Fetal anemia due to non-Rhesus-D red-cell alloimmunization

Fetal anemia: Diagnosis and management

Fetal anemia has been known for many years as a dangerous complication of pregnancy. Its most common causes are maternal alloimmunization and parvovirus B19 infection, although it can be associated with many different pathological conditions including fetal aneuploidies, vascular tumors, and arteriovenous malformations of the fetus or placenta and inherited conditions such as alpha-thalassemia or genetic metabolic disorders. Doppler ultrasonographic assessment of the peak velocity of systolic blood flow in the middle cerebral artery for the diagnosis of fetal anemia and intravascular intrauterine transfusion for its treatment are the current practice standards. Live birth rates as high as 95% have been reported in recent years. The additional role of intravenous immunoglobulin therapy and the long-term consequences of the condition are the subjects of active ongoing research.

Antibody-mediated immunosuppression can result from RBC antigen loss independent of Fcγ receptors in mice

BACKGROUND

Anti-RhD administration can prevent de novo anti-RhD formation following RhD+ red blood cell (RBC) exposure, termed antibody-mediated immunosuppression (AMIS). Recent studies suggest that AMIS may occur through target antigen alterations, known as antigen modulation. However, studies suggest that AMIS may occur independent of antigen modulation. In particular, AMIS to RBCs that transgenically express the fusion hen egg lysozyme-ovalbumin-Duffy (HOD) antigen have been shown to occur independent of activating Fcγ receptors (FcγRs) thought to be required for antigen modulation. Therefore, we sought to determine the mechanism behind AMIS following HOD RBC exposure.

STUDY DESIGN AND METHODS

Following transfer of HOD RBCs into wild-type or FcγR-chain knockout recipients in the presence or absence of monoclonal anti-hen egg lysozyme (HEL) antibody, individually or in combination, HOD antigen levels and anti-HOD antibody formation were examined.

RESULTS

Our results demonstrate that anti-HEL antibodies individually or in combination suppressed anti-HOD IgM, which correlated with the rate of detectable decrease in HEL on HOD RBCs. Furthermore, exposure to anti-HEL antibodies alone or in combination equally suppressed anti-HOD IgG formation. Unexpectedly, combination or individual anti-HEL antibodies induced AMIS and antigen modulation in an FcγR-independent manner. Pre-exposure of HOD RBCs to anti-HEL antibodies reduced antigen levels and suppressed anti-HOD antibody formation following HOD RBC exposure.

CONCLUSION

These results suggest that antibody-mediated antigen modulation may reflect a mechanism of AMIS that can occur independent of activating FcγRs and may provide a surrogate to identify antibodies capable of inducing AMIS against different RBC antigens.

Marginal Zone B Cells Induce Alloantibody Formation Following RBC Transfusion

Red blood cell (RBC) alloimmunization represents a significant immunological challenge for some patients. While a variety of immune constituents likely contribute to the initiation and orchestration of alloantibodies to RBC antigens, identification of key immune factors that initiate alloantibody formation may aid in the development of a therapeutic modality to minimize or prevent this process. To define the immune factors that may be important in driving alloimmunization to an RBC antigen, we determined the specific immune compartment and distinct cells that may initially engage transfused RBCs and facilitate subsequent alloimmunization. Our findings demonstrate that the splenic compartment is essential for formation of anti-KEL antibodies following KEL RBC transfusion. Within the spleen, transfused KEL RBCs are found within the marginal sinus, where they appear to specifically co-localize with marginal zone (MZ) B cells. Consistent with this, removal of MZ B cells completely prevented alloantibody formation following KEL RBC transfusion. While MZ B cells can mediate a variety of key downstream immune pathways, depletion of follicular B cells or CD4 T cells failed to similarly impact the anti-KEL antibody response, suggesting that MZ B cells may play a key role in the development of anti-KEL IgM and IgG following KEL RBC transfusion. These findings highlight a key contributor to KEL RBC-induced antibody formation, wherein MZ B cells facilitate antibody formation following RBC transfusion.

Complement serves as a switch between CD4+ T cell-independent and -dependent RBC antibody responses

RBC alloimmunization represents a significant immunological challenge for patients requiring lifelong transfusion support. The majority of clinically relevant non-ABO(H) blood group antigens have been thought to drive antibody formation through T cell-dependent immune pathways. Thus, we initially sought to define the role of CD4+ T cells in formation of alloantibodies to KEL, one of the leading causes of hemolytic transfusion reactions. Unexpectedly, our findings demonstrated that KEL RBCs actually possess the ability to induce antibody formation independent of CD4+ T cells or complement component 3 (C3), two common regulators of antibody formation. However, despite the ability of KEL RBCs to induce anti-KEL antibodies in the absence of complement, removal of C3 or complement receptors 1 and 2 (CR1/2) rendered recipients completely reliant on CD4+ T cells for IgG anti-KEL antibody formation. Together, these findings suggest that C3 may serve as a novel molecular switch that regulates the type of immunological pathway engaged following RBC transfusion.

The Role of the Immunological Synapse in Differential Effects of APC Subsets in Alloimmunization to Fresh, Non-stored RBCs

Background: Each year, over 5 million red blood cell (RBC) transfusions are administered to patients in the USA. Despite the therapeutic benefits of RBC transfusions, there are associated risks. RBC-specific alloantibodies may form in response to antigenic differences between RBC donors and recipients; these alloantibodies can be a problem as they may mediate hemolysis or pose barriers to future transfusion support. While there is currently no reliable way to predict which RBC recipients will make an alloantibody response, risk factors such as inflammation have been shown to correlate with increased rates of RBC alloimmunization. The underlying mechanisms behind how inflammation mediates alloantibody production are incompletely defined.

Methods: To assess erythrophagocytosis, mice were treated with PBS or inflammatory stimuli followed by a transfusion of allogeneic RBCs labeled with a lipophilic dye. At multiple time points, RBC consumption and expression of activation makers by leukocytes was evaluated. To determine which antigen presenting cell (APC) subset(s) were capable of promoting allogeneic T cell activation, sorted leukocyte populations (which had participated in erythrophagocytosis) were co-cultured in vitro with allogeneic CD4+ T cells; T cell proliferation and ability to form immunological synapses with APCs were determined.

Results: Upon transfusion of fresh allogeneic RBCs, multiple APCs consumed transfused RBCs. However, only CD8+ and CD11b+ dendritic cells formed productive immunological synapses with allogeneic T cells and stimulated proliferation. Importantly, allogeneic T cell activation and RBC alloantibody production occurred in response to RBC transfusion alone, and transfusion in the context of inflammation enhanced RBC consumption, the number of immune synapses, allogeneic T cell proliferation, and the rate and magnitude of alloantibody production.

Conclusions: These data demonstrate that regardless of the ability to participate in RBC consumption, only a subset of APCs are capable of forming an immune synapse with T cells thereby initiating an alloantibody response. Additionally, these data provide mechanistic insight into RBC alloantibody generation.

Predicting anti-Kell-mediated hemolytic disease of the fetus and newborn: diagnostic accuracy of laboratory management

BACKGROUND

There is controversy on critical cut-off values of laboratory testing to select pregnancies at increased risk for anti-Kell-mediated hemolytic disease of the fetus and newborn. Without early detection and treatment, anti-Kell-mediated hemolytic disease of the fetus and newborn may result in progressive fetal anemia, fetal hydrops, asphyxia, and perinatal death.

OBJECTIVE

We aimed to determine the value of repeated anti-Kell titer determination and biological activity measurement using the antibody-dependent cellular cytotoxicity test determination in the management of pregnancies at risk for anti-Kell-mediated hemolytic disease of the fetus and newborn.

STUDY DESIGN

This was a retrospective cohort study of pregnancies with anti-Kell and a Kell-positive fetus, identified from January 1999 through April 2015. Laboratory test results and clinical outcome were collected from the Dutch nationwide screening program and the national reference center for fetal therapy in The Netherlands, the Leiden University Medical Center. Diagnostic accuracy was measured (receiver operating characteristic curves, sensitivity, specificity, positive and negative predictive values) for anti-Kell titers and antibody-dependent cellular cytotoxicity test. The relationship between the titer and antibody-dependent cellular cytotoxicity measurements and the 2 foregoing measurements were computed with a Pearson product-moment correlation coefficient.

RESULTS

In a 16-year unselected cohort, representing screening results of 3.2 million pregnancies resulting in live births in The Netherlands, we identified 1026 Kell-immunized pregnancies. In all, 93 pregnant women had anti-Kell and a Kell-positive child, without other red cell alloantibodies. In all, 49 children (53%) needed intrauterine or postnatal transfusion therapy. The first anti-Kell titer showed already a high diagnostic accuracy with an area under the curve of 91%. The optimal cut-off point for the titer was 4 (sensitivity 100%; 95% confidence interval, 91-100), specificity 27% (95% confidence interval, 15-43), and positive predictive value 60% (49-71%). The antibody-dependent cellular cytotoxicity test was not informative to select high-risk pregnancies. Linear regression showed no significant change during pregnancy, when antibody titer and antibody-dependent cellular cytotoxicity test results were compared with every 2 foregoing measurements (P < .0001).

CONCLUSION

Early determination of the anti-Kell titer is sufficient to select pregnancies at increased risk for hemolytic disease of the fetus and newborn with need for transfusion therapy. If the Kell status of the fetus is known to be positive, a titer of ≥4 can be used to target intensive clinical monitoring.

ABO incompatibility and RhIG immunoprophylaxis protect against non-D alloimmunization by pregnancy

BACKGROUND

Hemolytic disease of the fetus and newborn (HDFN) is caused by maternal antibodies against fetal red blood cell antigens, most often anti-D, -K, or -c. ABO incompatibility between mother and child and anti-D immunoprophylaxis (RhIG) are known to reduce the risk of D immunization and subsequent HDFN. However, no immunoprophylaxis has been developed to prevent non-D immunizations.

STUDY DESIGN AND METHODS

We evaluated whether ABO incompatibility has a preventive effect on formation of non-D alloantibodies, by performing a case-control study including pregnant women with newly detected non-D antibodies, identified within a nationwide data set, immunized during their first pregnancy and/or delivery. Subsequently, we assessed a possible protective effect of RhIG in a subgroup with non-Rh antibodies only. The proportions of previous ABO incompatibility and of RhIG administrations of these women were compared to the known rate of 19.4% ABO incompatibility and 9.9% RhIG administrations (D- women carrying a D+ child) in the general population of pregnant women.

RESULTS

A total of 11.9% of the 232 included immunized women had a possible ABO incompatibility in their first pregnancy (vs. expected 19.4%; 95% confidence interval [CI], 7.3-18.8; p = 0.036). Furthermore, 1.0% women with non-Rh antibodies were D-, delivered a D+ child, and had therefore received RhIG, whereas 9.9% was expected (95% CI, 0.18-5.50; p = 0.003).

CONCLUSION

We found that ABO incompatibility and RhIG reduce the risks not only for D, but also for non-Rh immunizations, suggesting that antibody-mediated immune suppression in this condition is not antigen specific.

Fc-Glycosylation in Human IgG1 and IgG3 Is Similar for Both Total and Anti-Red-Blood Cell Anti-K Antibodies

After albumin, immunoglobulin G (IgG) are the most abundant proteins in human serum, with IgG1 and IgG3 being the most abundant subclasses directed against protein antigens. The quality of the IgG-Fc-glycosylation has important functional consequences, which have been found to be skewed toward low fucosylation in some antigen-specific immune responses. This increases the affinity to IgG1-Fc-receptor (FcγR)IIIa/b and thereby directly affects downstream effector functions and disease severity. To date, antigen-specific IgG-glycosylation have not been analyzed for IgG3. Here, we analyzed 30 pregnant women with anti-K alloantibodies from a prospective screening cohort and compared the type of Fc-tail glycosylation of total serum- and antigen-specific IgG1 and IgG3 using mass spectrometry. Total serum IgG1 and IgG3 Fc-glycoprofiles were highly similar. Fc glycosylation of antigen-specific IgG varied greatly between individuals, but correlated significantly with each other for IgG1 and IgG3, except for bisection. However, although the magnitude of changes in fucosylation and galactosylation were similar for both subclasses, this was not the case for sialylation levels, which were significantly higher for both total and anti-K IgG3. We found that the combination of relative IgG1 and IgG3 Fc-glycosylation levels did not improve the prediction of anti-K mediated disease over IgG1 alone. In conclusion, Fc-glycosylation profiles of serum- and antigen-specific IgG1 and IgG3 are highly similar.

The incidence and outcome of clinically significant antibodies detected in Rhesus-D positive pregnant women of the Northern Territory

BACKGROUND

Haemolytic disease of the fetus/newborn secondary to clinically significant non-Rhesus-D antibodies has risen in importance since the advent of immunoprophylactic anti-D administration to Rhesus-D negative women. Of interest is the incidence of these antibodies in Rhesus-D positive women, who receive less frequent antenatal alloantibody screening. This is of particular concern if the antibodies arise late in pregnancy and may go undetected.

AIMS

To assess the proportion of Rhesus-D positive pregnant women with late developing clinically significant antibodies for haemolytic disease of the fetus/newborn, and whether these resulted in adverse fetal outcomes.

MATERIALS AND METHODS

A retrospective analysis over a 12-month period at a tertiary hospital in the Northern Territory. Group and antibody screen results in addition to clinical data regarding pregnancy/newborn were collected.

RESULTS

Sixty-four of 2612 women (2.5%) had red blood cell antibodies detected during their pregnancy. Of these, 21 clinically significant antibodies were detected in 19 women (0.7% of initial cohort). The most common antibody detected was anti-c (28.5%). In six of these women (0.23% of initial cohort), the antibodies were late developing. Mild jaundice was noted in three newborns with phototherapy required in one.

CONCLUSIONS

Although clinically significant antibodies were detected during pregnancy, and in a small proportion of cases as a late developing antibody undetected in the first trimester screening, clinical outcomes for the newborn were mild. As such, the cost of retesting all Rhesus-D positive pregnant women in the third trimester would be considerable and unlikely to result in any meaningful clinical benefit.

Preeclampsia: novel insights from global RNA profiling of trophoblast subpopulations

BACKGROUND

The maternal signs of preeclampsia, which include the new onset of high blood pressure, can occur because of faulty placentation. We theorized that transcriptomic analyses of trophoblast subpopulations in situ would lend new insights into the role of these cells in preeclampsia pathogenesis.

OBJECTIVE

Our goal was to enrich syncytiotrophoblasts, invasive cytotrophoblasts, or endovascular cytotrophoblasts from the placentas of severe preeclampsia cases. Total RNA was subjected to global transcriptional profiling to identify RNAs that were misexpressed compared with controls.

STUDY DESIGN

This was a cross-sectional analysis of placentas from women who had been diagnosed with severe preeclampsia. Gestational age-matched controls were placentas from women who had a preterm birth with no signs of infection. Laser microdissection enabled enrichment of syncytiotrophoblasts, invasive cytotrophoblasts, or endovascular cytotrophoblasts. After RNA isolation, a microarray approach was used for global transcriptional profiling. Immunolocalization identified changes in messenger RNA expression that carried over to the protein level. Differential expression of non-protein-coding RNAs was confirmed by in situ hybridization. A 2-way analysis of variance of non-coding RNA expression identified particular classes that distinguished trophoblasts in cases vs controls. Cajal body foci were visualized by coilin immunolocalization.

RESULTS

Comparison of the trophoblast subtype data within each group (severe preeclampsia or noninfected preterm birth) identified many highly differentially expressed genes. They included molecules that are known to be expressed by each subpopulation, which is evidence that the method worked. Genes that were expressed differentially between the 2 groups, in a cell-type-specific manner, encoded a combination of molecules that previous studies associated with severe preeclampsia and those that were not known to be dysregulated in this pregnancy complication. Gene ontology analysis of the syncytiotrophoblast data highlighted the dysregulation of immune functions, morphogenesis, transport, and responses to vascular endothelial growth factor and progesterone. The invasive cytotrophoblast data provided evidence of alterations in cellular movement, which is consistent with the shallow invasion often associated with severe preeclampsia. Other dysregulated pathways included immune, lipid, oxygen, and transforming growth factor-beta responses. The data for endovascular cytotrophoblasts showed disordered metabolism, signaling, and vascular development. Additionally, the transcriptional data revealed the differential expression in severe preeclampsia of 2 classes of non-coding RNAs: long non-coding RNAs and small nucleolar RNAs. The long non-coding RNA, urothelial cancer associated 1, was the most highly up-regulated in this class. In situ hybridization confirmed severe preeclampsia-associated expression in syncytiotrophoblasts. The small nucleolar RNAs, which chemically modify RNA structure, also correlated with severe preeclampsia. Thus, we enumerated Cajal body foci, sites of small nucleolar RNA activity, in primary cytotrophoblasts that were isolated from control and severe preeclampsia placentas. In severe preeclampsia, cytotrophoblasts had approximately double the number of these foci as the control samples.

CONCLUSION

A laser microdissection approach enabled the identification of novel messenger RNAs and non-coding RNAs that were misexpressed by various trophoblast subpopulations in severe preeclampsia. The results suggested new avenues of investigation, in particular, the roles of PRG2, Kell blood group determinants, and urothelial cancer associated 1 in syncytiotrophoblast diseases. Additionally, many of the newly identified dysregulated molecules might have clinical utility as biomarkers of severe preeclampsia.

The Incidence and Effects of Alloimmunization in Pregnancy During the Period 2000 - 2013

INTRODUCTION

The objective of the analysis was to examine the epidemiological aspects of maternal alloimmunization and to determine the most common antibody specificities resulting in hemolytic disease of the newborn (HDN).

MATERIALS AND METHODS

The retrospective epidemiological study encompasses all pregnant women who underwent immunohematological screening and the newborn treated for HDN in the period from 2000 to 2013 in the Herzegovina region.

RESULTS

The indirect Coombs test (ICT) detected antibodies against antigens in 384 (2.4%) pregnant women of the 18 800 who were tested at the Department of Transfusion Medicine. The direct Coombs test (DCT) detected antibodies against antigens in 160 (0.8%) newborn treated for HDN. The results of our 13-year study, in which 60% of the pregnant women had non-RhD antibodies, confirms this finding.

CONCLUSION

However, we have reached the 21st century and the burden of alloimmunisation in pregnancy is still on our backs. The problem of immunization and HDN is still present in our region, which is a neonatal and public health problem.

Haemolytic and nonhaemolytic neonatal jaundice have different risk factor profiles

AIM

This study examined maternal and pregnancy risk factors for haemolytic and nonhaemolytic neonatal jaundice in a large population-based cohort study.

METHODS

We conducted a cohort study of 1 019 220 singleton live births from the Swedish medical birth register from 1987 to 2002, using information on neonatal jaundice and maternal and pregnancy characteristics. Diagnoses of gestational hypertensive disorders were obtained by linkage to the national inpatient register. Multivariate logistic regression analysis provided odds ratios for the risk factors of both forms of jaundice.

RESULTS

A total of 6057 (0.6%) births were affected by haemolytic jaundice and 36 869 (3.6%) by nonhaemolytic jaundice. The strongest risk factors for haemolytic jaundice were maternal alloimmunisation, blood group O and neonatal jaundice in older siblings. For nonhaemolytic jaundice, the strongest risk factors were preterm birth, neonatal jaundice in older siblings, maternal origin from East or South-East Asia and maternal obesity. We estimated that 13% of haemolytic jaundice was attributable to alloimmunisation and 39% of nonhaemolytic jaundice was attributable to preterm birth.

CONCLUSION

Haemolytic and nonhaemolytic neonatal jaundice had different risk factor profiles. Interventions to reduce maternal alloimmunisation, preterm birth and maternal obesity may lower the prevalence of neonatal jaundice and the risk of consequent neurological complications.

Antigen specificity determines anti-red blood cell IgG-Fc alloantibody glycosylation and thereby severity of haemolytic disease of the fetus and newborn

Haemolytic disease of the fetus and newborn (HDFN) is a severe disease in which fetal red blood cells (RBC) are destroyed by maternal anti-RBC IgG alloantibodies. HDFN is most often caused by anti-D but may also occur due to anti-K, -c- or -E. We recently found N-linked glycosylation of anti-D to be skewed towards low fucosylation, thereby increasing the affinity to IgG-Fc receptor IIIa and IIIb, which correlated with HDFN disease severity. Here, we analysed 230 pregnant women with anti-c, -E or -K alloantibodies from a prospective screening cohort and investigated the type of Fc-tail glycosylation of these antibodies in relation to the trigger of immunisation and pregnancy outcome. Anti-c, -E and -K show - independent of the event that had led to immunisation - a different kind of Fc-glycosylation compared to that of the total IgG fraction, but with less pronounced differences compared to anti-D. High Fc-galactosylation and sialylation of anti-c correlated with HDFN disease severity, while low anti-K Fc-fucosylation correlated with severe fetal anaemia. IgG-Fc glycosylation of anti-RBC antibodies is shaped depending on the antigen. These features influence their clinical potency and may therefore be used to predict severity and identify those needing treatment.

Bortezomib decreases the magnitude of a primary humoral immune response to transfused red blood cells in a murine model

BACKGROUND

Few therapeutic options currently exist to prevent or to mitigate transfusion-associated red blood cell (RBC) alloimmunization. We hypothesized that bortezomib, a proteasome inhibitor currently being utilized for HLA alloantibody and ADAMTS13 autoantibody reduction, may be beneficial in a transfusion setting. Herein, we utilized a reductionist murine model to test our hypothesis that bortezomib would decrease RBC alloimmune responses.

STUDY DESIGN AND METHODS

Wild-type mice were treated with bortezomib or saline and transfused with murine RBCs expressing the human KEL glycoprotein. Levels of anti-KEL immunoglobulins in transfusion recipients were measured by flow cytometry. The impact of bortezomib treatment on recipient plasma cells (PCs) and other immune cells was also assessed by flow cytometry and immunofluorescence.

RESULTS

After bortezomib treatment, mice had a 50% reduction in splenic white blood cells and a targeted reduction in marrow PCs. Mice treated with bortezomib before the transfusion of KEL RBCs became alloimmunized in three of three experiments, although their serum anti-KEL IgG levels were 2.6-fold lower than those in untreated mice. Once a primary antibody response was established, bortezomib treatment did not prevent an anamnestic response from occurring.

CONCLUSION

To the extent that these findings are generalizable to other RBC antigens and to humans, bortezomib monotherapy is unlikely to be of significant clinical benefit in a transfusion setting where complete prevention of alloimmunization is desirable. Given the impact on PCs, however, it remains plausible that bortezomib therapy may be beneficial for RBC alloimmunization prevention or mitigation if used in combination with other immunomodulatory therapies.

Red cell alloimmunization in RhD positive pregnant women and neonatal outcome

The frequency of red blood cell (RBC) alloimmunization in RhD positive pregnant women is not known in our population. We planned to determine its frequency and correlation with neonatal outcome. We included 1000 RhD positive pregnant women: 500 had 'normal pregnancy' (Group I) and another 500 had 'high risk pregnancy' (Group II). ABO and extended Rh phenotyping were done by tube technique, antibody screening and identification by gel technique. For alloimmunized women, the paternal and neonatal ABO and extended Rh typing were done. Neonatal direct antiglobulin test (DAT) was also done and their clinical outcome observed. The frequency of RBC alloimmunization was 0.7% (7/1000) and all these women were from group II (p = 0.015). The alloantibodies were anti-E (85.7%), anti-c (71.4%), anti-Cw (14.3%) and anti-S (14.3%). Also, 6 women had history of transfusion (p < 0.01). Of the 7 neonates born to alloimmunized mothers, 4 (57.14%) had a positive DAT. The mean duration of phototherapy was higher in the DAT positive neonates (p < 0.01) and 2 (50%) required exchange transfusion. Thus, the frequency of alloimmunization was 0.7% in RhD positive pregnant women. High risk pregnancies and antenatal patients having a history of blood transfusion should be considered for regular antibody screening.

Erythrophagocytosis by plasmacytoid dendritic cells and monocytes is enhanced during inflammation

BACKGROUND

Generation of antibodies against red blood cell (RBC) antigens can be a clinically significant problem. The underlying mechanisms that regulate the production of RBC antibodies are only partially understood; however, factors such as inflammation significantly increase the rates of RBC antibody generation. Humoral alloimmunization begins with consumption of transfused RBCs by antigen-presenting cells (APCs). Recently, it has become appreciated that there are multiple different types of APCs. The relative contribution of APC subsets to RBC antibodies has not been described in either the quiescent or the inflamed states.

STUDY DESIGN AND METHODS

To evaluate the types of APCs that consume RBCs, and how inflammation affects this process, C56Bl/6 mice were treated with polyinosinic-polycytidylic acid (poly(I:C)) to induce an inflammatory response and/or were transfused with 3,3'-dihexadecyloxacarbocyanine perchlorate-labeled syngeneic RBCs. Erythrophagocytosis (both at baseline and during inflammation) was analyzed for different subsets of macrophages (MΦ), dendritic cells (DCs), B cells, and monocytes, by a combined approach using flow cytometry and fluorescent microscopy technology.

RESULTS

In four independent experiments, erythrophagocytosis at baseline was predominately performed by red pulp MΦ; however, during inflammation both plasmacytoid DCs (pDCs) and monocytes increased RBC consumption. Furthermore, pDCs up regulated MHC-II and activation markers CD80 and CD86. In addition to changing patterns of erythrophagocytosis, inflammation also led to a significant decrease in CD11c+ conventional DC populations and an increase in granulocytes.

CONCLUSIONS

The nature of APCs that consume transfused RBCs is changed by inflammation. Given that APCs initiate humoral immune responses, these findings provide potential mechanistic insight into how inflammation regulates RBC alloimmunization.

Hemolytic disease of the fetus and newborn: managing the mother, fetus, and newborn

Hemolytic disease of the fetus and newborn (HDFN) affects 3/100 000 to 80/100 000 patients per year. It is due to maternal blood group antibodies that cause fetal red cell destruction and in some cases, marrow suppression. This process leads to fetal anemia, and in severe cases can progress to edema, ascites, heart failure, and death. Infants affected with HDFN can have hyperbilirubinemia in the acute phase and hyporegenerative anemia for weeks to months after birth. The diagnosis and management of pregnant women with HDFN is based on laboratory and radiographic monitoring. Fetuses with marked anemia may require intervention with intrauterine transfusion. HDFN due to RhD can be prevented by RhIg administration. Prevention for other causal blood group specificities is less studied.

Noninvasive Antenatal Determination of Fetal Blood Group Using Next-Generation Sequencing

Hemolytic disease of the fetus and newborn (HDFN) is a condition characterized by a decreased lifespan of fetal red blood cells caused by maternally produced allospecific antibodies transferred to the fetus during pregnancy. The antibodies bind to the corresponding blood group antigens on fetal red blood cells and induce hemolysis. Cell-free DNA derived from the conceptus circulates in maternal blood. Using next-generation sequencing (NGS), it can be determined if this cell-free fetal DNA encodes the corresponding blood group antigen that is the target of the maternal allospecific antibodies. This determination carries no risk to the fetus. It is important to determine if the fetus is at risk of hemolysis to enable timely intervention. Many tests for blood groups are based solely on the presence or absence of a single nucleotide polymorphism (SNP). Antenatal determination of fetal blood group by NGS analysis holds advantages over polymerase chain reaction (PCR) determination based on allele specific amplification.

Harmless Pregnancy-Induced Warm Autoantibodies to Red Blood Cells

Background

There is little information concerning the development and significance of autoantibodies (aab) to red blood cells (RBCs) during pregnancy.

Methods

Unselected pregnant women were routinely screened for the presence of unexpected antibodies to RBCs using standard techniques.

Results

Between 2009 and 2013, 153,612 pregnant women were tested. The antibody screening test was positive in 1,721 women (1.12%). In 1,602 (1.04%) cases, immune and/or non-immune alloantibodies and cold-reactive aab were detected, whereas warm-reactive aab were found in 119 women (0.08%). In almost all cases, warm-reactive aab belonged to the IgG class. No evidence of the presence of significant haemolysis in affected women was observed.

Conclusion

Pregnant women may rarely develop aab to RBCs, which do not appear to cause haemolytic anaemia. Further clarification is required on the reasons behind the development of these aab and their clinical insignificance.

Society for Maternal-Fetal Medicine (SMFM) Clinical Guideline #8: the fetus at risk for anemia--diagnosis and management

OBJECTIVE

We sought to provide evidence-based guidelines for the diagnosis and management of fetal anemia.

METHODS

A systematic literature review was performed using MEDLINE, PubMed, EMBASE, and the Cochrane Library. The search was restricted to English-language articles published from 1966 through May 2014. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion. Evidence reports and published guidelines were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology was used for defining the strength of recommendations and rating the quality of evidence. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence.

RESULTS AND RECOMMENDATIONS

We recommend the following: (1) middle cerebral artery peak systolic velocity (MCA-PSV) measured by ultrasound Doppler interrogation be used as the primary technique to detect fetal anemia; (2) amniotic fluid delta OD450 not be used to diagnosis fetal anemia; (3) MCA-PSV assessment be reserved for those patients who are at risk of having an anemic fetus (proper technique for MCA-PSV evaluation includes assessment of the middle cerebral artery close to its origin, ideally at a zero degree angle without angle correction); (4) if a fetus is deemed at significant risk for severe fetal anemia (MCA greater than 1.5 multiples of the median or hydropic), fetal blood sampling be performed with preparation for an intrauterine transfusion, unless the pregnancy is at a gestational age when the risks associated with delivery are considered to be less than those associated with the procedure; (5) if a fetus is deemed at significant risk for severe fetal anemia, the patient be referred to a center with expertise in invasive fetal therapy; (6) MCA-PSV be considered to determine the timing of a second transfusion in fetuses with anemia, and, alternatively, a predicted decline in fetal hemoglobin may be used for timing the second procedure; and (7) pregnancies with a fetus at significant risk for fetal anemia be delivered at 37-38 weeks of gestation unless indications develop prior to this time.

Haemolytic disease of the fetus and newborn

Haemolytic Disease of the Fetus and Newborn (HDFN) is caused by maternal alloimmunization against red blood cell antigens. In severe cases, HDFN may lead to fetal anaemia with a risk for fetal death and to severe forms of neonatal hyperbilirubinaemia with a risk for kernicterus. Most severe cases are caused by anti-D, despite the introduction of antental and postnatal anti-D immunoglobulin prophylaxis. In general, red blood cell antibody screening programmes are aimed to detect maternal alloimmunization early in pregnancy to facilitate the identification of high-risk cases to timely start antenatal and postnatal treatment. In this review, an overview of the clinical relevance of red cell alloantibodies in relation to occurrence of HDFN and recent views on prevention, screening and treatment options of HDFN are provided.

The Significance of Imunohematology Research in Relation to Menagement of Hemolitical Diseases of the Newborn in Republic of Macedonia

AIM: Prompt discovery of allosensibilisation to RBC’s antigens during pregnancy and successful management of HDFN in Republic of Macedonia, in order to decrease morbidity and mortality of the fetus and the newborn.MATERIALS AND METHODS: The study comprises in total 23,800 patients, 14,858 pregnant women and 8,842 newborn babies.RESULTS: The screening and identification of anti RBC’s antibodies detected in total 216 alloantibodies, out of which 81% (175) had a clinical significance. Out of the above mentioned 164 alloantibodies (65.9%) belong to the Rh system. The most often reason for a severe hemolytic disease is the anti-D antibody. The HDFN symptoms of mild and moderate degree demonstrated 32.5%, and 18.9% had symptoms of severe fetal suffering, and almost half of them (48%) were with or with mild HDFN and had no need of therapy. In 15% it was about alloantibodies of other Rg antigens: anti-C, anti-E and anti-c, at which in most cases there were no signs of HDFN, or it showed weak symptoms (89%), just one case of anti-c ended with intrauterine death.CONCLUSIONS: Anti D antibody represents the most often reason for severe HDFN and displays a need of intrauterine transfusion and exsangvino transfusion. Anti-c is the only antibody that demonstrated the same potential for severe HBN as the anti-D. The most often reason for alloimmunisation of the mother is the lack of RhIG prophylaxis (97.8): postnatal, antenatal and in case of possible sensible conditions during pregnancy. Thus, there is a need and an outmost importance of elaboration and adoption of the National programe for RhIG prophylaxis in Republic of Macedonia.

Hemolytic disease of fetus and newborn due to maternal red blood cell alloantibodies in the Malay population

Background:

Maternal red blood cell (RBC) alloimmunization may lead to production of harmful antibodies that result in hemolytic disease of fetus and newborn (HDFN). There is insufficient data on the prevalence of HDFN due to RBC alloantibodies in the Malay neonatal population.

Aim:

The aim of this study was to determine the incidence of HDFN in the Malay neonatal population due to clinically significant RBC alloantibodies.

Subjects and Methods:

A cross sectional study was conducted in Transfusion Medicine Unit, Hospital Universitiy Sains Malaysia over one year period from January to December 2009. A total of 5163 Malay pregnant women who attended labor room for delivery were collected and analyzed prospectively. The blood samples were subjected to the standard immunohematological procedure for RBC antibody screening and identification using reagents of Diamed-ID Gel microtyping system. All the newborns with RBC alloantibody were investigated for the evidence of HDFN.

Results:

Thirty (0.58%) women were found to have clinically significant RBC alloantibodies. Most of the alloantibodies belonged to Rhesus (Rh) system (56.7%) where anti-E (33.3%) was the most common followed by anti-D (10.0%). Rh antibodies were the main cause of HDFN in fourteen (0.27%) neonates. Anti-D and anti-c were identified to cause moderate to very severe HDFN.

Conclusions:

With the low prevalence of clinically significant RBC alloantibodies and HDFN, routine antenatal antibody screening practice may not be advised as a routine practice at present, preferably reserved for those women of RhD negative or with history of HDFN, significantly of those attributed to anti-c.

Urgent global opportunities to prevent birth defects

Birth defects are an urgent global health priority. They affect millions of births worldwide. But their prevalence and impact are largely under-ascertained, particularly in middle- and low-income countries. Fortunately, a large proportion of birth defects can be prevented. This review examines the global prevalence and primary prevention methods for major preventable birth defects: congenital rubella syndrome, folic acid-preventable spina bifida and anencephaly, fetal alcohol syndrome, Down syndrome, rhesus hemolytic disease of the fetus and the newborn; and those associated with maternal diabetes, and maternal exposure to valproic acid or iodine deficiency during pregnancy. Challenges to prevention efforts are reviewed. The aim of this review is to bring to the forefront the urgency of birth defects prevention, surveillance, and prenatal screening and counseling; and to help public health practitioners develop population-based birth defects surveillance and prevention programs, and policy-makers to develop and implement science-based public health policies.

Associations of Rhesus and non-Rhesus maternal red blood cell alloimmunization with stillbirth and preterm birth

BACKGROUND

Although the risks of adverse pregnancy outcomes associated with anti-D antibodies are well-recognized, much less is known concerning alloimmunization with other red blood cell antibodies detected during routine maternal screening. To date, most reports of adverse pregnancy outcomes associated with non-anti-D antibodies have been from small case studies. The aim of this study was to examine the associations of maternal alloimmunization with specific red blood cell antibodies and the risks of preterm birth and stillbirth in the Swedish population.

METHODS

All antibody screening, outcome and covariate data were obtained through linkages of Swedish national health and data registers. Follow-up in these population-based registers was available up to 31 December 2002. The final study sample consisted of 1,022,569 singleton births from 668,952 mothers during 1987-2002.

RESULTS

In total, 1.3% of the 1,022,569 study pregnancies were alloimmunized. In adjusted logistic regression models, compared with having no antibodies, alloimmunization with anti-D, anti-E, anti-C and anti-c was associated with increased risk of both stillbirth and preterm birth. In addition, anti-Kell was associated with increased risk of preterm birth and anti-Lea with increased risk of stillbirth. Compared with firstborn children, risk of preterm birth associated with alloimmunization was greater in subsequent births

CONCLUSIONS

In the largest study to date, alloimmunization with Rhesus, K- and -Lea red blood cell antibodies increased the risk of preterm birth and/or stillbirth. The association of anti-Lea with stillbirth was an unexpected finding. Further study of the consequences of non-anti-D alloimmunization is warranted.

Integration of noninvasive prenatal prediction of fetal blood group into clinical prenatal care

Incompatibility of red blood cell blood group antigens between a pregnant woman and her fetus can cause maternal immunization and, consequently, hemolytic disease of the fetus and newborn. Noninvasive prenatal testing of cell-free fetal DNA can be used to assess the risk of hemolytic disease of the fetus and newborn to fetuses of immunized women. Prediction of the fetal RhD type has been very successful and is now integrated into clinical practice to assist in the management of the pregnancies of RhD immunized women. In addition, noninvasive prediction of the fetal RhD type can be applied to guide targeted prenatal prophylaxis, thus avoiding unnecessary exposure to anti-D in pregnant women. The analytical aspect of noninvasive fetal RHD typing is very robust and accurate, and its routine utilization has demonstrated high sensitivities for fetal RHD detection. A high compliance with administering anti-D is essential for obtaining a clinical effect. Noninvasive fetal typing of RHC/c, RHE/e, and KEL may become more widely used in the future.

Anti S enigma in a pregnant patient

Among the antibodies of the MNS blood group system, anti S antibody is generally IgG antibody reacting at 37 °C. It is rarely implicated in hemolytic transfusion reaction; however, it can lead to potentially severe transfusion reactions. Anti S is also capable of causing mild to severe fatal hemolytic disease of newborn. We report a case of anti S antibody in a pregnant patient with complicated falciparum malaria.

A mouse model of hemolytic disease of the newborn

In this issue of Blood, Stowell et al describe a novel mouse model of hemolytic disease of the fetus and newborn (HDFN) that recapitulates many of the key features of human disease.1 Recently, this same group of researchers described a transgenic mouse that expresses the human KEL2 (Chellano) red cell surface protein from the Kell system on red cells, and subsequently demonstrated that Kell differences on transfused blood induce antibody responses and hemolytic transfusion reactions similar to those seen in patients. In this latest report, Stowell et al demonstrate that similar to some patients, Kell differences between mother and father can lead to maternal antibody generation and hemolytic disease in utero. In so doing, they provide experimental confirmation of a long sought after animal model of HDFN.

Anti-Emm in a pregnant patient--case report

A 23-year-old primigravida of North African origin presented with a positive antibody screen at booking at 15 weeks of gestation. An antibody to a high-frequency antigen (HFA) of unknown identity was detected, which was reactive with the red blood cells of the father. This led to several challenges including antibody identification, clinical monitoring to detect signs of haemolytic disease of the foetus and newborn (HDFN) and compatible blood in case perinatal transfusion was needed. Anti-Emm was identified 2 months post-partum. This is the first published case which describes a pregnant patient with anti-Emm.