive red blood cell (RBC) transfusions. This study systematically identified and appraised randomized controlled trials (RCTs) where the intervention was 'transfusion of red blood cells' from searches of multiple databases. Primary review outcomes were mortality, neurodevelopmental and respiratory endpoints. Two reviewers extracted data and assigned overall quality. Twenty-seven RCTs were identified and grouped into four predefined categories: trials comparing RBC transfusion versus no transfusion/placebo (n = 3); different thresholds for transfusion (n = 6); differing doses or administration schedule (n = 4), or different types or products of RBC (n = 14). In the threshold group of trials, enrolling 679 neonates, no significant differences in mortality (relative risk 1·22, 95% confidence interval 0·84-1·75) or chronic lung disease were found. Only two trials assessed neurodevelopment outcomes, both within the threshold group, but with differing results. The largest subgroup of RCTs by number evaluated different media for storage of red cells (n = 7), enrolling 221 neonates. The methodological quality of many RCTs was poor. The design of future RCTs can be informed by the lessons from this review. Many trials failed to report on outcomes that would be considered of primary importance to clinicians. Consistent reporting of adverse events is required, and endpoints need to include neurodevelopmental outcomes.

Red-blood-cell alloimmunization and number of red-blood-cell transfusions

BACKGROUND

Patients receiving red-blood-cells may form antibodies against the alloantigens expressed by red-blood-cells, with the risk of serious morbidity and the need for extensive phenotype-matching in subsequent transfusions. The incidence of alloimmunization is considered variable for specific patient groups and for first time antibody formation. We therefore studied the cumulative incidence of the first formed alloantibody as a function of red-blood-cells exposure.

METHODS

We performed a new-user cohort among all previously non-transfused non-alloimmunized patients that received non-extended matched (ABO and RhD) red-blood-cells transfusions from January 2005 to December 2009 in our university medical centre. Alloimmunization incidences were estimated by Kaplan-Meier survival-analysis.

RESULTS

A total of 3002 previously non-transfused patients received 31103 red-blood-cell units. A first time alloantibody forming event was experienced by 54 (1·8%) patients. The cumulative incidence of alloimmunization was 1·0% at 5 units, 2·4% at 10 units, 3·4% at 20 units and 6·5% at 40 units of red-blood-cells transfused.

CONCLUSION

The risk to develop a first red-blood-cells alloantibody increases up to the 40th transfusion and is similar for men and women. More data are needed to examine the risk after 40th transfusion.

Rapid clearance of transfused murine red blood cells is associated with recipient cytokine storm and enhanced alloimmunogenicity

BACKGROUND

Fourteen-day stored red blood cells (RBCs) containing an RBC-specific transgenic antigen (HOD) induce a recipient proinflammatory cytokine storm and are significantly more immunogenic compared to fresh RBCs. Given that recipient mice clear transfused stored RBCs more rapidly than fresh RBCs, we hypothesized that rapid RBC clearance was associated with adverse transfusion outcomes.

STUDY DESIGN AND METHODS

HOD RBCs were treated by two distinct methods known to lead to rapid posttransfusion RBC clearance: phenylhydrazine or heat. HOD antigen expression was analyzed on the treated cells before transfusion, and RBC recovery, recipient cytokine response, and recipient anti-HOD alloimmunization response were measured after transfusion.

RESULTS

Phenylhydrazine and heat treatment each led to near complete RBC clearance in recipients by 24 hours posttransfusion, without significantly altering HOD antigen expression on the transfused RBCs. Recipients of phenylhydrazine- or heat-treated RBCs had elevated circulating levels of keratinocyte-derived chemokine/CXCL-1, monocyte chemoattractant protein-1, and interleukin-6 after transfusion. Furthermore, phenylhydrazine- or heat-treated RBCs were significantly more immunogenic than control RBCs, with a mean 25.1- and 10.3-fold enhancement, respectively, of anti-HOD alloimmunization magnitude by flow cytometric crossmatch.

CONCLUSIONS

Three separate insults to RBCs (storage, phenylhydrazine, or heat treatment) result in rapid posttransfusion clearance, with a recipient proinflammatory cytokine storm and enhanced alloimmunogenicity. These data are consistent with the hypothesis that rapid clearance of RBCs is causally involved in these outcomes and suggest that human donor RBCs with favorable posttransfusion clearance profiles may be less immunogenic.

Detection and clinical evaluation of antineutrophil antibodies in neonates who had a blood transfusion or exchange transfusion

BACKGROUND

The aim of this study was to detect and investigate the clinical effects of antineutrophil antibodies in neonates who had received a blood transfusion or exchange transfusion.

METHODS

Venous blood samples were drawn from 34 neonates at pretransfusion (sample 0), immediately after transfusion (sample 1), 2-3 weeks (sample 2) and 8-12 weeks (sample 3) after transfusion. Ten healthy neonates were in the control group. Antineutrophil antibodies were detected using flow cytometric assay.

RESULTS

Antineutrophil antibody was detected in the sera of 20 (58.8%) neonates in the study group. Of these 20 neonates, nine had antineutrophil antibodies in serum samples 0, 1 and 2, which were probably due to the passive transfer of maternal antibodies. Nine neonates had antineutrophil antibodies in serum samples 1 and 2, which were probably due to neutrophil antibodies being present in the donor's blood. In two neonates, antineutrophil antibodies were not detected in samples 0 and 1, but appeared in sample 2, which were probably actively produced by the neonates. All of the antineutrophil antibodies disappeared in the serum samples, except in one neonate. Only one preterm newborn developed neutropenia, which resolved spontaneously in a week. The presence of antineutrophil antibody in transfused neonates was significantly higher than in non-transfused neonates.

CONCLUSIONS

The presence of neutrophil specific antibodies in transfused neonates is not rare and antineutrophil antibodies may be found more often in transfused neonates compared to non-transfused neonates. The clinical significance of those antibodies needs to be assessed since they are transient and their clinical effects are not evident.

Alloimmunization to red blood cell antigens after universal leucodepletion. A regional multicentre retrospective study

Leucodepletion has been shown to reduce human leucocyte antigen immunization, but studies on the effect of leucodepletion on red cell alloimmunization reported discordant results. We conducted a retrospective multicentre study to determine whether prestorage filter leucodepletion alters the development of clinically significant red blood cell alloimmunization against the Rhesus, Kell, Duffy, Kidd and MSs blood group systems. Two periods were investigated, 2 years before and 2 years after universal leucodepletion. Comparisons were made between the transfused patient cohorts. To control for changes not related to leucoreduction, we compared antibody incidence with antibody prevalence in the two study periods. Newly detected antibodies (n = 4770) were found in 4115 patients from 19 participating hospitals. Of these, 857 antibodies in 659 patients were because of transfusions given in the study periods. The immunization risk was 0.13% for both periods. No differences were found regarding incidence of new antibodies, nor for patients regarding age, sex, previous antibodies, multiple antibodies, additional antibodies, number of transfusions, transfusions episodes and days from transfusion to date of immunization. In conclusion, compared with buffy-coat leucoreduction, universal prestorage filter leucodepletion did not alter the development of clinically significant red blood cell alloimmunization.

Low frequency of observed anti-HLA among transfused preterm infants

BACKGROUND

Although low-birth-weight infants (LBWI) often receive multiple transfusions, there is controversial information on their development of antibodies against WBCs or platelets.

STUDY DESIGN AND METHODS

A total of 52 LBWI with birth weights less than 1500 g were randomly assigned to receive either RBCs that had been WBC- reduced (n = 25) or nonfiltered blood (n = 27). Serum samples collected from 37 infants at 3 months of age and from 30 children when they were 5 to 11 years old were tested. Anti-HLA was assayed with an anti-human globulin-augmented lymphocytotoxicity test against a panel consisting of 13 lymphocytes and against parental cells.

RESULTS

None of 52 transfused LBWI of either group developed anti-HLA (95% CI, 0%-6.8% for overall, 0%-13.7% for the WBC-reduced group, and 0%-12.7% for the nonfiltered group).

CONCLUSION

Multiply transfused LBWI rarely produced antibodies to HLA of blood donors and to noninherited maternal antigens. The benefits of WBC reduction to prevent HLA alloimmunization during infancy were not supported by this study and need further investigation.

Early primary immune response against erythrocytes: a case report

BACKGROUND

Primary immune response against red blood cell (RBC) antigens often takes weeks or months to be detected. In previous reports, for children receiving multiple units of blood components, ranging from five to 81 units, the elapsed time between the first RBC transfusion and antibody detection ranged from 18 to 78 days. Cytomegalovirus (CMV) is sometimes associated with immunohaematologic findings and may modulate immune response.

CASE REPORT

A 24-week-old male infant with interstitial pneumonia and hepatitis because of CMV developed an RBC auto antibody and two RBC alloantibodies: anti-Jka, detected in tube 11 days after a single RBC transfusion, and anti-K, detected only in papain gel test 18 days later.

CONCLUSION

As anti-Jka is not a naturally occurring antibody, this is the most rapid primary immune response against an RBC antigen after a single RBC transfusion ever described, in the youngest child ever described.

Effectiveness of WBC reduction in neonates: what is the evidence of benefit?

BACKGROUND

The presence of WBCs in RBCs is thought to be associated with a number of significant adverse effects in recipients. In adults, WBC reduction has been shown to reduce the frequency of HLA alloimmunization, CMV and HTLV infections, and febrile nonhemolytic transfusion reactions. However, neonates are unique, given that they have an immature immune system and are frequently transfused with RBCs. Thus, the aims of this systematic review were to determine whether WBC reduction of RBCs transfused to neonates decreases the transmission of CMV, reduces the ability to develop HLA antibodies, or reduces the risk of immunomodulation. In addition, nosocomial infection, mortality, and duration of stay were identified and analyzed.

STUDY DESIGN AND METHODS

All studies of WBC reduction were identified by a systematic review of the literature. Studies meeting the inclusion criteria were grouped based on study outcome. Where appropriate, studies were pooled to obtain an overall measure of effect.

RESULTS

Nine eligible studies were identified from the systematic literature search, and six were deemed evaluable. Two studies evaluated WBC reduction and the development of CMV, with different results. The pooled OR was 0.19 (95% Cl, 0.01-3.41), suggesting a clinical but nonsignificant effect. Two studies evaluated WBC reduction and HLA antibody development. As with CMV, the two studies were not congruent in their results. The pooled OR was 0.17 (95% Cl, 0.01-2.43). As for immunomodulation, two small studies presented evidence of a statistically significant change in lymphocyte subsets. No studies were identified with a primary objective of evaluating the impact of WBC reduction on nosocomial infection, mortality, or duration of stay.

CONCLUSION

Current evidence suggests that WBC reduction may be effective in neonates; however, further studies are needed. The lack of convincing data and the significant cost of WBC reduction mandate evaluations to determine the clinical and economic impact.

In utero development of a warm-reactive autoantibody in a severely jaundiced neonate

BACKGROUND

The fetus and neonate are widely considered to be immunologically immature. However, there are rare case reports of RBC alloantibody and autoantibody development.

STUDY DESIGN AND METHODS

This report describes the case of a severely jaundiced full-term boy neonate presenting at birth with an IgG warm-reactive autoantibody.

RESULTS

Mother and neonate were both blood group A, D+. The mother had a negative antibody screen at 18 weeks' gestation and a negative DAT and antibody screen at the time of delivery. The neonate was born with a strongly reactive DAT (IgG) and a panreactive eluate. The serum also contained a panreactive antibody, and all crossmatches were incompatible. The neonate had a bilirubin of 12.5 mg per dL at birth, which peaked at 22.5 mg per dL. However, there was no overt evidence of hemolysis, as evidenced by normal serial Hct levels and reticulocyte counts. The neonate responded well to phototherapy and did not require either simple or exchange transfusion. The neonate's warm-reactive autoantibody maintained its original strength of reactivity on follow-up testing performed at 2 weeks and 2 months of age.

CONCLUSIONS

This report describes a rare case of apparent in utero RBC autoantibody development. The fetal/neonatal immune response to blood group antigens is reviewed.

Alloimmunization in preterm infants after repeated transfusions of WBC-reduced RBCs from the same donor

BACKGROUND

Preterm infants are among the most heavily transfused of patient groups, yet multiply transfused infants only rarely produce alloantibodies against RBC or WBC antigens. It is not known whether rates of alloimmunization might be increased by repeated exposure to RBCs and WBCs from the same donor, as in limited-donor-exposure programs, or whether infants might benefit from WBC-reduced RBC components as a means of diminishing the risk of possible alloimmunization.

STUDY DESIGN AND METHODS

Preterm infants (birth weight 0.6-1.3 kg) received prestorage WBC-reduced RBCs from dedicated donors, collected in AS-3 as a means of limiting donor exposures. Blood samples were collected serially from infants shortly after birth until either discharge or age 6 months and were studied for RBC and WBC antibodies-the latter with reactivity against either HLA class I or neutrophil-specific antigens.

RESULTS

Thirty preterm infants received 139 transfusions (mean, 4.6; median, 4 transfusions per infant), with 81 percent of transfusions obtained from one donor per infant. Eighty-four blood samples (mean, 2.7/infant) were studied, and no infant produced RBC antibodies. Twenty-seven percent of infants exhibited WBC antibodies, but only 13 percent actually produced WBC antibodies (passive maternal antibody excluded). Of the WBC antibodies produced by infants, three were against HLA class I and one was against neutrophil-specific antigens; none were linked to adverse effects.

CONCLUSIONS

Because infants only rarely produce RBC antibodies, no changes in blood banking practices are necessary for limited-donor-exposure programs. Although the production of WBC antibodies by infants occurs, it seems to be uncommon; thus, the possible benefits, if any, of WBC reduction are uncertain, and further study is required before changes in practice can be justified.

Immune effects of blood transfusion

Blood is a complicated tissue that has been routinely applied over the past century. Since the recognition of the principles of species specificity (1818) and major compatibility for red cell antigens (1900), considerable attention has been given in the second half of this century to leukocyte-determined immune effects following transfusion. Most reactions are febrile and nonhemolytic and show, in limited situations, true relation to immune activity of transfused white blood cells. The complete picture is not yet finished; however, the more important immune effects are stimulation and modulation, tolerance and suppression. Here most work done is ex vivo and in animal experiments. Little clinical evidence has been obtained or assessment done. Most publications therefore relate to laboratory work, extrapolating results to the bedside. The most interesting publication over the review period with regard to the core immune effects of blood transfusion relates to measured concentrations of active, soluble molecules like HLA class I and II and Fas ligand molecules and to their in vitro immunomodulating effect as well as effects on induction of apoptosis. Stored red cell preparations show an increase in soluble molecules and death of viable leukocytes. Platelet preparations show similar phenomena, although information on numbers of white blood cells and storage conditions are lacking. The authors propose selective use of these aged components in specific clinical settings to allow immune suppression, induction of cell anergy, and apoptosis, whereas fresher products not showing increased levels of soluble molecules could be applied in clinical settings in which immunosuppression is not wanted. No reference is found to scientifically support and substantiate the global universal leukodepletion movement.