[Relative Quantification for Obtaining the IgG Blood Group Antibodies in Plasma by the Absorption and Elution Test].

OBJECTIVE: To establish the absorption and elution test for relatively quantitive obtaining anti-A and anti-B blood group IgG antibodies in the plasma of O-type RhD-positive pregnant women. METHODS: 95 cases of the O-type RhD-positive pregnant women plasma samples were randomly selected for obtaining the IgG antibodies of anti-A and anti-B blood group, with absorption test under 37 ℃ and elution test under 56 ℃, and the IgG anti-A and anti-B antibody titers of plasma and elution were determined by the microcolumn gel anti-human globulin test. The differences and correlation between the titers of IgG antibodies in the eluent and plasma were compared and analyzed. RESULTS: After a logarithmic transformation (Log2), there was no statistically difference between IgG antibody anti-A difference value and anti-B difference value in the eluent and plasma (P >0.05). The titer of IgG antibody in the eluent was positively correlated with the titer of IgG antibody in the plasma (r =0.914). The linear equation for IgG antibody titers fitted by a scatter plot between the eluent and plasma was Y=-3.55+0.96X. CONCLUSION: The absorption and elution test can be used to obtain the anti-A and anti-B IgG antibodies in the plasma of O-type RhD-positive pregnant women, whose plasma origin IgG titer is greater than 8. Meanwhile, the acquisition of anti-A antibodies was as effective as anti-B antibodies at the same time, and the antibodies obtained are positive proportional to their respective concentrations in the plasma.

[Analysis of the causes of incompatible cross-matching induced by two Rh blood group antibodies and corresponding laboratory treatment].

Objective To analyze the serological characteristics and clinical significance of IgG anti-D and anti-C combined antibodies and anti-E and anti-c combined antibodies in patients negative for RhDC and RhEc antigens. Methods The clinical data and laboratory results of 12 cases with two types of irregular antibodies were recorded and analyzed, including age, sex, history of blood transfusion/pregnancy, ABO and RhD blood group identification, Rh antigen typing, irregular antibody screening, antibody-specific identification, absorption-elution tests, antibody titer determination and cross-matching tests. Results Among the 12 patients, the mean age was 51.4±16.9 years. Nine patients had a history of blood transfusion; eight patients had a history of pregnancy; five patients had both. Serological tests showed positive antibody screening and incompatible cross-matching. The results of antibody-specific identification and absorption-elution tests showed the presence of both IgG anti-D and anti-C antibodies in three patients, with anti-D titers at 16-32, and anti-C titers at 8-16. Nine patients had both IgG anti-E and anti-c antibodies, with the titers of anti-E and anti-c antibodies at 8-16. From the patients with combined anti-D and anti-C antibodies, suspended red blood cells of ABO identical type, RhD negative and other Rh antigens as ccee were selected. From patients with combined anti-E and anti-c antibodies, suspended red blood cells of ABO identical type, RhD positive and other Rh antigens as CCee were selected. Cross-matching blood test results showed no agglutination or hemolysis in saline, polycoagulant and anti-human globulin media. Conclusion Blood transfusion and/or pregnancy are the primary causes of irregular antibodies in two Rh systems, leading to positive antibody screening and cross-match incompatibility. Routine compatibility transfusion of Rh antigens, based on ABO homotypic blood transfusion, is of great value and significance for the safety of clinical blood transfusion and the prevention of hemolytic disease of the newborn.

[Detection of Rh phenotype in clinical blood transfusion and the necessity of homotype transfusion].

Objective To explore the importance of Rh phenotype detection and homotype blood transfusion. Methods The Rh phenotypes (CcDEe) of 3411 patients with repeated blood transfusions and 4735 blood donors were detected by the microcolumn gel test, and the positive rate of irregular antibodies was counted. A statistical analysis was conducted on the transfusion effectiveness between the Rh homotype transfusion group and the random transfusion group. Results The distribution of Rh antigen and its phenotype in our research is consistent with the reported results. Rh CCDee and Rh CcDEe are high-frequency phenotypes, and the antibodies of the Rh blood group system are high-frequency irregular antibodies, accounting for 62.42% of the detected antibodies. The positive rates of irregular antibodies in Rh system and direct antiglobulin test in random transfusion group were 6.67% and 10%, respectively, while those in Rh homotype transfusion group were 0% and 3.3%, respectively. There were three cases of adverse transfusion reactions in the random transfusion group, whereas no adverse transfusion reactions occurred in the Rh homotype transfusion group. The increase in hemoglobin was more significant after red blood cell transfusion in Rh homotype transfusion group. Conclusion In patients with repeated blood transfusions, Rh phenotype detection and the use of Rh homotype transfusion can avoid the difficulties associated with Rh blood group identification and cross-matching caused by random blood transfusions. It can effectively reduce the risk of immune and adverse reactions related to the Rh blood group system, improve the effectiveness of blood transfusion, and ensure the safety of clinical blood transfusions.

Frequency of Duffy, Kidd, Lewis, and Rh Blood Group Antigens and Phenotypes Among Donors in the Al-Ahsa Region, Saudi Arabia.

BACKGROUND: In Al-Ahsa, Saudi Arabia, the high consanguinity rates contribute to the prevalence of inherited hemoglobinopathies such as sickle cell disease and thalassemia, which frequently require blood transfusions. These transfusions carry the risk of alloimmunization, necessitating a precise blood component matching to mitigate health risks. Local antigen frequency data is vital for optimizing transfusion practices and enhancing the safety of these medical procedures for the Al-Ahsa population. METHODS: This study investigated the distribution of Duffy, Kidd, Lewis, and Rh blood group antigens in 1,549 individuals from the region; comparing the frequencies with global data. RESULTS: Serological analyses revealed a high prevalence of the Fy(a+b-) and Jk(a+b+) phenotypes in the Duffy and Kidd blood groups, respectively, with Jk(a-b-) being notably scarce. The Lewis blood group exhibited a significant presence of Le(a-b+) and Le(a+b-) phenotypes, whereas Le(a+b+) was less common. In the Rh system, the D antigen was most prevalent, with other antigens following in descending order of frequency. CONCLUSIONS: The study underscores the regional variation in antigen frequencies, emphasizing the need for local blood banks to adapt their screening and matching practices to mitigate the risk of alloimmunization and enhance transfusion safety. These findings are pivotal for refining transfusion strategies and understanding the immunohematology landscape in Al-Ahsa.

Application of RhD Blood Group to Simulate Antibody Identification Test in Immunohematology Education.

BACKGROUND: Immunohematology skill education is an important part of the transfusion medicine professional training. We tried to solve the difficulty of obtaining suitable and sufficient positive samples in the immunohematology education. METHODS: Different identification panels and panel cells were created by RhD-positive red blood cells (RBCs) and RhD-negative RBCs, according to the underlying antibodies. Diluted anti-D reagent was used as simulated plasma for identification. RESULTS: The antibody identification of single antibody with dose-effect and two antibodies present at the same time were successfully simulated. CONCLUSIONS: It is a practical and cheap method for antibody identification training to use RhD blood group, especially when positive samples are short.

Rh Blood Group Antigens and Alloimmunization Risk of Pregnant Women in South Western, Nigeria.

BACKGROUND: Rh blood group antigens are the second most important blood group antigens in clinical transfusion due to their immunogenicity and prevalence. Childbirth, miscarriage, and other obstetrics events are risk factors for alloimmunization in women which increases the likelihood of haemolytic blood transfusion reaction and hemolytic disease of the fetal/newborn (HDNF/B). Even though there are several data on the RhD status of our populations. However, there is a dearth of data on pregnant women's C, E, c, and e status, their alloimmunization risk, and rates in Nigeria. OBJECTIVES: This study aims to provide information on the distribution of the Rh major antigens and risk factors for alloimmunization in pregnant women in southwestern Nigeria. MATERIALS AND METHODS: This was a descriptive cross-sectional study of 133 pregnant women attending routine ante-natal clinics. Questionnaires were administered to collect biodata and obstetrics history. ABO blood grouping and Rh phenotyping were carried out on their blood samples using RAPID LABS Monoclonal Rhesus Typing Reagent. RESULTS AND DISCUSSION: Rh blood group antigen c was present in 100% of the women, followed by e (98.5%) and D (95.5%). C and E are the least prevalent antigens and probably the ones to which antibodies may be formed. The commonest Rh phenotype was Dce. Of all the pregnant women, alloimmunization was present in 0.8%. Of those who were RhD negative, alloimmunization was present in 16.7%. Pregnant women are more likely to be alloimmunized against C and E antigens than c and e antigens due to their low and high frequencies respectively.

CONTEXTE: Les antigènes du groupe sanguin Rh sont les seconds plus importants en transfusion clinique en raison de leur immunogénicité et de leur prévalence. L'accouchement, la fausse couche et d'autres événements obstétriques sont des facteurs de risque d'alloimmunisation chez les femmes, augmentant ainsi la probabilité de réactions hémolytiques lors de transfusions sanguines et de maladies hémolytiques du fœtus/nouveau-né (HDNF/B). Bien qu'il existe plusieurs données sur le statut RhD de nos populations, il y a un manque de données sur le statut des antigènes C, E, c et e chez les femmes enceintes, leur risque d'alloimmunisation et les taux associés au Nigéria. OBJECTIFS: Cette étude vise à fournir des informations sur la distribution des principaux antigènes Rh et les facteurs de risque d'alloimmunisation chez les femmes enceintes dans le sud-ouest du Nigéria. MÉTHODOLOGIE: Il s'agit d'une étude descriptive transversale de 133 femmes enceintes fréquentant les cliniques prénatales de routine. Des questionnaires ont été administrés pour collecter des données biodémographiques et des antécédents obstétriques. La détermination des groupes sanguins ABO et le phénotypage Rh ont été réalisés sur leurs échantillons de sang à l'aide du réactif de typage Rh monoclonal RAPID LABS. RÉSULTATS ET DISCUSSION: L'antigène c du groupe sanguin Rh était présent chez 100 % des femmes, suivi de e (98,5 %) et D (95,5 %). Les antigènes C et E sont les moins prévalents et probablement ceux contre lesquels des anticorps peuvent être formés. Le phénotype Rh le plus courant était Dce. Parmi toutes les femmes enceintes, l'alloimmunisation était présente chez 0,8 %. Parmi celles qui étaient RhD négatives, 'alloimmunisation était présente chez 16,7 %. Les femmes enceintes sont plus susceptibles de développer une alloimmunisation contre les antigènes C et E que contre les antigènes c et e en raison de leurs fréquences respectives faibles et élevées. MOTS-CLÉS: Antigènes du groupe sanguin Rh, Phénotype, Alloanticorps érythrocytaires, Femmes enceintes.

Why do RhD negative pregnant women still become anti-D immunized despite prophylaxis with anti-D immunoglobulin?

Maternal allo-anti-D in RhD negative pregnant women may cause mild to severe hemolytic disease of the fetus and newborn. Although several other antibodies may also destroy red blood cells of the fetus and newborn, preventive measures with anti-D immunoglobulin are only available for D antigen. Targeted antenatal care together with postpartum prophylaxis with anti-D immunoglobulin has significantly reduced the D-alloimmunization risk. Potentially sensitizing events like trauma to the pregnant abdomen, vaginal bleeding, and amniocentesis may lead to fetomaternal hemorrhage and necessitate additional doses. Despite comprehensive programs with these targeted measures, allo-anti-D is still the most common reason for severe hemolytic disease of the fetus and newborn. Where do we fail then? Here, in this review, I would therefore like to discuss the reasons for D-alloimmunizations hoping that the greater focus will pave the way for further reduction in the number of pregnancy-related allo-anti-Ds.

The prevalence of alloantibodies and ABO RhD blood groups in a cohort of Aboriginal and non-Aboriginal cardiac surgery patients from Australia.

INTRODUCTION: Limited evidence exists on the distribution of ABO RhD blood groups and prevalence and specificity of red blood cell (RBC) alloantibodies in Aboriginal and Torres Strait Islander peoples of Australia. We investigated RBC alloantibody prevalence and ABO RhD groups in Aboriginal patients undergoing cardiac surgery at a South Australian (SA) tertiary hospital, a major cardiac surgical referral centre for Northern Territory (NT) patients METHODS: Retrospective analysis of all consecutive patients undergoing cardiac surgery at Flinders Medical Centre (FMC) between January 2014 and June 2019. ABO and RhD blood groups, and RBC alloantibody prevalence, specificity, and clinical significance in Aboriginal and non-Aboriginal cardiac patients were determined at time of surgery and on follow up to 2021. RESULTS: 2327 patients were included, 588 (25.3 %) were from NT, and 420 (18.0 %) were Aboriginal. Aboriginal patients had a higher prevalence of ABO group O (59.8 % vs 43.9 %) and RhD positive (99.0 % vs 83.8 %). One-hundred-and-eleven patients had 154 RBC alloantibodies, 57/420 (13.6 %) Aboriginal versus 54/1907 (2.8 %) non-Aboriginal (p < 0.0001). There were higher numbers of IgM alloantibodies in Aboriginal patients (59/77, 76.6 %), with Lewis, P1 and M more common. Sixty patients had antibodies detected at time of surgery, 14 NT patients with previously detected alloantibodies, prior to surgery, presented with a negative antibody screen and 37 had new antibodies detected after cardiac surgery. CONCLUSION: A high prevalence of IgM alloantibodies was found in Aboriginal compared to non-Aboriginal cardiac surgery patients. The clinical significance of these IgM alloantibodies in Aboriginal peoples requires further investigation.

Serologic profiling of D variants in donor routine: unveiling the impact on false-negative results and alloimmunization.

The high number of D variants can lead to the unnecessary use of Rh immune globulin, overuse of D- RBC units, and anti-D allommunization. D variant prevalence varies among ethnic groups, and knowledge of the main variants present in a specific population, their behavior in serologic tests, and their impact on clinical practice is crucial to define the best serologic tests for routine use. The present study aimed to explore the serologic profile of D variants and to determine which variants are most associated with false-negative D typing results and alloimmunization. Donor samples were selected in two study periods. During the first period, D typing was performed on a semi-automated instrument in microplates, and weak D tests were conducted in tube or gel tests. In the second period, D typing was carried out using an automated instrument with microplates, and weak D tests were performed in solid phase. Samples from patients typed as D+ with anti-D were also selected. All samples were characterized by molecular testing. A total of 37 RHD variants were identified. Discrepancies and atypical reactivity without anti-D formation were observed in 83.4 percent of the samples, discrepant D typing results between donations were seen in 12.3 percent, and D+ patients with anti-D comprised 4.3 percent. DAR1.2 was the most prevalent variant. Weak D type 38 was responsible for 75 percent of discrepant samples, followed by weak D type 11, predominantly detected by solid phase. Among the D variants related to alloimmunization, DIVa was the most prevalent, which was not recognized by serologic testing; the same was true for DIIIc. The results highlight the importance of selecting tests for donor screening capable of detecting weak D types 38 and 11, especially in populations where these variants are more prevalent. In pre-transfusion testing, it is crucial that D typing reagents demonstrate weak reactivity with DAR variants; having a serologic strategy to recognize DIVa and DIIIc is also valuable.

A patient with anti-f in India identified by extensive immunohematologic workup.

Anti-f is produced by exposure to the compound antigen ce (f) on red blood cells (RBCs), expressed when both c and e are present on the same protein (cis position). Although anti-f was discovered in 1953, there are few cases reported worldwide because the presence of anti-f is often masked by anti-c or anti-e and is not generally found as a single antibody. In the present case, anti-f was identified by using three-cell screening and 11-cell identification panels. The identification of anti-f was further supported by additional testing, including (1) Rh antigen typing; (2) antibody identification panels (enzyme-treated panel [ficin] and an in-house-constructed Rh panel); (3) look-back and phenotyping of donor RBC units, which were responsible for alloimmunization; and (4) molecular testing of the patient's RBCs.

The Variation of RhD Blood Group in Different Periods in a Patient with Systemic Lupus Erythematosus.

BACKGROUND: Autoimmune hemolytic anemia disease often produces a large number of various autoantibodies, and some autoantibodies may be related to Rh blood group. In rare cases, autoantibodies can specifically target Rh antigen, thus interfering with the identification of Rh blood group. METHODS: A case of systemic lupus erythematosus (SLE) with inconsistent RhD blood group identification results in different periods was reported and the reasons were analyzed. RESULTS: Some autoantibodies can completely block D antigen on red blood cells, resulting in no redundant D sites on red blood cells binding to reagent anti D. In addition, the immunity of the body is extremely low, and the expression of red blood cell blood group antigens in part of the body is inhibited, which will cause the weakening of the expression of Rh antigen in red blood cells. Therefore, when testing the RhD blood type of the patient, the reagent anti D does not agglutinate with the patient's red blood cells, and a false negative result of the initial screening appears. Through the RhD negative confirmation test, the patient's blood type is a serologically weak D phenotype. CONCLUSIONS: If the result of serological preliminary screening test is RhD negative or RhD variant, the recipient should be treated as RhD negative, and RhD negative red blood cells should be transfused during blood transfusion. Conditional laboratories can implement RHD genotyping, which is conducive to improving the precise blood transfusion management level of RhD negative blood recipients, saving rare blood resources and improving the treatment efficiency of patients.

Disease severity in subsequent pregnancies with RhD immunization: A nationwide cohort.

BACKGROUND AND OBJECTIVES: To evaluate the severity of haemolytic disease of the foetus and newborn (HDFN) in subsequent pregnancies with RhD immunization and to identify predictive factors for severe disease. MATERIALS AND METHODS: Nationwide prospective cohort study, including all pregnant women with RhD antibodies. All women with at least two pregnancies with RhD antibodies and RhD-positive foetuses were selected. The main outcome measure was the severity of HDFN in the first and subsequent pregnancy at risk. A subgroup analysis was performed for the group of women where RhD antibodies developed after giving birth to an RhD-positive child and thus after receiving anti-D at least twice (group A) or during the first pregnancy at risk for immunization (group B). RESULTS: Sixty-two RhD immunized women with a total of 150 RhD-positive children were included. The severity of HDFN increased for the whole group significantly in the subsequent pregnancy (p < 0.001), although it remained equal or even decreased in 44% of women. When antibodies were already detected at first trimester screening in the first immunized pregnancy, after giving birth to an RhD-positive child (group A), severe HDFN in the next pregnancy was uncommon (22%). Especially when no therapy or only non-intensive phototherapy was indicated during the first immunized pregnancy (6%) or if the antibody-dependent cell-mediated cytotoxicity result remained <10%. Contrarily, women with a negative first trimester screening and RhD antibodies detected later during the first pregnancy of an RhD-positive child (group B), often before they had ever received anti-D prophylaxis, were most prone for severe disease in a subsequent pregnancy (48%). CONCLUSION: RhD-mediated HDFN in a subsequent pregnancy is generally more severe than in the first pregnancy at risk and can be estimated using moment of antibody detection and severity in the first immunized pregnancy. Women developing antibodies in their first pregnancy of an RhD-positive child are at highest risk of severe disease in the next pregnancy.

Antenatal RHD screening to guide antenatal anti-D immunoprophylaxis in non-immunized D- pregnant women.

In pregnancy, D- pregnant women may be at risk of becoming immunized against D when carrying a D+ fetus, which may eventually lead to hemolytic disease of the fetus and newborn. Administrating antenatal and postnatal anti-D immunoglobulin prophylaxis decreases the risk of immunization substantially. Noninvasive fetal RHD genotyping, based on testing cell-free DNA extracted from maternal plasma, offers a reliable tool to predict the fetal RhD phenotype during pregnancy. Used as a screening program, antenatal RHD screening can guide the administration of antenatal prophylaxis in non-immunized D- pregnant women so that unnecessary prophylaxis is avoided in those women who carry a D- fetus. In Europe, antenatal RHD screening programs have been running since 2009, demonstrating high test accuracies and program feasibility. In this review, an overview is provided of current state-of-the-art antenatal RHD screening, which includes discussions on the rationale for its implementation, methodology, detection strategies, and test performance. The performance of antenatal RHD screening in a routine setting is characterized by high accuracy, with a high diagnostic sensitivity of ≥99.9 percent. The result of using antenatal RHD screening is that 97-99 percent of the women who carry a D- fetus avoid unnecessary prophylaxis. As such, this activity contributes to avoiding unnecessary treatment and saves valuable anti-D immunoglobulin, which has a shortage worldwide. The main challenges for a reliable noninvasive fetal RHD genotyping assay are low cell-free DNA levels, the genetics of the Rh blood group system, and choosing an appropriate detection strategy for an admixed population. In many parts of the world, however, the main challenge is to improve the basic care for D- pregnant women.

Neonatal and Obstetrical Outcomes of Pregnancies Complicated by Alloimmunization.

BACKGROUND AND OBJECTIVES: Despite advances in the prevention of rhesus (Rh)(D) alloimmunization, alloantibodies to Rh(D) and non-Rh(D) red blood cell antigens continue to be detected in ∼4% of US pregnancies and can result in hemolytic disease of the fetus and newborn (HDFN). Recent reports on HDFN lack granularity and are unable to provide antibody-specific outcomes. The objective of this study was to calculate the frequency of alloimmunization in our large hospital system and summarize the outcomes based on antibody specificity, titer, and other clinical factors. METHODS: We identified all births in a 6-year period after a positive red blood cell antibody screen result during pregnancy and summarized their characteristics and outcomes. RESULTS: A total of 707 neonates were born after a positive maternal antibody screen result (3.0/1000 live births). In 31 (4%), the positive screen result was due to rhesus immune globulin alone. Of the 676 neonates exposed to alloantibodies, the direct antibody test (DAT) result was positive, showing antigen-positivity and evidence of HDFN in 37% of those tested. Neonatal disease was most severe with DAT-positive anti-Rh antibodies (c, C, D, e, E). All neonatal red blood cell transfusions (15) and exchange transfusions (6) were due to anti-Rh alloimmunization. No neonates born to mothers with anti-M, anti-S, anti-Duffy, anti-Kidd A, or anti-Lewis required NICU admission for hyperbilirubinemia or transfusion. CONCLUSIONS: Alloimmunization to Rh-group antibodies continues to cause a majority of the severe HDFN cases in our hospital system. In neonates born to alloimmunized mothers, a positive DAT result revealing antigen-positivity is the best predictor of anemia and hyperbilirubinemia.

Donor/recipient Rh-mismatched allogeneic hematopoietic stem cell transplantation: transfusion strategy and allo-immunization to red blood cell antigens.

In the case of donor/recipient rhesus (Rh)-incompatibility after allogeneic hematopoietic stem cell transplantation (alloHSCT), the transfusion policy in France is to transfuse red blood cells (RBC) in the donor's Rh phenotype from the day of transplantation, leading to a risk of allo-immunization, either of donor or recipient origin. In this single-center retrospective study, the incidence of donor/recipient Rh incompatibility was 7.1% over an 8-year period including 1012 alloHSCT. Six of 58 evaluable patients (10.3%) developed alloantibodies to RBC antigens within one year of alloHSCT. None of these allo-immunizations were directed against the donor-mismatched Rh antigens and none could have been prevented by the transfusion of recipient and donor Rh-compatible RBC units. None of these allo-immunizations led to immune-mediated hemolytic anemia. We observed a statistically significant higher incidence of chronic GVHD among patients with anti-RBC allo-immunization. In the context of donor/recipient Rh incompatibility, the transfusion of packed RBC units in the donor's Rh phenotype from the day of alloHSCT is feasible and not associated with a high risk of allo-immunization. The generalization of this strategy could be discussed even when donor and recipient Rh phenotypes could be respected, to allow the preservation of units of infrequent phenotypes for other indications.

Anti-D immunization after D positive platelet transfusions in D negative recipients: A systematic review and meta-analysis.

BACKGROUND: Anti-D can be formed after D-incompatible platelet transfusions due to contaminating D+ red blood cells. These antibodies are of particular importance in women of childbearing potential, because anti-D is most often involved in severe cases of hemolytic disease of the fetus and newborn. This systematic review determined the frequency of anti-D after D+ platelet transfusions and risk factors for D alloimmunization. STUDY DESIGN AND METHODS: Relevant literature was searched using PubMed, Embase and Web of Science until December 2022. Overall anti-D frequency and risk factors were estimated using a random effects meta-analysis. RESULTS: In 22 studies, a total of 3028 D- patients received a mean of six D+ platelet transfusions. After a mean follow-up of seven months 106 of 2808 eligible patients formed anti-D. The pooled anti-D frequency was 3.3% (95% CI 2.0-5.0%; I2 71%). After including only patients with an undoubtable follow-up of at least 4 weeks, 29 of 1497 patients formed anti-D with a pooled primary anti-D rate of 1.9% (95% CI 0.9-3.2%, I2 44%). Women and patients receiving whole blood derived platelets had two and five times higher anti-D rates compared with men and patients receiving apheresis derived platelets, respectively. DISCUSSION: Anti-D immunization is low after D incompatible platelet transfusions and dependent on recipients' sex and platelet source. We propose anti-D prophylaxis in girls and women, capable of becoming pregnant in the future, that received D+ platelets, regardless of platelet source, to reduce the risk of anti-D induced hemolytic disease of the fetus and newborn.

A cold case of hemolytic disease of the fetus and newborn resolved by genomic sequencing and population studies to define a new antigen in the Rh system.

BACKGROUND: We report an obstetric case involving an RhD-positive woman who had developed a red blood cell (RBC) antibody that was not detected until after delivery of a newborn, who presented with a positive direct antiglobulin test result. Immunohematology studies suggested that the maternal antibody was directed against a low-prevalence antigen on the paternal and newborn RBCs. RESULTS: Comprehensive blood group profiling by targeted exome sequencing revealed a novel nonsynonymous single nucleotide variant (SNV) RHCE c.486C>G (GenBank MZ326705) on the RHCE*Ce allele, for both the father and newborn. A subsequent genomic-based study to profile blood groups in an Indigenous Australian population revealed the same SNV in 2 of 247 individuals. Serology testing showed that the maternal antibody reacted specifically with RBCs from these two individuals. DISCUSSION: The maternal antibody was directed against a novel antigen in the Rh blood group system arising from an RHCE c.486C>G variant on the RHCE*Ce allele linked to RHD*01. The variant predicts a p.Asn162Lys change on the RhCE protein and has been registered as the 56th antigen in the Rh system, ISBT RH 004063. CONCLUSION: This antibody was of clinical significance, resulting in a mild to moderate hemolytic disease of the fetus and newborn (HDFN). In the past, the cause of such HDFN cases may have remained unresolved. Genomic sequencing combined with population studies now assists in resolving such cases. Further population studies have potential to inform the need to design population-specific red cell antibody typing panels for antibody screening in the Australian population.

Receipt of RhD-positive whole blood for life-threatening bleeding in female children: A survey in alloimmunized mothers regarding minimum acceptable survival benefit relative to risk of maternal alloimmunization to anti-D.

BACKGROUND: Low-titer group O whole blood (LTOWB) for treatment of hemorrhagic shock sometimes necessitates transfusion of RhD-positive units due to short supply of RhD-negative LTOWB. Practitioners must choose between using RhD-positive LTOWB when RhD-negative is unavailable against the risk to a female of childbearing potential of becoming RhD-alloimmunized, risking hemolytic disease of the fetus and newborn (HDFN) in future children, or using component therapy with RhD-negative red cells. This survey asked females with a history of red blood cell (RBC) alloimmunization about their risk tolerance of RhD alloimmunization compared to the potential for improved survival following transfusion of RhD-positive blood for an injured RhD negative female child. STUDY DESIGN AND METHODS: A survey was administered to RBC alloimmunized mothers. Respondents were eligible if they were living in the United States with at least one red cell antibody known to cause HDFN and if they had at least one RBC alloimmunized pregnancy. RESULTS: Responses from 107 RBC alloimmmunized females were analyzed. There were 32/107 (30%) with a history of severe HDFN; 12/107 (11%) had a history of fetal or neonatal loss due to HDFN. The median (interquartile range) absolute improvement in survival at which the respondents would accept RhD-positive transfusions for a female child was 4% (1%-14%). This was not different between females with and without a history of severe or fatal HDFN (p = .08 and 0.38, respectively). CONCLUSION: Alloimmunized mothers would accept the risk of D-alloimmunization in a RhD-negative female child for improved survival in cases of life-threatening bleeding.

Transfusion management and hemoglobin-based oxygen carrier treatment in a patient with anti-Rh17 antibody.

BACKGROUND: A 54-year-old Hispanic OPos female with known history of anti-Rh17 antibodies was diagnosed with Philadelphia-Chromosome positive (Ph+) acute lymphoblastic leukemia (ALL). Rh17, also known as Hr0, is a high-frequency antigen composed of several epitopes on the RhCE protein. Anti-Rh17 antibodies can be made by individuals with missing or varied C/c, E/e antigens. Anti-Rh17 antibodies are clinically significant given multiple case reports of hemolytic disease of the fetus and newborn (HDFN). Finding compatible units for patients with anti-Rh17 can be particularly difficult given that only 1 in 100,000 people are Rh17 negative. STUDY DESIGN AND METHODS: Search for compatible units was conducted by the American Rare Donor Program (ARDP) with no leads. After chemotherapy induction and despite erythropoiesis stimulating agent administration, the patient's hemoglobin continued to trend down to a nadir of 2.8 g/dL. Here we report transfusion of incompatible pRBC to this patient with critically symptomatic anemia. HBOC-201 (Hemopure) was obtained and administered under an emergency compassionate/expanded access designation from the Food and Drug Administration (FDA) under an emergency Investigational New Drug (IND) application. RESULTS AND DISCUSSION: Overall difficulties in this case included the challenge of finding compatible units, dilemma of transfusing incompatible units in a patient with severe anemia and obtaining alternatives to blood products. This case report demonstrates the successful use of HBOC-21 in treating life-threatening anemia.

Prediction of the antigenic regions in eight RhD variants identified by computational biology.

BACKGROUND AND OBJECTIVES: Changes in RHD generate variations in protein structure that lead to antigenic variants. The classical model divides them into quantitative (weak and Del) and qualitative (partial D). There are two types of protein antigens: linear and conformational. Computational biology analyses the theoretical assembly of tertiary protein structures and allows us to identify the 'topological' differences between isoforms. Our aim was to determine the theoretical antigenic differences between weak RhD variants compared with normal RhD based on structural analysis using bioinformatic techniques. MATERIALS AND METHODS: We analysed the variations in secondary structures and hydrophobicity of RHD*01, RHD*01W.1, W2, W3, RHD*09.03.01, RHD*09.04, RHD*11, RHD*15 and RHD*21. We then modelled the tertiary structure and calculated their probable antigenic regions, intra-protein interactions, displacement and membrane width and compared them with Rhce. RESULTS: The 10 proteins are similar in their secondary structure and hydrophobicity, with the main differences observed in the exofacial coils. We identified six potential antigenic regions: one that is unique to RhD (R3), one that is common to all D (R6), three that are highly variable among RhD isoforms (R1, R2 and R4), one that they share with Rhce (R5) and two that are unique to Rhce (Ra and Rbc). CONCLUSION: The alloimmunization capacity of these subjects could be explained by the variability of the antigen pattern, which is not necessarily recognized or recognized with lower intensity by the commercially available antibodies, and not because they have a lower protein concentration in the membrane.