The effect of extended c, E and K matching in females under 45 years of age on the incidence of transfusion-induced red blood cell alloimmunisation.

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%.

Optimizing transfusion management of multiple myeloma patients receiving daratumumab-based regimens.

BACKGROUND: Daratumumab, a human anti-CD38 monoclonal antibody used to treat multiple myeloma, interferes with pretransfusion testing and can mask alloantibodies. Incidence of alloimmunization in patients on daratumumab has not been well characterized, and optimal transfusion guidelines regarding prophylactic antigen matching, accounting for both patient safety and efficiency, have not been well established for these patients. METHODS: Records of patients who received daratumumab between January 1, 2014 and July 2, 2019 were reviewed. Daratumumab interference with pretransfusion testing was managed by testing with reagent red blood cells (RBCs) treated with 0.2 M dithiothreitol. When daratumumab was present during antibody testing, patients were transfused with RBC units prophylactically matched for D, C, c, E, e, and K antigens per hospital policy. RESULTS: Out of 90 patients identified, 52 received a total of 638 RBC transfusions (average of 12.3 units per patient, SD 17.2, range 1-105, median 5 among those transfused). Alloantibodies existing before daratumumab initiation were identified in seven patients. No new alloantibodies were detected in any patients after starting daratumumab treatment. CONCLUSIONS: The incidence of alloimmunization in patients receiving daratumumab is low. Whether this is due to the effect of daratumumab, underlying pathophysiology, or other factors, is unknown. Because these patients require a large number of RBC transfusions overall and have little observed alloimmunization, phenotype matching (beyond RhD) may be unnecessary. Since the use of dithiothreitol cannot rule out the presence of anti-K, we recommend transfusion of ABO-compatible units, prophylactically matched for the D and K antigens only.

The lysophospholipid-binding molecule CD1D is not required for the alloimmunization response to fresh or stored RBCs in mice despite RBC storage driving alterations in lysophospholipids.

BACKGROUND: Despite the significant adverse clinical consequences of RBC alloimmunization, our understanding of the signals that induce immune responses to transfused RBCs remains incomplete. Though RBC storage has been shown to enhance alloimmunization in the hen egg lysozyme, ovalbumin, and human Duffy (HOD) RBC alloantigen mouse model, the molecular signals leading to immune activation in this system remain unclear. Given that the nonclassical major histocompatibility complex (MHC) Class I molecule CD1D can bind to multiple different lysophospholipids and direct immune activation, we hypothesized that storage of RBCs increases lysophospholipids known to bind CD1D, and further that recipient CD1D recognition of these altered lipids mediates storage-induced alloimmunization responses. STUDY DESIGN AND METHODS: We used a mass spectrometry-based approach to analyze the changes in lysophospholipids that are induced during storage of mouse RBCs. CD1D knockout (CD1D-KO) and wild-type (WT) control mice were transfused with stored HOD RBCs to measure the impact of CD1D deficiency on RBC alloimmunization. RESULTS: RBC storage results in alterations in multiple lysophospholipid species known to bind to CD1D and activate the immune system. Prior to transfusion, CD1D-deficient mice had lower baseline levels of polyclonal immunoglobulin (IgG) relative to WT mice. In response to stored RBC transfusion, CD1D-deficient mice generated similar levels of anti-HOD IgM and anti-HOD IgG. CONCLUSION: Although storage of RBCs leads to alteration of several lysophospholipids known to be capable of binding CD1D, storage-induced RBC alloimmunization responses are not impacted by recipient CD1D deficiency.

HLA class II eplet mismatch load improves prediction of dnDSA development after living donor kidney transplantation.

HLA donor-specific antibodies developed de novo after transplant remain a major cause of chronic allograft dysfunction. Our study main purpose was to determine whether HLA MM, assessed traditionally and by HLA total and AbVer eplet mismatch load (EptMM and EpvMM) assessed with HLAMatchMaker, had impact on dnDSA development after living donor kidney transplantation (LDKT). We retrospectively analysed a cohort of 96 LDKT between 2008 and 2017 performed in Hospital Santo António. Seven patients developed dnDSA-II and EpvMM and EptMM were greater in dnDSA-II group compared to the no dnDSA-II (18.0 ± 8.7 versus 9.9 ± 7.9, p = .041 and 41.3 ± 18.9 versus 23.1 ± 16.7, p = .018), which is not observed for AgMM (2.29 versus 1.56; p = .09). In a multivariate analysis, we found that preformed DSA (HR = 7.983; p = .023), living unrelated donors (HR = 8.052; p = .024) and retransplantation (HR = 14.393; p = .009) were predictors for dnDSA-II (AUC = 0.801; 0.622-0.981). HLA-II EpvMM (HR = 1.105; p = .028; AUC = 0.856) showed to be a superior predictor of dnDSA-II, when compared to AgMM (HR = 1.740; p = .113; AUC = 0.783), when adjusted for these clinical variables. Graft survival was significantly lower within dnDSA-II patient group (36% versus 88%, p < .001). HLA molecular mismatch analysis is extremely important to minimize risk for HLA-II dnDSA development improving outcome and increasing chance of retransplant lowering allosensitization.

Impact of HLA compatibility in recipients of kidneys from expanded criteria donors: A Collaborative Transplant Study Report.

Due to a widespread organ shortage, the use of expanded criteria donors (ECDs) in kidney transplantation has increased persistently, reaching approximately 40% in recent years. Whether human leucocyte antigen (HLA) matching between donor and recipient should be part of allocation algorithms in transplantation of ECD kidneys, and especially of ECD kidneys from ≥70-year-old donors, is still in question. To this end, 135,529 kidney transplantations performed between 2000 and 2017 and reported to the Collaborative Transplant Study were analysed and the impact of HLA-A+B+DR mismatches on death-censored graft and patient survival as well as on rejection episodes was investigated. Results were stratified according to donor status (standard criteria donor (SCD) versus ECD) and age of ECD. HLA incompatibility increased the five-year death-censored graft failure risk similarly strong in recipients of ECD and SCD transplants (hazard ratio (HR) per HLA mismatch 1.078 and 1.075, respectively; p < .001 for both). Its impact on rejection treatments during the first post-transplant year was also significant but slightly weaker for recipients of ECD transplants (risk ratio (RR) per HLA mismatch 1.10 for ECD transplants and 1.13 for SCD transplants; p < .001 for both). Mortality increased gradually from zero to six HLA mismatches in recipients of SCD transplants, whereas for ECD transplants a significant increase was notable only from zero to more than zero mismatches. A significant but slightly less pronounced impact of HLA incompatibility on graft failure was observed in transplants from ≥70- compared with <70-year-old ECDs (HR per mismatch 1.047 and 1.093; p = .009 and < 0.001, respectively). The influence of HLA mismatches on rejection treatments was the same for both ECD age groups (RR = 1.10, p < .001 and p = .004, respectively). Our data indicate that HLA matching should be part of allocation algorithms not only in transplantation of kidneys from SCDs but also from ECDs.

Simultaneous fluorescence imaging of distinct nerve and blood vessel patterns in dual Thy1-YFP and Flt1-DsRed transgenic mice.

Blood vessels and nerve tissues are critical to the development and functionality of many vital organs. However, little is currently known about their interdependency during development and after injury. In this study, dual fluorescence transgenic reporter mice were utilized to observe blood vessels and nervous tissues in organs postnatally. Thy1-YFP and Flt1-DsRed (TYFD) mice were interbred to achieve dual fluorescence in the offspring, with Thy1-YFP yellow fluorescence expressed primarily in nerves, and Flt1-DsRed fluorescence expressed selectively in blood vessels. Using this dual fluorescent mouse strain, we were able to visualize the networks of nervous and vascular tissue simultaneously in various organ systems both in the physiological state and after injury. Using ex vivo high-resolution imaging in this dual fluorescent strain, we characterized the organizational patterns of both nervous and vascular systems in a diverse set of organs and tissues. In the cornea, we also observed the dynamic patterns of nerve and blood vessel networks following epithelial debridement injury. These findings highlight the versatility of this dual fluorescent strain for characterizing the relationship between nerve and blood vessel growth and organization.

B cells as antigen-presenting cells in transplantation rejection and tolerance.

Transplantation of fully allogeneic organs into immunocompetent recipients invariably elicits T cell and B cell responses that lead to the production of donor-specific antibodies (DSA). When immunosuppression is inadequate donor-specific T cell and B cell responses escape, leading to T cell-mediated rejection (TCMR), antibody mediated (ABMR) rejection, or mixed rejection (MR) exhibiting features of both TCMR and ABMR. Current literature suggests that ABMR is a major cause of late graft loss, and that new therapies to curtail the donor-specific humoral response are necessary. The majority of research into B cell responses elicited by allogeneic allografts in both preclinical models and clinical studies, has focused on the function of B cells as antibody-secreting cells and the pathogenic effects of DSA as mediators of ABMR. However, it has long been recognized that the DSA response to allografts is T cell-dependent, and that B cells engage in cognate interactions with T cells that provide "help" and promote B cell differentiation into antibody-secreting cells (ASCs). This review focusses the function of B cells as antigen-presenting cells (APCs) to T cells in lymphoid organs, how they may be critical APCs to T cell in the allograft, and the functional consequences of these interactions.

Predicting Humoral Alloimmunity from Differences in Donor and Recipient HLA Surface Electrostatic Potential.

In transplantation, development of humoral alloimmunity against donor HLA is a major cause of organ transplant failure, but our ability to assess the immunological risk associated with a potential donor-recipient HLA combination is limited. We hypothesized that the capacity of donor HLA to induce a specific alloantibody response depends on their structural and physicochemical dissimilarity compared with recipient HLA. To test this hypothesis, we first developed a novel computational scoring system that enables quantitative assessment of surface electrostatic potential differences between donor and recipient HLA molecules at the tertiary structure level [three-dimensional electrostatic mismatch score (EMS-3D)]. We then examined humoral alloimmune responses in healthy females subjected to a standardized injection of donor lymphocytes from their male partner. This analysis showed a strong association between the EMS-3D of donor HLA and donor-specific alloantibody development; this relationship was strongest for HLA-DQ alloantigens. In the clinical transplantation setting, the immunogenic potential of HLA-DRB1 and -DQ mismatches expressed on donor kidneys, as assessed by their EMS-3D, was an independent predictor of development of donor-specific alloantibody after graft failure. Collectively, these findings demonstrate the translational potential of our approach to improve immunological risk assessment and to decrease the burden of humoral alloimmunity in organ transplantation.

Impact of Human Leucocyte Antigen epitope matched platelet transfusions in alloimmunised aplastic anaemia patients.

AIMS/OBJECTIVES: To explore the impact of Human Leucocyte Antigen (HLA)-A and B epitope-matched platelets on the outcome of platelet transfusions in alloimmunised patients with aplastic anaemia (AA). The relevance of HLA-C epitope mismatches was also investigated. BACKGROUND: Patients who become immunologically refractory (IR) to random platelet transfusions can experience an adequate rise in platelet count through the provision of HLA-compatible platelets using an antigen-matching algorithm. This approach has been shown to be effective in patients with a low calculated reaction frequency, but it is not always successful in highly sensitised patients. The use of HLA epitopes-selected platelets has been suggested as an alternative to the antigen matching approach. METHODS: The effect of HLA epitope matching (both Eplets and Triplets) on the outcome of platelet transfusion was analysed in 37 highly immunised AA patients previously transfused with HLA-A and B antigen-matched platelets. Epitope matching was determined using the HLAMatchmaker programme. The outcome of the transfusions was assessed by the platelet count increments (PCIs) obtained 1 and 24 hours post-transfusions. RESULTS: HLA-A and B epitope matching was equivalent to HLA antigen matching in raising platelet counts. There was no significant difference in PCI when HLA-C epitope mismatches were considered. In addition, transfusions with fewer than two antigen mismatches resulted in significantly higher PCIs compared to transfusions with more than two antigen mismatches. CONCLUSIONS: HLA epitope-matched platelet provision may represent a clinically effective transfusion strategy for patients IR to random platelet transfusions. Further prospective studies are required.

Anti-donor MHC Class II Alloantibody Induces Glomerular Injury in Mouse Renal Allografts Subjected to Prolonged Cold Ischemia.

BACKGROUND: The mechanisms underlying the effects of prolonged cold-ischemia storage on kidney allografts are poorly understood. METHODS: To investigate effects of cold ischemia on donor-reactive immune responses and graft pathology, we used a mouse kidney transplantation model that subjected MHC-mismatched BALB/c kidney allografts to cold-ischemia storage for 0.5 or 6 hours before transplant into C57BL/6 mice. RESULTS: At day 14 post-transplant, recipients of allografts subjected to 6 versus 0.5 hours of cold-ischemia storage had increased levels of anti-MHC class II (but not class I) donor-specific antibodies, increased donor-reactive T cells, and a significantly higher proportion of transplant glomeruli infiltrated with macrophages. By day 60 post-transplant, allografts with a 6 hour cold-ischemia time developed extensive glomerular injury compared with moderate pathology in allografts with 0.5 hour of cold-ischemia time. Pathology was associated with increased serum levels of anti-class 2 but not anti-class 1 donor-specific antibodies. Recipient B cell depletion abrogated early macrophage recruitment, suggesting augmented donor-specific antibodies, rather than T cells, increase glomerular pathology after prolonged cold ischemia. Lymphocyte sequestration with sphingosine-1-phosphate receptor 1 antagonist FTY720 specifically inhibited anti-MHC class II antibody production and abrogated macrophage infiltration into glomeruli. Adoptive transfer of sera containing anti-donor MHC class II antibodies or mAbs against donor MHC class II restored early glomerular macrophage infiltration in FTY720-treated recipients. CONCLUSIONS: Post-transplant inflammation augments generation of donor-specific antibodies against MHC class II antigens. Resulting MHC class II-reactive donor-specific antibodies are essential mediators of kidney allograft glomerular injury caused by prolonged cold ischemia.

Pretransplant Desensitization with Costimulation Blockade and Proteasome Inhibitor Reduces DSA and Delays Antibody-Mediated Rejection in Highly Sensitized Nonhuman Primate Kidney Transplant Recipients.

BACKGROUND: Patients with broad HLA sensitization have poor access to donor organs, high mortality while waiting for kidney transplant, and inferior graft survival. Although desensitization strategies permit transplantation via lowering of donor-specific antibodies, the B cell-response axis from germinal center activation to plasma cell differentiation remains intact. METHODS: To investigate targeting the germinal center response and plasma cells as a desensitization strategy, we sensitized maximally MHC-mismatched rhesus pairs with two sequential skin transplants. We administered a proteasome inhibitor (carfilzomib) and costimulation blockade agent (belatacept) to six animals weekly for 1 month; four controls received no treatment. We analyzed blood, lymph node, bone marrow cells, and serum before desensitization, after desensitization, and after kidney transplantation. RESULTS: The group receiving carfilzomib and belatacept exhibited significantly reduced levels of donor-specific antibodies (P=0.05) and bone marrow plasma cells (P=0.02) compared with controls, with a trend toward reduced lymph node T follicular helper cells (P=0.06). Compared with controls, carfilzomib- and belatacept-treated animals had significantly prolonged graft survival (P=0.02), and renal biopsy at 1 month showed significantly reduced antibody-mediated rejection scores (P=0.02). However, four of five animals with long-term graft survival showed gradual rebound of donor-specific antibodies and antibody-mediated rejection. CONCLUSIONS: Desensitization using proteasome inhibition and costimulation blockade reduces bone marrow plasma cells, disorganizes germinal center responses, reduces donor-specific antibody levels, and prolongs allograft survival in highly sensitized nonhuman primates. Most animals experienced antibody-mediated rejection with humoral-response rebound, suggesting desensitization must be maintained after transplantation using ongoing suppression of the B cell response.

Transient hemolysis due to anti-D and anti-A1 produced by engrafted donor's lymphocytes after allogeneic unmanipulated haploidentical hematopoietic stem cell transplantation.

BACKGROUND: Development of de novo alloantibodies against recipient's red blood cell (RBC) antigens by engrafted donor's lymphocytes is a known phenomenon in the setting of allogeneic hematopoietic stem cell transplantation (HSCT). This situation is usually clinically insignificant. We report a case of early clinically relevant hemolytic anemia in a blood group A1 D+ patient, due to a limited production of anti-D and anti-A1 produced by nonpreviously sensitized newly engrafted donor's immune system. CASE REPORT: A 31-year-old Caucasian woman, blood group A1 , D+, with Hodgkin's lymphoma, received an unmanipulated haploidentical allogeneic peripheral blood HSCT after a nonmyeloablative conditioning regimen. Donor blood group was A2 B, D-. The patient had an uneventful course until Day +34, when she developed clinically significant hemolytic anemia with a positive direct antiglobulin test. Anti-D and anti-A1 produced by the donor-engrafted lymphocytes were detected both in serum and in eluate. The hemolysis produced an accelerated group change, turning the patient's ABO group into A2 B 2 weeks after the detection of the alloantibodies. As the residual patient's RBCs progressively disappeared, anti-D and anti-A1 production decreased and were not detected in serum by Day +41. CONCLUSION: This case illustrates that de novo alloantibody production against ABO and D antigens by the newly engrafted donor's lymphocytes can occasionally cause clinically significant anemia. To our knowledge, this is the first case reported of clinically significant hemolytic anemia due to a transient anti-D anti-A1 alloimmunization after T-cell-repleted haploidentical HSCT.

B cells require Type 1 interferon to produce alloantibodies to transfused KEL-expressing red blood cells in mice.

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/ß) regulate antiviral immunity and autoimmune pathology, the hypothesis that IFN-α/ß 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/ß 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/ß 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/ß-associated conditions may have an elevated risk of alloimmunization and benefit from personalized transfusion protocols.

The Impact of High-resolution HLA-A, HLA-B, HLA-C, and HLA-DRB1 on Transplant-related Outcomes in Single-unit Umbilical Cord Blood Transplantation in Pediatric Patients.

Current practice for selecting donor units for umbilical cord blood transplant (UCBT) involves matching at HLA-A and HLA-B by low-resolution typing and the HLA-DRB1 allele by high-resolution (HR) typing. We retrospectively studied the impact of HR allele matching at HLA-A, HLA-B, HLA-C, and HLA-DRB1 on transplant-related outcomes in 60 single-unit UCBTs in pediatric patients with malignant and nonmalignant conditions. Five-year overall survival of our cohort was 71% (95% confidence interval, 58-81); 27% experienced primary graft failure. Applying HR typing, donor-recipient mismatch variability increased ranging from 1/8 to 8/8, however, no impact on primary graft failure, graft-versus-host disease or posttransplant infection was observed. UCBTs with ≥6/8 HR matches did have a better overall survival (P=0.04) and decreased transplant-related mortality (P=0.02) compared with <6/8 HR matches. Using standard HLA typing, we showed an increased incidence of acute graft-versus-host disease (grade II to IV) and decreased transplant-related mortality in comparing the matched (6/6) versus ≤5/6 group (P=0.05 and 0.05, respectively). These data support the use of current guidelines for umbilical cord blood selection and encourage utilization of HR typing to select umbilical cord blood units matched at ≥6/8 especially when appropriate ≥5/6 units are available.

Red cell alloimmunisation in patients with different types of infections.

Red cell alloantigen exposure can cause alloantibody-associated morbidity. Murine models have suggested that inflammation modulates red cell alloimmunisation. This study quantifies alloimmunisation risks during infectious episodes in humans. We performed a multicentre case-control study within a source population of patients receiving their first and subsequent red cell transfusions during an 8-year follow-up period. Patients developing a first transfusion-induced red cell alloantibody (N = 505) were each compared with two similarly exposed, but non-alloimmunised controls (N = 1010) during a 5-week 'alloimmunisation risk period' using multivariate logistic regression analysis. Transfusions during 'severe' bacterial (tissue-invasive) infections were associated with increased risks of alloantibody development [adjusted relative risk (RR) 1·34, 95% confidence interval (95% CI) 0·97-1·85], especially when these infections were accompanied with long-standing fever (RR 3·06, 95% CI 1·57-5·96). Disseminated viral disorders demonstrated a trend towards increased risks (RR 2·41, 95% CI 0·89-6·53), in apparent contrast to a possible protection associated with Gram-negative bacteraemia (RR 0·58, 95% CI 0·13-1·14). 'Simple' bacterial infections, Gram-positive bacteraemia, fungal infections, maximum C-reactive protein values and leucocytosis were not associated with red cell alloimmunisation. These findings are consistent with murine models. Confirmatory research is needed before patients likely to develop alloantibodies may be identified based on their infectious conditions at time of transfusion.

The long-term and extensive efficacy of low dose thalidomide in a case of an untransfusable patient with Non-Transfusion-Dependent Thalassemia.

Patients with Non-Transfusion-Dependent Thalassemia may require regular transfusion therapy. However, these patients are at risk of developing irregular antibodies, making them untransfusable. Second line treatment usually includes hydroxyurea, which however is not effective in all patients. Other treatment options include thalidomide, which has been reported to be safe and effective in selected patients. We report the case of a patient who experienced improvement of hemoglobin levels and of a part of NTDT related complications, following 36months of continuous therapy with low doses of thalidomide.

Regulatory B cells (CD19(+)CD38(hi)CD24(hi)) in alloimmunized and non-alloimmunized children with ß-thalassemia major.

BACKGROUND: ß-Thalassemia major (BTM) is considered the most common hemoglobinopathy in Egypt and is one of the major health problems in our locality. MATERIALS & METHODS: We investigated the frequency of B-regulatory cells (CD19(+)CD38(hi)CD24(hi)); (Bregs) among polytransfused alloimmunized and non-alloimmunized children with BTM. The study included 110 polytransfused pediatric patients with ß-thalassemia major. Clinical and transfusion records of all studied patients were reviewed. Indirect antiglobulin test was performed to detect the presence of alloantibodies. We used flow cytometry for detection of CD19(+)CD38(hi)CD24(hi) regulatory B cells. RESULTS: Alloimmunization was detected in 35.5% of thalassemic patients (39/110). The analysis of our data showed a significantly higher frequency of Bregs (CD19(+)CD38(hi)CD24(hi)) in the peripheral blood of both alloimmunized and non-alloimmunized patients as compared to healthy controls. CONCLUSIONS: Our data showed that the frequencies of CD19(+)CD24(hi)CD38(hi) Bregs cells were significantly increased in children with BTM. Our data suggested that Bregs cells could play a role in the clinical course of BTM. The relationship of Bregs to immune disorders in BTM children remains to be determined. Further longitudinal study with a larger sample size is warranted to explore the mechanisms of Breg cells in the disease process in BTM patients.

Detection rate of blood group alloimmunization based on real-world testing practices and kinetics of antibody induction and evanescence.

BACKGROUND: Failure to detect non-ABO blood group alloantibodies places patients at risk for hemolytic reactions. Suboptimal alloantibody detection could result from posttransfusion testing performed too early, too late, or not at all. Testing performed too early may precede antibody induction, while testing performed too late could miss antibodies that have evanesced. Taking these factors into account, our goal was to determine the percentage of alloantibodies detected with real-world testing practices. STUDY DESIGN AND METHODS: The alloantibody detection rate in a general hospital setting was determined based on the frequency and timing of antibody testing after red blood cell (RBC) transfusions and rates of antibody induction and evanescence. Intervals to follow up testing after RBC transfusions (n = 561 RBC units in 100 random patients) were determined retrospectively. Best-fit lines and equations for antibody induction and evanescence were computed on previously published data. RESULTS: Nearly half (271/561; 48.3%) of RBC infusions had either no follow-up antibody screen or testing too soon (<30 days) after transfusion to detect alloimmunization. Of the remaining RBC units, 10.3% (58/561) had follow-up testing 30 to 112 days posttransfusion, 28.7% (161/561) were followed up at more than 112 days, and 12.7% (71/561) were tested at both 30 to 112 days and more than 112 days. By inputting these timing data into best-fit line equations for antibody induction and evanescence, we calculated an alloantibody detection rate of 31.6%. CONCLUSION: Posttransfusion antibody testing was inadequately timed for optimal alloantibody detection. Real-world compatibility testing was predicted to detect less than one-third of non-ABO antibodies, thereby exposing patients to risks of mismatched transfusion.

The state of therapy for removal of alloantibody producing plasma cells in transplantation.

The current evidence clearly points towards donor specific alloantibody as a major cause of allograft loss. In order to mitigate allograft loss due to antibodies, treating the source of antibody production, the plasma cell is essential. Therapies that lack effect on the terminally differentiated (long-lived) plasma cell, such as rituximab, intravenous immune globulin and, plasmapheresis were the therapies used prior to 2007. In studies, their ability to remove antibody was found to be incomplete and/or cost prohibitive. In 2007, a proteasome inhibitor, bortezomib, was used for the first time in transplant due to its ability to deplete plasma cells. Through multiple case reports it has demonstrated consistent success in DSA reduction and removal, with only a few reports of failure to date. This review discusses the plasma cell, the alloantibody, and the current data supporting proteasome inhibitor use in transplant.

Primary B cell repertoire remodeling to achieve humoral transplantation tolerance.

The current mainstay of immunotherapy in clinical transplantation is T lymphocyte directed. However, it has long been appreciated that the emergence of an alloimmune response mounted by the B lymphocyte compartment and detectable as donor-specific antibodies is a critical challenge to long-term graft survival. Thus, achieving robust transplantation tolerance will require induction of tolerance in both the T- and B-cell compartments. Here we propose that the natural developmental propensity of the B-lymphocyte compartment acquisition of tolerance to self-antigens can be recapitulated to achieve humoral transplantation tolerance. It is our contention B-lymphocyte directed induction immunotherapy would be an important component of emerging strategies for induction of Transplantation tolerance.