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.

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.

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.

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.

HLA-DRB1 molecules and the presentation of anchor peptides from RhD, RhCE, and KEL proteins.

BACKGROUND: Antigens from the Rh and Kell systems are recognized as the most immunogenic in clinical practice. This study evaluated the possible molecular mechanisms involved in the interaction of antigenic peptides with the DRB1 molecules, which help to explain the high frequency of anti-K and association of D + C antibodies in transfusion and incompatible pregnancy. STUDY DESIGN AND METHODS: We included 201 patients with antibodies against antigens from the Rh and Kell systems and compare them with 174,015 controls. HLA-DRB1 genotyping and in silico analysis were performed. The NetMHCIIpan software was used to identify RhD-, RhCE-, and KEL-derived anchor peptides that bind to DRB1 molecules. RESULTS: HLA-DRB1*15 is associated with an increased risk of D, C, E, and K alloimmunization, while the HLA-DRB1*01 and *12 alleles are overrepresented in patients with anti-C and anti-D, respectively. In silico analysis showed that three polymorphic points (60I, 68S, and 103S) common to C and D antigens can be presented by several DRB1 molecules, including DRB1*15:01. The DRB1*09:01 molecule, although not showing statistical significance, was able to interact strongly with almost all five anchor peptides from the sequence containing the polymorphic determinants of E antigen, except 217-WMFWPSVNS-225. CONCLUSION: The DRB1*15 molecule has specific physicochemical characteristics in residues 11P and 13R in the P4 pocket that can favor the response to various antigenic peptides. Anti-K alloimmunization is unrestricted for interaction with specific DRB1 molecules, which suggests that almost all individuals in our population have DRB1 molecules capable of binding to KEL-derived anchor peptides and produce anti-K when stimulated.

Do blood groups play a role in etiology of rosacea?

BACKGROUND: The pathogenesis of rosacea is not fully understood. The innate immune system is impaired in patients with rosacea. This leads to abnormal inflammatory cytokine release. It has been proposed that the molecular mechanism for the role of the ABO antigenic system in human diseases may arise from its relationship with the von Willebrand factor and several pro-inflammatory and adhesion molecules. To our knowledge, the relationship between ABO-Rh groups and rosacea has not been investigated previously. MATERIALS AND METHODS: One hundred and fourteen patients with rosacea and 258 healthy individuals who had blood group record were included in this study. The results were analyzed statistically. RESULTS: In terms of ABO blood groups, 54 (47.4%) patients had A, 14 (12.3%) patients had B, 7 (6.1%) patients had AB, and 39 (34.2%) patients had O blood groups in the patient group. In the control group, 109 (42.2%) individuals had A, 45 (17.5%) individuals had B, 29 (11.2%) individuals had AB, and 75 (29.1%) individuals had O blood group. There was no significant difference between the groups (P > .05). In terms of Rh groups, 103 (90.4%) patients were Rh (+) and 11 (9.6%) patients were Rh (-). In the control group, 220 (85.3%) individuals were Rh (+) and 38 (14.7%) were Rh (-). There was no significant difference between the groups (P > .05). CONCLUSION: We did not find a relationship between blood groups and rosacea. But, we think this is an interesting hypothesis. To clarify this possible relationship, comprehensive and further studies are needed in different races and geographic regions.

Acute Hemolytic Transfusion Reaction Due to the "Anti-E" Rhesus Antibody in a Patient with Crohn's Disease.

BACKGROUND: The rhesus (Rh) system is the second most important blood group system after ABO, with highly immunogenic antigens. Although the anti-E Rh antibody has been reported to cause hemolytic disease of the newborn and delayed hemolytic transfusion reactions, acute hemolytic transfusion reactions (AHTR) have been rarely reported. METHODS: Peripheral blood (PB) samples were screened for irregular antibodies using a commercial ID-Diacell I - II antibody screening Panel (Bio-Rad Laboratories, Glattbrugg, Switzerland) and ID-cards "LISS/Coombs" (Bio-Rad, Switzerland). The antibody was confirmed using ID DiaPanel, an antibody identification panel (Bio-Rad, Switzerland). Rh phenotyping was performed for RhC/c and RhE/e antigens using an immediate-spin tube test with monoclonal anti-C, -c, -E, and -e (OrthoClinical Diagnostics, High Wycombe, UK) in saline-filled test-tubes. RESULTS: The patient was negative for antibody screening test before transfusion. After receiving a total of 6 units of cross-matching negative RBC transfusion, the antibody screening test result increased to 2+ after showing traces and the antibody was confirmed as anti-E Rh antibody. The Rh phenotype of the patient was C (+), c (+), E (-), and e (+). In addition, we verified that all the six units of RBCs transfused were E (+) except for the two units transfused before surgery. CONCLUSIONS: Here is an unusual case of an AHTR due to the anti-E Rh antibody after E-positive RBC transfusion in a patient with Crohn's disease. Because anemia is common in patients with Crohn's disease, it is important to determine the cause of the anemia and necessary to examine the Rh phenotype before transfusions because of the high need for transfusion due to any cause. Awareness of this possibility will ensure safe blood transfusion with special care to screen for antibodies and perform Rh phenotyping, thereby minimizing morbidity and preventing potential mortality.

Biocompatible coupling of therapeutic fusion proteins to human erythrocytes.

Carriage of drugs by red blood cells (RBCs) modulates pharmacokinetics, pharmacodynamics, and immunogenicity. However, optimal targets for attaching therapeutics to human RBCs and adverse effects have not been studied. We engineered nonhuman-primate single-chain antibody fragments (scFvs) directed to human RBCs and fused scFvs with human thrombomodulin (hTM) as a representative biotherapeutic cargo (hTM-scFv). Binding fusions to RBCs on band 3/glycophorin A (GPA; Wright b [Wrb] epitope) and RhCE (Rh17/Hr0 epitope) similarly endowed RBCs with hTM activity, but differed in their effects on RBC physiology. scFv and hTM-scFv targeted to band 3/GPA increased membrane rigidity and sensitized RBCs to hemolysis induced by mechanical stress, while reducing sensitivity to hypo-osmotic hemolysis. Similar properties were seen for other ligands bound to GPA and band 3 on human and murine RBCs. In contrast, binding of scFv or hTM-scFv to RhCE did not alter deformability or sensitivity to mechanical and osmotic stress at similar copy numbers bound per RBCs. Contrasting responses were also seen for immunoglobulin G antibodies against band 3, GPA, and RhCE. RBC-bound hTM-scFv generated activated protein C (APC) in the presence of thrombin, but RhCE-targeted hTM-scFv demonstrated greater APC generation per bound copy. Both Wrb- and RhCE-targeted fusion proteins inhibited fibrin deposition induced by tumor necrosis factor-α in an endothelialized microfluidic model using human whole blood. RhCE-bound hTM-scFv more effectively reduced platelet and leukocyte adhesion, whereas anti-Wrb scFv appeared to promote platelet adhesion. These data provide a translational framework for the development of engineered affinity ligands to safely couple therapeutics to human RBCs.

Red cell alloimmunization & role of advanced immunohaematological support in liver transplantation.

BACKGROUND & OBJECTIVES: Transfusion support forms an integral part of liver transplantation programme. Advanced immunohaematology services are required to deal with complex serological problems that can complicate transfusion therapy in these patients. Here, we report on red cell alloimmunization and presence of alloimmunization in donors and patients undergoing liver transplantation in a tertiary care hospital in north India. METHODS: Records of 1433 liver transplants performed from January 2009 to March 2015 were retrieved and reviewed. Antibody screening was performed both for liver donors, and recipients and antibody identification was performed for the screen-positive patients. RESULTS: Of the 1433 liver recipients, 32 (2.3%) developed antibodies. Seventeen patients had one or more alloantibodies, five had autoantibodies with an underlying alloantibody and 10 had only autoantibodies in their plasma. The overall alloimmunization rate was 1.5 per cent with 25 alloantibodies identified in 22 patients. Anti-E was the most common specificity identified. INTERPRETATION & CONCLUSIONS: The presence of alloantibodies can complicate transfusion therapy in patients undergoing liver transplantation, who are already at a high risk of being heavily transfused owing to the nature of surgery and the haemostatic dysfunction from chronic liver disease. Therefore, screening for irregular red cell alloantibodies combined with a rational blood transfusion policy may be essential for these patients.

ABO blood groups, Rhesus factor, and anaphylactic reactions due to Hymenoptera stings.

INTRODUCTION: Numerous publications indicate that the prevalence of some infectious, neoplastic and immunological diseases are associated with ABO blood groups. OBJECTIVE: The aim of this study was to verify whether ABO and Rh blood groups are associated with severe anaphylactic reactions after Hymenoptera stings. MATERIAL AND METHODS: A study was undertaken of 71,441 Caucasian subjects living in the same geographic area. The study group included 353 patients with diagnosed systemic anaphylaxis to Hymenoptera venom. Control group included 71,088 healthy blood donors. Frequencies of ABO and Rhesus groups in the study and control groups were compared using univariate and multivariate analyses. RESULTS: No statistically significant interactions were observed between the ABO blood group and anaphylactic reactions to Hymenoptera.

NGS and blood group systems: State of the art and perspectives.

Molecular analysis, or genotyping, of genes involved in the expression of blood group antigens has been a standard strategy used in immunohaematology laboratories routinely. For the past ten years, next-generation sequencing (NGS), or second-generation sequencing, has become the reference method in genetics. Extensive study of distinct targets, large genomic regions, and even whole genome is henceforth possible by this approach at minimal cost. Blood group genotyping has thus taken advantage of this technological advent. A few preliminary studies have open the way to NGS in this field by studying one or several genes, in a wide range of samples (donors and patients) by using several different platforms. These works have helped in the identification of both the benefits and limitations of the technology. Other recently published studies have benefited from these preliminary data to improve the methodology, specificity and accuracy of output data. In parallel novel strategies, i.e. third-generation sequencing, which can sequence long DNA regions at the single-molecule level, have emerged and shown promise for the potential resolution of complex rearrangements involving genes of the Rh and MNS blood group systems respectively. As technological and methodological hurdles have been overcome, these approaches may be used in a clinical situation in a near future.

Enhanced Effector Functions Due to Antibody Defucosylation Depend on the Effector Cell Fcγ Receptor Profile.

Abs of the IgG isotype are glycosylated in their Fc domain at a conserved asparagine at position 297. Removal of the core fucose of this glycan greatly increases the affinity for FcγRIII, resulting in enhanced FcγRIII-mediated effector functions. Normal plasma IgG contains ∼94% fucosylated Abs, but alloantibodies against, for example, Rhesus D (RhD) and platelet Ags frequently have reduced fucosylation that enhances their pathogenicity. The increased FcγRIII-mediated effector functions have been put to use in various afucosylated therapeutic Abs in anticancer treatment. To test the functional consequences of Ab fucosylation, we produced V-gene-matched recombinant anti-RhD IgG Abs of the four different subclasses (IgG1-4) with and without core fucose (i.e., 20% fucose remaining). Binding to all human FcγR types and their functional isoforms was assessed with surface plasmon resonance. All hypofucosylated anti-RhD IgGs of all IgG subclasses indeed showed enhanced binding affinity for isolated FcγRIII isoforms, without affecting binding affinity to other FcγRs. In contrast, when testing hypofucosylated anti-RhD Abs with FcγRIIIa-expressing NK cells, a 12- and 7-fold increased erythrocyte lysis was observed with the IgG1 and IgG3, respectively, but no increase with IgG2 and IgG4 anti-RhD Abs. Notably, none of the hypofucosylated IgGs enhanced effector function of macrophages, which, in contrast to NK cells, express a complex set of FcγRs, including FcγRIIIa. Our data suggest that the beneficial effects of afucosylated biologicals for clinical use can be particularly anticipated when there is a substantial involvement of FcγRIIIa-expressing cells, such as NK cells.

A rare, potentially life-threatening presentation of passenger lymphocyte syndrome.

BACKGROUND: Passenger lymphocyte syndrome occurs when donor lymphocytes are transplanted with a solid organ and produce alloantibodies that react with antigens on the recipient's red blood cells (RBCs). Typically, passenger lymphocyte syndrome presents as immunoglobulin G antibody-mediated, extravascular hemolytic anemia with reticulocytosis. Often, the donor was alloimmunized before transplantation. CASE REPORT: A 34-year-old Group O, D+ man with a negative antibody screen received a liver transplant from a Group O, D- donor. Twenty Group O, D+ RBC units were transfused on Postoperative Days (PODs) 0 through 2. On POD 7, the patient developed anemia, a weakly positive antibody screen, and a positive direct antiglobulin test with anti-D in the eluate. After POD 8, a D- transfusion protocol was initiated. Despite laboratory evidence of hemolysis, two initial peripheral blood smears showed no increase in schistocytes or spherocytes, the reticulocyte count was depressed, and a marrow biopsy revealed erythroid hyperplasia. Eventually, anemia resolved after a period of medication non-compliance; however, a positive direct antiglobulin test persisted to the last follow-up date (POD 233). RESULTS: Other potential causes of aplastic anemia were investigated, but no alternative cause was found. History excluded passive anti-D. D+, LW- cells were reactive, excluding anti-LW. Genotyping showed no evidence of a partial D genotype. Chart review revealed that the liver donor had a history of anti-D. A diagnosis of passenger lymphocyte syndrome was reached. CONCLUSION: Although antibody-mediated hemolytic anemia has been reported to cause reticulocytopenia in the presence of marrow erythroid hyperplasia, this report of passenger lymphocyte syndrome causing a similar post-transplant anemia in association with reticulocytopenia is noteworthy.

Prophylactic RhCE and Kell antigen matching: impact on alloimmunization in transfusion-dependent patients with myelodysplastic syndromes.

BACKGROUND AND OBJECTIVES: Thirty to 80 per cent of patients with myelodysplastic syndromes (MDS) become transfusion-dependent and are at risk for red blood cell (RBC) alloimmunization. This study compared alloimmunization rates in transfusion-dependent patients with MDS at an institution with a policy of prophylactic antigen matching for RhCE and K (PAM) with those transfused at institutions without such a policy (non-PAM). MATERIALS AND METHODS: Transfusion records were retrospectively reviewed to determine total number of RBC transfusions received, whether RBC phenotyping was performed, the type and date of first alloantibody development and receipt of prophylactic antigen matching for RhCE and K. RESULTS: In 176 transfusion-dependent patients with MDS, the overall rate of new alloimmunization was 17%; the majority of patients (87%) developed at least one alloantibody to Rh or Kell antigens. The alloimmunization rate at the institution with a PAM policy was 11% compared with 23% at non-PAM institutions (P = 0·06). The rate of Rh/K alloimmunization was 7 vs. 22%, respectively (P = 0·008). No patient who received PAM developed a Rh/K alloantibody. CONCLUSION: The rate of alloimmunization was 11% at an institution with a PAM policy which was non-significantly lower than 23% at institutions without a PAM policy. However, rates of Rh/K alloimmunization were significantly lower. Such a policy should be considered in transfusion-dependent patients with MDS, although further studies on cost-effectiveness and careful consideration of resource availability in the local context are required.

Severe Hemolytic Anemia Following Intravenous Immunoglobulin in an Infant With Kawasaki Disease.

Severe hemolytic anemia (HA) is an uncommon adverse reaction of intravenous immunoglobulin (IVIg) administration. Previous reports assume that antibodies contained in IVIg preparations are the cause of hemolysis. We report a 10-month-old infant with Kawasaki disease who was treated with high-dose IVIg and developed severe HA. The patient's Rh blood type was D+C+c+E-e+. He developed anti-C and anti-e antibodies following treatment with IVIg, and, after considering all possible causes of hemolysis, we concluded that this was a case of autoimmune HA induced by immunoglobulin treatment. The hyperinflammatory condition associated with Kawasaki disease may have contributed to the severity of anemia.

Cryopreserved Arterial Allografts and ABO and Rhesus Compatibility.

BACKGROUND: Arterial cryopreserved allografts are conduit of choice for arterial bypass in case of infection. They are sometimes submitted to accelerated degeneration: stenosis, thrombosis, or aneurysmal evolution. We hypothesized that ABO group and Rhesus compatibility could play a role in arterial cryopreserved allograft complications. METHODS: Patients who benefit from allograft bypass from 2006 to 2011 were retrospectively compared, regarding ABO or rhesus compatibility and irregular agglutinins. RESULTS: Seventy-two patients were included. Regarding ABO mismatch, there was no difference in terms of death (51% vs. 43%, P = 0.820), thrombosis (25% vs. 32%, P = 0.78), rupture (9% vs. 0%, P = 0.247), stenosis (3% vs. 12%, P = 0.331), aneurysmal degeneration (16% vs. 12%, P = 1), and 5 years of secondary patency rate (34% vs. 39%, P = 0.141). There was also no difference regarding Rhesus mismatch. CONCLUSIONS: Allograft degeneration does not seem to be related to ABO mismatch. This degeneration could be related to another way of immunogenicity, particularly Human Leukocyte Antigen mismatch, and needs further exploration.

Third trimester screening for alloimmunisation in Rhc-negative pregnant women: evaluation of the Dutch national screening programme.

OBJECTIVE: To evaluate the effect of red blood cell (RBC) antibody screening in the 27th week of pregnancy in Rhc-negative women, on detection of alloimmunisation, undetected at first trimester screening ('late' alloimmunisation), and subsequent haemolytic disease of the fetus and newborn (HDFN), to assess risk factors for late alloimmunisation. DESIGN: Prospective cohort and nested case-control study. SETTING: The Netherlands. POPULATION: Two-year nationwide cohort. METHODS: Prospective inclusion of Rhc-negative women with negative first trimester screening and of screen-negative controls. Assessment of incidence and numbers needed to screen (NNS) of late alloimmunisation and HDFN; logistic regression analysis to establish risk factors for late alloimmunisation. MAIN OUTCOME MEASURES: Late alloimmunisation, HDFN. RESULTS: Late alloimmunisation occurred in 99 of 62 096 (0.159%) Rhc-negative women; 90% had c/E antibodies and 10% non-Rhesus antibodies. Severe HDFN (fetal/neonatal transfusion) occurred in two of 62 096 (0.003%) of Rhc-negative women and 2% of late alloimmunisations; moderate HDFN (phototherapy) occurred in 20 children [22.5%; 95% confidence interval (CI), 13.8-31.1%]. Perinatal survival was 100%. The NNS to detect one HDFN case was 2823 (31 048 for severe, 3105 for moderate HDFN). Significant risk factors were former blood transfusion [odds ratio (OR), 10.4; 95% CI, 1.14-94.9], parity (P-1: OR, 11.8; 95% CI, 3.00-46.5; P > 1: OR, 7.77; 95% CI, 1.70-35.4) and amniocentesis/chorionic villus sampling during current pregnancy (OR, 9.20; 95% CI, 1.16-72.9). CONCLUSIONS: Additional screening of Rhc-negative women improved the detection of late alloimmunisation and HDFN, facilitating timely treatment, with a NNS of 2823. Independent risk factors for late alloimmunisation were blood transfusion, parity and chorionic villus sampling/amniocentesis in the current pregnancy. The occurrence of most factors before the current pregnancy suggests a secondary immune response explaining most late alloimmunisations. TWEETABLE ABSTRACT: Third trimester screening for alloimmunisation in Rhc-neg women improves detection and treatment of severe HDFN.

Weak D alleles in Japanese: a c.960G>A silent mutation in exon 7 of the RHD gene that affects D expression.

BACKGROUND AND OBJECTIVES: The molecular basis of the weak D phenotype has been investigated for many years, and more than 80 different alleles producing weak D phenotypes have been identified. Most alleles producing weak D phenotypes have a single missense mutation in exons corresponding to a transmembrane domain of the RhD polypeptide. We report here RHD alleles with single nucleotide mutations in Japanese accounting for weak expression of D antigen. METHODS: Seventy-five blood samples with a weak D phenotype were detected from 763 408 blood donors by standard serological methods. Forty-five of the 75 blood donors were available for RHD gene analysis by PCR and sequencing using genomic DNA and reticulocyte mRNA. Real-time PCR was performed to estimate the relative amounts of the RHD transcripts. RESULTS: We detected 16 different RHD alleles in the 45 individuals with weak D by nucleotide sequencing; 12 were newly identified. Thirty-two of the 45 individuals had an RHD allele with a single missense mutation, while the other 13 individuals had RHD with a c.960G>A silent mutation in exon 7. Red blood cells of these 13 individuals showed direct agglutination with anti-D at a strength of 3+ or less. Semi-quantitative analysis of the RHD transcripts by real-time PCR revealed that the cDNA samples with the c.960G>A mutation showed a significant increment of exon 7 skipping compared with the common RHD. CONCLUSION: Reduced expression of D antigen is caused not only by missense mutation of the RHD gene, but also by silent mutation that may affect splicing.