Immuno-Hematologic Complexity of ABO-Incompatible Allogeneic HSC Transplantation.

ABO incompatibility is not considered a contraindication for hematopoietic stem cell transplantation (HSCT). Approximately 30% of transplants from related donors and up to 50% of transplants from unrelated donors are ABO incompatible. Immuno-hematologic investigations allow to estimate donor/recipient ABO mismatch and anti-A/B isohemagglutinin (IHA) titration in the pre-HSCT phase. Immediate hemolysis or delayed complications (passenger lymphocyte syndrome and pure red cell aplasia) can occur post HSCT. Some preventive measures take into consideration either decision-making algorithms based on the recipient's IHA titration or clinical protocols for the removal/reduction of IHAs through plasma exchange or immunoadsorption procedures. Product manipulation through red blood cell (RBC) and/or plasma depletion can also be taken into account. Currently, the best approach in the management of ABO-incompatible transplant is not defined in expert consensus documents or with solid evidence. In addition, the methods for IHA titration are not standardized. A transfusion strategy must consider both the donor's and recipient's blood group systems until the RBC engraftment catches on and ABO conversion (forward and reverse typing) is confirmed on two consecutive and independent samples. Therefore, ABO incompatibility in HSCT represents a demanding immuno-hematologic challenge and requires all necessary preventive measures, including the appropriate selection of ABO blood components for transfusion.

The ABO blood group antigens in patients with oral lichenoid reaction.

Evaluating the association of ABO blood group with different delayed hypersensitivity reactions, such as oral lichenoid reaction (OLR), can provide a new perspective for clinical practice. Therefore, this study designed to investigate ABO blood group antigens in OLR patients. In this case-control study, the ABO blood group of 112 OLR patients and 117 individuals without oral lesions were included. Gender, age, characteristics of the lesions, medications and restorative materials recorded. Chi-square test used to compare the frequency of ABO blood groups in OLR patients with controls. The O blood group was significantly higher in OLR patients and all its subtypes. Also, there were significant relation between O blood group, and severity of lesions. The frequency of dysplasia was non-statistically significant higher in OLR patients with O blood group than other blood group. Based on the results of the present study, O blood group was significantly more in patients with lichenoid reaction than control group, and AB blood group was the lowest. Also, O blood group showed a positive association with the more severe form of OLR lesions and frequency of dysplasia.

Akkermansia muciniphila exoglycosidases target extended blood group antigens to generate ABO-universal blood.

Matching donor and recipient blood groups based on red blood cell (RBC) surface ABO glycans and antibodies in plasma is crucial to avoid potentially fatal reactions during transfusions. Enzymatic conversion of RBC glycans to the universal group O is an attractive solution to simplify blood logistics and prevent ABO-mismatched transfusions. The gut symbiont Akkermansia muciniphila can degrade mucin O-glycans including ABO epitopes. Here we biochemically evaluated 23 Akkermansia glycosyl hydrolases and identified exoglycosidase combinations which efficiently transformed both A and B antigens and four of their carbohydrate extensions. Enzymatic removal of canonical and extended ABO antigens on RBCs significantly improved compatibility with group O plasmas, compared to conversion of A or B antigens alone. Finally, structural analyses of two B-converting enzymes identified a previously unknown putative carbohydrate-binding module. This study demonstrates the potential utility of mucin-degrading gut bacteria as valuable sources of enzymes for production of universal blood for transfusions.

Consideration for alpha-gal syndrome in two critically ill persons with group O blood who received group B plasma.

BACKGROUND: The U.S. Centers for Disease Control and Prevention (CDC) has reported increasing rates of alpha-gal syndrome, an allergic response after meat ingestion (AGS). AGS has been associated with prior exposure to tick bites or other biologics characterized by a life-threatening immunoglobulin E (IgE)-mediated hypersensitivity to galactose-alpha-1,3-galactose (alpha-gal) an oligosaccharide structurally similar to the group B antigen on red blood cells (RBC) found in most non-primate mammalian meat and products derived from these mammals. In 2023, Transfusion reported 3 group O recipients of group B plasma in the Washington, D.C. metropolitan area with no history of meat allergy who had anaphylactic transfusion reactions compatible with AGS. AIMS: We investigated allergic reactions in 2 additional patients who received ABO minor-incompatible blood products at 2 hospitals in the D.C. area during fall 2023. METHODS: For both patients, a medical chart review was performed and IgE levels to alpha-gal were measured. RESULTS: The first patient, a 64-year-old, O-positive patient status post heart transplant with no known allergies, was admitted with acute COVID-19 induced antibody-mediated transplant rejection and placed on extracorporeal membrane oxygenation (ECMO). While undergoing plasma exchange (PLEX) (50% albumin/50% fresh frozen plasma (FFP)), the patient tolerated 2 units of group O FFP and 1 unit of group A FFP before becoming hemodynamically unstable during transfusion of 1 unit of B-positive FFP. PLEX was stopped. The patient later died of sepsis from underlying causes. The second patient, a 57-year-old O-positive man with a history of melanoma and neuro fibromatosis type 1, was undergoing an abdominal resection including transfusion of 3 units of O-positive RBC when he suffered hypotension and ventricular tachycardia requiring intraoperative code after receiving 2 units of group B FFP. Hiveswere noted after resuscitation. The patient had a history of tick bites but no known allergies. He is alive 5 months after the possible allergic event. Both patients had full transfusion reaction evaluations and immunology testing results above the positive cutoff for anti-alpha-gal IgE. DISCUSSION AND CONCLUSION: Two patients with O-positive blood and no known allergies experience danaphyl axis after transfusion with group B FFP. The symptoms cannot definitively be imputed to an allergic transfusion reaction, but the presence of IgE against alpha-gal supports an association. Medicating patients with antihistamines and IV steroids pre-transfusion may prevent allergic reactions. Restricting group B plasma-containing products (plasma, platelets, cryoprecipitate) for patients who experience AGS-like symptoms may be considered.

[Feasibility Analysis of Establishing Combat Readiness Blood Bank Based on Low Titer Group O Whole Blood and Group A Plasma].

OBJECTIVE: To explore the feasibility of establishing combat readiness blood bank with low titer group O whole blood and group A plasma. METHODS: The Galileo automatic blood analyzer was used to detect the titers of IgM anti-A and anti-B antibodies in the samples of group O blood donors and IgM anti-B titer in the samples of group A blood donors. Group O blood donors with antibody titers below 128 were selected and included in the mobile blood bank for combat readiness, group A plasma with anti-B titer lower than 128 and group O whole blood with antibody titers below 128 were included in the combat readiness entity blood bank. RESULTS: A total of 1 452 group O blood donors were selected, and the anti-A/B antibody titers were detected. Both antibody titers were distributed below 512, and both peak values of sample distribution were at titer 4. The proportion of samples with titers>128 for both antibodies was relatively low. There was a significant positive correlation between the titers of the two antibodies (r =0.383), and the proportion of samples with IgM anti-A titer higher than IgM anti-B titer was relatively high. 1 335(91.94%) group O blood donors with IgM anti-A and anti-B antibody titers <128 could be included in the mobile blood bank. The anti-B titer of group A blood was detected in 512 cases and the results showed that as the antibody titer increased, the proportion of blood donors gradually decreased. 99.8% of group A blood donors had anti-B antibody titer less than 128, and only one case did not meet the inclusion criteria. CONCLUSION: The proportion of group O blood donors whose whole blood meet the low antibody titer standard is high, and almost all plasma of group A blood donors meet the low titer standard, which improves the blood supply rate in emergencies.

Experience with Tandem Pre-Dilution Online Hemodiafiltration and Centrifugal Plasma Exchange in Pretransplant Desensitization for Abo-Incompatible Kidney Transplantation: A Case Report.

BACKGROUND: In the use of therapeutic plasma exchange (TPE) as antibody removal therapy for ABO-incompatible (ABOi) kidney transplantation, it is technically possible to perform online hemodiafiltration (OHDF) and TPE simultaneously for patients who are receiving OHDF. In this study, we report tandem therapy of pre-dilution OHDF and centrifugal plasma exchange (cTPE), instead of membrane plasma exchange, which is the mainstay of TPE in Japan. METHODS: A total of 14 sessions of tandem cTPE and pre-dilution OHDF were performed as preoperative antibody removal therapy for 6 ABOi kidney transplant recipients. cTPE intra-circuit pressure, decreased antibody titer, and adverse events were evaluated. The study was carried out following the ethical standards of the Declaration of Helsinki and Istanbul. Donors were not prisoners or individuals who were coerced or paid. RESULTS: The tandem therapy was completed safely in 12 of the 14 sessions, with no problems such as pressure upper and lower limit alarms or circuit coagulation. In 2 sessions, the tandem therapy had to be interrupted due to coagulation on the dialysis circuit side. Antibody titers were reduced by a median of 3-fold for both IgG and IgM. There was no acute antibody-associated rejection. CONCLUSIONS: In preoperative apheresis therapy for ABOi kidney transplantation, tandem therapy of pre-dilution OHDF and cTPE may be a useful treatment option that can be performed safely and results in sufficient reduction of antibody levels.

ABO non-identical platelet transfusions, immune platelet refractoriness and platelet support.

ABO-non-identical (ABO-ni) platelets may be another risk factor for immune platelet transfusion refractoriness (i-PTR). We examined the effect of such platelets on i-PTR and subsequent platelet support through retrospective analysis of 17 322 New Zealand patients receiving ≥1 platelets. Immune PTR was defined as PTR with anti-HLA-I/HPA positivity. Univariate and multivariate analyses determined the independent risk factors for i-PTR. One hundred and eighty-eight patients (1.1%) had i-PTR and received more ABO-ni platelets than non-refractory patients (53.2% vs. 29.5%; p < 0.001). More non-O than group O patients had received ABO-ni platelets before i-PTR diagnosis (67.6% vs. 32.5%; p < 0.001). Female sex (p < 0.001), age ≤ 60 years (p = 0.004), haematology patients (p < 0.001) and ≥2 ABO-ni platelets (p < 0.001) were the independent risk factors for i-PTR. More i-PTR patients with anti-HLA-I were non-O compared to group O (90.1% vs. 75.3%; p = 0.007). More with anti-HLA-I + anti-HPA were group O than non-O (24.7% vs. 9.0%; p = 0.003). ABO-ni platelet-exposed i-PTR patients required matched platelets for longer than those receiving only ABO-i platelets (96.5 vs. 59.0 days; p = 0.02). ABO-ni platelets may be a risk factor for i-PTR with dose effect. ABO-i platelets should be considered whenever possible for at-risk patients.

Haemolytic transfusion reactions caused by non-ABO red cell antibodies reported to the Norwegian Haemovigilance System 2004-2020.

BACKGROUND AND OBJECTIVES: The aim of this study was to analyse the reports received in the Norwegian Haemovigilance System from 2004 to 2020 on acute and delayed haemolytic transfusion reactions caused by non-ABO red cell antibodies. MATERIALS AND METHODS: Antibody specificity, clinical symptoms and outcomes were included when available. RESULTS: After transfusion of 3.7 million red cell concentrates, reports on 78 cases of haemolytic transfusion reactions caused by non-ABO red cell antibodies were received, corresponding to an incidence of 1 in 47,000 transfused red cell concentrates. There were 30 acute and 48 delayed haemolytic transfusion reactions. A total of 113 red cell antibodies were found: 82 alloantibodies, 6 autoantibodies and 25 cases where the antibody specificity could not be determined. Two fatalities occurred: one caused by anti-Wra and one caused by an unidentified red cell antibody. The most frequently reported antibody specificities were those in the Rh and Kidd blood group systems, representing 24% and 14%, respectively, of all the antibodies identified. In six cases, errors occurred, leading to the issuing of blood units without the required phenotype match. CONCLUSIONS: Despite the possible underreporting, the low number of serious haemolytic transfusion reactions reflects an adequate pre-transfusion practice by the Norwegian blood banks.

Effect of Induction Therapy Dose on Survival in Abo-Incompatible Kidney Transplantation: A Network Meta-Analysis Using Recent Data.

BACKGROUND: Rituximab is an essential induction immunosuppressant for ABO-incompatible kidney transplantation (KT) (ABOi-KT). However, studies on the optimal dose of rituximab are insufficient, and there are dosage differences between transplant centers and countries. Therefore, we conducted a study to determine the survival outcomes of patients receiving the most effective and safe dose of rituximab during ABOi-KT. METHODS: Studies on rituximab dose were divided into four groups: ABO compatible, 1) placebo, 2) rituximab 200 mg, 3) rituximab 200-500 mg, and 4) rituximab 500 mg. We searched the CENTRAL, MEDLINE, EMBASE, and Science Citation Index Expanded databases from 1970 to February 2022.9 . The inclusion criteria were adult patients (>18 years old). Reviews, observational studies, and clinical trials that did not clearly define outcomes or that did not have graft failure as an outcome were excluded. We performed direct and indirect network meta-analyses using Bayesian models and ranked different rituximab doses using a generation mixed treatment comparison (GeMTC) and Stata version 13. The NMA approach was evaluated using the GRADE framework, which specifies four levels of certainty for a given result: high, moderate, low, and very low. The outcomes included patient survival, graft failure, and bacterial and viral infections. RESULTS: Twenty-five trials, including 5,378 subjects, were divided into the following four groups: 1) placebo, 2) rituximab 200 mg, 3) rituximab 200-500 mg, and 4) rituximab 500 mg. We focused on survival outcomes according to the dose of rituximab when patients received induction therapy for ABOi-KT. The mortality rate was significantly lower in the ABO-compatible and rituximab 200 mg groups (odds ratio [OR] 0.27, 95% CrI: 0.071-0.91 and OR 0.14, 95% CrI 0.036-0.47), compared with that in the placebo group. CONCLUSIONS: We found that low-dose rituximab in ABO-i KT was effective compared to the high-dose and placebo in maintaining the survival rate. However, large-scale and long-term data are necessary for further validation of our findings. Additionally, the use of smaller doses of rituximab will require further discussion.

High-Dose Intravenous Immunoglobulin to Treat Anti-Thymocyte Globulin Induction-Related BK Virus and Cytomegalovirus Infection in Patients with ABO-Incompatible Kidney Transplantation.

BACKGROUND: ABO-incompatible (ABOi) transplantation is a novel method transplantation method that carries a heightened risk of infection caused by the use of high immunosuppressant doses. This elevated risk is particularly concerning for viral infections, such as cytomegalovirus (CMV) and the BK virus (BKV) increases. Herein, we present a case where high-dose intravenous immunoglobulin (IVIG) was effective in treating viral infections after transplantation. METHODS: A 41-year-old man underwent an ABOi transplantation. The initial isoagglutinin titer was 1:32. The patient received 200 mg of rituximab, and 3 rounds of plasmapheresis were performed. Subsequently, renal function remained normal; however, 7 months later, the renal function declined, and BK nephropathy and CMV infection were diagnosed through biopsy and serologic tests. The FK level was reduced, and mycophenolate mofetil was discontinued. Although ciprofloxacin and leflunomide were administered, their effects were minimal. Therefore, high-dose IVIG (1 g/kg) was administered 5 times over 5 weeks, which led to a reduction in BK viral load and CMV infectivity in the serum. CONCLUSIONS: High-dose IVIG may serve as a promising alternative treatment to mitigate early transplant rejection and BKV and CMV infections.

Low titer group O whole blood and risk of RhD alloimmunization: Rationale for use in Finland.

BACKGROUND: Prehospital low-titer group O whole blood (LTOWB) used for patients with life-threatening hemorrhage is often RhD positive. The most important complication following RhD alloimmunization is hemolytic disease of the fetus and newborn (HDFN). Preceding clinical use of RhD positive LTOWB, we estimated the risk of HDFN due to LTOWB prehospital transfusion in the Finnish population. STUDY DESIGN AND METHODS: We collected data on prehospital transfusions in Tampere and Helsinki University Hospital areas. Using the mean of reported alloimmunization rates in trauma studies (24%) and a higher reported rate representing trauma patients of 13-50 years old (42.7%), we estimated the risk of HDFN and extrapolated it to the whole of Finland. RESULTS: We estimated that in Finland, with the current prehospital transfusion rate we would see 1-3 cases of severe HDFN due to prehospital LTOWB transfusions every 10 years, and fetal death due to HDFN caused by LTOWB transfusion less than once in 100 years. DISCUSSION: The estimated risk of serious HDFN due to prehospital LTOWB transfusion in the Finnish population is similar to previous estimates. As Finland routinely screens expectant mothers for red blood cell antibodies and as the contemporary treatment of HDFN is very effective, we support the prehospital use of RhD positive LTOWB in all patient groups.

Why Blood Type Seems to Be Linked With COVID-19 Risk.

This Medical News article discusses new research that may explain why type A blood has been linked with a higher risk of SARS-CoV-2 infection.

ABO blood types and SARS-CoV-2 infection assessed using seroprevalence data in a large population-based sample: the SAPRIS-SERO multi-cohort study.

ABO blood type has been reported as a potential factor influencing SARS-CoV-2 infection, but so far mostly in studies that involved small samples, selected population and/or used PCR test results. In contrast our study aimed to assess the association between ABO blood types and SARS-CoV-2 infection using seroprevalence data (independent of whether or not individuals had symptoms or sought for testing) in a large population-based sample. Our study included 67,340 French participants to the SAPRIS-SERO multi-cohort project. Anti-SARS-CoV-2 antibodies were detected using ELISA (targeting the proteins spike (S) and nucleocapsid (NP)) and seroneutralisation (SN) tests on dried blood spots collected in May-November 2020. Non-O individuals (and especially types A and AB) were more likely to bear anti SARS-CoV-2 antibodies (ELISA-S, 2964 positive cases: ORnon-Ovs.O = 1.09[1.01-1.17], ORAvs.O = 1.08[1.00-1.17]; ELISA-S/ELISA-NP/SN, 678 triple positive cases: ORnon-Ovs.O = 1.19 [1.02-1.39], ORAvs.O = 1.19[1.01-1.41], ORABvs.O = 1.43[1.01-2.03]). Hence, our results provided additional insights into the dynamic of SARS-CoV-2 infection, highlighting a higher susceptibility of infection for individuals of blood types A and AB and a lesser risk for blood type O.

Evaluating the Potential for ABO-incompatible Islet Transplantation: Expression of ABH Antigens on Human Pancreata, Isolated Islets, and Embryonic Stem Cell-derived Islets.

BACKGROUND: ABO-incompatible transplantation has improved accessibility of kidney, heart, and liver transplantation. Pancreatic islet transplantation continues to be ABO-matched, yet ABH antigen expression within isolated human islets or novel human embryonic stem cell (hESC)-derived islets remain uncharacterized. METHODS: We evaluated ABH glycans within human pancreata, isolated islets, hESC-derived pancreatic progenitors, and the ensuing in vivo mature islets following kidney subcapsular transplantation in rats. Analyses include fluorescence immunohistochemistry and single-cell analysis using flow cytometry. RESULTS: Within the pancreas, endocrine and ductal cells do not express ABH antigens. Conversely, pancreatic acinar tissues strongly express these antigens. Acinar tissues are present in a substantial portion of cells within islet preparations obtained for clinical transplantation. The hESC-derived pancreatic progenitors and their ensuing in vivo-matured islet-like clusters do not express ABH antigens. CONCLUSIONS: Clinical pancreatic islet transplantation should remain ABO-matched because of contaminant acinar tissue within islet preparations that express ABH glycans. Alternatively, hESC-derived pancreatic progenitors and the resulting in vivo-matured hESC-derived islets do not express ABH antigens. These findings introduce the potential for ABO-incompatible cell replacement treatment and offer evidence to support scalability of hESC-derived cell therapies in type 1 diabetes.

The human gut symbiont Ruminococcus gnavus shows specificity to blood group A antigen during mucin glycan foraging: Implication for niche colonisation in the gastrointestinal tract.

The human gut symbiont Ruminococcus gnavus displays strain-specific repertoires of glycoside hydrolases (GHs) contributing to its spatial location in the gut. Sequence similarity network analysis identified strain-specific differences in blood-group endo-ß-1,4-galactosidase belonging to the GH98 family. We determined the substrate and linkage specificities of GH98 from R. gnavus ATCC 29149, RgGH98, against a range of defined oligosaccharides and glycoconjugates including mucin. We showed by HPAEC-PAD and LC-FD-MS/MS that RgGH98 is specific for blood group A tetrasaccharide type II (BgA II). Isothermal titration calorimetry (ITC) and saturation transfer difference (STD) NMR confirmed RgGH98 affinity for blood group A over blood group B and H antigens. The molecular basis of RgGH98 strict specificity was further investigated using a combination of glycan microarrays, site-directed mutagenesis, and X-ray crystallography. The crystal structures of RgGH98 in complex with BgA trisaccharide (BgAtri) and of RgGH98 E411A with BgA II revealed a dedicated hydrogen network of residues, which were shown by site-directed mutagenesis to be critical to the recognition of the BgA epitope. We demonstrated experimentally that RgGH98 is part of an operon of 10 genes that is overexpresssed in vitro when R. gnavus ATCC 29149 is grown on mucin as sole carbon source as shown by RNAseq analysis and RT-qPCR confirmed RgGH98 expression on BgA II growth. Using MALDI-ToF MS, we showed that RgGH98 releases BgAtri from mucin and that pretreatment of mucin with RgGH98 confered R. gnavus E1 the ability to grow, by enabling the E1 strain to metabolise BgAtri and access the underlying mucin glycan chain. These data further support that the GH repertoire of R. gnavus strains enable them to colonise different nutritional niches in the human gut and has potential applications in diagnostic and therapeutics against infection.

Establishment of a Hyperacute Rejection Model of ABO-Incompatible Renal Transplantation in Nonhuman Primates.

The establishment of a hyperacute rejection (HAR) model of ABO-incompatible kidney transplantation (ABOi-KTx) in nonhuman primates is of great significance for the study of the relevant clinical pathophysiological processes and related interventions in ABOi-KTx. In this study, blood group B cynomolgus monkeys were presensitized with synthetic blood group A-antigen conjugated to keyhole limpet hemocyanin (A-KLH) to boost circulating anti-A antibody levels. The serum anti-A antibody levels were measured by flow cytometry using type A human reagent red blood cells (RBCs) or monkey primary renal tubular epithelial cells (RTECs) as target cells. ABOi-KTx was performed in type B monkeys using type A monkeys as donors. After 14 days of A-KLH sensitization, 12 of 16 (75%) type B monkeys had significantly elevated anti-A antibody levels. We found that in order to avoid irregular results in the detection of blood group antibodies by flow cytometry, it was more effective to use RTECs rather than RBCs as target cells. In the absence of presensitization, ABOi-KTx in three monkeys with relatively high levels of natural anti-A antibodies did not produce HAR. However, when four Type B monkeys with significantly increased anti-A antibodies after presensitization were randomly selected as recipients for ABOi-KTx, the allografts in all four monkeys developed HAR with typical pathologic characteristics. Thus, we have successfully established a monkey model of HAR in ABOi-KTx via blood group antigen presensitization, which will be helpful for the further study of rejection, accommodation, and clinical intervention in ABOi-KTx.

Red blood cell blood group A antigen level affects the ability of heparin and PfEMP1 antibodies to disrupt Plasmodium falciparum rosettes.

BACKGROUND: The histo-blood group ABO system has been associated with adverse outcomes in COVID-19, thromboembolic diseases and Plasmodium falciparum malaria. An integral part of the severe malaria pathogenesis is rosetting, the adherence of parasite infected red blood cells (RBCs) to uninfected RBCs. Rosetting is influenced by the host's ABO blood group (Bg) and rosettes formed in BgA have previously been shown to be more resilient to disruption by heparin and shield the parasite derived surface antigens from antibodies. However, data on rosetting in weak BgA subgroups is scarce and based on investigations of relatively few donors. METHODS: An improved high-throughput flow cytometric assay was employed to investigate rosetting characteristics in an extensive panel of RBC donor samples of all four major ABO Bgs, as well as low BgA expressing samples. RESULTS: All non-O Bgs shield the parasite surface antigens from strain-specific antibodies towards P. falciparum erythrocyte membrane protein 1 (PfEMP1). A positive correlation between A-antigen levels on RBCs and rosette tightness was observed, protecting the rosettes from heparin- and antibody-mediated disruption. CONCLUSIONS: These results provide new insights into how the ABO Bg system affects the disease outcome and cautions against interpreting the results from the heterogeneous BgA phenotype as a single group in epidemiological and experimental studies.

Passenger lymphocyte syndrome after ABO-incompatible allogeneic hematopoietic stem cell transplantation; dynamics of ABO allo-antibody and blood type conversion.

Passenger lymphocyte syndrome (PLS) is a specific subtype of graft versus host disease (GVHD) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) characterized by an immune-mediated hemolysis caused by donor-derived B cells. However, precise nature of PLS has not been well characterized due to its rarity. We herein report two cases of PLS following ABO-incompatible HSCT whose clinical course and dynamics of anti-ABO allo-antibody and blood type conversion were closely examined. Both cases demonstrated acute hemolysis upon engraftment, and the presence of high titer allo-antibody against recipients' red blood cells (RBCs) helped us to reach the diagnosis of PLS. Hemolysis in both cases showed spontaneous improvement with prednisolone and supportive therapy including transfusion and fluid support. In one case with blood type O, the patient recursively developed PLS in the second and the third HSCT from ABO-mismatch donors, leading to a hypothesis that original blood type O may serve as a background for acute elevation of serum anti-ABO antibody and therefore a risk for developing PLS in multiple ABO-incompatible HSCTs. When hemolysis is noted following ABO-incompatible HSCTs, PLS should be considered and measurement of anti-ABO antibodies is warranted.

ABO antibody titer performance characteristics and correlates between two automated platforms.

BACKGROUND: AABB standards require a policy for assessing transfusing ABO-incompatible plasma. After a fatal hemolytic event with incompatible plasma, our institution instituted platelet donor population titer method for ABO antibodies on the PK7300, with high-titer being defined as having isohemagglutinin titers greater than 256. We recently switched titering platforms to the Neo Iris and we seek to determine the equivalent isohemagglutinin high-titer cutoff on the Neo Iris as compared to the PK7300. METHODS: We measured the titers on 299 apheresis platelet donors and compared its performance characteristics at various cutoffs to the PK7300 reference standard. Discrepant results were manually diluted and retested on the Neo Galileo. Furthermore, since the Neo Iris is able to determine isotype and antigen specific titers, we also characterized these features in our donor population. RESULTS: IgM titer of 128 on the Neo Iris has better accuracy compared to the titer of 64 (94 % vs 93.6 %). Eleven of sixteen discordant results were in agreement with Neo Iris. Blood group O had the highest IgG antibody titers for both anti-A and anti-B (p = 8.4E-17 and 4.3E-09, respectively). Additionally, group O donors exhibited lower anti-A2 than anti-A1 IgG titers. DISCUSSION: The Neo Iris titer cut-off of 128 had the best overall accuracy and correlation with a 256 cut-off on our laboratory developed test on the PK7300 platform. Additionally, we found that group O donors had the highest titer antibodies, with typically higher IgG titers than IgM, and generally multiple dilution levels greater than other blood types.

No increase in anti-A isohemagglutinin titer after SARS-CoV-2 infection: A retrospective cohort analysis of group O apheresis platelet donors.

The risk of a hemolytic reaction during the transfusion of ABO non-identical PC is determined by the presence of natural anti-A IgM antibodies, the titer of which may increase after infections. The aim of the study was to evaluate the titer of anti-A isohemagglutinins in platelet concentrate (PC) obtained by apheresis from group O donors who experienced SARS-CoV-2 infection, and to compare the titer before and after infection. A retrospective single-center analysis of 21 PC donors with a previous COVID-19 history was performed. The results showed neither a statistically important increase in the anti-A IgM antibody titers nor a significant correlation between the anti-A IgM antibody level and anti-SARS-CoV-2S1 antibody titer in the donors with an asymptomatic or mild COVID-19. Further population-based studies on anti-A titers are necessary for a comprehensive assessment of this phenomenon.