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Under the ISBT, the Working Party (WP) for Red Cell Immunogenetics and Blood Group Terminology is charged with ratifying blood group systems, antigens and alleles. This report presents the outcomes from four WP business meetings, one located in Basel in 2019 and three held as virtual meetings during the COVID-19 pandemic in 2020 and 2021.As in previous meetings, matters pertaining to blood group antigen nomenclature were discussed. New blood group systems and antigens were approved and named according to the serologic, genetic, biochemical and cell biological evidence presented.Seven new blood group systems, KANNO (defined numerically as ISBT 037), SID (038), CTL2 (039), PEL (040), MAM (041), EMM (042) and ABCC1 (043) were ratified. Two (039 and 043) were de novo discoveries, and the remainder comprised reported antigens where the causal genes were previously unknown. A further 15 blood group antigens were added to the existing blood group systems: MNS (002), RH (004), LU (005), DI (010), SC (013), GE (020), KN (022), JMH (026) and RHAG (030).The ISBT now recognizes 378 antigens, of which 345 are clustered within 43 blood group systems while 33 still have an unknown genetic basis. The ongoing discovery of new blood group systems and antigens underscores the diverse and complex biology of the red cell membrane. The WP continues to update the blood group antigen tables and the allele nomenclature tables. These can be found on the ISBT website (http://www.isbtweb.org/working-parties/red-cell-immunogenetics-and-blood-group-terminology/).

Hypoxia-mediated red blood cell (RBC) sickling is central to the pathophysiology of sickle cell disease (SCD). The signalling nucleoside adenosine is thought to play a significant role in this process. This study investigated expression of the erythrocyte type 1 equilibrative nucleoside transporter (ENT1), a key regulator of plasma adenosine, in adult patients with SCD and carriers of sickle cell trait (SCT). Relative quantitative expression analysis of erythrocyte ENT1 was carried out by Western blot and flow cytometry. Patients with SCD with steady state conditions, either with SS or SC genotype, untreated or under hydroxycarbamide (HC) treatment, exhibited a relatively high variability of erythrocyte ENT1, but with levels not significantly different from normal controls. Most strikingly, expression of erythrocyte ENT1 was found to be significantly decreased in patients with SCD undergoing painful vaso-occlusive episode and, unexpectedly, also in healthy SCT carriers. Promoting hypoxia-induced adenosine signalling, the reduced expression of erythrocyte ENT1 might contribute to the pathophysiology of SCD and to the susceptibility of SCT individuals to altitude hypoxia or exercise to exhaustion.

To determine the existence of guidelines regarding the appropriate clinical use of blood and blood components, transfusion requests, and blood issuing/reception documents and procedures. The different bedside transfusion organizations/processes and hemovigilance are also analyzed. The ultimate objective is to identify safe potential options in order to improve blood safety at the lowest cost. Data emanating from eight Arabic eastern/southern Mediterranean countries who responded to five surveys were collected and tabulated. National recommendations for the clinical use of blood components especially for hemoglobinopathies are lacking in some countries. In matter of good practices in the prescription, issuing and reception of BCs, efforts were made either on national or local basis. Procedures regarding patient information and ethical issues are still lacking. Almost all Mediterranean countries apply two blood testing procedures on each patient sample. Only Morocco, Tunisia and Algeria perform bed side blood group testing; Egypt and Lebanon perform antibody screen and antiglobulin cross matching universally. Automation for blood testing is insufficiently implemented in almost all countries and electronic release is almost absent. National hemovigilance policy is implemented in Tunisia, Morocco, and Lebanon but the reporting system remains inoperative. Insufficient resources severely hinders the implementation of expensive procedures and programs; however, the present work identifies safe procedures that might save resources to improve other parts in the transfusion process (e.g. electronic release to improve safety in issuing). Moreover, setting up regulations regarding ethics in transfusing recipients along with local transfusion committees are crucially needed to implement hemovigilance in transfusion practice.

X-linked chronic granulomatous disease (CGD) is a primary immunodeficiency caused by mutations in the CYBB gene (located on Xp21.1). Patients with large deletions on chromosome Xp21.1 can present with the McLeod phenotype and also Duchenne muscular dystrophy or retinitis pigmentosa. The objective of the present study was to describe a series of French patients with CGD and the McLeod phenotype. We retrospectively collected data from the medical records of 8 patients with CGD and the McLeod phenotype registered at the French National Reference Center for blood types. The median age at diagnosis of CGD was 1.2 years, the median age at diagnosis of the McLeod phenotype was 4.5 years, and the median length of follow-up was 15.2 years. Four patients displayed allo-immunization, with anti-KEL20 and anti-XK1 (formerly known as anti-KL) antibodies. Five of the 6 patients with available blood smears had acanthocytosis. Neuropsychiatric, muscle-related, and ocular manifestations were present in 4, 2, and 1 of the patients, respectively. Three of the 4 patients having undergone allogeneic hematopoietic stem cell transplantation (HSCT) are alive. Overall, 5 patients are alive, and 3 are alive and well. This is the largest yet descriptive study of a series of patients with X-linked CGD and the McLeod phenotype. Although this disease combination is rare, the timely, accurate diagnosis of the McLeod phenotype is critical because of the serious post-transfusion complications. However, HSCT can be considered in these patients.

Recent genome-wide association and murine studies identified the human neutrophil antigen -3a/b polymorphism (HNA-3a/b) in SLC44A2 (rs2288904-G/A) as a risk factor in venous thromboembolism (VTE). The choline transporter-like protein CTL2 encoded by the SLC44A2 gene plays an important role in platelet aggregation and neutrophil interaction with the von Willebrand factor. By investigating alloantibodies to a high-prevalence antigen of unknown specificity, found in patients with a rare blood type, we showed that CTL2 is also expressed in red blood cells and carries a new blood group system. Furthermore, we identified three siblings of European ancestry who are homozygous for a large deletion in SLC44A2, resulting in complete CTL2 deficiency. Interestingly, the first-ever reported CTL2-deficient individuals suffer from progressive hearing impairment, recurrent arterial aneurysms and epilepsy. In contrast to Slc44a2-/- mice, CTL2null individuals showed normal platelet aggregation and do not suffer from any apparent hematological disorders. In addition, CD34+ cells from CTL2null patients undergo normal ex vivo erythropoiesis, indicating that CTL2 is not essential for erythroid proliferation and differentiation. Overall, our findings confirm the function of CTL2 in hearing preservation and provide new insights into the possible role of this protein in maintaining cerebrovascular homeostasis.

The rare PEL-negative phenotype is one of the last blood groups with an unknown genetic basis. By combining whole-exome sequencing and comparative global proteomic investigations, we found a large deletion in the ABCC4/MRP4 gene encoding an ATP-binding cassette (ABC) transporter in PEL-negative individuals. The loss of PEL expression on ABCC4-CRISPR-Cas9 K562 cells and its overexpression in ABCC4-transfected cells provided evidence that ABCC4 is the gene underlying the PEL blood group antigen. Although ABCC4 is an important cyclic nucleotide exporter, red blood cells from ABCC4null/PEL-negative individuals exhibited a normal guanosine 3′,5′-cyclic monophosphate level, suggesting a compensatory mechanism by other erythroid ABC transporters. Interestingly, PEL-negative individuals showed an impaired platelet aggregation, confirming a role for ABCC4 in platelet function. Finally, we showed that loss-of-function mutations in the ABCC4 gene, associated with leukemia outcome, altered the expression of the PEL antigen. In addition to ABCC4 genotyping, PEL phenotyping could open a new way toward drug dose adjustment for leukemia treatment.

Background Mta (MNS14) is a low-prevalence antigen of the MNS system. A few cases of hemolytic disease of the fetus and newborn caused by anti-Mta have been reported in the literature, but up to now this antibody has never been associated with a hemolytic transfusion reaction (HTR). Case report A 38-year-old male with sickle cell disease undergoing exchange transfusion presented with shivering, nausea, dyspnea, and pain in the lower limbs. Biologic parameters showed increased hemolysis. The administered red blood cell (RBC) units had been issued by electronic crossmatch due to a negative antibody screening test. In the posttransfusion investigations, crossmatch of the transfused RBC units with the patient's serum showed incompatibility of one unit. The presence of an antibody against a low-prevalence antigen was suspected and further serologic testing was performed for identification. Results Anti-Mta was identified in the patient's serum. The RBCs of the incompatible unit implicated in the HTR were Mt(a+). An eluate of a posttransfusion blood sample of the patient was nonreactive with the incompatible RBCs, and the direct antiglobulin test was negative. Conclusion To our knowledge, this is the first case report of an HTR associated with anti-Mta .

Background and Objectives: Non-invasive assays for predicting foetal blood group status in pregnancy serve as valuable clinical tools in the management of pregnancies at risk of detrimental consequences due to blood group antigen incompatibility. To secure clinical applicability, assays for non-invasive prenatal testing of foetal blood groups need to follow strict rules for validation and quality assurance. Here, we present a multi-national position paper with specific recommendations for validation and quality assurance for such assays and discuss their risk classification according to EU regulations. Materials and Methods: We reviewed the literature covering validation for in-vitro diagnostic (IVD) assays in general and for non-invasive foetal RHD genotyping in particular. Recommendations were based on the result of discussions between co-authors. Results: In relation to Annex VIII of the In-Vitro-Diagnostic Medical Device Regulation 2017/746 of the European Parliament and the Council, assays for non-invasive prenatal testing of foetal blood groups are risk class D devices. In our opinion, screening for targeted anti-D prophylaxis for non-immunized RhD negative women should be placed under risk class C. To ensure high quality of non-invasive foetal blood group assays within and beyond the European Union, we present specific recommendations for validation and quality assurance in terms of analytical detection limit, range and linearity, precision, robustness, pre-analytics and use of controls in routine testing. With respect to immunized women, different requirements for validation and IVD risk classification are discussed. Conclusion: These recommendations should be followed to ensure appropriate assay performance and applicability for clinical use of both commercial and in-house assays. (Less)

International audience; Myeloproliferative neoplasms (MPNs) are a group of disorders characterized by clonal expansion of abnormal hematopoietic stem cells leading to hyperproliferation of one or more myeloid lineages. The main complications in MPNs are high risk of thrombosis and progression to myelofibrosis and leukemia. MPN patients with high risk scores are treated by hydroxyurea (HU), interferon-α, or ruxolitinib, a tyrosine kinase inhibitor. Polycythemia vera (PV) is an MPN characterized by overproduction of red blood cells (RBCs). ABCG2 is a member of the ATP-binding cassette superfamily transporters known to play a crucial role in multidrug resistance development. Proteome analysis showed higher ABCG2 levels in PV RBCs compared to RBCs from healthy controls and an additional increase of these levels in PV patients treated with HU, suggesting that ABCG2 might play a role in multidrug resistance in MPNs. In this work, we explored the role of ABCG2 in the transport of ruxolitinib and HU using human cell lines, RBCs, and in vitro differentiated erythroid progenitors. Using stopped-flow analysis, we showed that HU is not a substrate for ABCG2. Using transfected K562 cells expressing three different levels of recombinant ABCG2, MPN RBCs, and cultured erythroblasts, we showed that ABCG2 potentiates ruxolitinib-induced cytotoxicity that was blocked by the ABCG2-specific inhibitor KO143 suggesting ruxolitinib intracellular import by ABCG2. In silico modeling analysis identified possible ruxolitinib-binding site locations within the cavities of ABCG2. Our study opens new perspectives in ruxolitinib efficacy research targeting cell types depending on ABCG2 expression and polymorphisms among patients.

Background The correct determination of D antigen could help to avoid alloimmunization in pregnant women and patients receiving blood transfusions. However, there are limitations in the identification of D variants as the partial and weak D phenotypes make the determination of D antigen a great challenge in the transfusion routine.’ Study design and methods The molecular characterization of D variants was performed on blood donors from southeastern Brazil with atypical D typing. Furthermore, the serological profile of all RHD variant alleles identified was analyzed using different Anti-D clones. The prevalence of RHD alleles and genotypes found was compared with those described in other countries and in other regions from Brazil. Results Atypical serologic D typing occurred in 0.79 % of blood donors. The majority of RHD variant alleles (88 %) were first characterized by multiplex PCR and PCR-SSP as RHD*weak partial 4 (47 %), followed by RHD*weak D type 3 (29.9 %), RHD*weak D type 2 (3.9 %) and RHD*weak D type 1 (3.1 %). Genomic DNA sequencing characterized the RHD*weak partial 4 variants found in RHD*DAR1.2 (weak 4.2.2) (22 %), RHD*DAR3 (weak 4.0.1) (2.4 %), RHD*DAR3.1 (weak 4.0) (22 %) and RHD*DAR4 (weak 4.1) (0.8 %). RHD variant alleles associated with partial D, such as, RHD*DAU-4 (1.6 %), RHD*DAU-5 (2.4 %), RHD*DAU-6 (1.6 %), RHD* DIII type 8 (1.6 %), RHD*DVII (3.9 %) and RHD* DMH (0.8 %) were also observed. Conclusion The prevalence of RHD variant alleles observed in this cohort differ from those found in other populations, including Brazilians from other regions. RHD allele distribution in specific regions should be considered for implementation of algorithms and genotyping strategies aiming at a more effective and safe transfusion.

This is a related article to: Nucleoside ENTry modulates erythropoiesis (cf ci-dessous); International audience; Abstract The tight regulation of intracellular nucleotides is critical for the self-renewal and lineage specification of hematopoietic stem cells (HSCs). Nucleosides are major metabolite precursors for nucleotide biosynthesis and their availability in HSCs is dependent on their transport through specific membrane transporters. However, the role of nucleoside transporters in the differentiation of HSCs to the erythroid lineage and in red cell biology remains to be fully defined. Here, we show that the absence of the equilibrative nucleoside transporter (ENT1) in human red blood cells with a rare Augustine-null blood type is associated with macrocytosis, anisopoikilocytosis, an abnormal nucleotide metabolome, and deregulated protein phosphorylation. A specific role for ENT1 in human erythropoiesis was demonstrated by a defective erythropoiesis of human CD34+ progenitors following short hairpin RNA-mediated knockdown of ENT1. Furthermore, genetic deletion of ENT1 in mice was associated with reduced erythroid progenitors in the bone marrow, anemia, and macrocytosis. Mechanistically, we found that ENT1-mediated adenosine transport is critical for cyclic adenosine monophosphate homeostasis and the regulation of erythroid transcription factors. Notably, genetic investigation of 2 ENT1null individuals demonstrated a compensation by a loss-of-function variant in the ABCC4 cyclic nucleotide exporter. Indeed, pharmacological inhibition of ABCC4 in Ent1−/− mice rescued erythropoiesis. Overall, our results highlight the importance of ENT1-mediated nucleotide metabolism in erythropoiesis.

Background Adenosine is a major signaling nucleoside that activates cellular signaling pathways through a family of four different G protein-coupled adenosine receptors (ARs), A 1, A 2A, A 2B, and A 3. At steady state conditions, extracellular levels of adenosine remain low (10 to 200 nM) either through its rapid cellular uptake by specialized nucleoside transporters, mainly through the equilibrative nucleoside transporter 1 (ENT1), or its degradation by adenosine deaminases. However, the extracellular levels of adenosine can be rapidly elevated up to 100 μM in response to hypoxia, inflammation, or tissue injury. Under pathophysiological conditions, adenosine signaling is involved in modulating inflammation, fibrosis, and ischemic tissue injury. In sickle cell disease (SCD), adenosine signaling is enhanced and contributes to the pathophysiology of the disease. Despite the importance of adenosine signaling in regulating cell proliferation, and stem cell regeneration, as well as in red blood cell functions and adaptation to hypoxia, very little is known about its implication in hematopoiesis, and more specifically during erythropoiesis. Here, we aimed to investigate the effects of high extracellular adenosine on the erythroid commitment and differentiation of hematopoietic progenitors, and to decipher the implication of ARs in these processes. Results To investigate the role of high extracellular adenosine in regulating erythroid commitment and differentiation of hematopoietic progenitors, we performed ex vivo erythropoiesis of healthy CD34 + cells in the presence or absence of increased extracellular adenosine concentrations ranging from 10 to 200 µM. Our results showed that adenosine decreases erythroid proliferation in a dose dependent manner. High adenosine levels (>50μM) inhibited the proliferation of erythroid precursors and increased apoptosis via a cell cycle arrest in G1. Accordingly, western blots revealed the accumulation of p53 and its downstream target p21, a well-known mediator of G1 cell-cycle arrest, in adenosine-treated cells. Moreover, adenosine treatment led to the persistence of a non-erythroid GPA neg subpopulation expressing myeloid markers (CD18, CD11a, CD13, CD33). May-Grünwald Giemsa staining of this subset revealed granular cells at different stages of differentiation. The culture of FACS-sorted CD36 + and CD36 - cells suggested that this adenosine-induced GPA neg population originates from the survival of CD36 - myeloid progenitors even in the presence of erythropoietin. Importantly, these effects were specific to adenosine as neither guanosine, uridine nor cytidine affected the proliferation and differentiation of erythroid precursors. Furthermore, we have recently shown that ENT1-mediated adenosine uptake is essential for optimal erythroid differentiation. Therefore, we suggested that elevated extracellular adenosine perturbs erythropoiesis via its signaling upon ARs activation. To confirm this hypothesis, we assessed the effect of ARs activation during erythropoiesis. Given that A 2B and A 3 are the only known ARs expressed in human hematopoietic progenitors and erythroid precursors, we used BAY60-6583 and CI-IB-MECA, two highly selective agonists for A 2B and A 3 receptors, respectively. Both BAY60-6583 and CI-IB-MECA increased apoptosis and decreased erythroblast maturation and enucleation, while only Cl-IB-MECA led to the upregulation of CD33 and CD11a myeloid markers and promoted the differentiation of a GPA neg myeloid subpopulation. Conclusion Overall, our results place adenosine signaling as a new player in hematopoiesis regulation. Adenosine signaling via A 3 perturbs erythropoiesis and promotes the survival and differentiation of myeloid progenitors even in an erythroid favoring environment. While the activation of A 2B hampers optimal erythropoiesis without impacting the myeloid differentiation. As both ineffective erythropoiesis and increased leucocyte counts are reported in SCD, and given the detrimental role of high adenosine levels in its pathophysiology, further studies are ongoing to address the impact of adenosine signaling on hematopoiesis in this disease. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Le phenotype erythrocytaire Emm- a ete decrit en 1973 mais reste l’un des derniers groupes sanguins de base genetique inconnue (antigene de prevalence elevee de la serie 901). Il avait ete propose qu’Emm serait porte par une proteine ancree a la membrane du globule rouge (GR) par un glycosylphosphatidylinositol (GPI) car l’expression de cet antigene est fortement reduite dans les GRs de patients atteints d’hemoglobinurie paroxystique nocturne (HPN). Cette maladie est causee par des mutations somatiques du gene PIGA, implique dans la synthese du GPI. En utilisant une approche genomique basee sur le sequencage d’exome chez 3 rarissimes individus Emm- (dont le cas index), nous avons identifie des mutations homozygotes sur un gene commun implique dans la synthese du GPI, PIGG. En utilisant l’approche Crispr/Cas-9, nous avons developpe des lignees cellulaires deficientes pour plusieurs genes PIGs impliques dans la synthese et le trafic des proteines ancrees au GPI. L’analyse de ces cellules par cytometrie en flux et western blot en utilisant un anticorps anti-Emm a montre que Emm est porte par un GPI libre et que l’epitope est forme par le 2e et 3e ethanolamine du squelette du GPI. Nous avons montre que l’anticorps anti-Emm detecte parfaitement les defauts de synthese du GPI, causes par des mutations germinales dans les genes PIGs et responsables de pathologies neurologiques severes. Il est a noter que le cas index etait atteint d’un deficit intellectuel et que l’absence de PIGG semble donc etre associee a des troubles du developpement du systeme nerveux central. Ce travail a permis d’etablir Emm comme un nouveau systeme de groupe sanguin chez l’Homme (n°42, ISBT 2020) ( Fig. 1 ).

Patients with sickle cell disease (SCD) show a high prevalence of red blood cell (RBC) alloimmunization, but few studies have focused on children. We aimed to study the prevalence and risk factors of RBC alloimmunization in SCD children. We retrospectively analysed the medical and transfusion files for 245 SCD children hospitalized in our centre in 2014 and included 175 patients who had received at least one RBC unit in their lifetime. The main clinical and immuno-haematological characteristics of alloimmunized and non-alloimmunized patients were compared. The prevalence of alloimmunization was 13·7% [95% confidence interval (CI) (8·6-18·6)], and 7·4% [95% CI (3·5-11·3)] after excluding the probable irregular natural antibodies (anti-M, anti-Lea , anti-Leb , anti-Lex ). Main risk factors for alloimmunization were increased number of RBC units received (median of 65 vs. 10 units per patient; P = 0·01) and the presence of one or more red cell autoantibodies (46·2% vs. 4·7%; P < 0·0001). The alloimmunization rate was higher for episodically transfused than chronically transfused patients (1·43 vs. 0·24/100 units received; P < 0·001). The presence of red cell autoantibodies appears to be a major risk factor for alloimmunization in SCD children and could justify specific transfusion guidelines.

International audience; The Cromer blood group system consists of 19 antigens (16 of high prevalence and 3 of low prevalence). This study describes the identification and characterization of a new Cromer high-prevalence antigen, named CORS. The CORS-negative proband carries a c.713G>A substitution in the CD55 gene, resulting in the substitution of glycine 238 into a glutamic acid (p.Gly238Glu).

A workshop on the clinical significance of red blood cell alloantibodies, organized by the Executive Committee of the Working Party on Immunohaematology of the International Society of Blood Transfusion (ISBT), took place in Dubai, United Arab Emirates, on 9 September 2016, in conjunction with the 34th International Congress of the ISBT. This event was funded by the ISBT Academy, founded in 2011, to support educational and knowledge activities. This report is a summary of that meeting.

MtA 38-year-old male with sickle cell disease undergoing exchange transfusion presented with shivering, nausea, dyspnea, and pain in the lower limbs. Biologic parameters showed increased hemolysis. The administered red blood cell (RBC) units had been issued by electronic crossmatch due to a negative antibody screening test. In the posttransfusion investigations, crossmatch of the transfused RBC units with the patient's serum showed incompatibility of one unit. The presence of an antibody against a low-prevalence antigen was suspected and further serologic testing was performed for identification.Anti-MtTo our knowledge, this is the first case report of an HTR associated with anti-Mt

Extended blood group genotyping is an invaluable tool used for prevention of alloimmunization. Genotyping is particularly suitable when antigens are weak, specific antisera are unavailable, or accurate phenotyping is problematic because of a disease state or recent transfusions. In addition, genotyping facilitates establishment of mass-scale patient-matched donor databases. However, standardization of genotyping technologies has been hindered by the lack of reference panels. A well-characterized renewable reference panel for standardization of blood group genotyping was developed. The panel consists of genomic DNA lyophilized and stored in glass vials. Genomic DNA was extracted in bulk from immortalized lymphoblastoid cell lines, generated by Epstein-Barr virus transformation of peripheral blood lymphocytes harvested from volunteer blood donors. The panel was validated by an international collaborative study involving 28 laboratories that tested each DNA panel member for 41 polymorphisms associated with 17 blood group systems. Overall, analysis of genotyping results showed >98% agreement with the expected outcomes, demonstrating suitability of the material for use as reference. Highest levels of discordance were observed for the genes CR1, CD55, BSG, and RHD. Although limited, observed inconsistencies and procedural limitations reinforce the importance of reference reagents to standardize and harmonize results. Results of stability and accelerated degradation studies support the suitability of this panel for use as reference reagent for blood group genotyping assay development and standardization.

The blood group antigen Vel has been one of immunohematology’s greatest enigmas: the variation in antigen strength from one individual to another, the property of anti-Vel to readily hemolyze Vel+ red blood cells (RBCs), and the difficulty to screen for sufficient numbers of Vel– blood donors had made Vel a tough nut to crack. In 2013, a small, previously unknown protein called small integral membrane protein 1 (SMIM1) was identified on the RBC by three independent research groups using different approaches, and all three groups demonstrated that Vel– RBCs lacked SMIM1. This discovery correlated with homozygosity for deletion c.64_60del in SMIM1 and meant that for the first time there was a universal method to screen for Vel– blood donors. This finding was not the whole answer, however, and an explanation behind the variability in antigen strength was later shown to be due to polymorphism in SMIM1 intron 2, a region that is responsible for gene transcription. Clinically, anti-Vel is important and has caused severe transfusion reactions, although hemolytic disease of the fetus and newborn caused by anti-Vel is uncommon. However, while screening for Vel– blood donors has become easier, the function of SMIM1 is still unknown, and despite its well-conserved sequence across the animal kingdom, the enigma continues. Immunohematology 2017;33:56–59.

International audience

Background and objectives: The International Society of Blood Transfusion (ISBT) Working Party for Red Cell Immunogenetics and Blood Group Terminology meets in association with the ISBT congress and has met three times since the last report: at the international meetings held in Dubai, United Arab Emirates, September 2016 and Toronto, Canada, June 2018; and at a regional congress in Copenhagen, Denmark, June 2017 for an interim session. Methods: As in previous meetings, matters pertaining to blood group antigen nomenclature and classification were discussed. New blood group antigens were approved and named according to the serologic and molecular evidence presented. Results and conclusions: Fifteen new blood group antigens were added to eight blood group systems. One antigen was made obsolete based on additional data. Consequently, the current total of blood group antigens recognized by the ISBT is 360, of which 322 are clustered within 36 blood groups systems. The remaining 38 antigens are currently unassigned to a known system. Clinically significant blood group antigens continue to be discovered, through serology/sequencing and/or recombinant or genomic technologies.

International audience; BACKGROUND : Sickle cell disease (SCD) patients undergo multiple red blood cell (RBC) transfusions and are regularly exposed to low‐prevalence (LP) antigens specific to individuals of African descent. This study evaluated the prevalence of antibodies against LP antigens in SCD patients and the need to identify these antibodies in everyday practice.STUDY DESIGN AND METHODS : Plasma from 211 SCD patients was tested with RBCs expressing the following LP antigens: RH10 (V), RH20 (VS), RH23 (DW), RH30 (Goa), KEL6 (Jsa), and MNS6 (He).RESULTS : Nine LP antibodies were found in eight patients (3.8%): five anti‐RH23, two anti‐RH30, and two anti‐MNS6. The exposure risk, calculated for each LP antigen, was below 3% per RBC unit, for all antigens tested. Thus, in this cohort of transfused SCD patients, the prevalence of LP antibodies was similar to that of antibodies against antigens of the FY, JK, and MNS blood group systems. These findings also reveal the occurrence of anti‐RH23 in SCD patients. No anti‐RH20 or anti‐KEL6 were found, despite the high frequency of mismatch situations.CONCLUSION : These results highlight the immunogenicity of these LP antigens, and the evanescence of antibodies against LP antigens. They also highlight the importance of appropriate pretransfusion testing for patients frequently transfused, who are likely to be exposed to multiple types of blood group antigens.

Une enfant de 17 mois est amenee aux urgences pour asthenie progressive et syncopes repetees. Le bilan biologique d’entree revele : – une anemie severe a 31 g/L ; – un test direct a l’anti globuline fortement positif de type IgG ; – la presence d’anticorps anti-erythrocytaires libres dans le plasma de specificite anti-publique, d’une composante anti-RH5 puissante et de temoins autologues positifs. Son phenotype est RH :1, 2, − 3, 4, 5. Des pathologies dysimmunitaires ont ete diagnostiquees dans sa fratrie. Devant ce profil classique d’anemie hemolytique auto-immune (AHAI) a auto-anticorps chauds, un traitement immunosuppresseur est entrepris et l’enfant est transfusee avec des unites RH :-3. Des echanges plasmatiques s’averent necessaires devant la constatation d’une hemoglobinurie et de mauvais rendements transfusionnels. Des echantillons sont adresses au CNRGS qui identifie un anticorps anti-RH17 (absence de reactivite sur hematies D− –) de titre 16 et une puissante reactivite anti-RH5 (titre 1000). Ce profil est frequent dans les AHAI. L’etude du gene RHCE, en ne revelant aucune mutation, conforte l’origine auto-immune des anticorps. L’instabilite clinique de l’enfant justifie la decision de recourir a 2 fractions d’une unite rare de phenotype D− –. Le rendement transfusionnel est excellent, avec amelioration spectaculaire de l’etat clinique et sortie d’unite de soins continus. Malgre une nouvelle poussee d’hemolyse survenue quelques jours plus tard, aucune autre unite rare D− – n’a ete necessaire. Cette observation peu frequente illustre l’interet d’un recours ponctuel, mais avec un net benefice, d’unites de sang rare compatibles avec des auto-anticorps de specificite anti-publique.

L’antigene G (RH12) est exprime aussi bien par la proteine RhD que les proteines RhCe ou RhCE. Une immunisation anti-G se presente ainsi comme une image d’anti-D + C (anti-RH1 + RH2). Les femmes enceintes presentant une immunisation anti-G ou anti-G + C peuvent etre ainsi faussement etiquetees comme ayant une immunisation anti-D + C. Elles ne beneficient alors pas, a tort, du traitement par immunoprophylaxie anti-D et leurs grossesses peuvent etre inutilement lourdement surveillees, les anti-G et anti-C n’etant en general pas responsables d’atteinte hemolytique antenatale. La preuve de la presence d’anti-G et d’absence d’anti-D se fait par fixations-elutions (FE) successives, afin d’isoler les anticorps anti-D, -C et -G. Cette methode est chronophage et lourde a mettre en œuvre. L’allele rare RHD*01 N.07 n’exprime aucun epitope de la proteine RhD, tout en conservant l’expression de l’antigene G. Lorsqu’il est associe a un allele RH*cE, il definit l’haplotype r”G. Les sujets porteurs de cet haplotype a l’etat homozygote ou associe a un haplotype dcE ou dce sont donc de phenotype D-C-G+ (RH :-1,-2,12). Les serums de patientes pour lesquelles l’exploration d’une image d’anti-D + C avait ete realisee par FE successives ont ete testes sur une hematie D-C-G+ traitee par papaine. Par cette methode, nous mettons effectivement en evidence la presence de l’anti-G dans 12 echantillons/12 connus positifs et son absence dans 2 cas/2 connus negatifs. La recherche d’un anticorps anti-G peut ainsi etre realisee facilement et rapidement sur des hematies de phenotype rare D-C-G+. En cas de negativite, il n’est pas necessaire de recourir aux methodes par FE pour conclure a une immunisation anti-D.

L’arrete du 15 mai 2018 fixant les conditions de realisation des examens d’IH erythrocytaire a abroge l’arrete du 26 avril 2002, apportant des modifications qui precisent les exigences d’accreditation. Ces changements peuvent etre apprehendes dans une demarche qualite par une gestion de projet type 5 M. Materiel Informatique Des demandes d’evolution des systemes informatises sont faites : anteriorites des RAI sur le compte-rendu, nomenclature internationale du phenotype RH-KEL. Pour le transfert informatique des donnees IH il s’agissait deja d’une exigence de 2002. Matiere Abonnement a un CIQ C3d pour l’EDA. Arret des editions de cartes de groupes. Main d’œuvre information en CME des prescripteurs pour la determination unique, suivi de l’efficacite par indicateurs et EPP (taux de suppression des GS, doubles determinations sans transfusion). Formulaires de prescription modifies tracant le contexte transfusionnel avere. Methode Formalisation de la verification du seuil de detection a 10 ng/mL des RAI et EDC. Les procedures ont ete revisees pour les regles d’exclusion (RAI) et la definition des resultats critiques. Milieu Le LBM doit s’assurer que la procedure d’identitovigilance de l’etablissement de sante respecte les exigences de l’arrete (service des admissions…). Versant depot, travail a effectuer avec les LBM en dehors de l’ES : transmission des RAI des parturientes, liaisons informatiques pour les donnees IH. Discussion L’application d’un arrete est attendue des sa parution. Neanmoins l’ampleur des changements imposes necessitera du temps pour les LBM, notamment ceux en lien avec l’informatique avec des necessites de parametrage des systemes informatises.

Les cas de maladie hemolytique du nouveau-ne (MHNN) chez le phenotype Bombay Oh sont rarement rapportes dans la litterature. Ce phenotype est defini par une absence totale d’antigene H sur les hematies et les secretions associee a la presence d’un puissant anticorps anti-H. Aussi nous rapportons le cas d’une dame originaire de la Reunion chez qui nous avons decouvert lors de sa premiere grossesse son groupe Oh RH1, 2, −3, −4, 5 KEL-1 avec un anti-H associe a un anti-LE2. La biologie moleculaire a retrouve l’haplotype Bombay caracterise par une mutation faux-sens de FUT1 a l’etat homozygote c.725T→G entrainant le remplacement de la leucine en position 242 par une arginine et par une deletion du gene FUT2. Le suivi des grossesses a ete fait avec les RAI et les titrages des IgG anti-H apres destruction au DTT des IgM : – titre reste stable a 64 de la 22e a la 38e SA lors de la 1ere grossesse ; – titre passe de 128 a la 22e SA et a 32 de la 30e a la 38e SA lors de la 2e grossesse. Les suivis par doppler de l’artere cerebrale moyenne du fœtus n’ont pas retrouve d’anemie fœtale. Une anticipation des besoins transfusionnels a ete realisee par des prelevements de transfusion autologue programmee et mise en place d’un Cell Saver. Les accouchements se sont bien deroules. Les nouveau-nes de groupe A n’ont pas pose de probleme particulier : leurs TDA etaient negatifs et leurs taux de bilirubine totale n’excedaient pas 40 μmol/L. Conclusion L’ anti-H du phenotype Bombay considere comme dangereux n’est pas responsable de MHNN lors des 2 grossesses alors que l’equipe de Moores PP a decrit 2MHNN necessitant une exsanguino-transfusion avec des CGR Oh chez les nouveau-nes qui etaient de groupe O.

BACKGROUND Transfusion support of S-s- patients is very challenging but can now be alleviated by genotyping mutations in the GYPB gene to predict their U- or U+(var) phenotype. However, the phenotype predicted by genotyping does not always correspond to the observed phenotype of red blood cells (RBCs), which requires further investigation to avoid such a typing discrepancy in the future. In this study, we elucidated the case of an S-s- female patient of African origin who was predicted to be S+s- by our genotyping platform. STUDY DESIGN AND METHODS Long-range polymerase chain reaction (PCR) amplification and extended Sanger sequencing were required. RESULTS The Ss typing discrepancy in the proband resulted from a converted GYPB allele that encodes neither S nor s due to the replacement of Exon B4 of GYPB by the homologous Exon A4 of GYPA. In this novel GYPB-A-B hybrid gene, the GYPA segment actually starts just downstream of Exon B2, causing a MN typing discrepancy too. While the proband's RBCs were M+N-, the genotyping predicted the M+N+ phenotype. CONCLUSION The reported GYPB-A-B hybrid gene constitutes a limitation for the accurate prediction of the MN and Ss phenotypes by current genotyping methods. A PCR assay was therefore developed to detect its presence.

The Kidd blood group system currently comprises two polymorphic and antithetical antigens, Jka and Jkb, and one high-prevalence antigen, Jk3. Jknull individuals do not express any of the Kidd antigens, and are at risk of developing an anti-Jk3 which is known to be dangerous and responsible for acute or delayed hemolytic transfusion reaction. We report a case of an immunized Jknull patient, who was scheduled to undergo a heart transplant. In order to organize his blood provision management, two conference calls were held between the clinical team and the different staff involved in this challenging blood supply. In light of the blood needs, the available resources, and the constraints, a mix of fresh and frozen units were used. As the supply from France was not sufficient, Finland and New Zealand provided the majority of the fresh units. We report here how this international supply chain was organized, including the difficulties that we encountered. Anticipation, communication and flexibility were essential in making this heart transplant possible without needing to transfuse incompatible units.

Antigens of the Gerbich blood group system are expressed on glycophorin C (GPC) and glycophorin D (GPD), minor sialoglycoproteins of human erythrocytes. GPC and GPD help maintain erythrocyte shape of and contributes to the stability of its membrane. There are six high-prevalence Gerbich antigens: Ge2, Ge3, Ge4, GEPL (GE10), GEAT (GE11), GETI (GE12) and five low-prevalence Gerbich antigens: Wb (GE5), Lsa (GE6), Ana (GE7), Dha (GE8), GEIS (GE9). Some Gerbich antigens (Ge4, Wb, Dha, GEAT) are expressed only on GPC, two (Ge2, Ana) are expressed only on GPD, while others (Ge3, Lsa, GEIS, GEPL, GETI) are expressed on both GPC and GPD. Antibodies recognizing GPC/GPD may arise naturally (so-called "naturally-occurring RBC antibodies") or as the result of alloimmunization, and some of them may be clinically relevant. Gerbich antibodies usually do not cause serious hemolytic transfusion reactions (HTR); autoantibodies of anti-Ge2- or anti-Ge3 specificity can cause autoimmune hemolytic anemia (AIHA).

The blood group antigen Vel has been one of immunohematology's greatest enigmas: the variation in antigen strength from one individual to another, the property of anti-Vel to readily hemolyze Vel+ red blood cells (RBCs), and the difficulty to screen for sufficient numbers of Vel- blood donors had made Vel a tough nut to crack. In 2013, a small, previously unknown protein called small integral membrane protein 1 (SMIM1) was identified on the RBC by three independent research groups using different approaches, and all three groups demonstrated that Vel- RBCs lacked SMIM1. This discovery correlated with homozygosity for deletion c.64_60del in SMIM1 and meant that for the first time there was a universal method to screen for Vel- blood donors. This finding was not the whole answer, however, and an explanation behind the variability in antigen strength was later shown to be due to polymorphism in SMIM1 intron 2, a region that is responsible for gene transcription. Clinically, anti-Vel is important and has caused severe transfusion reactions, although hemolytic disease of the fetus and newborn caused by anti-Vel is uncommon. However, while screening for Vel- blood donors has become easier, the function of SMIM1 is still unknown, and despite its well-conserved sequence across the animal kingdom, the enigma continues.

Background The rare amorph Rhnull phenotype is caused by silent alleles at the RH locus and usually arises in consanguineous families. To date, only five molecular backgrounds have been identified in five unrelated families. Subjects with Rhnull red blood cells (RBCs) readily produce alloantibodies to high-prevalence Rh antigens. Study Design and Methods RBCs from a pregnant woman (G5P3) from Libya, with a positive indirect antiglobulin test were phenotyped by hemagglutination. RHD and RHCE genes were analyzed at the genomic level and mutation inheritance pattern was assessed in the patient's family. Results Hemagglutination testing showed a D–C–E–c–e– phenotype in the proposita associated with the presence of a high titer anti-Rh29 (4096). Molecular analysis revealed a deletion of RHD and presence of a novel RHCE allele with a 7-bp duplication in Exon 7. This duplication is predicted to introduce a frameshift after His350, a new C-terminal sequence, and a premature stop codon resulting in shortened predicted protein with only 402 amino acids. The mutated allele was found at homozygous state in the proposita and heterozygous state in her parents and one brother. Conclusion This report describes a novel RHCE mutation causing the loss of RhCE antigen expression in association with RHD deletion, leading to an amorph Rhnull phenotype.

Background The rare S−s− phenotype is typically found in persons of African origin. Three genetic bases underlying this phenotype have been identified so far: a large deletion including the GYPB gene, which encodes the S and s antigens, and two mutations affecting GYPB splicing (commonly called “P2” and “NY”). The discovery of the S−s− phenotype in a Swiss patient prompted this study. Study Design and Methods The GYPB genotype of the patient was analyzed with Beadchip technology and Sanger sequencing. GYPB haplotype analysis was also carried out in the patient's family. A functional splicing assay was developed to determine the impact of the identified mutation on GYPB splicing. Results Sanger sequencing of GYPB in the patient indicated that she was homozygous for a GYPB*s allele carrying a novel mutation in the splice donor site of Intron 5 (c.270+5G>A). Analysis of GYPB haplotypes in the patient's family revealed that she actually inherited this mutated GYPB*s allele from her mother of Swiss ancestry and a deleted GYPB allele from her father of Egyptian ancestry. Using a minigene-based splicing assay, we showed that GYPB mutation c.270+5G>A causes the skipping of Exon B5, as previously reported for the P2 mutation (c.270+5G>T). Consistently, the patient's red blood cells were found to be S−s−U+var. Conclusion A novel GYPB mutation (c.270+5G>A) accounting for the S−s−U+var phenotype was identified. In contrast with P2 and NY mutations, which also drive this rare phenotype, this novel GYPB mutation inactivates a GYPB*s allele and does not appear to be of African origin.

Introduction Most blood antigen-carrying proteins have important functions not only in red blood cells (RBCs) but also in other tissues. Hence, because of their polymorphisms and the existence of natural null phenotypes, blood groups also represent powerful tools to investigate human diseases. The PEL-negative rare blood type is one of the last with an unknown genetic basis. Family studies showed that the PEL-negative phenotype was inherited as an autosomal recessive trait, but the PEL locus remained undetermined since the first description of the corresponding antibody in French-Canadian individuals in 1996. Results Combining whole-exome sequencing and comparative global proteomic approaches using genomic DNA and red cell membrane proteins from four unrelated French-Canadian PEL-negative individuals and from controls, we identified i) the Multidrug Resistance-Associated Protein 4 (MRP4), also known as ABCC4, as the only missing protein in all PEL-negative RBCs and ii) a large deletion removing the last 10 exons of the ABCC4 gene. Western blot analyses confirmed that ABCC4 was present in the membrane of PEL-positive control RBCs but totally absent in the PEL-negative RBCs (Fig 1A). Western blot and flow cytometry analyses of transfected HEK293 cells revealed that over-expression of ABCC4 results in a significant increase in PEL antigen cell-surface expression (Fig 1B). Conversely, similar analyses of ABCC4-knockout K562 cells generated by the CRISPR-Cas9 strategy showed that the complete loss of ABCC4 abolished the expression of the PEL antigen (Fig 1C). PEL-negative individuals are therefore the first ever reported population lacking the complete expression of the ABCC4 protein. Surprisingly, despite the expected biological importance of ABCC4 as a cyclic nucleotide transporter, no apparent mutual symptoms or diseases were identified after investigation of the clinical history of the 12 PEL-negative members within the 4 families analyzed in this study. However, platelet investigation from one PEL-negative individual supported the role of this protein in the modulation of platelet aggregation, as previously observed in ABCC4-knockout mice studies To better understand the function of ABCC4 in mature RBCs, we measured the intracellular cGMP level in RBCs from 5 PEL-negative individuals and 5 controls. We showed that the cGMP level was not significantly impaired in the absence of ABCC4 suggesting that another cGMP transporter could compensate for the absence of ABCC4 on the RBC membrane. Interestingly, proteomic and flow cytometry analyses indicated that among the five other ABC transporters (ABCC1, ABCA7, ABCB6, ABCC5 and ABCG2) expressed on RBCs, only ABCG2 was increased in PEL-negative/ABCC4null RBCs compared to controls (1.3-fold; p=0.0007). This suggested that the absence of ABCC4 in PEL-negative individuals could be compensated by the over-expression of ABCG2. Our data, together with previous studies indicating that both ABCC4 and ABCG2 export cGMP, strongly suggest that the over-expression of ABCG2 in PEL-negative RBCs represents a compensatory mechanism for the lack of ABCC4, which could explain the absence of hematological abnormalities in PEL-negative individuals. Discussion Using genetic, molecular and cellular approaches, we demonstrated that ABCC4 is the gene underlying the novel PEL blood group system and that homozygosity for a large deletion in this gene is responsible for the rare PEL-negative phenotype. ABCC4 represents the third ABC transporter carrying a blood group system after ABCG2 (JR) and ABCB6 (LAN). The expression level of ABCC4 is strongly involved in drug resistance and toxicity, and in the clinical course of leukemia. As ABCC4 carries the PEL antigen, PEL phenotyping could be useful in the adjustment of an optimal drug dose and prevention of chemotherapy side effects in leukemia. Our findings are of immediate and important relevance in transfusion medicine and in a personalized medicine approach for chemotherapy treatment follow-up in leukemia. Furthermore, the exceptional natural "knockouts" of ABC transporters are highly valuable in understanding their function, not only in erythroid cells, but also in other cells or tissues. Disclosures Hermine: Novartis: Research Funding; Celgene: Research Funding; AB Science: Consultancy, Equity Ownership, Honoraria, Research Funding.