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Anti-KEL1 antigen (also referred to as anti-Kell, or anti-K) alloimmunisation is the second most common cause of severe haemolytic disease of the fetus and newborn, after anti-rhesus D antigen, and can cause substantial fetal morbidity and mortality. Both fetal erythropoietic suppression and haemolysis contribute to anaemia. Typically, once a clinically significant alloantibody is identified during pregnancy, antibody titration is performed as a screening test to predict the risk of anaemia and the need for maternal-fetal medicine referral. The titre is a semiquantitative laboratory method based on the underlying principle that increased maternal antibody concentrations are associated with an increased risk of fetal anaemia. Because some studies report that anti-K alloantibodies can lead to severe anaemia even at a low antibody titration, guidelines are inconsistent with respect to the role of titration testing. Some experts recommend maternal-fetal medicine referral and middle cerebral artery Doppler ultrasound without titration testing or with the use of a very low cutoff titre. This Viewpoint evaluates management for pregnancies affected by anti-K alloantibodies and highlights literature regarding the predictive value of anti-K titration testing., Competing Interests: Declaration of interests GC is a medical advisor to Perinatal Screening Ontario and has received travel support to international congresses from the International Society for Blood Transfusion. GC is the Secretary General for the International Society for Blood Transfusion. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Hemolytic disease of the fetus and newborn (HDFN) due to an antibody in the Kell blood group system can be associated with severe fetal anemia. This case report details the challenges of managing a Kell null mother with anti-Ku that affected her fetus/newborn. A gravida 4 para 3 woman at term underwent an emergency lower caesarean section because of fetal distress. The baby was intubated because of low oxygen saturation. An urgent request for a hematology workup showed severe anemia and erythroblastosis fetalis. Unfortunately, no compatible blood was found, and the baby died. The case was referred to the National Blood Centre, and anti-Ku was confirmed in a sample sent from the mother. When she presented with her fifth pregnancy, meticulous planning was used to manage this pregnancy. Her family screening revealed one brother with a matching phenotype. Three blood donations were planned for the brother-for freezing, for intrauterine transfusion, and for standby during delivery. Serial anti-Ku titrations of maternal samples were performed, and the fetus was monitored for anemia through middle cerebral artery Doppler scans. Although the anti-Ku titers reached as high as 1024, fetal anemia was never diagnosed. The neonate was delivered safely but was diagnosed with severe pathologic jaundice and anemia secondary to HDFN and congenital pneumonia. The baby was transfused with K 0 packed red blood cells and later discharged to home., (© 2024 Siti A. Wan Mohd Hasni et al., published by Sciendo.)

Objective: To systematically review and meta-analyze alloimmunization among recipients of red blood cells (RBCs) matched for ABO blood type and Rhesus D (ABO+D) antigen compared with those also matched for c, E, and Kell (cEK)., Data Sources: Four online databases (Medline, Scopus, EMBASE, ClinicalTrials.gov ) were searched from March 28, 2023, to April 1, 2024. The search protocol was peer reviewed and published on PROSPERO ( CRD42023411620 )., Methods of Study Selection: Studies reporting alloimmunization as the primary outcome among recipients of RBCs matched for ABO+D or additional cEK matching were included. Patients transfused with unmatched RBCs or a mixture of matching regimens were excluded. Risk of bias was assessed with Cochrane Tool to Assess Risk of Bias in Cohort Studies and Tool for Risk of Bias. Random-effects meta-analysis was used to combine effect estimates., Tabulation, Integration, and Results: Ten studies met criteria. Risk of bias was low. Overall, 91,221 patients were transfused, of whom 40,220 (44.1%) received additional cEK-matched RBCs. The overall rate of alloimmunization was 6.2% (95% CI, 2.5-14.9%) for ABO+D-only matching and 1.9% (95% CI, 0.7-5.1%) when cEK was added. Time of follow-up antibody testing ranged from 6 to 18 months after transfusion. Additional cEK match was associated with significantly less alloimmunization compared with standard ABO+D match (odds ratio [OR] 0.37, 95% CI, 0.20-0.69). This association remained when chronically transfused patients were excluded (OR 0.65, 95% CI, 0.54-0.79) and for alloimmunization to c, E, or K antigens only (OR 0.29, 95% CI, 0.18-0.47)., Conclusion: Additional cEK RBC matching protocols were associated with lower odds of recipient alloimmunization. Given severe sequelae of alloimmunization in pregnancy, routine cEK matching for transfusion in people with pregnancy potential younger than age 50 years in the United States merits consideration., Systematic Review Registration: PROSPERO, CRD42023411620 ., Competing Interests: Financial Disclosure Andra H. James has received honoraria from the Cerus Corp. Jerome J. Federspiel has received honoraria from Hemosquid, SA. The other authors did not report any potential conflicts of interest., (Copyright © 2024 by the American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.)

Background: Antibodies against blood group antigens play a key role in the pathophysiology of haemolytic transfusion reactions (HTRs) and haemolytic disease of the fetus and newborn (HDFN). This study aimed to determine the frequencies of alleles, genotypes, and risk of alloimmunisation of clinically significant blood group systems in ethnic northeastern Thais., Methods: In total, 345 unrelated, healthy, ethnic northeastern Thais were tested using the in-house PCR-sequence specific primers (PCR-SSP) method for simultaneously genotyping of RHCE, Kell, Duffy, Kidd, Diego and MNS glycophorin hybrids and results confirmed by Sanger sequencing., Results: In this cohort, the alleles RHCE*C (81.0%) and RHCE*e (84.8%) were more prevalent than RHCE*c (19.0%) and RHCE*E (15.2%). The most common predicted haplotype combinations of the RHCE alleles were C+c-E-e+(R 1 R 1 ) (59.4%) followed by the C+c+E+e+ (R 1 R 2 ) (20.6%) and C+c+E-e+ (R 1 r) (11.3%). The KEL*01 allele was not found in this study. The frequencies of FY*01 and FY*02 were 88.3% and 11.7%, respectively. The genotype FY*02/02 was found in four samples (1.2%). The frequencies of JK*01 and JK*02 were 52.5% and 47.5%, respectively. Homozygous JK*02/02 was found in 81 samples (23.5%). The frequencies of DI*01 and DI*02 were 0.6% and 99.4%, respectively. In total, 64 samples (18.6%) were found to carry the MNS glycophorin hybrids., Conclusions: Our results indicated a possible high risk of c, E, Fy b , Jk a , Jk b and Mi a alloimmunisation in these populations. Moreover, methods established for genotyping clinically significant blood groups in this study can now be utilised in routine clinical application., (© 2024 British Blood Transfusion Society.)

Introduction: Rh and Kell blood group systems are amongst the most important blood group systems; being highly immunogenic after ABO system. The aim of this study was to evaluate the frequencies of Rh antigens, haplotypes and K antigen among blood donors belonging to various ethnicities in Samtah, Jazan, Saudi Arabia., Methods: This study was conducted during January 2019 and August 2020 at Samtah General Hospital, Samtah. Records of all blood donors recruited during this period were included for data acquisition. A total of 4977 blood donors' records were reviewed and data were analysed. A total of 3863 donors' results were considered in the final analysis., Results: In comparison to Saudi blood donors, C antigen was less frequent in Sudanese donors (69.7% and 34.0%), the c antigen was less frequent in Indian (79.2% and 59.3%) and Philippine (79.2% and 40.0%) donors and more frequent in Sudanese (79.2% and 97.9%) donors, the E antigen was less frequent in Yemini (27.0% and 19.5%) and the e antigen was more frequent in Yemini (96.7% and 99.2%) donors. The DcE haplotype was less frequent (3.1% and 0.7%) and the ce haplotype was more frequent (4.3% and 7.6%) in Yemini donors. The K antigen was less frequent in Pakistani (11.9% and 4.1%; p = .041) and Indian (11.9% and 1.9%; p = .023) donors., Conclusion: Rh and K antigens showed marked variations in their frequencies among blood donors of different ethnicities. Utilization of blood from various ethnicities warrant extended phenotyping of Rh and K antigens to avoid the risk of alloimmunization in multiply transfused patients., (© 2022 John Wiley & Sons Ltd.)

Maternal alloantibodies directed against fetal red blood cell (RBC) antigens may cause potentially life-threatening haemolytic disease of the fetus and newborn (HDFN). Dutch transfusion guidelines therefore prescribe preventive cEK matching for all (pre-)fertile females. To quantify the impact of cEK matching, we compared overall and antigen-specific cumulative RBC alloimmunisation incidences in females and males aged <45 years. Among a multicentre cohort comprised of patients who received their first and subsequent RBC unit between 2005 and 2019, first-formed RBC alloantibodies were detected in 47 of 2998 (1·6%) females and 49 of 2507 (2·0%) males. Comparing females and males, overall alloimmunisation incidences were comparable (3·1% [95% confidence interval (CI) 2·1-4·4] versus 3·5% (95% CI 2·4-4·9, P = 0·853) after 10 units transfused). However, cEK alloimmunisation incidences were significantly lower among females (0·6% (95% CI 0·3-1.5) versus 2·2% (95% CI 1·5-3·4, P = 0·001) after 10 units transfused). Yet, despite cEK-matching guidelines being in effect, 6·5%, 3·6% and 0·2% of all RBC units remained mismatched for c, E or K antigens respectively. Most of these mismatches were almost always due to emergency settings. Even though cEK alloimmunisation was not prevented completely, implementation of cEK matching resulted in an alloantigen-exposure risk reduction of up to 98%., (© 2021 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Background: During pregnancy, maternal red blood cell (RBC) antibodies can lead to life-threatening fetal hemolysis and anemia. Women can become immunized by a pregnancy or an unmatched transfusion. Our aim was to quantify the effect of a nationwide K-matched transfusion policy for women of childbearing age potential to prevent K-immunization in pregnancy., Study Design and Methods: In this nation-wide policy change evaluation study we determined the occurrence of RBC antibodies before and after introduction of a K-matched transfusion policy and evaluated the cause K alloimmunization 10 years after introduction of this measure. K-matched transfusion for females under 45 years of age is advised in the Dutch transfusion guideline since 2004. We used laboratory data from pregnancies with RBC antibodies identified in the period 1999-2018 obtained as part of a population-based screening program in the Netherlands., Results: Tests of 36 286 pregnancies produced a positive antibody screening result which concerned anti-K in 1550 pregnancies. The occurrence of anti-K decreased from 67.9 to 20.2 per 100 000 pregnancies. The relative risk reduction was 0.70 which largely exceeded the relative risk reduction of 0.27 for antibodies against RBC antigens for which no preventive matching is required. The number of pregnancies at risk for anti-K-mediated disease decreased from 9.7 to 4.2 per 100 000 pregnancies., Conclusions: A K-matched transfusion policy is associated with a major decrease in a number of pregnant women with anti-K and pregnancies at risk for anti-K-mediated disease. A relatively simple measure is now shown to impact prevention of hemolytic disease in the fetus and newborn., (© 2021 The Authors. Transfusion published by Wiley Periodicals LLC. on behalf of AABB.)

The development of hemolytic erythrocyte alloantibodies and autoantibodies complicates transfusion therapy in thalassemia patients. These antibodies ultimately increase the need for blood and intensify transfusion complications. There is a scanty data on the frequency of RBC alloimmunization and autoimmunization in Egyptian β thalassemia patients as pretransfusion antibody screening is not routinely performed. We studied the frequency of alloimmunization and autoimmunization among 200 multiply transfused β thalassemia patients and investigated the factors that possibly affect antibody formation. Of the 200 patients in our study, 94 were males and 106 females, with the age range of 2-37 years. Alloantibodies were detected in 36 (18%) of the patients, while autoantibodies were detected in 33 (16.5%). The dominant alloantibodies were directed against Kell (33%) and Rh (24.4%) groups. Alloimmunization had a significant relationship with treatment duration and the frequency of transfusion (P = 0.007, 0.001, respectively). The presence of autoantibodies was significantly related to age (P = 0.001), total number of transfused units (P = 0.000) and splenectomy (P = 0.000). The high prevalence of alloimmunization in the study population disclosed the need for providing phenotypically matched cells for selective antigens especially for Kell and Rh subgroups to reduce risk of alloimmunization and increase the efficiency of blood transfusion.

Maternal alloantibody-mediated hemolytic disease of the fetus and newborn (HDFN) ranges from no or mild symptoms to severe hydrops and intrauterine fetal demise. Hemolytic anti-D-mediated HDFN proceeds via a long-known mechanism, to which three other pathways to fetal/neonatal anemia may be added: (0) Fetal erythrocyte destruction can proceed by extravascular phagocytosis. (1) An apoptotic pathway has been described for anti-Kell, and anti-Ge3. (2) Erythropoietic suppression may arise from altered or deformed erythroblast architecture in anti-M-mediated disease. (3) Clonal escape from erythropoietic suppression is hypothesized to arise from maternal anti-Jr a immune pressure, albeit this requires further elucidation. Alloantibody-mediated anemic disease of the fetus and newborn (ADFN) is a designation we favor for cases when hemolysis or hyperbilirubinemia are not the dominant features, such as those provoked by anti-Kell, anti-Ge3, anti-M, and anti-Jr a ., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Human immunoglobulin G (hIgG) includes four different subtypes (IgG1, IgG2, IgG3, and IgG4). Due to genetic variations, each IgG subtype contains different isoallotypes. It was previously shown that a Food and Drug Administration-approved monoclonal anti-IgG failed to recognize 2 of 15 recombinant, human IgG3 anti-Kell (K1) isoallotypes (rIgG3-03 and rIgG3-13) by indirect antiglobulin test (IAT)., Study Design and Methods: We expressed and purified 15 recombinant human rIgG3 anti-K1 isoallotypes and investigated their antigen binding and ability to induce phagocytosis using homozygous (KK) and heterozygous (Kk) K1-positive red blood cells (RBCs) by gel IAT, flow cytometry, and a monocyte monolayer assay (MMA) with peripheral blood monocytes and cultured inflammatory (M1) and anti-inflammatory (M2) macrophages., Results: MMA results showed that differences in the Fc region of rIgG3 anti-K1 led to distinctive phagocytic activity with both monocytes and M1 macrophages. rIgG3-18 and rIgG3-19 showed an enhanced ability to induce phagocytosis. Differences in Fc regions also led to variations in the number of antibodies bound to KK RBCs. Despite the differences in phagocytic activity, all 15 rIgG3 clones are predicted to induce clinically significant hemolysis if K1-positive blood was transfused into patients., Conclusion: These results argue that antiglobulin reagents that fail to detect isoallotype rIgG3-03 or rIgG3-13 could present a transfusion risk or lack of detection of a potentially clinically significant anti-K1 in hemolytic disease of the fetus and newborn., (© 2020 AABB.)

High-titer antibodies are a cause of false-negative reactions in red blood cell antigen phenotyping, an event referred to as blocked antigen phenomenon (BAP). In hemolytic disease of the fetus and newborn, BAP complicates laboratory workups as fetal phenotype is helpful in confirming the responsible antibody. Acid elution techniques, techniques using ethylenediaminetetraacetic glycine acid, as well as those using chloroquine diphosphate have been used to resolve BAP; however, ethylenediaminetetraacetic glycine acid destroys K-antigen expression and chloroquine diphosphate is not always effective. We report a case of severe hemolytic disease of the fetus and newborn from anti-K where a modified gentle heat elution resolved BAP. Although infrequently considered with isolated reports in the literature, heat elution is simple, is effective, and involves readily available materials in most blood banks., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Several Kell-system antibodies are known to cause direct agglutination. Also, some specificities, such as anti-Ku, have been reported to react only via the indirect antiglobulin test (IAT)., Methods: Herein, we describe the case of a 61-year-old alloimmunized white woman who presented to an outside hospital with a gastrointestinal (GI) bleed and a "possible anti-Ku" was reported with 3+ reactivity at PEG-IAT and at Ficin-IAT; in addition to an unidentified cold antibody. Subsequently, when the patient presented to a second outside hospital, an anti-Ku that caused 3+ to 4+ reactions at saline-immediate spin (IS) was identified. The reactivity was evaluated with 0.01-M dithiothreitol (DTT) treatment of the plasma., Results: It was determined that the strong agglutination with saline-IS was caused by immunoglobulin (Ig)M anti-Ku., Conclusion: To our knowledge, this is the first reported case of an IgM anti-Ku., (© American Society for Clinical Pathology 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Only a fraction of red blood cell (RBC) transfusion recipients form alloantibodies, and variables determining responsiveness or nonresponsiveness are poorly understood. We and others have previously shown in animal models that pretreatment with toll-like receptor agonists that mimic different types of infections impacts the magnitude or frequency of RBC alloantibody responses. We hypothesized that influenza infection, coexistent with transfusion, would impact responses to transfused RBCs in a manner dependent on Type 1(α/β) interferon (IFN) signaling and tested this in a murine model., Study Design and Methods: Wild-type mice or mice lacking the ability to respond to Type 1 IFN were infected with influenza prior to the transfusion of transgenic murine RBCs (K1) expressing the human KEL glycoprotein or the triple fusion HOD protein. Alloantibody responses were measured longitudinally after transfusion by flow cytometric crossmatch, and posttransfusion RBC recovery and survival was evaluated., Results: Influenza-infected mice transfused with K1 RBCs developed robust anti-KEL alloantibodies, whereas animals transfused in the absence of infection remained nonresponders; influenza-associated RBC alloimmunization was also observed after transfusion of HOD RBCs. Recipient Type 1 IFN production was critical to the mechanism of action of influenza-induced RBC alloimmunization, with alloimmunization being significantly decreased in mice unable to sense Type 1 IFN (through antibody blockade or genetic approaches)., Conclusion: These and other data suggest that Type 1 IFN responses to toll-like receptor agonists or infections regulate RBC alloantibody responses. Studies investigating whether such a correlation exists in humans may be informative., (© 2019 AABB.)

Background & Objectives: : Sickle cell disease (SCD) patients require red cell transfusion during different clinical complications of the disease. Such patients are at a high risk for developing alloantibody against red cell antigens. From India, there are limited data available on alloantibody formation in multiply transfused SCD patients. The present study was thus undertaken to fill up this lacunae by looking at the development of red cell alloantibodies in SCD and β-thalassaemia patients on regular transfusion., Methods: : All sickle cell disease patients undergoing red cell transfusion between 2008 and 2016, were included. During this period, a large number of β-thalassaemia major patients also underwent regular red cell transfusion. These thalassaemia patients were also included to compare the tendency of antibody formation between SCD and β-thalassaemia major patients. All patients before regular transfusion were regularly assessed for the development of red cell antibody. Red cell antigen, antibody screen crossmatch and antibody identification were done using the standard technique., Results: : A total of 138 patients with SCD aged between 4 and 53 yr (mean 17.6 yr) consisting of 83 males and 55 females (male:female, 1.5:1) along with 333 transfusion-dependent β-thalassaemia patients were studied. Over the last eight years, 15 patients with SCD and four patients with thalassaemia developed alloantibody (P <0.001). Antibody specificity of their alloantibodies was against Rhc, RhE, Kell, Fy a and Fy b only. Sickle cell disease patients with and without alloantibody required on the average 11.8 and 8.6 units of red cell concentrate, respectively (P <0.05)., Interpretation & Conclusions: : About 11 per cent of the transfused sickle cells patients developed alloantibodies. The antibody specificity was restricted to Rh, Kell and Duffy blood group systems. Extended antigen matching involving Rh, Kell and Duffy antigens may prevent alloantibody in such patients., Competing Interests: None

Background: There is controversy on critical cut-off values of laboratory testing to select pregnancies at increased risk for anti-Kell-mediated hemolytic disease of the fetus and newborn. Without early detection and treatment, anti-Kell-mediated hemolytic disease of the fetus and newborn may result in progressive fetal anemia, fetal hydrops, asphyxia, and perinatal death., Objective: We aimed to determine the value of repeated anti-Kell titer determination and biological activity measurement using the antibody-dependent cellular cytotoxicity test determination in the management of pregnancies at risk for anti-Kell-mediated hemolytic disease of the fetus and newborn., Study Design: This was a retrospective cohort study of pregnancies with anti-Kell and a Kell-positive fetus, identified from January 1999 through April 2015. Laboratory test results and clinical outcome were collected from the Dutch nationwide screening program and the national reference center for fetal therapy in The Netherlands, the Leiden University Medical Center. Diagnostic accuracy was measured (receiver operating characteristic curves, sensitivity, specificity, positive and negative predictive values) for anti-Kell titers and antibody-dependent cellular cytotoxicity test. The relationship between the titer and antibody-dependent cellular cytotoxicity measurements and the 2 foregoing measurements were computed with a Pearson product-moment correlation coefficient., Results: In a 16-year unselected cohort, representing screening results of 3.2 million pregnancies resulting in live births in The Netherlands, we identified 1026 Kell-immunized pregnancies. In all, 93 pregnant women had anti-Kell and a Kell-positive child, without other red cell alloantibodies. In all, 49 children (53%) needed intrauterine or postnatal transfusion therapy. The first anti-Kell titer showed already a high diagnostic accuracy with an area under the curve of 91%. The optimal cut-off point for the titer was 4 (sensitivity 100%; 95% confidence interval, 91-100), specificity 27% (95% confidence interval, 15-43), and positive predictive value 60% (49-71%). The antibody-dependent cellular cytotoxicity test was not informative to select high-risk pregnancies. Linear regression showed no significant change during pregnancy, when antibody titer and antibody-dependent cellular cytotoxicity test results were compared with every 2 foregoing measurements (P < .0001)., Conclusion: Early determination of the anti-Kell titer is sufficient to select pregnancies at increased risk for hemolytic disease of the fetus and newborn with need for transfusion therapy. If the Kell status of the fetus is known to be positive, a titer of ≥4 can be used to target intensive clinical monitoring., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Parvovirus B19 has tropism for red line blood cells, causing immune hydrops during pregnancy. A positive anti-Kell Coombs reaction usually happens during pregnancy when there is production of antibodies that target Kell antigens, but cross reactions to other antigens may occur. A 24-year-old Gypsy primigravida, 0 Rhesus positive, presented with persistent isolated hyperthermia for 2 weeks and a positive indirect Coombs test result with anti-Kell antibodies at routine tests. She had a 19-week live fetus. The blood tests revealed bicytopenia with iron deficiency anemia, leucopoenia with neutropenia, and elevated C-reactive protein. She was medicated with imipenem, and had a slow clinical recovery. Blood, urine and sputum samples were taken to perform cultures and to exclude other systemic infections. Escherichia coli was isolated in the urine, which most probably caused a transient cross anti-Kell reaction. Haemophilus influenza in the sputum and seroconversion to parvovirus B19 was confirmed, causing unusual deficits in the white cells, culminating in febrile neutropenia. Despite the patient's lack of compliance to the medical care, both maternal and fetal/neonatal outcomes were good. This a rare case report of 2 rare phenomena, a cross anti-Kell reaction to E. coli and parvovirus B19 infection with tropism for white cells causing febrile neutropenia, both events occurring simultaneously during pregnancy., Competing Interests: The authors have no conflicts of interest to report., (Thieme Revinter Publicações Ltda Rio de Janeiro, Brazil.)

Background: The antibody primarily responsible for fetal anemia may influence treatment and prognosis. The primary objective was to compare ante- and postnatal management and the outcomes of maternal red blood cell (RBC) alloimmunizations according to the antibody involved. The secondary objective was to compare anti-D alloimmunizations according to associated number of antibodies., Study Design and Methods: A single-center study from 1999 to 2015 including maternal RBC alloimmunizations requiring intrauterine transfusion (IUT) was conducted. Patients were classified according to the antibody involved: anti-D, other Rh (anti-c and anti-E), and anti-K1. Obstetric data, IUT characteristics, and neonatal outcome were compared. A specific study on the anti-D, when isolated or associated, was then conducted., Results: There were 106 pregnancies included, with 77.4% having anti-D, 9.4% having another anti-Rh (Rh group), and 13.2% having anti-K1. No significant difference between the anti-D and Rh groups was found for management and prognosis. The hemoglobin level in the first IUT was higher in the anti-D group than in the Kell group (6.8 vs. 4.7 g/dL, p = 0.008). Newborns in the anti-D group had significantly higher bilirubin levels and phototherapy duration than those in the Kell group. The mean estimated daily decrease in hemoglobin and that between the first two IUTs were lower with an isolated anti-D, compared with anti-D associated with two antibodies (p = 0.04)., Conclusion: Anti-K1 alloimmunizations seem to cause more severe fetal anemia than anti-D alloimmunizations. Moreover, a decrease in hemoglobin appears to be more rapid when anti-D is associated with other antibodies., (© 2018 AABB.)

Background: Alloantibodies to red blood cell (RBC) antigens can cause significant hemolytic events. Prior studies have demonstrated that inflammatory stimuli in animal models and inflammatory states in humans, including autoimmunity and viremia, promote alloimmunization. However, molecular mechanisms underlying these findings are poorly understood. Given that Type 1 interferons (IFN-α/β) regulate antiviral immunity and autoimmune pathology, the hypothesis that IFN-α/β regulates RBC alloimmunization was tested in a murine model., Study Design and Methods: Leukoreduced murine RBCs expressing the human KEL glycoprotein were transfused into control mice (WT), mice lacking the unique IFN-α/β receptor (IFNAR1 -/- ), or bone marrow chimeric mice lacking IFNAR1 on specific cell populations. Anti-KEL IgG production, expressed as mean fluorescence intensity (MFI), and B-cell differentiation were examined., Results: Transfused WT mice produced anti-KEL IgG alloantibodies (peak response MFI, 50.4). However, the alloimmune response of IFNAR1 -/- mice was almost completely abrogated (MFI, 4.2; p < 0.05). The response of bone marrow chimeric mice lacking IFNAR1 expression in all hematopoietic cells or specifically in B cells was also diminished (MFI, 3.8 and 5.4, respectively, compared to control chimeras, MFI, 65.6; p < 0.01). Accordingly, transfusion-induced differentiation of IFNAR1 -/- B cells into germinal center B cells and plasma cells was significantly reduced, compared to WT B cells., Conclusions: This study demonstrates that B cells require signaling from IFN-α/β to produce alloantibodies to the human KEL glycoprotein in mice. These findings provide a potential mechanistic basis for inflammation-induced alloimmunization. If these findings extend to human studies, patients with IFN-α/β-associated conditions may have an elevated risk of alloimmunization and benefit from personalized transfusion protocols., (© 2017 AABB.)

Objective: The aim of this study was to present a new method for fetal Kell genotyping by means of the allelic discrimination of K1 and K2 in real-time polymerase chain reaction (PCR)., Methods: Real-time quantitative polymerase chain reaction incorporating an allele-specific primer was developed for detecting the K allele of KEL., Results: By means of this method, the K1/K2 genotype was able to be determined in all blood samples analyzed. Results using cell-free fetal DNA (cffDNA) from two Kell-negative pregnant women confirmed the Kell-positive genotype of fetuses. The real-time PCR analysis also allowed the determination of the fetal fraction using the quantification of Kell-positive DNA., Conclusion: An efficient and reliable strategy for Kell genotyping is herein presented. The method was optimized on cffDNA to create a non-invasive prenatal test which could be routinely used for the prevention of hemolytic disease of the fetus and the newborn (HDFN)., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: This study aims at alloantibody screening, determination of the types of these antibodies in multiple-transfused patients with chronic hematologic diseases., Patients and Methods: This descriptive study was performed on 240 patients with chronic hematological diseases referred to public hospitals in Iran. Single blood sample was taken and tested for the presence of antibodies. In case of a positive antibody screening, antibody identification was performed using granulocyte agglutination test (GAT), granulocyte indirect immunofluorescence test (GIIFT), platelet indirect immunofluorescence test (PIIFT), monoclonal antibody-specific immobilization of platelet antigen (MAIPA) and panel cells., Results: Out of 240 patients, 105 patients (43.75 %) had been alloimmunized. The incidence of alloantibodies against red blood cells (RBCs) in positive alloantibodies patients were 84.76% (89/105). The most common alloantibody was against antigens of the kell (anti-K) and Rh (anti-E) and (anti D) systems (46.66%, 18.09% and 11.43% respectively). The overall incidence of anti- human leukocyte antigen (HLA) antibodies were 65.7% (69/105). Polymorphonuclear (PMN)-specific antibodies were found in 6.66% (7/105). Also from 105 patients, 14 patients had alloantibodies against platelet., Discussion: In general, it is recommend that to decrease the rate of alloantibody synthesis, the packed cells should be cross matched for minor blood groups especially for Rh (E) and kell. In addition, the use of leukodepleted blood products can decrease the frequency of alloimmunization against platelet (PLT), PMN and HLA antigens., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Introduction: Kell antigen is highly immunogenic and is the common cause of antibody production in mismatched blood transfusions, haemolytic transfusion reaction (HTR) and maternal alloimmunization, which causes severe anaemia in neonates. The aim of this study is to determine the prevalence and ethnic variation of the Kell phenotype among pregnant women in Sokoto, Nigeria., Methods: Kell antigen status of 150 pregnant women aged 18-45 years and mean age 27.19 ±4.69 years attending antenatal clinic in UDUTH Sokoto Nigeria was determined using the conventional tube method and anti-Kell reagents (Lorne Laboratories, UK)., Results: Among the 150 subjects studied, 3 (2.0%) of subjects were positive and 147 (98.0) were negative for K antigen. Of the 150 pregnant subjects; 32 (21.3%) were primigravidae while 118 (78.7%) were multigravidae. Kell phenotype was more prevalent among primigravidae (3.1%) compared to multigravidae (1.7%) women. The distribution of Kell phenotype among the pregnant subjects was compared based on ethnicity. The prevalence of Kell antigen was significantly higher among the Hausa ethnic group (3.2%) compared to other ethnic groups which indicated zero prevalence (p = 0.001). Kell negative phenotype was ≥ 96.8% among all the ethnic groups., Conclusion: Our observed prevalence of Kell phenotype is consistent with previous studies among Blacks and Asians but significantly lower than values observed in previous studies among Caucasians. We recommend that all pregnant women should be screened for the presence clinically significant red cell antigens including Kell antigen on their first antenatal visit. Kell negative red cell should be routinely provided for all pregnant women and women with child bearing potential to reduce the risk of Kell-associated HDFN. There is need to introduce routine screening of pregnant women for clinically significant red cell antibodies to facilitate the effective management of HDFN as well as prevent HTR. There is also need for sustained health education of pregnant women in the area to encourage early booking for antenatal care.

Introduction: Thalassemia major is a common hemoglobinopathy in Albania. However, there are no data available on the frequency of RBC alloimmunization and autoimmunization in transfusion-dependent Albanian patients with thalassemia., Methods: A total of 118 patients with thalassemia receiving regular transfusions were studied during 5 years with antibody screening. During this period, they were exclusively transfused with blood matched for ABO, Rhesus and Kell system. These patients were previously exposed to unmatched blood because of blood shortages., Results: Fourteen of 118 (11, 8%) patients developed alloantibodies. Twelve (10, 1%) were already present at the start of the study. Only 2 (1, 7%) were formed after the application of a strict Rh and Kell matching policy. The most common antibody was anti-K, followed by anti-D, anti-C, anti-E, anti-c, anti-e, anti-Jk(b) , and anti-C(w) . Three patients developed anti-D plus anti-C. Anti-K was combined with Rh antibodies in two of five cases. Anti-c was combined with anti-E in two of three cases. The majority of antibodies (10/14) belonged to the Rh blood group system. With the exception of the anti-Jk(b) and the anti-C(w) , all antibodies were already present at the beginning of the follow-up period. During our follow-up, 27 patients (22.8%) developed autoantibodies. A strong coincidence was found between the presence of alloantibodies and autoantibodies. Eleven of 14 (78%) of the patients with alloantibodies had also autoantibodies, whereas autoantibodies were found in 16 of 104 (15%) of patients with thalassemia without autoantibodies. The rate of alloantibody formation dropped from 10.1% to 1.7% after application of a strict Rh and Kell matching policy., Conclusion: A policy of Rhesus and Kell matching without occasional exceptions greatly reduced the development of new alloantibodies and autoantibodies. Self-sufficiency through regular blood donation is necessary for the full implementation of an extended match policy and the prevention of antibody formation in our patients., (© 2015 John Wiley & Sons Ltd.)

Background: In Pakistan routine blood group typing of thalassemia patients identifies ABO and Rh(D) antigens only. Therefore, other antigen incompatibilities between blood donor and blood recipient may cause alloimmunisation., Objective: The aim of this study was to estimate the frequency of alloimmunisation and to evaluate the risk factors associated with its development in beta (β)-thalassemia patients receiving regular blood transfusions., Materials and Methods: In total 162 β thalassemia patients were included in this study. An extended red cell antigen panel was performed to detect antibodies. Patients received red cell concentrates, which were matched for ABO and Rh(D) antigens. Clinical and laboratory data were collected and analysed to estimate the frequency of alloantibodies and the factors influencing immunisation in patients on regular blood transfusion., Results: The median age of patients was 6·7 (range: 0·5-25) years. A total of 14 (8·6%) patients developed alloantibodies against red cell antigens. The most frequently occurring alloantibodies was anti-E (2·5%), anti-K (1·8%), anti-e (1·2%) and anti-D (0·6%). Five (3·1%) patients developed more than one red blood cell (RBC) alloantibody. Age at first transfusion in alloimmunised patients was 1·22 ± 0·87 years. The frequency of blood transfusion in alloimmunised patients was 23 ± 8·81 days and in those without alloimmunisation was 31·8 ± 16 days (p = 0·02). Logistic regression analysis showed no independent risk factor associated with alloimmunisation., Conclusion: The frequency of transfusion was increased in patients who developed alloantibodies. Typing patients and donors to match for Rh and Kell antigens would prevent more than 90% of RBC alloantibodies and reduce the frequency of transfusion in thalassemia patients., (© 2015 British Blood Transfusion Society.)

We report a case of Kell sensitized pregnancy with good neonatal outcome. Anti-K antibodies were detected in maternal serum in early pregnancy as a part of routine antibody screening test. The middle cerebral artery doppler monitoring and serial titers were carried out to screen for foetal anaemia. Despite of rising antibody titers, serial middle cerebral artery doppler was normal and did not showed foetal anaemia. The pregnancy was carried out till term and patient delivered at 37 weeks of pregnancy with no evidence of foetal anaemia. This case underlines the need of general screening on rare antibodies in all pregnant women and that non-invasive monitoring of foetal anaemia can be done with anti-k titers and middle cerebral artery Doppler.

Fetal and neonatal haemolytic diseases result from maternal allo-immunisation to fetal antigens. Maternal antibodies cross the placenta causing red cell haemolysis, resulting in fetal anaemia and, in severe cases, hydrops and perinatal death. Intravascular intrauterine blood transfusion (IUT) has markedly reduced perinatal mortality and is now a standard procedure. IUT is considered to be a safe procedure with fetal loss rate reported to be less than 5% and no reported increase in the rate of neurodevelopment impairment. In this report, we are presenting a case of bilateral cystic encephalomalacia following fetal anaemia secondary to anti-Kell iso-immunisation treated with multiple IUTs. Such a significant adverse outcome following IUT for anti-Kell iso-immunisation has not been reported in the literature. This case highlights the need for appropriate parental counselling and routine postnatal head ultrasound in all babies delivered following multiple IUTs., (2015 BMJ Publishing Group Ltd.)

Background & Objectives: The development of alloantibodies can significantly complicate transfusion therapy and results in difficulties in cross-matching of blood. Most literature on alloimmunization is limited to multitransfused individuals, with very few studies on the general hospital patients. This study was aimed at assessing the frequency and type of unexpected red cell antibodies in the general patient population at a multispecialty tertiary care centre in New Delhi, India., Methods: The results of 49,077 antibody screening tests carried out on patients, from January 2009 to December 2012 were analyzed. The clinical and transfusion records were reviewed. The data were compiled and statistically analysed., Results: A total of 49,077 (29,917; 60.96% males and 19,160; 39.04% females) patient samples were screened for the presence of unexpected antibodies. Antibody screening was positive in 403 patients (0.82%). In the serum samples of 164 patients only autoantibodies were identified, 27 revealed autoantibodies with one or more underlying alloantibodies, while 212 patients had only alloantibody/ies in their serum. The overall alloimmunization rate was 0.49 per cent. Antibodies against the Rh system were the most frequent (64.1%), the most common alloantibody identified being anti E (37.2%), followed by anti D (19.2%)., Interpretation & Conclusions: Since clinically significant antibodies are frequently detected in our patient population, antibody screening and if required, identification is the need of the hour. Since antibodies against the common Rh and Kell blood group antigens are the most frequent, provision of Rh and Kell matched red cells may be of protective value.

Background: Kell is a complex blood group system comprising 35 antigens. Kell antigens are absent from rare red cells of the Ko (null) phenotype and expressed only weakly in the Kmod phenotype. Molecular analysis of three uncommon KEL alleles elucidated the obscure pattern of inheritance of Kell antigens in one family., Materials and Methods: Standard serological methods were employed. All exons, flanking intronic sequence and introns 15 and 16 of KEL were sequenced from genomic DNA. cDNA was obtained from erythroid cells cultured from progenitor cells isolated from peripheral blood., Results: The Kmod propositus was heterozygous for two KEL mutations: c.2107G>A, p.Gly703Arg and a synonymous mutation, c.1719C>T, in the codon for p.573Gly. Sequencing of cDNA revealed that c.1719C>T caused skipping of exon 16, resulting in a silent allele. Her KEL:3,-4 brother was heterozygous for KEL*03/04 and c.1719C/T., Conclusion: A synonymous mutation caused complete exon skipping, despite being located 16 bases downstream of the 3′ splice site, resulting in a null KEL allele. The combined effects of two mod alleles, one responsible for KEL3 expression and the other for p.Gly703Arg, were probably responsible for an unexpected KEL:3,-4 phenotype.

Although most warm red blood cell (RBC) autoantibodies react broadly with panel cells in addition to the patient's own RBCs, occasionally an autoantibody with specificity for a specific blood group antigen is encountered. Rare cases of warm autoantibodies with specificity for the Kpb antigen of the Kell blood group system have been described. We report a pediatric transplant recipient with anemia, immune-mediated hemolysis, thrombocytopenia, and a warm autoantibody with apparent anti-Kpb specificity. The patient's autoimmune anemia and thrombocytopenia responded well to discontinuing the immunosuppressant tacrolimus, trans- fusions with Kp(b-) RBCs, and intravenous immunoglobulin therapy, with disappearance of the pathologic antibody. During the autoimmune hemolysis, the patient's RBCs did not react with antisera specific for Kpb. However, repeat testing of the patient's RBCs with Kpb-specific antisera 15 months after the resolution of hemolysis showed reactivity, indicating that the RBC autoantibody was associated with a transient disappearance of the Kpb antigen.

Background: There is an ongoing controversy regarding provision of usually matched blood (i.e. matched for ABO-D antigens) or phenotypically matched blood (also matched for Rh and Kell antigens) for multiply transfused thalassaemics, especially in developing countries. A pilot study conducted at our centre revealed an alloimmunisation rate of 3.79% with Rh and Kell alloantibodies accounting for 90% of all antibodies. The present cross-sectional study was conducted to assess the impact of a policy of partial better matching (for Rh cDE and Kell antigens) of blood on alloimmunisation in thalassaemics., Material and Methods: In this cross-sectional study three groups of patients were considered. Group 1 comprised 211 thalassaemics who received usually matched (UM) blood until April 2009. Their rates of alloimmunisation have already been published in a prior study. Group 2 consisted of 46 thalassaemics who were enrolled after April 2009 and have received partially better matched (PBM) blood (matched for ABO, Rh cDE and Kell antigens) since the initiation of transfusion therapy. Group 3 (UM→PBM) comprised the patients from group 1 who, from April 2009, were given partial better matched blood. Antibody screening (using a 3-cell panel) and antibody identification (11-cell panel) were carried out to detect the presence of alloantibodies., Results: None of the thalassaemic patients in group 2 (PBM) developed alloantibodies. Eight thalassaemics in group 3 (UM→PBM) developed new alloantibodies (after April 2009)., Discussion: According to the results of the present study, providing at least partially better matched blood appears to improve the efficacy of transfusion for chronically transfused thalassaemics. Large-scale, comprehensive, multicentre studies need to be carried out to formulate realistic, evidence-based, economically feasible transfusion policies for thalassaemic children based on the red blood cell antigen profile of the population.

Background: Red blood cell (RBC) alloantibodies to nonself antigens may develop after transfusion or pregnancy, leading to morbidity and mortality in the form of hemolytic transfusion reactions or hemolytic disease of the newborn. A better understanding of the mechanisms of RBC alloantibody induction, or strategies to mitigate the consequences of such antibodies, may ultimately improve transfusion safety. However, such studies are inherently difficult in humans., Study Design and Methods: We recently generated transgenic mice with RBC-specific expression of the human KEL glycoprotein, specifically the KEL2 or KEL1 antigens. Herein, we investigate recipient alloimmune responses to transfused RBCs in this system., Results: Transfusion of RBCs from KEL2 donors into wild-type recipients (lacking the human KEL protein but expressing the murine KEL ortholog) resulted in dose-dependent anti-KEL glycoprotein immunoglobulin (Ig)M and IgG antibody responses, enhanced by recipient inflammation with poly(I:C). Boostable responses were evident upon repeat transfusion, with morbid-appearing alloimmunized recipients experiencing rapid clearance of transfused KEL2 but not control RBCs. Although KEL1 RBCs were also immunogenic after transfusion into wild-type recipients, transfusion of KEL1 RBCs into KEL2 recipients or vice versa failed to lead to detectable anti-KEL1 or anti-KEL2 responses., Conclusions: This murine model, with reproducible and clinically significant KEL glycoprotein alloantibody responses, provides a platform for future mechanistic studies of RBC alloantibody induction and consequences. Long-term translational goals of these studies include improving transfusion safety for at-risk patients., (© 2013 American Association of Blood Banks.)

Background: The management of pregnant women with anti-Jsb is challenging due to the paucity of antigen-negative blood for fetal and neonatal transfusion., Case Report: A 29-year-old woman with anti-Jsb was referred for assessment of recurrent fetal losses. With the presence of the sister as a historically matched donor, she was planned for active surveillance for fetal anemia during pregnancy., Study Design and Methods: The fetus remained well until 21 weeks of gestation when signs of fetal anemia and early hydrops fetalis were noted. Anti-Jsb titer was at 128. The sister's red blood cells (RBCs) were cross-match incompatible. Urgent intrauterine transfusion (IUT) was performed with washed irradiated maternal RBCs, donated after cessation of heparin. The mother was given intravenous iron (IV-Fe) and continued on weekly recombinant human erythropoietin (rHu-EPO)., Results: Repeated IUTs were needed every 1 to 3 weeks. Throughout a 7-week period, three maternal donations were performed with total donated whole blood volume of 1250 mL, supporting four IUTs. At 29 weeks of gestation, the procedure was complicated by umbilical cord hematoma necessitating urgent cesarean section. A male newborn was delivered, transfused at birth, and subsequently treated with phototherapy and five top-up transfusions., Conclusion: This case represents a successful example of managing hemolytic disease of the fetus due to a rare antibody using maternal blood. It also supports previous data on safety of maternal donations during pregnancy and the use of combination of rHu-EPO and IV-Fe as a supportive measure., (© 2013 American Association of Blood Banks.)

Objective: To determine the antenatal course of severe red cell alloimmunisation in pregnancies requiring intrauterine fetal transfusion., Study Design: A retrospective cohort study over 16 years in a single national quaternary fetal medicine centre. From 1996 to 2011, 242 red cell intrauterine transfusions (IUT) were performed in 102 alloimmunised pregnancies. Antibody type was categorized into Rh(D) and non-Rh(D) (including Rh(c), Kell and Rh(E)). Women with Rh(D) antibodies were further stratified into those with and without additional red cell antibodies. Data were compared using the Mann-Whitney U and Fisher's exact tests. Two-tailed P values at the 5% level were considered significant., Results: Comparing Rh(D) and non-Rh(D) pregnancies, there were no differences in either gestational age or fetal haemoglobin at first IUT, number of transfusions required, gestation at delivery, caesarean delivery rates or perinatal losses. In women sensitized to Rh(D), the presence of additional antibodies did not influence the degree of fetal anaemia or the first transfusion-delivery interval, although rates of fetal hydrops were higher in the presence of multiple antibodies. The "procedure-related" loss rate was 1.7% per procedure in our institution., Conclusion: Antibody status does not appear to influence clinical outcomes following fetal transfusion for alloimmunisation., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Background: The number of KEL alleles associated with new antigens or loss of expression of high-prevalence antigens continues to increase. We investigated KEL in five samples: two with K0 (null) phenotypes and three with normal Kell expression and antibodies to high-prevalence antigens., Study Design and Methods: Red blood cell (RBC) typing and antibody identification were by standard methods. Genomic DNA was isolated from white blood cells and DNA array testing and sequencing of KEL exons was performed by standard methods., Results: Proband 1, an Asian woman with Kp(b+) RBCs, presented with alloanti-Kp(b) . Four years later, the antibody was reactive with all RBCs except K0 . She was homozygous for KEL c.877C>T change (p.Arg293Trp), and the high-prevalence antigen absent from her RBCs was named KHUL. Probands 2 and 3, both Japanese and homozygous for KEL c.875G>A (p.Arg292Gln), presented with an antibody reactive with all except K0 RBCs. The antibody, named KYOR, recognizes an antigen antithetical to KYO (KEL31). Proband 4, a pregnant Middle Eastern woman, presented with alloanti-Kp(b) , but her RBCs did not express Kell antigens. She was homozygous for KEL c.230G>T (p.Cys77Phe). Proband 5, a multiply transfused Caucasian female with an antibody reactive with all RBCs except K0 and lacking Kell antigens, was a compound heterozygote carrying a silenced allele c.574C>T (p.Arg192Stop) in trans to c.1664G>A (p.Gly555Glu)., Conclusion: We describe two new high-prevalence Kell antigens, KHUL (ISBT 006037; KEL37) and KYOR (ISBT 006038; KEL38), and two novel alleles encoding K0 phenotypes. We caution that antibodies produced by individuals with K0 RBCs or lacking high-prevalence antigens can present as anti-Kp(b) ., (© 2013 American Association of Blood Banks.)

Background: Antibodies to Kell antigens can be clinically important but only limited data are published regarding anti-Ku. Missense nucleotide changes in KEL account for the numerous Kell antigens, the K(mod) phenotype, and even the K(null) phenotype., Study Design and Methods: DNA and RNA were extracted from white blood cells and polymerase chain reaction-based assays, cloning, and sequencing were done using standard protocols., Results: The anti-Ku in Proband 1, which caused hemolytic disease and anemia of the fetus and newborn, was a mixture of immunoglobulin (Ig)G1 and IgG2 and gave macrophage indexes ranging from 47.8 to 59.3 (>20 is clinically significant) in a monocyte monolayer assay. The proband, her daughter, and compatible sister had a heterozygous deletion of a G in Exon 18 (Nucleotide c.1972&#95;1975delG) in a KEL*02 allele causing a frameshift. The mechanism for silencing of the other KE*02 allele was undetermined. Proband 2 was heterozygous for a nonsense change (KEL*382C/T; Arg128Stop), a missense change (KEL*244T/C; Cys82Arg), and KEL*578T/C (KEL*01/KEL*02). Direct sequencing of cDNA and cloning showed that the KEL*01 allele had 244C, 382C, 578T and the KEL*02 allele carried 244T, 382T, 578C., Conclusions: We report a novel single-nucleotide deletion, a novel nonsense allele, and a novel missense allele all resulting in the K(null) phenotype. The anti-Ku from Proband 1 was clinically important., (© 2013 American Association of Blood Banks.)

Background: The numerous antigens in the Kell blood group system result from missense nucleotide changes in KEL. Antibodies to antigens in this system can be clinically important. We describe six probands whose plasma contained antibodies to high-prevalence Kell antigens and discuss their relationship., Study Design and Methods: Polymerase chain reaction amplification, direct sequencing, restriction fragment length polymorphism assays, hemagglutination, flow cytometry, and protein modeling were performed by standard methods., Results: Proband 1 (KUCI) and her serologically compatible sister were heterozygous for a nucleotide change in Exon 11 (KEL*1271C/T; Ala424Val). Proband 2 (KANT) was heterozygous for KEL*1283G/T (Arg428Leu) and KEL*1216C/T (Arg406Stop) in Exon 11. Red blood cells (RBCs) from Proband 1 and her sister were not agglutinated by plasma from Proband 2; however, RBCs from Proband 2 were agglutinated by plasma from Proband 1. Probands 3, 4, 5, and 6 had the KEL*1391C>T change associated with the previously reported KETI- phenotype. Proband 5 was also homozygous for KEL*905T>C encoding the K11-K17+ phenotype. Hemagglutination studies revealed an association between KUCI, KANT, KETI, and K11. Protein modeling indicated that whereas Ala424 and Arg428 are clustered, Val302 and Thr464 are not., Conclusion: Ala424 in the Kell glycoprotein is associated with the high-prevalence Kell antigen, KUCI (ISBT 006032), which is detected by the antibody of Proband 1. Arg428 is associated with the high-prevalence Kell antigen, KANT (ISBT 006033). The association between KUCI, KANT, KETI, and K11 and the results of protein modeling are discussed., (© 2013 New York Blood Center. Transfusion © 2013 American Association of Blood Banks.)

Background: The Kell system, encoded by the KEL gene, is one of the most clinically important blood group systems. Molecular defects may lead to the absence of Kell antigen expression. The very rare KEL:5 results from silent KEL genes, also called KELnull alleles. In a few cases, the rare KEL:1,-2 phenotype may be associated with silent KEL*02 alleles., Study Design and Methods: The aim of this study was to perform DNA investigations to identify silent KEL alleles among 10 KEL:-5 patients and 121 individuals presenting the rare KEL:1,-2 phenotype. Serologic investigations were performed on patients' red blood cells and serum. The KEL gene analysis was done by using a BeadChip assay (HEA Version, 1.2, Immucor), real-time polymerase chain reaction, and/or sequencing of all 19 exons of the KEL gene., Results: In KEL:-5 patients, two novel KELnull alleles were described: 821G>A being the second described KELnull allele on a KEL*01 backbone and 184Tdel. In the 121 KEL:1,-2 individuals, nine (7.4%) were found to display a discordant KEL:1,-2 phenotype and KEL*01/KEL*02 genotype. Three novel silent KEL*02 alleles were described: 1084C>A, 1708G>A, and IVS11+5g>a., Conclusion: The number of silent KEL alleles and the notion that KEL null alleles are on a KEL*02 background may evolve in the coming years. Systematic DNA analysis showed that the number of discordant phenotype/genotype results, related to silent KEL*02 alleles was higher than expected in France. These data emphasize that clinical practice based on DNA analysis for blood group antigens requires caution and should improve the performance of the blood group phenotype prediction., (© 2013 American Association of Blood Banks.)

Exposure to nonself red blood cell (RBC) antigens, either from transfusion or pregnancy, may result in alloimmunization and incompatible RBC clearance. First described as a pregnancy complication 80 years ago, hemolytic disease of the fetus and newborn (HDFN) is caused by alloimmunization to paternally derived RBC antigens. Despite the morbidity/mortality of HDFN, women at risk for RBC alloimmunization have few therapeutic options. Given that alloantibodies to antigens in the KEL family are among the most clinically significant, we developed a murine model with RBC-specific expression of the human KEL antigen to evaluate the impact of maternal/fetal KEL incompatibility. After exposure to fetal KEL RBCs during successive pregnancies with KEL-positive males, 21 of 21 wild-type female mice developed anti-KEL alloantibodies; intrauterine fetal anemia and/or demise occurred in a subset of KEL-positive pups born to wild type, but not agammaglobulinemic mothers. Similar to previous observations in humans, pregnancy-associated alloantibodies were detrimental in a transfusion setting, and transfusion-associated alloantibodies were detrimental in a pregnancy setting. This is the first pregnancy-associated HDFN model described to date, which will serve as a platform to develop targeted therapies to prevent and/or mitigate the dangers of RBC alloantibodies to fetuses and newborns.

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

Introduction: Blood groups are inherited biological characteristics that do not change throughout life in healthy people. Blood groups represent antigens found on the surface of red blood cells. Kell blood group system consists of 31 antigens. Kell antigen (K) is present in 0.2% of the population (the rare blood group). Cellano antigen is present in more than 99% (the high-frequency antigen). These antigens have a distinct ability to cause an immune response in the people after blood transfusion or pregnancy who, otherwise, did not have them before., Case Report: This paper presents a blood donor with a rare blood group, who was found to have an irregular antibody against red blood cells by indirect antiglobulin test. Further testing determined the specificity of antibody to be anti-Cellano. The detected antibody was found in high titers (1024) with erythrocyte phenotype Kell-Cellano+. The blood donor was found to have a rare blood group KellKell. This donor was excluded from further blood donation. It is difficult to find compatible blood for a person who has developed an antibody to the high-frequency antigen. The donor's family members were tested and Cellano antigen was detected in her husband and child. A potential blood donor was not found among the family members. There was only one blood donor in the Register of blood donors who was compatible in the ABO and Kell blood group system., Conclusion: For the successful management of blood transfusion it is necessary to establish a unified national register of donors of rare blood groups and cooperate with the International Blood Group Reference Laboratory in Bristol with the database that registers donors of rare blood groups from around the world.

Background: Titration is a semiquantitative method used to estimate red blood cell (RBC) alloantibody reactivity. The conventional tube test (CTT) technique is the traditional method for performing titration studies. The gel microcolumn assay (GMA) is also a sensitive method to detect RBC alloantibodies. The aim of this study was to compare a GMA with the CTT technique in the performance of Rh and K alloantibody titration., Study Design and Methods: Patient serum samples that contained an RBC alloantibody with a singular specificity were identified by routine blood bank workflow. Parallel titration studies were performed on these samples by both the CTT method and a GMA (ID-Micro Typing System anti-IgG gel card, Micro Typing Systems, Inc., an Ortho-Clinical Diagnostics Company)., Results: Forty-eight samples were included, including 11 anti-D, five anti-c, 13 anti-E, one anti-C, three anti-e, and 15 anti-K. Overall, the two methods generated identical results in 21 of 48 samples. For 42 samples (87.5%) the two methods generated results that were within one serial dilution, and for the remaining six samples, results were within two dilutions., Conclusion: GMA systems may perform comparably to the CTT in titrating alloantibodies to Rh and Kell antigens., (© 2012 American Association of Blood Banks.)

The mental decline of King Henry VIII from being a jovial, charismatic and athletic young man into an increasingly paranoid, brutal tyrant in later life, ever more concerned at his lack of one or more male heirs, has attracted many medical diagnostic theories. Previous hypotheses have included diabetes, syphilis and hypothyroidism, among others. However, these inadequately explain Henry's failure to produce a male heir, despite multiple pairings. The latest postulated diagnoses for Henry are the coexistence of both Kell blood group antigenicity (possibly inherited from Jacquetta Woodville, Henry's maternal great grandmother) causing related impaired fertility, and McLeod syndrome, causing psychotic changes. As the mutated McLeod protein of the syndrome significantly reduces the expression, effectively inactivating the Kell antigen, we critically review this theory, examining in detail the pathophysiology of these conditions and assessing the genealogy of Henry VIII and its effect in subsequent generations.

Background: Alloanti-Kp(b) is a rare, clinically significant antibody against high frequency red cell antigen Kp(b) of Kell blood group system. We report here a case of Haemolytic disease of newborn (HDN) due to anti-Kp(b), which manifested as severe anaemia at the age of 1 month., Aim: To diagnose and successfully manage anti-Kp(b) induced HDN., Methodology: Direct antiglobulin test (DAT), antigen typing, irregular antibody screening and identification were done by polyspecific LISS Coombs Gel card and standard methods., Results: At presentation the neonate had severe anemia with reticulocytopenia. Blood group was B, Rh D positive and DAT was 2+. Anti-Kp(b) was detected in mother's serum. Due to unavailability of Kp(b) negative red cells and incompatible blood group of mother (A(1)B Rh D positive) infant was transfused group B Rh D, Kp(b) positive PRBCs under steroid cover. He was symptom free at 4 months of age and DAT became negative at 6 months., Conclusion: Anti-Kp(b) is capable of causing severe late HDN. Infants born to irregular antibody positive mothers should be investigated and closely monitored for several weeks after birth for immune HDN even if asymptomatic at birth., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: KEL1, also known as "K", is one of the most immunogenic red blood cell (RBC) antigens. KEL2, also known as "k," differs from KEL1 by a single amino acid. Anti-Kell system antibodies can lead to significant adverse clinical outcomes in humans, including hemolytic complications in alloimmunized transfusion recipients or in infants of alloimmunized mothers. To provide a platform for in-depth immunologic studies of alloimmunization and subsequent sequelae, we generated transgenic mice expressing the human KEL1 or KEL2 antigens., Study Design and Methods: Vectors were created in which cDNAs encoding either KEL1 or KEL2 were regulated by an erythroid specific β-globin promoter and enhancer. Pronuclear microinjections were carried out into a C57BL6 background, and founder pups were identified by polymerase chain reaction and screened for expression by flow cytometry. RBC life span and antigen stability were assessed by dye labeling RBCs, transfusing into agammaglobulinemic (µMT) recipients, and tracking by flow cytometry., Results: The expression of either KEL1 or KEL2 is RBC specific and first occurs on early RBC precursors. Both KEL1 and KEL2 RBCs have a normal circulatory life span and stable antigen expression. Expression of KEL1 or KEL2 does not result in altered levels of murine Kell, and resulting RBCs have normal hematologic variables., Conclusion: The KEL1 and KEL2 mice represent the first murine system of RBC immunity with antithetical antigens, allowing a more precise modeling of human RBC immunology in general and also a platform for development of novel therapeutics to prevent or minimize the dangers of RBC alloimmunization to the KEL1 and KEL2 antigens in particular., (© 2012 American Association of Blood Banks.)

The K blood group remains an important target in hemolytic disease of the newborn (HDN), with no immune prophylaxis available. The aim was to characterize the Th response to K as a key step in designing specific immunotherapy and understanding the immunogenicity of the Ag. PBMCs from K-negative women who had anti-K Abs after incompatible pregnancy, and PBMCs from unimmunized controls, were screened for proliferative responses to peptide panels spanning the K or k single amino acid polymorphism. A dominant K peptide with the polymorphism at the C terminus elicited proliferation in 90% of alloimmunized women, and it was confirmed that responding cells expressed helper CD3(+)CD4(+) and "memory" CD45RO(+) phenotypes, and were MHC class II restricted. A relatively high prevalence of background peptide responses independent of alloimmunization may contribute to K immunogenicity. First, cross-reactive environmental Ag(s) pre-prime Kell-reactive Th cells, and, second, the K substitution disrupts an N-glycosylation motif, allowing the exposed amino acid chain to stimulate a Th repertoire that is unconstrained by self-tolerance in K-negative individuals. The dominant K peptide was effective in inducing linked suppression in HLA-transgenic mice and can now be taken forward for immunotherapy to prevent HDN because of anti-K responses.

Objective: To determine the clinical spectrum of hemolytic disease due to irregular blood subgroup incompatibility in hospitalized neonates., Study Design: The medical records of the all hospitalized newborn patients diagnosed with indirect hyperbilirubinemia due to subgroup incompatibility in Kell, C, c, E, and e systems were included in the study. Data from 106 newborns with hemolytic jaundice due to irregular blood subgroups were retrospectively evaluated, and clinical and laboratory findings were compared between patients . The treatment modalities given to the patients of each subgroup types and the laboratory findings and treatment modalities of the cases according to Coombs tests results were also analyzed. Fetal affection of the hemolysis and also fetal losses due to irregular red-cell alloimmunization were not detected in prenatal course, as there was no follow-up of these pregnancies., Results: The mean postnatal hospitalizing age was 6.1 ± 5.2 days after birth. The mean total bilirubin level and the mean hemoglobin value on hospitalization were 343.7 ± 63.3 µmol/L (=20.1 ± 3.7 mg/dL) and 14.9 ± 3.4 g/dL, respectively. Of 106 patients identified with irregular subgroup incompatibility, 40 infants (37.7%) were associated with C, 22 (20.8%) with c, 30 (28.3%) with E, 9 (8.5%) with e, and 5 (4.7%) with Kell subgroup system. Positive Coombs tests (either direct and/or indirect) occurred in 28.3% of the study cases. Hydrops fetalis was determined in 5 of 106 neonates (4.7%). Twenty-two of 106 (20.8%) patients required total exchange transfusion. Positive Coombs test in cases required total exchange transfusion was 63.6%., Conclusion: Our data expose the magnitude and spectrum of the potential developing severe hemolytic disease and immune hydrops due to irregular subgroup incompatibility. Minor group antibody screening is recommended both in the mother and the high-risk infants with hyperbilirubinemia and hemolytic disease of the newborn., (Copyright © 2012 Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA.)