Severe Rejection Episodes Research Articles

Analysis of Immunological Biomarkers Associated With Rejection After Uterus Transplantation in Human.

Uterus transplantation (UTx) is an emerging therapy for women with uterine infertility. However, critical questions remain with this procedure including the mechanisms involved in graft rejection. In this study, we analyzed the immune profile of ectocervical biopsies from 5 patients after UTx before and during their first episode of rejection using RNA sequencing, quantitative polymerase chain reaction, and imaging mass cytometry. We identified 530 upregulated and 207 downregulated genes associated with graft rejection. Enrichment databases revealed abnormalities of skin-associated genes and the immune system, in particular activation of T and B lymphocytes, and macrophages. Imaging mass cytometry confirmed these observations; in cervical biopsies of 3 women, rejection was associated with the presence of B-cell structures linked to tertiary lymphoid structures, and 2 biopsies from 1 woman with severe rejection episodes and poor prognosis of graft function (repeated miscarriage and implantation failures) were associated with an accumulation of HLA-DR- macrophages, producing granzyme B at the surface of the epithelium. We showed that rejection of a UTx graft was associated with major alterations of immune markers including the involvement of tertiary lymphoid structures, the most organized of which may be a sign of chronic rejection, and with an increase in HLA-DR- macrophages expressing granzyme B in the case of grade 3 rejection episodes according Mölne's classification. We identified potential emerging biomarkers to predict or diagnose graft rejection (Keratin 1 granzyme B, IL1β). These findings could lead to development of improved strategies for the identification, prevention, and/or treatment of uterus graft rejection.

Cardiac magnetic resonance imaging characterization of acute rejection in a porcine heterotopic heart transplantation model.

Preclinical disease models are important for the advancement of therapeutics towards human clinical trials. One of the difficult tasks of developing a well-characterized model is having a reliable modality with which to trend the progression of disease. Acute rejection is one of the most devastating complications that can occur following organ transplantation. Specifically in cardiac transplantation, approximately 12% of patients will experience at least one episode of moderate or severe acute rejection in the first year. Currently, the gold standard for monitoring rejection in the clinical setting is to perform serial endomyocardial biopsies for direct histological assessment. However, this is difficult to reproduce in a porcine model of acute rejection in cardiac transplantation where the heart is heterotopically transplanted in an abdominal position. Cardiac magnetic resonance imaging is arising as an alternative for serial screening for acute rejection in cardiac transplantation. This is an exploratory study to create and define a standardized cardiac magnetic resonance screening protocol for characterizing changes associated with the presence of acute rejection in this preclinical model of disease. Results demonstrate that increases in T1 mapping, T2 mapping, left ventricular mass, and in late gadolinium enhancement are significantly correlated with presence of acute rejection.

Total Lymphoid Irradiation in the Treatment of Heart Transplant Rejection: Single Institution Long-Term Results

Acute cardiac allograft rejection is a major cause of morbidity and mortality post-transplant. Total lymphoid irradiation (TLI) has been shown to cause long-lasting alterations in lymphocyte sub-sets, and thereby induces a state of partial response that is useful to prevent organ transplant rejection. In our previous report, treatment with TLI resulted in decreased episodes of acute rejection and steroid dosage requirements for up to 9.1 years post cardiac transplantation. In this study, we report an update on the short- and long-term effects of TLI in the treatment of cardiac transplant rejection. We performed a retrospective analysis of patients with intractable cardiac allograft transplantation evaluated in the department of radiation oncology at our institution over 23 years (1998-2021). Cardiac allograft rejection was defined as multiple or persistent episodes of rejection despite aggressive immunosuppressive therapy. The prescribed dose was 8 Gy in 10 fractions to be delivered over 5 weeks. All episodes of pathologic acute cardiac rejection, duration of immunosuppression, and episodes of acute infection requiring treatment before and after TLI were documented. Overall survival (OS) was analyzed using Kaplan-Meier method. The median time to first cardiac allograft rejection and the median time to first acute rejection was monitored. Of the 29 patients included, 21 (72.4%) had ISHLT grade 1R, 5 (17.2%), grade 2R, and 2(6.9%) grade 3R rejection. Rejection grade was unknown for 1 patient. The mean number of acute rejections after transplant was 14.4 episodes per patient (range 1-44) with median time to first rejection of 0.63 months. The median radiation dose was 8 Gy (range 7.2-8 Gy) delivered over a mean of 31 days. Treatment was stopped early in 2 (6.5%) patients (after 7.2 Gy and 7.9 Gy) for severe bone marrow suppression and drop in CD4 counts, respectively. The number of rejections dropped from 14.2 to 3.97 per patient over a median time of 29.0 months vs 28.1 months pre and post TLI (p = 0.01). The frequency of ISHLT acute grade 3R rejections decreased from 0.58 to 0.06 episodes per patient pre and post TLI (p = 0.02). Immunosuppressant requirements decreased from 2.83 before TLI to 2.69 after TLI (p = 0.71). Infection rates per patient were 0.71 pre TLI and remained at 0.63 post TLI. Treatment was well tolerated with 4 (13.8%) grade 2 or higher radiation toxicity. Median follow up was 76.3 months. Median and 3-year OS were 53.4 months and 60.9%, respectively. TLI is a safe and effective treatment for control of intractable cardiac rejection. The episodes of acute rejection and immunosuppressant requirements are decreased, but with long-term follow up, these patients continue to experience rejection. However, TLI lowers the frequency of ISHLT moderate to severe rejection episodes for up to 6.4 years. There was no increased risk of severe infections and there were only minimal short- and long-term grade 2 or higher radiation toxicities.

Conversion to belatacept after lung transplantation: Report of 10 cases.

Calcineurin inhibitors (CNIs) remain the cornerstone of maintenance immunosuppression (IS) after lung transplantation (LTx), although CNI-related life-threatening toxic effects may occur. Belatacept, a novel immunosuppressant that blocks a T-cell co-stimulation pathway, is a non-nephrotoxic drug indicated as an alternative to CNIs in kidney Tx. In LTx, there are only a few reports of belatacept conversion as a CNI-free or CNI-sparing IS treatment. We reviewed a series of 10 LTx recipients with conversion to a CNI-free belatacept IS regimen within the first year post-LTx (n = 7) or a belatacept/low-dose CNI combination after the first year (n = 3). Use of belatacept was triggered by severe renal failure in 9 patients and under-IS with previous other IS-related toxicities in 1 patient. Mean estimated glomerular filtration rate after starting belatacept significantly improved at 6 months after initiation and at the last-follow-up (p = 0.006, and p = 0.002 respectively). The incidence of recurrent and/or severe acute cellular rejection (ACR) episodes was high in patients with CNI-free belatacept-based IS (n = 4/7). Chronic graft allograft dysfunction developed in 2 of 9 recipients under belatacept IS. Belatacept was stopped in 6 patients because of recurrent/severe ACR (n = 3), recurrent opportunistic infections (n = 1), center modified policy (n = 1), or other cause (n = 1). Early conversion to CNI-free belatacept-based IS improved renal function in this series but was counterbalanced by a high incidence of recurrent ACR, including life-threatening episodes. Other studies are needed to better determine the indications for its use after LTx, possibly with lower immunological risk IS regimens, such as CNI-sparing belatacept.

Impact of psychosocial factors on medication level variability index and outcomes in pediatric liver transplant recipients.

Caregivers play an important role in maintaining a functioning graft after pediatric liver transplantation. Therefore, the psychosocial factors of both patients and caregivers can have a critical impact on transplant outcomes. Appropriate assessment and recognition of these factors pre-transplantation may allow transplant teams to better define the needs of pediatric organ recipients and develop specific countermeasures, which may then contribute toward improving transplant outcomes. We studied 136 pediatric LT recipients followed at Texas Children's Hospital. Licensed social workers conducted comprehensive pre-transplant assessments on each patient, consisting of 22 psychosocial variables that were thought to impact adherence, which were reviewed during our study period. Non-adherence was determined using the MLVI for up to 4 years after transplantation. Biopsy-confirmed rejection episodes were assessed in the first 3 years after liver transplantation. Factors significantly associated with non-adherence (defined as MLVI >2) included parental age and parental education level at assessment, type of insurance, and household income. The number of ACR episodes trended higher in patients with non-adherence, and these patients had a higher number of moderate to severe rejection episodes but this trend was not statistically significant. Psychosocial characteristics such as parental age, education level, insurance, and household income may contribute significantly to suboptimal adherence to medications after transplantation. Identification of these psychosocial factors and early intervention is essential to the success and equitable care of our pediatric LT recipients.

Intestinal Transplantation in a Country Without Home Parenteral Nutrition: The Largest Report from the Middle East.

Background:Many regions of the world, especially middle- and low-income countries, lack facilities for home parenteral nutrition and thus cannot follow existing guidelines for intestinal transplantation. Herein, we report our experiences with treatment protocols, intraoperative management, and early postoperative outcomes among patients undergoing either isolated intestinal transplantation or multivisceral transplantation in our center.Methods:During a 1-year period from March 2019 to March 2020, a total of 9 intestinal transplantations including 6 isolated intestinal transplantations and 3 multivisceral transplantations were performed in our center. We reported on donor selection strategies, surgical treatment, anesthesiology care and protocols for total parenteral nutrition, immunosuppression regimen, and pathology evaluation.Results:Mean (standard deviation) age of patients was 37.5 ± 12.5 years. The majority of patients were females (7/9). The median (interquartile range) waiting time for patients from diagnosis to transplantation was 79 (34, 164) days. Our 7-day survey of the amount of fluid therapy after transplantation revealed that the greatest need for fluid therapy was seen on the second postoperative day. After transplantation, 2 patients showed a total of 3 episodes of severe rejection, 1 of which was antibody-mediated. The 1-year survival was 66.6% and the 2-year survival was 44.5% in our study population. The median (interquartile range) time to death was 157 (26.5, 382) days. The most common cause of death was sepsis in our series (3/5).Conclusion:Acceptable outcomes can be obtained with intestinal transplantation in countries without home parenteral nutrition by application of specific treatment protocols.

The Effect of the COVID-19 Pandemic in Intestinal Rehabilitation and Transplant Patients: Initial Results of the Intestinal Rehabilitation and Transplant Association's International Survey.

The Effect of the COVID-19 Pandemic in Intestinal Rehabilitation and Transplant Patients: Initial Results of the Intestinal Rehabilitation and Transplant Association's International Survey.

The role of the electrocardiogram in the recognition of cardiac transplant rejection: A systematic review and meta-analysis.

BackgroundIn cardiac transplant recipients, the electrocardiogram (ECG) is a noninvasive measure of early allograft rejection. The ECG can predict an acute cellular rejection, thus shortening the time to recognition of rejection. Earlier diagnosis has the potential to reduce the number and severity of rejection episodes.MethodologyA systematic literature review was conducted to identify and select the original research reports on using electrocardiography in diagnosing cardiac transplant rejection in accordance with the PRISMA guidelines. Studies included reported sensitivity and specificity of ECG readings in heart transplant recipients during the first post‐transplant year. Data were analyzed with Review manager version 5.4. p‐value was used in testing the significant difference.ResultsAfter the removal of duplicates, 98 articles were eligible for screening. After the full‐text screening, a total of 17 papers were included in the review based on the above criteria. A meta‐analysis of five studies was done.ConclusionIn heart transplant recipients, a noninvasive measure of early allograft rejection has the potential to reduce the number and severity of rejection episodes by reducing the time and cost of surveillance of rejection and shortening the time to recognition of rejection.

Belatacept as salvage maintenance immunosuppression in a liver transplant recipient

Belatacept is a novel fusion protein that blocks signal two of T cell activation. Belatacept was approved in 2015 for the prevention of acute rejection in kidney transplant recipients. Results from a 2014 phase II clinical trial in liver transplant recipients was terminated early due to an increased risk of death and graft loss, leading to a black box warning for its use in liver transplant recipients. Here we describe the clinical course of a 55 year old male patient who underwent a liver transplant for cholestatic liver disease. His post-transplant course was complicated by multiple episodes of severe acute cellular rejection as well as multiple complications from maintenance immunosuppression including chronic kidney disease (CKD), steroid-induced diabetes, mycophenolate-associated colitis, and mammalian target of rapamycin (mTOR) inhibitor-induced lung injury. Belatacept was initiated 5 years post-transplant as a last-line option for maintenance immunosuppression. Six months post-initiation, the patient has had stabilization of his CKD, improvement in lung function, and remains without evidence of acute or chronic rejection.

Extracellular vesicles derived from injured vascular tissue promote the formation of tertiary lymphoid structures in vascular allografts.

Tertiary lymphoid structures (TLS) accumulate at sites of chronic injury where they function as an ectopic germinal center, fostering local autoimmune responses. Vascular injury leads to the release of endothelial‐derived apoptotic exosome‐like vesicles (ApoExo) that contribute to rejection in transplanted organs. The purpose of the study was to evaluate the impact of ApoExo on TLS formation in a model of vascular allograft rejection. Mice transplanted with an allogeneic aortic transplant were injected with ApoExo. The formation of TLS was significantly increased by ApoExo injection along with vascular remodeling and increased levels of antinuclear antibodies and anti‐perlecan/LG3 autoantibodies. ApoExo also enhanced allograft infiltration by γδT17 cells. Recipients deficient in γδT cells showed reduced TLS formation and lower autoantibodies levels following ApoExo injection. ApoExo are characterized by proteasome activity, which can be blocked by bortezomib. Bortezomib treated ApoExo reduced the recruitment of γδT17 cells to the allograft, lowered TLS formation, and reduced autoantibody production. This study identifies vascular injury‐derived extracellular vesicles (ApoExo), as initiators of TLS formation and demonstrates the pivotal role of γδT17 in coordinating TLS formation and autoantibody production. Finally, our results suggest proteasome inhibition with bortezomib as a potential option for controlling TLS formation in rejected allografts.

Blood proteome profiling using aptamer-based technology for rejection biomarker discovery in transplantation

Face transplantation is a promising solution for patients with devastating facial injuries who lack other satisfactory treatment options. At the same time, this type of transplantation is accompanied with high risks of acute transplant rejection. The limitations of traditional skin biopsy and the need to frequently monitor the condition of face transplant call for less invasive biomarkers to better diagnose and treat acute rejection. Discovery of peripheral serum proteins accurately reflecting the transplant status would represent a reasonable solution to meet this demand. However, to date, there is no clinical data available to address the feasibility of this approach. In this study, we used the next generation aptamer-based SOMAscan proteomics platform to profile 1305 proteins of peripheral blood serum in twenty-four samples taken from 6 patients during no-rejection, nonsevere rejection, and severe rejection episodes. Also, we provide a detailed description of biosample processing and all steps to generate and analyze the SOMAscan dataset with hope it will assist in performing biomarker discovery in other transplantation centers using this platform.

P2472Two-dimensional speckle tracking echocardiography in heart transplant patients: five year follow-up of right and left ventricular function

Abstract Background Evolution of left and right ventricular (LV and RV) function after heart transplantation (HT) has not been well described. Our objective was to evaluate the normal evolution of echocardiographic parameters of both ventricles and to explore if there is a link between the decrease of strain values and acute rejection (AR) or coronary allograft vasculopathy (CAV) Methods We followed 29 HT recipients with serial echocardiograms performed between 2011 and 2018, with a median follow-up of 5 years. LV global longitudinal strain (LV GLS) was analyzed by speckle tracking in 12 LV segments in 4 and 2 chamber views, and RV free wall longitudinal strain (RV free Wall LS) was measured in 4 chamber view. Acute rejection was diagnosed by EMB following our HT protocol. We take into consideration only moderate or severe rejection episodes (grade ≥2R).The presence of CAV was studied by coronariography or IVUS one year post-HT. Results As shown in the table below, LVEF was preserved from the begining of the follow up while LV GLS reached the normality in the 6th month, and both remained in normal ranges untill the 5th year. Regarding RV function, TAPSE was impaired in the early post-HT period and increased progressively and reached normality 1 year after HT. RV lateral wall LS rose during follow-up as well, reaching normal values 6 months after HT. Nevertheless, we noticed an impairment in this parameter at 5 years (−20.1±2.7, p=0.001), although it remained within normal ranges compared to guidelines reference parameters. We did not find any correlation between any parameter evaluated and the presence of AR or CAV at five years of follow-up. LV and RV function parameters LVEF LV GLS TAPSE FAC RV free wall LS Basal (14 days) 63.0±7.9 −17.2±3.6 12.1±2.9* 43.7±9.8 −19.3±4.2 3 months 65.0±8.6 −17.7±2.8 14.8±3.4* 45.3±8.2 −22.0±4.6 6 months 65.8±9.6 −18.7±3.4 16.1±3.6 44.6±9.6 −24.6±4.9* 1 year 63.5±8.1 −18.1±2.2 17.1±4.1 44.0±8.1 −26.7±7.1* 2 years 63.8±6.8 −18.3±9.0 19.4±3.7 45.3±7.9 −27.6±6.3* 5 years 64.4±7.3 −18.1±3.3 17.9±3.9 46.6±12.1 −20.1±2.8 P (Anova) 0.85 0.85 <0.001 0.82 <0.001 Conclusion As we show in this series of HT recipients with uneventful postoperative course, all LV and RV function parameters showed normal values 1 year after HT and manteined them during long-term follow-up. The presence of AR or CAV did not have any influence in ventricular function.

Time to Therapeutic Tacrolimus Serum Concentrations and the Impact on Early Acute Cellular Rejection in Adult Lung Transplant Recipients

Purpose Acute cellular rejection (ACR) affects up to 55% of lung transplant recipients (LTR) within the first year post-transplant. Maintenance immunosuppression regimens include calcineurin inhibitors, antimetabolites, and corticosteroids. Previous studies have shown that early ACR can lead to more severe rejection episodes within the first year post-transplant. The aim of this study is to evaluate the relationship between the time to therapeutic tacrolimus trough concentrations immediately after lung transplant and early clinical ACR post lung transplant. Methods This was a single center, retrospective cohort study of 208 adult LTR transplanted between March 1, 2012 and December 31, 2015 at NewYork-Presbyterian Hospital, Columbia University Irving Medical Center. Recipients were stratified into four groups based on the time to therapeutic tacrolimus concentrations: 0-7, 8-14, 15-29, and ≥30 days post-transplant. Therapeutic tacrolimus trough concentrations were defined as two consecutive levels between 10-15 ng/mL. The primary outcome was the incidence of clinical ACR 6 weeks post-transplant. Clinical ACR included both biopsy proven rejection and treated rejection. Secondary outcomes included biopsy proven ACR 4 and 12 weeks post-transplant and the incidence of acute kidney injury 7, 14, and 30 days post-transplant. Multivariable logistic regression was performed to assess the primary outcome with adjustment for donor age, recipient age, recipient sex, primary graft dysfunction (PGD) within 72 hours post-transplant, and pre-transplant HLA sensitization. Results The incidence of clinical ACR within 6 weeks post-transplant did not differ between groups: 68%, 66%, 71%, and 71% in the 0-7, 8-14, 15-29, and ≥30 days post-transplant groups, respectively (p=0.94). No differences were seen in adjusted and unadjusted analysis. No difference was found in the incidence of AKI within 7 (p=0.25) or 30 (p=0.32) days post-transplant. The incidence of AKI within 14 days was higher in the 15-29 day group (26%), compared to 7%, 14%, 7% in groups 0-7, 8-14, and ≥30 days, respectively (p=0.05). Conclusion There was no difference in the incidence of early clinical ACR among adult LTR who achieved therapeutic tacrolimus trough concentrations 0-7, 8-14, 15-29, or ≥30 days post-transplant.

3281 Management of Acute Rejection in Penile Allotransplantation

3281 Management of Acute Rejection in Penile Allotransplantation

Predictors of Long Term Survival in Visceral Transplant Recipients

Background: Despite continual improvement in early survival, the long-term outcomes of visceral transplantation remain conservative. Study Design: Single-center retrospective analysis of all visceral allograft recipients who underwent visceral transplant between November 2003 and December 2013 with at least 3 year follow up data. Clinical data from a prospectively maintained database was used to assess outcomes including patient and graft survival. Results: Of 174 recipients, 90 (51.7%) were adults and 84 (48.3%) were pediatric patients. Types of visceral transplants were 98 (56.3%) isolated intestinal transplant, 44 (25.3%) combined liver intestinal transplant, and 32 (18.4%) multi-visceral transplant. Median follow up was 8.1 (3–13.2) years. 3-, 5-, and 10-year overall patient survival was 69.5%, 66%, and 63%, respectively, while 3-, 5-, and 10-year overall graft survival was 67%, 62%, and 61%, respectively. In univariable analysis, significant predictors of survival included pediatric recipient (odds ratio [OR] = 2.138; 95% CI, 1.251-3.656); P= 0.005), low donor/recipient weight ratio (odds ratio [OR] = 1.224; 95% CI, 1.017-1.473; P= 0.032), no episodes of severe acute rejection (odds ratio [OR] = 1.939; 95% CI, 1.160-3.243; P= 0.012), history of functional bowel problem (odds ratio [OR] = 1.950; 95% CI, 1.142-3.332; P= 0.014), no simultaneous kidney transplantation (odds ratio [OR] = 3.138; 95% CI, 1.250-7.880; P= 0.015) and less HLA-A mismatch (odds ratio [OR] = 1.815; 95% CI, 1.098-3.012; P= 0.02). In multivariable analysis, significant predictors of survival included pediatric recipient (odds ratio [OR] = 2.249; 95% CI, 1.256-4.027); P= 0.006), low donor/recipient weight ratio (odds ratio [OR] = 1.234; 95% CI, 1.023-1.488; P= 0.028) and no episodes of severe acute rejection (odds ratio [OR] = 2.032; 95% CI, 1.158-3.566; P= 0.013). Conclusions: Visceral transplantation remains a good option for treatment of end stage intestinal failure with parenteral nutritional complications. Proper graft selection and improvement of immunosuppression regimens could significantly improve the long-term survival.

Impact of donor age on cardiac transplantation outcomes and on cardiac function.

Although the impact of older donors on heart transplant outcomes has been previously published, the survival results are conflicting. We herein analyse the impact of older donors on transplant survival and myocardial function. The records of the patients who underwent heart transplant at Baylor University Medical Center at Dallas from November 2012 until March 2015 were reviewed and the data were extracted. The heart recipients were divided into two groups based on donors age; 50 years of age was the division point. The two groups were compared with regard to the following transplant outcomes: in-hospital and 1-year survival, severe (3R) rejection, primary graft dysfunction, myocardial performance as reflected by the inotropic score, left ventricular ejection fraction, intensive care unit and overall length of stay. Anoxia was more common cause of death in younger donors (43.9%), whereas intracranial bleeding was more frequent in older donors (48.1%, P = 0.016). The in-hospital survival and 1-year survival were the same between the two groups. Additionally, cardiac transplantation from older donors was not associated with higher incidence of graft dysfunction, higher inotropic support score, longer intensive care unit and total hospital length of stay or more frequent severe rejection episodes. The left ventricular ejection fraction was similar between the two groups. Heart transplant from older donors is not associated with lower in-hospital and mid-term survival if donors are carefully selected; furthermore, the graft function is comparable. The use of hearts from donors older than 50 years of age can be expanded beyond critically ill recipients in carefully selected recipients.

Intestine Transplantation Across a Positive Crossmatch With Preformed Donor-Specific Antibodies

BackgroundWe describe our experience using a modified protocol for immunosuppression for intestine transplantation across a positive crossmatch. Patients who underwent transplantation in 2013 were evaluated over a 12-month period for rejection and infectious events with comparison to procedure-matched controls on our standard protocol of immunosuppression. Patients and MethodsWe used a modified protocol for intestine and multivisceral transplantation for patients with a positive flow crossmatch. In addition to our standard protocol, patients with positive crossmatch were given rituximab and intravenous immunoglobulin (IVIg) preoperatively. DSA was sent for clinical evaluation at monthly intervals. Patients were screened for rejection by endoscopic evaluation. ResultsFour patients underwent transplantation within a single year across a positive crossmatch. Two received isolated intestine transplants and 2 had multivisceral transplantation (MVT). During the 12-month follow-up, 1 patients had an episode of severe acute cellular rejection, which was managed with increased immunosuppression. None of the patients had episodes of cytomegalovirus infection. One patient developed major infection and 3 patients developed minor bacterial infections. Among procedure-matched controls with negative final crossmatch on standard management (no preoperative rituximab or IVIg), 2 developed mild acute cellular rejection and 2 developed minor infections. One developed cytomegalovirus viremia with invasion to the colonic mucosa. ConclusionsWe report our protocol for immunosuppression for IT and MVT across a positive crossmatch. This allowed transplantation despite the presence of a positive crossmatch, with low rejection rates but potentially increased risk for major infections compared to the negative crossmatch controls on our standard protocol.

Monitoring B cell subsets and alloreactivity in kidney transplantation.

B cells are the precursors of antibody producing plasma cells that can give rise to the formation of donor-specific antibodies. However, recent data suggest that besides their role in antibody production, B cells participate in antibody-independent responses, potentially leading to allograft rejection or allograft tolerance. The presence of CD20(+) B cells in kidney graft biopsies has been shown during severe acute rejection episodes and during chronic rejection. Furthermore, operationally tolerant kidney transplant recipients showed a clear B cell dominated fingerprint of tolerance. Several techniques exist to study B cells on different levels. Numerous classification schemes allow for the distinction of many different B cell subsets using flow cytometry. Regardless, data on B cell subsets during stable graft function, rejection or tolerance remain scarce. To obtain a complete picture of the role of B cells during transplantation, antigen specific B cell assays may be required. Therefore, techniques have now been developed that allow for studying the specificity and frequency of HLA specific B cells. Here, we present an overview of the existent assays, panels and techniques intended to characterize peripheral B cells, and the currently available HLA specific B cell functional assays that may allow for monitoring the humoral alloimmune response in transplant recipients.

Assessment of Eculizumab (Anti-C5) Therapy For Treatment of Severe Antibody-Mediated Rejection Episodes (ABMR).

Assessment of Eculizumab (Anti-C5) Therapy For Treatment of Severe Antibody-Mediated Rejection Episodes (ABMR).

Impact of Mast Cells in Rejection of Allografts

Mast cells in the tissue are located close to nerves in and around the small vessels where they orchestrate important immune response after antigen recognition through Toll-like receptors. Mast cells can activate T and B lymphocytes and dendritic cells and have been postulated to act directly within tissue allografts and/or to induce indirect effects via inflammatory mediator release, therefore they have been shown to play an indispensable role in allograft tolerance. Major limitation in the success of transplantation is the immune response of the recipient to the donor tissue. The failure of tissue grafting is caused by an inflammatory reaction called rejection. Mast cells play a role during immune response and are elicited with transplanted allograft and also may exhibit their immune-regulatory effects directly through secretion of modulatory cytokines and activation of metabolic pathways. However, the role of mast cells in transplantation is poorly understood. The most severe rejection episodes have been found in patients with an increased number of mast cells. Mast cell mediators which can activate latent forms of TGF-β or increase angiotensin II levels are capable of inducing fibrosis through various mechanisms, activating fibroblasts and inducing collagen synthesis. Mast cells are also implicated in regulatory T-cell functions and are required to sustain peripheral tolerance via Treg, therefore there is an interaction between mast cells and Treg cells. Treg create IL-9 in enhancing mast cell growth and Chemotaxis, suggesting that Treg and mast cells form a functional unit that mediates graft tolerance. In this study we concentrate our attention on the role of mast cells in rejection of allografts and try to understand the role of mast cell-related immune mechanisms in organ transplantation.