The Rh blood group system: a review

Safety assessment of RhD-positive red cell transfusion in RhD-negative liver-transplant recipients: Single-centre report from India

Background & objectives:

The number of blood components required during a liver-transplant surgery is significant. It is challenging for blood transfusion services to provide the required RhD-negative red blood cells (RBCs) for recipients during the peri-operative period. This retrospective study presents safety data of transfusing RhD-positive RBCs in RhD-negative living donor liver-transplant (LDLT) recipients during the peri-operative period with six-month follow up for risk of developing alloantibodies.

Methods:

All RhD-negative patients who underwent LDLT and were transfused ABO-compatible but RhD-positive RBC units between January 2012 and May 2018 were included in the study. Twenty one RhD-negative patients who received a total of 167 RhD-positive RBCs peri-operatively were chosen for alloantibody screening. All the patients were started on triple immunosuppression drugs as per the standard hospital protocol. Blood grouping, cross-match and antibody screening were done by column agglutination technique.

Results:

Post-transplant antibody screen (weekly for 12 wk) was negative, and none of the patients developed anti-D alloantibodies till their last follow up (mean 21 months).

Interpretation & conclusions:

Our observations suggest that it may be safe to use RhD-positive RBCs peri-operatively in RhD-negative LDLT recipients with low risk of alloimmunization.

How a Paleogenomic Approach Can Provide Details on Bioarchaeological Reconstruction: A Case Study from the Globular Amphorae Culture

Ancient human remains have the potential to explain a great deal about the prehistory of humankind. Due to recent technological and bioinformatics advances, their study, at the palaeogenomic level, can provide important information about population dynamics, culture changes, and the lifestyles of our ancestors. In this study, mitochondrial and nuclear genome data obtained from human bone remains associated with the Neolithic Globular Amphorae culture, which were recovered in the Megalithic barrow of Kierzkowo (Poland), were reanalysed to gain insight into the social organisation and use of the archaeological site and to provide information at the individual level. We were able to successfully estimate the minimum number of individuals, sex, kin relationships, and phenotypic traits of the buried individuals, despite the low level of preservation of the bone samples and the intricate taphonomic conditions. In addition, the evaluation of damage patterns allowed us to highlight the presence of “intruders”—that is, of more recent skeletal remains that did not belong to the original burial. Due to its characteristics, the study of the Kierzkowo barrow represented a challenge for the reconstruction of the biological profile of the human community who exploited it and an excellent example of the contribution that ancient genomic analysis can provide to archaeological reconstruction.

Design, implementation, and assessment of an interactive simulation to teach undergraduate immunology students hemolytic disease of the newborn

Hemolytic disease of the newborn (HDN) is a potentially fatal condition caused by a Rhesus (Rh) antigen incompatibility between a mother and fetus. As a result, determining the Rh status of expectant parents is a routine clinical assessment. Both the physiological and immunological basis of this condition are taught to undergraduate students. At the University of South Australia, some undergraduate immunology students find this topic challenging. The author designed, implemented, and assessed the impact of an interactive simulation to facilitate student learning of HDN. The students were actively engaged in determining the blood grouping and Rh status of an expectant mother and father and then determining the possibility of developing HDN. The simulation was found to take only 15 min to complete yet led to a significant increase in student performance in an end of semester exam question. Student perceived understanding was found to significantly improve following the introduction of the simulation, even though the content had been covered in a formal lecture. Student feedback was highly positive of this learning approach. In conclusion, short, interactive simulations can be used effectively to enhance student learning of challenging concepts.

Serological screening and genetic analysis of RhCE variants in the Chinese Southern Han donors

OBJECTIVES

To screen RhCE variants in the Chinese Southern Han donors for molecular genetic analysis.

BACKGROUND

More than hundreds of RhCE variant alleles have been described to resulting in weak and/or partial expression of RhCE antigens, generation of low-prevalence antigens and/or absence of a high-prevalence antigen of Rh system, which mainly reported in the people of African origin. In this study, the serological screening and molecular genetic analysis of RhCE variants were performed in the Chinese Southern Han donors.

METHODS

The blood samples of E(+) donors were preliminarily collected. Then, RhCE antigens of the E(+) samples were further typed by using two sets of monoclonal anti-C, anti-c, anti-e and another anti-E. When weak expression of RhCE antigens was found, direct sequencing for 10 exons of RHCE gene, RH genotyping analysis by using multiplex ligation-dependent probe amplification, flow cytometric analysis and even cDNA sequencing were performed.

RESULTS

A total of 4487 E(+) samples were collected and four samples with weak expression of antigens were detected. RHCE*Ce375G and RHCE*Ce667T variant alleles were identified in two samples with weak expression of e antigen, respectively. But no variant alleles were found in another two samples with weak expression of C antigen.

CONCLUSION

The variant RHCE*Ce375G validated by mRNA sequencing and the deduced RHCE*Ce667T alleles were firstly identified in the Chinese population. The DCE haplotype might account for the weak expression of C antigen in two donors.

Risk Minimization of Hemolytic Disease of the Fetus and Newborn Using Droplet Digital PCR Method for Accurate Fetal Genotype Assessment of RHD, KEL, and RHCE from Cell-Free Fetal DNA of Maternal Plasma

The molecular pathology of hemolytic disease of the fetus and newborn (HDFN) is determined by different RHD, RHCE, and KEL genotypes and by blood group incompatibility between the mother and fetus that is caused by erythrocyte antigen presence/absence on the cell surface. In the Czech Republic, clinically significant antierythrocyte alloantibodies include anti-D, anti-K, anti C/c, and anti-E. Deletion of the RHD gene and then three single nucleotide polymorphisms in the RHCE and KEL genes (rs676785, rs609320, and rs8176058) are the most common. The aim of this study is to develop effective and precise monitoring of fetal genotypes from maternal plasma of these polymorphisms using droplet digital (dd)PCR. Fifty-three plasma DNA samples (from 10 to 18 weeks of gestation) were analyzed (10 RHD, 33 RHCE, and 10 KEL). The ddPCR methodology was validated on the basis of the already elaborated and established method of minisequencing and real-time PCR and with newborn phenotype confirmation. The results of ddPCR were in 100% agreement with minisequencing and real-time PCR and also with newborn phenotype. ddPCR can fully replace the reliable but more time-consuming method of minisequencing and real-time PCR RHD examination. Accurate and rapid noninvasive fetal genotyping minimizes the possibility of HDFN developing.

An agnostic study of associations between ABO and RhD blood group and phenome-wide disease risk

Background

There are multiple known associations between the ABO and RhD blood groups and disease. No systematic population-based studies elucidating associations between a large number of disease categories and blood group have been conducted.

Methods

Using SCANDAT3-S, a comprehensive nationwide blood donation-transfusion database, we modeled outcomes for 1217 disease categories including 70 million person-years of follow-up, accruing from 5.1 million individuals.

Results

We discovered 49 and 1 associations between a disease and ABO and RhD blood groups, respectively, after adjustment for multiple testing. We identified new associations such as a decreased risk of kidney stones and blood group B as compared to blood group O. We also expanded previous knowledge on other associations such as pregnancy-induced hypertension and blood groups A and AB as compared to blood group O and RhD positive as compared to negative.

Conclusions

Our findings generate strong further support for previously known associations, but also indicate new interesting relations.

Funding

Swedish Research Council.

Preliminary study on the function of TMEM50A and its correlation with the RH genes

OBJECTIVES

The purpose of this study was to investigate the association and impact of TMEM50A on RH genes activity and function.

BACKGROUND

SMP1 is located on chromosome 1p36.11 in the RH gene locus, between the RHD and RHCE gene, where its position may be linked to RH haplotypes and contribute to selective pressures regarding certain RH haplotypes. TMEM50A is encoded by the SMP1 located in the intergenic region of RH, its influence on the function of the RH genes remains unclear.

METHODS

The expression of TMEM50A was regulated by transfection of plasmid and siRNA in K562 cell model. Western blot and real-time PCR were used to detect possible expression changes in the RH. The ammonium transport function of cells was monitored using pH-sensitive dye, while transcriptome sequencing was used to predict the potential function of TMEM50A.

RESULTS

The overexpression of TMEM50A significantly up-regulated RHCE gene activity (63.56%). The inhibition of TMEM50A resulted in significantly decreased RHCE (41.82%) and RHD expression (27.35%). Compared to control group, there was no significant change in the NH₄ ⁺ transport function of cells in the overexpressed TMEM50A group. Transcriptome analysis showed that TMEM50A not only affected the transcription of target gene through splicing activities, but also played a role in the development of embryonic nervous system.

CONCLUSIONS

TMEM50A may regulate the expression of RH gene by affecting the stability of RH mRNA through splicing function. It speculates that TMEM50A may play an important role in the development of embryonic nervous system.

Prevalence of Rhesus D negativity among reproductive age women in Southern Ethiopia: a cross-sectional study

Background

The Rhesus (Rh) blood group system is the next most clinically significant blood group system following the ABO blood group. Rh D-negative women are at risk of alloimmunization following exposure to Rh D-positive blood. The exposure of Rh D-negative women to Rh D-positive fetal blood may cause hemolytic disease of the fetus or new-born due to Rh incompatibility. Knowing Rh blood phenotype has paramount importance to prevent the risk of sensitization and bad obstetric outcome in Rh D-negative women. Despite the aforementioned fact, the distribution of Rh D-negative phenotype of women was not explored in Arba Minch Zuria district, southern Ethiopia. This study was aimed to assess the prevalence of Rh D-negative blood phenotype among reproductive-age women in Arba Minch Zuria district, southern Ethiopia.

Methods and materials

A community-based cross-sectional study was conducted among reproductive-age women in Arba Minch Zuria district, Southern Ethiopia from March to April 2019. Socio-demographic data were collected using an interviewer-administered semi-structured questionnaire and blood phenotype determination was done by laboratory technicians using the slide method principle aseptically and Statistical Package for Social Science (SPSS) version 21 was used for analysis.

Result

The data were collected from 417 study participants with a 98.8% response rate. This study revealed that 2.1%, 1.9%, 1.2%, and 1% of study participants with blood group O, A, B, and AB were Rh D negative, respectively. In this study, the overall prevalence of Rh D negative phenotype was found 6.2% among reproductive-age women in Arba Minch Zuria district, Southern Ethiopia.

Conclusions

This study showed a high prevalence of Rh D negative factor among reproductive-age women in Arba Minch Zuria district. Therefore, counseling of reproductive age women on the importance of Rh D factor status determination would be worthy to avoid the potential risk of sensitization among Rh D negative women in order to prevent hemolytic disease of the fetus and new-born.

Optimization of diagnostic strategy for non-invasive cell-free foetal RHD determination from maternal plasma

BACKGROUND AND OBJECTIVES

The aim of the study was to optimize routine non-invasive prenatal detection of fetal RHD gene from plasma of RhD-negative pregnant women (the median of gestational age was 25 weeks, range 10-38) to detect RhD materno-fetal incompatibility and to avoid the redundant immunoprophylaxis.

MATERIALS AND METHODS

Initially only one exon of RHD gene (exon 10) was investigated in 281 plasma samples (144 verified after delivery), in the second phase three RHD exons (5, 7, 10) were analyzed in 246 samples of plasma and maternal genomic DNA (204 verified) by real-time PCR method. Detection of Y-chromosomal sequence DYS-14 and five X-chromosomal insertion/deletion polymorphisms was used to confirm the fetal cfDNA detectability in plasma. Specific polymorphisms in RHD gene were detected by sequence-specific primer PCR in nine samples.

RESULTS

When only the RHD exon 10 was tested, 2·8% of verified samples were false positive and 3·5% false negative. With three RHD exons (5, 7, 10) and maternal genomic DNA testing, only one case was false negative (0·5%). Nine samples were inconclusive due to RHD-positive results in maternal genomic DNA. These samples were analyzed for specific mutations in RHD gene. Combination of both methods for fetal cfDNA verification succeeded in 75% of tested group.

CONCLUSION

Implementation of analysis of three RHD exons and maternal genomic DNA to routine practice lowers dramatically the ratio of false positive and negative results. This method enables more accurate determination of fetal RHD status with the reduction of unnecessary medical care and RhD immunoprophylaxis.

The Rh blood group system and its role in alloimmunization rate among sickle cell disease and sickle thalassemia patients in Iran

INTRODUCTION

The alloimmunization following blood transfusion can be life-threatening. The Rh alloantibodies are one of the most common causes contributing to alloimmunization. This study aimed to evaluate the rate and causes of alloimmunization and to determine the Rh phenotypes and genotypes among sickle cell disease (SCD) and sickle thalassemia (Sβ).

MATERIALS AND METHODS

Our study included 104 SCD and Sβ patients referring to Baghaei 2 Hospital of Ahvaz in 2019 using a non-random simple sampling method. The blood samples were collected for Rh phenotypes, alloantibody screening and identification, and molecular tests. The SSP-PCR and RFLP methods with the Pst 1 enzyme were used.

RESULTS

The alloimmunization rate was 9.6% and 13.2% based on immunohematological tests and medical records, respectively. The main alloantibodies (90%) were anti-Rh, and 40% of the patients had multiple alloantibodies. A significant correlation was found between gender and alloimmunization. The phenotypes of DCce (37.5%), DCcEe (24%), Dce (20.2%), and dce (5.8%) and genotypes of R1r (25%), R1R2 (20.2%), R1R1 (18.3%), and R1R0 (10.6%) were the most prevalent. The R1R2 was a frequent genotype in Sβ.

CONCLUSION

R0r' and R1R0 genotypes were limited to our population in Iran. Due to the differences in RH genotypes between our population and others, the blood transfusion from other ethnicities increased our total alloimmunization rate.

Retrospective study of frequency of ABO and Rhesus blood group among population of Safdarabad and Faisalabad cities of Pakistan

Objective

The current study aimed to investigate the ABO and rhesus (Rh) blood group frequency in the people of District Faisalabad and Sheikhupura, Punjab Province, Pakistan. The retrospective study was conducted on more than thirty thousand people including both male and female patients admitted to the Tehsil Headquarter Hospital, Safdarabad and The Best Hospital, Faisalabad. Blood samples were taken from each subject and subsequently ABO and Rh blood groups were evaluated separately. The antigen antibody agglutination slide test for blood grouping (ABO) and Rh were used to assess the blood group frequencies.

Results

The frequencies of ABO blood group distribution indicated that blood group B was predominant in the people of Safdarabad followed by O, A and AB respectively. While, among people of Faisalabad, blood group O was predominant followed B, A and AB respectively. Rh negative phenotype was found lesser distributed as compared to the positive Rh phenotype.

Single molecule distribution of RhD binding epitopes on ultraflat erythrocyte ghosts

The Rh blood group system plays a key role in transfusion and organ transplant medicine. The complex transmembrane Rh polypeptides RhD and RhCE carry numerous antigens, including the extremely immunogenic D antigen. The Rh polypeptides form multimolecular Rh complexes with certain transmembrane and skeletal proteins, with so far only incompletely understood physiological functions. Determination of the energy landscape of individual Rh binding epitopes towards their specific interaction partners as well as their localization across the red blood cell (RBC) membrane requires single molecule approaches including large area high resolution recognition imaging. Atomic force microscopy based molecular recognition force spectroscopy in combination with single molecule recognition imaging fulfills these requirements. For unbiased single molecule results, nano-mechanical influences due to cell elasticity have to be eliminated. This is realized by generation of ultra flat erythrocyte ghosts on a solid support. We developed a protocol for the preparation of complete ultraflat erythrocyte ghosts and determined the molecular binding behaviour of different anti-D antibodies towards their binding epitopes on RhD positive and negative erythrocytes. Performing optimized topography and recognition imaging at 16 Mpixel resolution allowed localisation of individual RhD molecules at the single molecule level across an entire RBC. A map of Rh antigens across integer ultraflat RBC ghosts was generated with nanometer resolution. Here we show a homogeneous distribution on rim and dimple regions with comparable receptor densities. Furthermore, differences in the energy landscape between specific monoclonal antibodies were determined at the single molecule level.

Fetal Rhesus D Genotyping and Sex Determination from Maternal Plasma of Rhesus D-Negative Antenatal Population: The Usefulness of Conventional Polymerase Chain Reaction in Resource-limited Settings

Background

This prospective cohort study evaluated the usefulness of conventional PCR in genotyping fetal Rhesus D (RhD) and sex from the maternal plasma of RhD-negative (RhD−) antenatal population in resource-limited settings.

Methods

Thirty apparently healthy RhD− pregnant women with RhD positive (RhD+) partners were included. Blood samples were collected from each participant (in the third trimester of pregnancy) for DNA extraction/purification and fetal RhD genotyping.

Results

Out of the 30 samples, 26 (86.7%) were found to be RhD+ while 4 (13.3%) were RhD−. The RhD+ comprised 24 (80.0%) RhD+ based on exons 5, 7, and 10 combined. Exons 5 and 7 were detected in two additional samples but not exon 10. Serological phenotyping of neonatal blood confirmed 26 RhD+ and 4 RhD−. There was a perfect agreement between the fetal RhD genotype and neonatal RhD phenotyping after delivery for exons 5 and 7 (concordance = 100%, κ = 100.0%, diagnostic accuracy = 100%, p < 0.0001) while exon 10 presented with an almost perfect agreement (concordance = 93.3%, κ = 76.2%, diagnostic accuracy = 93.3%, p < 0.0001). Regarding the prenatal test for the SRY gene, 9 (30.0%) were predicted to be males and the remaining 21 (60.0%) were females. All the 9 and 21 anticipated males and females, respectively, were confirmed after delivery (concordance = 100%, κ = 100.0%, diagnostic accuracy = 100%).

Conclusion

Our study suggests that conventional PCR using the SRY, RhD exons 5 and 7 could be useful for predicting fetal sex and RhD from maternal peripheral blood in resource-limited settings.

Two Reliable Methodical Approaches for Non-Invasive RHD Genotyping of a Fetus from Maternal Plasma

Noninvasive fetal RHD genotyping is an important tool for predicting RhD incompatibility between a pregnant woman and a fetus. This study aimed to assess a methodological approach other than the commonly used one for noninvasive fetal RHD genotyping on a representative set of RhD-negative pregnant women. The methodology must be accurate, reliable, and broadly available for implementation into routine clinical practice. A total of 337 RhD-negative pregnant women from the Czech Republic region were tested in this study. The fetal RHD genotype was assessed using two methods: real-time PCR and endpoint quantitative fluorescent (QF) PCR. We used exon-7-specific primers from the RHD gene, along with internal controls. Plasma samples were analyzed and measured in four/two parallel reactions to determine the accuracy of the RHD genotyping. The RHD genotype was verified using DNA analysis from a newborn buccal swab. Both methods showed an excellent ability to predict the RHD genotype. Real-time PCR achieved its greatest accuracy of 98.6% (97.1% sensitivity and 100% specificity (95% CI)) if all four PCRs were positive/negative. The QF PCR method also achieved its greatest accuracy of 99.4% (100% sensitivity and 98.6% specificity (95% CI)) if all the measurements were positive/negative. Both real-time PCR and QF PCR were reliable methods for precisely assessing the fetal RHD allele from the plasma of RhD-negative pregnant women.

Educational Case: Partial D Phenotype and Role of RhoGAM

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040.¹.

Testing for weak D Antigen: Spectrum and its applied role in rhesus-negative transfusions in Andaman and Nicobar Islands

Objectives

Rhesus (Rh) blood group with variable expression of D antigen is one of the complex systems in immunohematology. Weak D antigen is a phenotype where the D antigen is weakly expressed on red blood cells, and this antigen cannot be detected by routine methods. This study was conducted to determine the frequency of Rh D negativity and weak D antigen among healthy blood donors and to review the clinical significance of weak D antigen pertaining to Rh D-negative transfusions.

Materials and Methods

This cross-sectional prospective study was conducted in G. B Pant Hospital from January 2016 to June 2017 in which all the blood donors from Port Blair and adjacent islands of Andaman and Nicobar were grouped for Rh D antigen and those who tested negative for the D antigen were further tested for weak D antigen by incubating for 30 min and subsequent addition of anti-human globulin sera.

Results

Out of 6415 donors, 6085 (94.86%) were Rh D positive and 330 (05.14%) were Rh D negative. Among the Rh D-negative donors, 05 (01.51%) were positive for weak D antigen. The frequency of Rh D negativity was 25.76% in a blood group, 25.15% in B, 07.88% in AB and 41.21% in O blood group phenotype.

Conclusion

Although the frequency of weak D antigen is low (01.51%), the strong immunogenicity of Rh D antigen discernates the need for appropriate testing for weak D antigen. This is of particular concern in Rh D-negative pregnant females as it can produce alloimmunization if accidentally given weak D antigen positive blood.

A Tutsi family harbouring two new RHCE variant alleles and a new haplotype in the Rh blood group system

BACKGROUND

RHCE*ceEK is a rare RH allele mostly encountered in people of African descent. This allele is defined by four single nucleotide substitutions: c.48G>C, c.712A>G, c.787A>G and c.800T>A. Until now, it has only been reported to segregate with either RHD*01N.01 or RHD*DAR1.00.

MATERIALS AND METHODS

Blood samples were drawn from a 32-year-old Tutsi pregnant woman during an antenatal visit in order to perform her type and screen. To further investigate the results found in the patient, a family study was conducted. Standard haemagglutination methods were used to investigate the subjects' red blood cells and plasma. Molecular workup on RHD and RHCE genes was carried out by DNA microarray, real-time PCR and DNA sequencing techniques.

RESULTS

The patient was phenotyped as group B, D+C-E-c+e+, Hr-. A complex mixture of anti-E, anti-c, anti-Hr and anti-hr^S was detected in her plasma. She was found to carry a normal RHD gene, a conventional RHCE*ceEK allele and an alternative RHCE*ceEK allele (RHCE*ceEK without c.48G>C). The family study showed that the conventional RHCE*ceEK and the alternative RHCE*ceEK alleles were associated with a RHD*01 allele and a RHD*01N.01 allele, respectively. Molecular analysis performed in the proband's mother showed a novel RHCE*ce variant allele on a RHCE*ce^S -like background (RHCE*ce^S with c.609G>A).

CONCLUSIONS

This case study brought out new associations between RHD and RHCE alleles encoding the rare Hr- phenotype: the conventional RHCE*ceEK allele linked to the RHD*01 allele and an alternative RHCE*ceEK allele associated with the RHD*01N.01 allele. A novel RHCE*ce variant (RHCE*ce^S with c.609G>A) was also reported.

Surface-anchored framework for generating RhD-epitope stealth red blood cells

Rhesus D (RhD) is one of the most important immunogenic antigens on red blood cells (RBCs). However, the supply of RhD-negative blood frequently faces critical shortages in clinical practice, and the positive-to-negative transition of the RhD antigen remains a great challenge. Here, we developed an alternative approach for sheltering the epitopes on RhD-positive RBCs using a surface-anchored framework, which is flexible but can achieve an optimal shield effect with minimal physicochemical influence on the cell. The chemical framework completely obstructed the RhD antigens on the cell surface, and the assessments of both blood transfusion in a mouse model and immunostimulation with human RhD-positive RBCs in a rabbit model confirmed the RhD-epitope stealth characteristics of the engineered RBCs. This work provides an efficient methodology for improving the cell surface for universal blood transfusion and generally indicates the potential of rationally designed cell surface engineering for transfusion and transplantation medicine.

Serologic strategy in detecting RHD altered alleles in Brazilian blood donors

Background

We evaluated different technological approaches and anti-D clones to propose the most appropriate serologic strategy in detecting the largest numbers of D variants in blood donors.

Methods

We selected 101 samples from Brazilian blood donors with different expressions of D in our donor routine. The tests were performed in immediate spin (IS) with eleven commercially available anti-D reagents in a tube and microplate. The D confirmatory tests for the presence of weak D included the indirect antiglobulin test (IAT) in a tube, gel and solid-phase red blood cell adherence (SPRCA). All DNA samples were extracted from peripheral blood and the D variants were classified using different molecular assays.

Results

The RHD variants identified by molecular analysis included weak D types (1, 2, 3, 11 and 38) and partial Ds (DAR1.2, DAR1, DAR3.1, DAU0, DAU2, DAU4, DAU5, DAU6, DMH and DVII). The monoclonal-monoclonal blend RUM-1/MS26 was the best anti-D reagent used in detecting the D antigen in the IS phase in a tube, reacting with 83.2% of the D variants, while the anti-D blend D175 + 415 was the best monoclonal antibody (MoAb) used in a microplate to minimize the need for an IAT, reacting with 83.2% of the D variants. The D confirmatory tests using SPRCA showed a reactivity (3 - 4+) with 100% of the D variant samples tested.

Conclusion

Our results show that, even using sensitive methods and MoAbs to ensure the accurate assignment of the D antigen, at least 17% of our donor samples need a confirmatory D test in order to avoid alloimmunization in D-negative patients.

Characterization of RHD locus polymorphism in D negative and D variant donors from Northwestern Argentina

BACKGROUND

A notable RHD variability has been observed in Central Argentina's current population attributed to the intermixing of different ethnic groups. The Northwestern region of the country is characterized by a markedly Amerindian genetic contribution. In this sense, the definition of the RHD polymorphism in individuals from this area was lacking.

STUDY DESIGN AND METHODS

A total of 757 donors from Northwestern Argentina, with D negative C and/or E positive (n = 526), and D variant (n = 231) phenotype defined by standard hemmaglutination tube techniques were genotyped using in-house PCR strategies, commercial SNP arrays and Sanger sequencing.

RESULTS

Among D negative C and/or E positive samples, RHD null (15.40%) and DEL alleles (3.23%) were identified. One unreported SNP c.1001T>A responsible for a null allele was found. RHD*01N.75 (4.18%) and RHD*DEL43 (2.66%) were the most prevalent variants following RHD*03N.01 (8.75%). The characterization of serologic weak D phenotypes showed that RHD*weak D type 1, 2, and 3 variants were found only in 37.24% of the samples, whereas RHD*weak D type 93 was the most prevalent allele (25.11%). Also, a previously unreported missense variation c.764G>A was identified.

CONCLUSIONS

A RHD genotyping strategy for patients and donors from Northwestern Argentina must consider the detection of the frequently found RHD*01N.75, RHD*DEL43, and RHD*weak D type 93 variants. Taking into account that RHD*DEL43 has scarcely been found in North Americans and Europeans whereas RHD*01N.75 and RHD*weak D type 93 have never been described in populations other than Argentineans, these RHD variants could be attributed to Native Amerindian genetic influence.

Amplicon Sequencing-Based Noninvasive Fetal Genotyping for RHD-Positive D Antigen-Negative Alleles

BACKGROUND

To avoid hemolytic disease of the fetus and newborn resulting from maternal alloantibodies against fetal Rh antigens, anti-D immunoglobulin is routinely administered to RhD-negative pregnant women in Japan. Fetal RHD genotyping using cell-free DNA may prevent unnecessary antibody administration; however, current PCR-based methods, which detect RHD deletion, do not address the higher rates of RHD-positive D antigen-negative alleles in nonwhite populations without additional inspections.

METHODS

We developed an amplicon-sequencing method that could estimate the type of paternally inherited fetal RHD allele from 4 major RHD alleles in the Japanese population: the D antigen-positive allele (RHD*01, 92.9%) and 3 D antigen-negative alleles (RHD*01N.01, 6.6%; RHD*01EL.01, 0.3%; RHD*01N.04, 0.1%) using cell-free DNA obtained from the blood plasma of pregnant women.

RESULTS

The method correctly determined the fetal RhD type even when RhD-negative pregnant women possessed an RHD-positive D antigen-negative allele: RHD*01EL.01 or RHD*01N.04.

CONCLUSIONS

This method is a reliable noninvasive fetal RHD genotyping method for Japanese and other East Asian populations. The genotyping principle of amplifying 2 different regions using the same primer pair and distinguishing them by their sequence difference during the subsequent mapping procedure is also theoretically applicable to RHD-positive D antigen-negative alleles prevalent in Africans. Therefore, this method offers an opportunity to consider targeted administration of anti-D immunoglobulin to RhD-negative pregnant women in East Asian and African countries and to increase the specificity of the fetal RHD genotyping implemented nationwide in several European countries.

Complete RHD next-generation sequencing: establishment of reference RHD alleles

The Rh blood group system (ISBT004) is the second most important blood group after ABO and is the most polymorphic one, with 55 antigens encoded by 2 genes, RHD and RHCE This research uses next-generation sequencing (NGS) to sequence the complete RHD gene by amplifying the whole gene using overlapping long-range polymerase chain reaction (LR-PCR) amplicons. The aim was to study different RHD alleles present in the population to establish reference RHD allele sequences by using the analysis of intronic single-nucleotide polymorphisms (SNPs) and their correlation to a specific Rh haplotype. Genomic DNA samples (n = 69) from blood donors of different serologically predicted genotypes including R₁R₁ (DCe/DCe), R₂R₂ (DcE/DcE), R₁R₂ (DCe/DcE), R₂R_Z (DcE/DCE), R₁r (DCe/dce), R₂r (DcE/dce), and R₀r (Dce/dce) were sequenced and data were then mapped to the human genome reference sequence hg38. We focused on the analysis of hemizygous samples, as these by definition will only have a single copy of RHD For the 69 samples sequenced, different exonic SNPs were detected that correlate with known variants. Multiple intronic SNPs were found in all samples: 21 intronic SNPs were present in all samples indicating their specificity to the RHD*DAU0 (RHD*10.00) haplotype which the hg38 reference sequence encodes. Twenty-three intronic SNPs were found to be R₂ haplotype specific, and 15 were linked to R₁, R₀, and R_Z haplotypes. In conclusion, intronic SNPs may represent a novel diagnostic approach to investigate known and novel variants of the RHD and RHCE genes, while being a useful approach to establish reference RHD allele sequences.

Random allogeneic blood transfusion in pigs: characterisation of a novel experimental model

Background

Organ cross-talk describes interactions between a primary affected organ and a secondarily injured remote organ, particularly in lung-brain interactions. A common theory is the systemic distribution of inflammatory mediators that are released by the affected organ and transferred through the bloodstream. The present study characterises the baseline immunogenic effects of a novel experimental model of random allogeneic blood transfusion in pigs designed to analyse the role of the bloodstream in organ cross-talk.

Methods

After approval of the State and Institutional Animal Care Committee, 20 anesthetized pig were randomized in a donor and an acceptor (each n = 8): the acceptor animals each received high-volume whole blood transfusion from the donor (35–40 ml kg⁻¹). Four animals received balanced electrolyte solution instead of blood transfusion (control group; n = 4). Afterwards the animals underwent extended cardiorespiratory monitoring for eight hours. Post mortem assessment included pulmonary, cerebral and systemic mediators of early inflammatory response (IL-6, TNF-alpha, iNOS), wet to dry ratio, and lung histology.

Results

No adverse events or incompatibilities occurred during the blood transfusion procedures. Systemic cytokine levels and pulmonary function were unaffected. Lung histopathology scoring did not display relevant intergroup differences. Neither within the lung nor within the brain an up-regulation of inflammatory mediators was detected. High volume random allogeneic blood transfusion in pigs neither impaired pulmonary integrity nor induced systemic, lung, or brain inflammatory response.

Conclusion

This approach can represent a novel experimental model to characterize the blood-bound transmission in remote organ injury.

Red Blood Cells: Chasing Interactions

Human red blood cells (RBC) are highly differentiated cells that have lost all organelles and most intracellular machineries during their maturation process. RBC are fundamental for the nearly all basic physiologic dynamics and they are key cells in the body's respiratory system by being responsible for the oxygen transport to all cells and tissues, and delivery of carbon dioxide to the lungs. With their flexible structure RBC are capable to deform in order to travel through all blood vessels including very small capillaries. Throughout their in average 120 days lifespan, human RBC travel in the bloodstream and come in contact with a broad range of different cell types. In fact, RBC are able to interact and communicate with endothelial cells (ECs), platelets, macrophages, and bacteria. Additionally, they are involved in the maintenance of thrombosis and hemostasis and play an important role in the immune response against pathogens. To clarify the mechanisms of interaction of RBC and these other cells both in health and disease as well as to highlight the role of important key players, we focused our interest on RBC membrane components such as ion channels, proteins, and phospholipids.

Quantitative high-throughput screening assays for the discovery and development of SIRPα-CD47 interaction inhibitors

CD47 is an immune checkpoint molecule that downregulates key aspects of both the innate and adaptive anti-tumor immune response via its counter receptor SIRPα, and it is expressed at high levels in a wide variety of tumor types. This has led to the development of biologics that inhibit SIRPα engagement including humanized CD47 antibodies and a soluble SIRPα decoy receptor that are currently undergoing clinical trials. Unfortunately, toxicological issues, including anemia related to on-target mechanisms, are barriers to their clinical advancement. Another potential issue with large biologics that bind CD47 is perturbation of CD47 signaling through its high-affinity interaction with the matricellular protein thrombospondin-1 (TSP1). One approach to avoid these shortcomings is to identify and develop small molecule molecular probes and pretherapeutic agents that would (1) selectively target SIRPα or TSP1 interactions with CD47, (2) provide a route to optimize pharmacokinetics, reduce on-target toxicity and maximize tissue penetration, and (3) allow more flexible routes of administration. As the first step toward this goal, we report the development of an automated quantitative high-throughput screening (qHTS) assay platform capable of screening large diverse drug-like chemical libraries to discover novel small molecules that inhibit CD47-SIRPα interaction. Using time-resolved Förster resonance energy transfer (TR-FRET) and bead-based luminescent oxygen channeling assay formats (AlphaScreen), we developed biochemical assays, optimized their performance, and individually tested them in small-molecule library screening. Based on performance and low false positive rate, the LANCE TR-FRET assay was employed in a ~90,000 compound library qHTS, while the AlphaScreen oxygen channeling assay served as a cross-validation orthogonal assay for follow-up characterization. With this multi-assay strategy, we successfully eliminated compounds that interfered with the assays and identified five compounds that inhibit the CD47-SIRPα interaction; these compounds will be further characterized and later disclosed. Importantly, our results validate the large library qHTS for antagonists of CD47-SIRPα interaction and suggest broad applicability of this approach to screen chemical libraries for other protein-protein interaction modulators.

Enhancement of red blood cell transfusion compatibility using CRISPR-mediated erythroblast gene editing

Regular blood transfusion is the cornerstone of care for patients with red blood cell (RBC) disorders such as thalassaemia or sickle‐cell disease. With repeated transfusion, alloimmunisation often occurs due to incompatibility at the level of minor blood group antigens. We use CRISPR‐mediated genome editing of an immortalised human erythroblast cell line (BEL‐A) to generate multiple enucleation competent cell lines deficient in individual blood groups. Edits are combined to generate a single cell line deficient in multiple antigens responsible for the most common transfusion incompatibilities: ABO (Bombay phenotype), Rh (Rh_null), Kell (K₀), Duffy (Fy_null), GPB (S−s−U−). These cells can be differentiated to generate deformable reticulocytes, illustrating the capacity for coexistence of multiple rare blood group antigen null phenotypes. This study provides the first proof‐of‐principle demonstration of combinatorial CRISPR‐mediated blood group gene editing to generate customisable or multi‐compatible RBCs for diagnostic reagents or recipients with complicated matching requirements.

Red Blood Cell Membrane Conductance in Hereditary Haemolytic Anaemias

Congenital haemolytic anaemias are inherited disorders caused by red blood cell membrane and cytoskeletal protein defects, deviant hemoglobin synthesis and metabolic enzyme deficiencies. In many cases, although the causing mutation might be known, the pathophysiology and the connection between the particular mutation and the symptoms of the disease are not completely understood. Thus effective treatment is lagging behind. As in many cases abnormal red blood cell cation content and cation leaks go along with the disease, by direct electrophysiological measurements of the general conductance of red blood cells, we aimed to assess if changes in the membrane conductance could be a possible cause. We recorded whole-cell currents from 29 patients with different types of congenital haemolytic anaemias: 14 with hereditary spherocytosis due to mutations in α-spectrin, β-spectrin, ankyrin and band 3 protein; 6 patients with hereditary xerocytosis due to mutations in Piezo1; 6 patients with enzymatic disorders (3 patients with glucose-6-phosphate dehydrogenase deficiency, 1 patient with pyruvate kinase deficiency, 1 patient with glutamate-cysteine ligase deficiency and 1 patient with glutathione reductase deficiency), 1 patient with β-thalassemia and 2 patients, carriers of several mutations and a complex genotype. While the patients with β-thalassemia and metabolic enzyme deficiencies showed no changes in their membrane conductance, the patients with hereditary spherocytosis and hereditary xerocytosis showed largely variable results depending on the underlying mutation.

Sequence diversity of the Rh blood group system in Basques

Basques show specific cultural, demographic, and genetic characteristics that have placed them as an isolated and unique population within Europe, such as their non-Indo-European language, Euskara. They have historically lived along the Western Pyrenees, between Spain and France, in one of the most important European glacial refugia during the Last Glacial Maximum. The most striking genetic characteristic is their highest frequency of the RhD blood group negative allele, a variant related to the hemolytic disease of the newborn. Both demographic and adaptive processes have been suggested as possible causes of the high frequency of RhD negative in Basques, but neither hypothesis has been clearly demonstrated. While previous studies on the Rh system in Basques have been mostly focused on serological and genotyping diversity, in this work we analyze genotyping and next generation sequencing data in order to provide a general framework of the genetic scenario of the system in Basques. In particular, we genotyped the most relevant variants of the system (D/d, E/e, and C/c), and sequenced three ~6 kb flanking regions surrounding the Rh genes in Basques and also in other populations for comparison. Our results are in agreement with previous studies, with Basques presenting the highest frequency of the RHD deletion (47.2%). Haplotype analyses of D/d, E/e, and C/c variants confirmed an association between the RhC allele, previously suggested to be under positive selection, and the RhD positive variant in non-sub-Saharan populations, including Basques. We also found extreme differentiation for the C/c variant when comparing sub-Saharan to non-sub-Saharan populations.

Neonatal hyperbilirubinemia secondary to combined anti e and anti C isoimmunisation: a literature review

A term male infant was admitted at 48 h of postnatal life to the neonatal unit for jaundice. The investigation showed total serum bilirubin (TSB) of 17.1 mg/dl, haemoglobin of 11 g/dl, reticulocyte count of 9.5% and peripheral smear was suggestive of macrocytic, normochromic red blood cell (RBC) with target cells and multiple spherocytes with occasional nucleated RBC. The infant's blood group was B positive. Direct antiglobulin test was strongly positive by gel method (3+). Mother's blood group was B positive and indirect antiglobulin test was positive when tested postnatally. Extended minor blood grouping and cross matching showed this as a case of combined anti e and anti C antibodies isoimmunisation. Infant was treated with phototherapy for 72 h and was shifted to mother side. Infant was serially monitored with TSB level every sixth hourly and American Academy of Pediatrics (AAP) phototherapy charts were followed to see for rebound hyperbilirubinemia. The neonate was discharged and there was no readmission for hyperbilirubinemia. It is very rare and we report the third case of its type till date.

Hereditary stomatocytosis: An underdiagnosed condition

Hereditary stomatocytoses are a wide class of hemolytic anemias characterized by alterations of ionic flux with increased cation permeability that results in inappropriate shrinkage or swelling of the erythrocytes, and water lost or gained osmotically. The last few years have been crucial for new acquisitions in this field in terms of identifying new causative genes and of studying their pathogenetic mechanisms. This review summarizes the main features of erythrocyte membrane transport diseases, dividing them into forms with either isolated erythroid phenotype (nonsyndromic) or extra-hematological manifestations (syndromic), and focusing particularly on the most recent advances regarding dehydrated forms of hereditary stomatocytosis and familial pseudohyperkalemia.

Rh blood phenotyping (D, E, e, C, c) microarrays using multichannel surface plasmon resonance imaging

The application of Surface Plasmon Resonance Imaging (SPRi) for the detection of transmembrane antigen of the Rhesus (Rh) blood group system is demonstrated. Clinically significant Rh blood group system antigens, including D, C, E, c, and e, can be simultaneously identified via solid phase immobilization assay, which offers significant time savings and assay simplification. Red blood cells (RBCs) flowed through the micro-channel, where a suitable condition for Rh blood group detection was an RBC dilution of 1:10 with a stop-flow condition. Stop flow showed an improvement in specific binding compared to continuous flow. Rh antigens required a longer incubation time to react with the immobilized antibody than A and B antigens due to the difference in antigen type and their location on the RBC. The interaction between the immobilized antibodies and their specific antigenic counterpart on the RBC showed a significant difference in RBC removal behavior using shear flow, measured from the decay of the SPR signal. The strength of the interaction between the immobilized antibody and RBC antigen was determined from the minimum wall shear stress required to start the decay process in the SPR signal. For a given range of immobilized antibody surface densities, the Rh antigen possesses a stronger interaction than A, B, and AB antigens. Identification of 82 samples of ABO and Rh blood groups using SPRi showed good agreement with the standard micro-column agglutination technique. A wider coverage of antigenic recognition for RBC when using the solid phase immobilization assay was demonstrated for the RBC with the antigenic site located on the transmembrane protein of the clinically significant Rh antigen. Given the level of accuracy and precision, the technique showed potential for the detection of the Rh minor blood group system.

Anti-D reagents should be chosen accordingly to the prevalence of D variants in the obstetric population

BACKGROUND

Resolving ambiguous results of D antigen typing is crucial for appropriate and rational administration of anti-D immunoprophylaxis and transfusion practice in obstetric population. The aim of the study was to establish selection criteria of anti-D reagents for our population.

METHODS

A total of 12 689 samples from primiparous women in Split-Dalmatia County, Croatia, were typed for RhD antigen during the period of 5 years. Ambiguous results were submitted to additional serologic investigation and genotyping. RHD genotyping was performed by commercial genotyping kits (Ready Gene weak D ^® and Ready gene CDE, Inno-Train, Kronberg, Germany). Relative frequencies and accompanying 95% confidence intervals were used to estimate the prevalence of variants.

RESULTS

The prevalence of D variants was 0.42% (95% CI 0.31; 0.53). The most common partial D variant was D Va (RHD*05.05), with the prevalence of 0.08% (95% CI 0.03; 0.13). All weak D variants were weak D types 1, 2 and 3 (RHD*weak D type 1, RHD*weak D type 2, RHD*weak D type 3). Weak D samples were distinguishable from partial D in routine typing due to the difference in reactivity of partial D samples with clones D7B8 and RUM-1. Cell line RUM-1 gives weak or negative reactions with partial DVa category.

CONCLUSION

The most common partial D variant in our population is DVa. It is recommended to use cell lines which do not strongly agglutinate DVa variant in routine RhD typing. The appropriate choice of reagents will enable the serology methods to recognize the cases in which RHD genotyping is required.

Rapid RHD Zygosity Determination Using Digital PCR

BACKGROUND

Paternal zygosity testing is used for determining homo- or hemizygosity of RHD in pregnancies that are at a risk of hemolytic disease of the fetus and newborn. At present, this is achieved by using real-time PCR or the Rhesus box PCR, which can be difficult to interpret and unreliable, particularly for black African populations.

METHODS

DNA samples extracted from 53 blood donors were analyzed using 2 multiplex reactions for RHD-specific targets against a reference (AGO1)² to determine gene dosage by digital PCR. Results were compared with serological data, and the correct genotype for 2 discordant results was determined by long-range PCR (LR-PCR), next-generation sequencing, and conventional Sanger sequencing.

RESULTS

The results showed clear and reliable determination of RHD zygosity using digital PCR and revealed that 4 samples did not match the serologically predicted genotype. Sanger sequencing and long-range PCR followed by next-generation sequencing revealed that the correct genotypes for samples 729M and 351D, which were serologically typed as R₁R₂ (DCe/DcE), were R₂r' (DcE/dCe) for 729M and R₁r″ (DCe/dcE), R₀r^y (Dce/dCE), or R_Zr (DCE/dce) for 351D, in concordance with the digital PCR data.

CONCLUSIONS

Digital PCR provides a highly accurate method to rapidly define blood group zygosity and has clinical application in the analysis of Rh phenotyped or genotyped samples. The vast majority of current blood group genotyping platforms are not designed to define zygosity, and thus, this technique may be used to define paternal RH zygosity in pregnancies that are at a risk of hemolytic disease of the fetus and newborn and can distinguish between homo- and hemizygous RHD-positive individuals.

Rhesus CE expression on patient red blood cells is an independent prognostic factor for adenocarcinoma of the lung

OBJECTIVES

The influence of blood group antigens on cancerogenesis is shown for distinct tumor types, yet the impact of Rhesus blood group antigens in lung cancer is not clarified.

MATERIALS AND METHODS

To investigate the impact of Rhesus blood groups a non-small cell lung cancer (NSCLC) collective (n = 1047) was analyzed retrospectively. Using a second cohort of n = 340 primarily operated stage I-III NSCLC patients, we evaluated immunohistochemistry of CD47-antibody stained tissue samples in correlation to histopathologic subtype and Rhesus blood group.

RESULTS AND CONCLUSION

In 516 of 1047 patients blood group data were available. Seven different RhCE phenotypes were grouped as "··ee," "ccE·," and "C·E·." Adenocarcinoma patients with Rh "··ee" revealed improved overall survival (29 (21.2-36.8) m; HR 1.00 [index]) compared with Rh "ccE·" (19 (1.9-36.1) m; HR 1.76 [1.15-2.70]) and Rh "C·E·" (10 (7.4-12.6) m; HR 2.65 [1.70-4.12]) univariately (P < .001) and multivariately (P < .001). Rh "··ee" showed reduced incidence of CNS-metastasis (P = .014) and metastasis count (P = .032) in stage IV adenocarcinoma. Immunohistochemistry associated CD47-positivity with adenocarcinomas (n = 340, P = .048). In n = 51 cases blood group data were available. The prognostic effect of Rh "··ee" compared with Rh "ccE·" and Rh "C·E·" was stated (P = .001), foremost in CD47-positive adenocarcinomas (Rh "··ee" vs. Rh "ccE·" and Rh "C·E·," P = .008). Inversely Rh "ccE·" or Rh "C·E·" was found beneficial in CD47-negative non-adenocarcinomas (P = .046). Phenotypic RhCE expression may be an independent prognostic factor for overall survival in adeno-NSCLC. We hypothesize an erythrocytic-immunologic interaction with tumor tissue, possibly altered by RhCE and CD47, resulting in a metastatic prone condition.

Importance of extended blood group genotyping in multiply transfused patients

Blood group antigen systems are not limited to the ABO blood groups. There is increasing interest in the detection of extended blood group systems on the red cell surface. The conventional method used to determine extended blood group antigens or red cell phenotype is by serological testing, which is based on the detection of visible haemagglutination or the presence of haemolysis. However, this technique has many limitations due to recent exposure to donor red cell, certain drugs or medications or other diseases that may alter the red cell membrane. We aimed to determine the red cell blood group genotype by SNP real time PCR and to compare the results with the conventional serological methods in multiply transfused patients. Sixty-three patients participated in this study whose peripheral blood was collected and blood group phenotype was determined by serological tube method while the genotype was performed using TaqMan^® Single Nucleotide Polymorphism (SNP) RT-PCR assays for RHEe, RHCc, Kidd and Duffy blood group systems. Discrepancies were found between the phenotype and genotype results for all blood groups tested. Accurate red blood cell antigen profiling is important for patients requiring multiple transfusions. The SNP RT-PCR platform is a reliable alternative to the conventional method.