Antibodies In Organ Transplantation Research Articles

New insights into maladaptive vascular responses to donor specific HLA antibodies in organ transplantation

Transplant vasculopathy (TV) causes thickening of donor blood vessels in transplanted organs, and is a significant cause of graft loss and mortality in allograft recipients. It is known that patients with repeated acute rejection and/or donor specific antibodies are predisposed to TV. Nevertheless, the exact molecular mechanisms by which alloimmune injury culminates in this disease have not been fully delineated. As a result of this incomplete knowledge, there is currently a lack of effective therapies for this disease. The immediate intracellular signaling and the acute effects elicited by anti-donor HLA antibodies are well-described and continuing to be revealed in deeper detail. Further, advances in rejection diagnostics, including intragraft gene expression, provide clues to the inflammatory changes within allografts. However, mechanisms linking these events with long-term outcomes, particularly the maladaptive vascular remodeling seen in transplant vasculopathy, are still being delineated. New evidence demonstrates alterations in non-coding RNA profiles and the occurrence of endothelial to mesenchymal transition (EndMT) during acute antibody-mediated graft injury. EndMT is also readily apparent in numerous settings of non-transplant intimal hyperplasia, and lessons can be learned from advances in those fields. This review will provide an update on these recent developments and remaining questions in our understanding of HLA antibody-induced vascular damage, framed within a broader consideration of manifestations and implications across transplanted organ types.

Antigen and Cell-Based Assays for the Detection of Non-HLA Antibodies.

To date, human leukocyte antigens (HLA) have been the major focus in the approach to acute and chronic antibody-mediated rejection (AMBR) in solid-organ transplantation. However, evidence from the clinic and published studies has shown that non-HLA antibodies, particularly anti-endothelial cell antibodies (AECAs), are found either in the context of AMBR or synergistically in the presence of donor-specific anti-HLA antibodies (DSA). Numerous studies have explored the influence of AECAs on clinical outcomes, yet the determination of the exact clinical relevance of non-HLA antibodies in organ transplantation is not fully established. This is due to highly heterogeneous study designs including differences in testing methods and outcome measures. Efforts to develop reliable and sensitive diagnostic non-HLA antibody tests are continuously made. This is essential considering the technical difficulties of non-HLA antibody assays and the large variation in reported incidences of antibodies. In addition, it is important to take donor specificity into account in order to draw clinically relevant conclusions from non-HLA antibody assays. Here, we provide an overview of non-HLA solid-phase and cell-based crossmatch assays for use in solid-organ transplantation that are currently available, either in a research setting or commercially.

Impact and production of Non-HLA-specific antibodies in solid organ transplantation.

Organ transplantation is an effective way to treat end-stage organ disease. Extending the graft survival is one of the major goals in the modern era of organ transplantation. However, long-term graft survival has not significantly improved in recent years despite the improvement of patient management and advancement of immunosuppression regimen. Antibody-mediated rejection is a major obstacle for long-term graft survival. Donor human leucocyte antigen (HLA)-specific antibodies were initially identified as a major cause for antibody-mediated rejection. Recently, with the development of solid-phase-based assay reagents, the contribution of non-HLA antibodies in organ transplantation starts to be appreciated. Here, we review the role of most studied non-HLA antibodies, including angiotensin II type 1 receptor (AT1 R), K-α-tubulin and vimentin antibodies, in the solid organ transplant, and discuss the possible mechanism by which these antibodies are stimulated.

Nonhuman leukocyte antigen antibodies that have impact in the heart transplant patient.

Despite human leukocyte antigen (HLA) matching and monitoring for donor-specific HLA antibodies, antibody-mediated rejection and chronic rejection in the form of allograft vasculopathy and chronic graft dysfunction continue to occur. There has been increasing interest in non-HLA antibodies as mediators of these changes. In this review, we discuss the recent literature describing the importance of non-HLA antibodies in organ transplantation and summarize the literature evaluating such antibodies in heart transplantation. Monitoring of non-HLA antibodies requires additional measurement standardization and correlation of specific antibodies with outcomes. However, there is promise that identification with newer immunoproteomic techniques and therapy toward such antibodies may improve long-term graft outcomes and decrease acute rejection and allograft vasculopathy.

HLA抗体の補体結合性についての検討

Various methods have been proposed for the detection of HLA antibodies in organ transplantation. However, the discrepancies in the results between LCT (CDC)-XM and the other methods, FCXM, LABScreen etc. are observed. We investigated the cause of these discrepancies using the LABScreen Single Antigen Test (LABScreen) and LABScreen Single C1q (C1qScreen). C1qScreen is detected the complement-binding HLA antibody. As a result, in 37 patients whose HLA antibodies positive by using LABScreen test, 28 patients (76%) and 25 patients (68%) whose HLA Class I and Class II antibodies positive, respectively. Moreover, it was only 11 patients (30%) that C1qScreen was positive in the patients whose Class I antibodies were positive. And it was 14 patients (40%) that C1qScreen was positive in the patients whose Class II was positive. Furthermore C1qScreen positive was 176 (31%) among 567 specificity of detected Class I antibodies, and C1qScreen positive was 171 (44%) among 392 specificity of Class II. Therefore, many HLA antibodies are not detected by LCT-XM. It is because these antibodies do not have complement-binding nature. And such antibodies could be detected by AHG-LCT, and it is supposed that these are not related to kidney-allograft failure.

Moving beyond HLA: A review of nHLA antibodies in organ transplantation

Given the finite graft life expectancy of HLA identical organ transplants and the recognition of humoral graft injury in the absence of donor directed anti-HLA antibodies, the clinical impact of antibodies against non-HLA (nHLA) antigens in transplant injury is being increasingly recognized. The recognition of the impact of nHLA antigen discrepancies between donor and recipient on transplant outcomes is timely given the advances in rapid and lower cost sequencing methods that can soon provide complete maps of all recipient and donor HLA and nHLA mismatch data. In this review, we present a summary of recent reports evaluating the role of nHLA antibodies and their relevance to the field of organ transplantation.

Role of non-HLA antibodies in organ transplantation

Humoral responses beyond major histocompatibility antigens receive an increased attention of the transplantation community. We aimed to summarize the data on discovery of new antigenic targets, novel experimental findings, recent diagnostic developments, and introduction of new technologies in the field of non-HLA antigens in solid organ transplantation. Non-HLA antibodies can be currently reliably detected by solid-phase assays (MICA, angiotensin type 1 receptor, collagen-V, vimentin), immunofluorescence (antibodies against antigens expressed on umbilical vein endothelial cells), or flow-crossmatch techniques (antibodies against donor endothelial progenitors). Influence of test positivity on transplant outcomes is variable and differs among non-HLA targets. Use of omics approach helped to identify a unique set of antigens in adult and pediatric patients with severe rejections and transplant glomerulopathy. Paradigms for effective monitoring of non-HLA humoral responses need to be established in order to utilize advances provided by the rapid diagnostic developments. A systematic longitudinal assessment of pretransplant sensitization together with monitoring of posttransplant changes would represent an important step forward.

De novo development of circulating anti-endothelial cell antibodies rather than pre-existing antibodies is associated with post-transplant allograft rejection

Anti-endothelial cell antibodies (AECAs) are thought to be involved in the development of renal allograft rejection. To explore this further, we determine whether AECAs play a role both in predicting the incidence of allograft rejection and long-term outcomes by analysis of serum samples from 226 renal allograft recipients for AECAs pre- and post-transplant. Surprisingly, the presence of pre-existing AECAs was not associated with either an increased risk of rejection or a detrimental impact on recipient/graft survival. Subsequent de novo AECAs, however, were associated with a significantly increased risk of early acute rejection. Moreover, these rejections tended to be more severe with a significantly increased incidence of both steroid-resistant and multiple episodes of acute rejection. The acute rejections associated with de novo AECAs did not correlate with C4d deposition at the time of renal biopsy, but did demonstrate an association with the presence of glomerulitis and peritubular capillary inflammation. Significantly more patients with de novo AECAs developed graft dysfunction. Thus, our prospective study suggests the emergence of de novo AECAs is associated with transplant rejection that may lead to allograft dysfunction.

Humoral Antibodies in Organ Transplantation: Angels or Demons?

Hidalgo et al. (1) found that the development of de novo donor-specific antibodies was associated both with specific histological lesions in kidney transplant biopsies done late in the posttransplant course and a poor prognosis. These authors suggested that a careful assessment of de novo donor-specific antibodies should be performed in connection with all late kidney transplant biopsies. Studies aimed to investigate the role of donor-specific antibodies in organ transplantation are welcome as they may help to better understand the pathogenesis of chronic humoral rejection. However, one wonders whether such a costly monitoring of donor-specific antibodies will have a beneficial impact in clinical practice. In my opinion, caution is needed to interpret the role of humoral antibodies in this situation. Few doubts exist that chronic allograft rejection is caused, at least in part, by circulating antibodies, but it is still unclear if the anti-donor antibodies we can detect in the circulation are the same as those causing graft injury. It is conceivable that are antibodies aimed at inducing ‘accommodation’ (2). Experimental evidence from animal studies indicates that anti-HLA antibodies participate in allograft ‘accommodation’ (3). Expressing antiapoptotic genes can also induce allograft accommodation (4). As pointed out by Chang and Platt (2), it is conceivable that antibodies favoring the resistance of graft to immune injury cannot be absorbed by an allograft damaged by a previous immunological attack. As a consequence, the level of those antibodies increases in the circulation. Because we cannot determine whether circulating antidonor antibodies are harmful or protective, we should be cautious in making therapeutic decisions based on their measurement. If antidonor antibodies actually have a detrimental effect on graft outcome, removal therapies should be started when allo-antibody is first detected to prevent chronic rejection and prolong renal allograft survival. At present, however, there is not convincing evidence that therapies based on apheresis, B-cell removal or proteasome inhibition are of any substantial benefit in the treatment or prevention of chronic rejection. On the other hand, if circulating protective allo-antibodies are also operating in human allografts, these therapies might even be harmful, through removal of potentially protective allo-antibodies. Because a reinforcement of immunosuppression may be accompanied by serious or even life-threatening side effects, it is perhaps safer (and wiser) to keep the intensity of immunosuppression unchanged until further studies are able to elucidate the true nature and the heterogeneity (harmful or protective) of circulating antibodies.

The role of major histocompatibility complex class I chain-related gene A antibodies in organ transplantation

Major histocompatibility complex class I chain-related gene A (MICA) antigens are expressed on the endothelium, they are polymorphic and have been shown to be recognized by antibodies produced by transplant recipients. Methods for detection of these antibodies have become available. In the 15th International Histocompatibility Workshop, a study for MICA antibody testing and of MICA genotyping was organized. Antibodies against MICA antigens have been determined either using cells transfected with MICA alleles or recombinant MICA antigens. MICA epitopes were characterized by empirical study of human sera and by correlation with MICA polymorphic amino acids. Sera were absorbed with cells transfected with MICA alleles and site-directed mutagenesis was employed to analyze complex sera. A number of clinical studies have shown associations of antibodies against MICA with decreased survival of kidney transplants and in one investigation with acute rejection in recipients of heart allografts. In addition to the HLA antigens, which elicit a strong immune response against allografted organs, the MICA antigens may be recognized as foreign and induce the production of MICA-specific antibodies. Antibodies against MICA have been associated with a decrease in the survival of organ allografts. The results suggest the MICA antigens are transplantation antigens that can induce an immune response associated with graft failure.

Anti–major histocompatibility complex class I-related chain A antibodies in organ transplantation

Candidate trigger antigens for alloreactive responses have been appearing continuously in the organ transplant scenario. Major histocompatibility complex class I-related chain A (MICA) is a polymorphic gene family, located near the HLA-B locus on chromosome 6, that encode a 62-kd cell surface glycoprotein. Endothelial cells, in addition to many cell lines, express MICA, whereas resting lymphocytes do not, making this polymorphic molecule a target for both cellular and humoral immune responses. Major histocompatibility complex class I-related chain A antigens are able to elicit the synthesis of alloantibodies in transplant recipients. These antibodies have been found in association with irreversible allograft rejection, an increased frequency of acute rejection episodes, and a significantly lower deceased donor graft survival, as well as in the eluates from rejected grafts. This review summarizes currently available information on MICA in the transplant setting. Undoubtedly, the questions that have surfaced surpass in excess the currently available answers.

Section Review: Biologicals & Immunologicals: Monoclonal antibodies in organ transplantation

Despite a large number of clinical trials during the last fifteen years, the success of antibodies in the field of organ transplantation is low. Only one antibody has become a widely accepted drug for the treatment of rejection and at least a possibility for rejection prophylaxis in the first week after transplantation in high risk patients. Most antibodies tested showed only weak immunosuppressive effects in vivo. Additionally, a number of new immunosuppressive drugs became available in many transplantation centres and this further reduced the interest in antibodies. However, antibodies are an effective and well-established means by which to block co-stimulatory signals. Blocking co-stimulatory signals can lead to tolerance induction, which is the only way in which to avoid long-term immu-nosuppression in organ transplant patients.

Monoclonal antibodies in organ transplantation: an overview

Monoclonal antibodies in organ transplantation: an overview

Monoclonal Antibodies in Organ Transplantation

I N 1975 Kohler and Milstein established the technology for the production of monoclonal antibodies. 1 This procedure combines the fusion of myeloma cells with immunized spleen cells to produce a hybridoma. This fusion provides the benefits of linking the immortality of the myeloma cell with the antibody production and secretion of the immunized spleen cell. The selected antigen is injected into a murine host. The animal's spleen cells (antibody-producing) are harvested at this time and mixed with mutant mouse myeloma cells and polyethylene glycol to promote fusion. The newly created hybridomas are assayed for antibody activity. Cells showing positive activity are placed into separate culture wells and cloned. The desired hybridomas are then either frozen for future use or are cultured for the production of the monoclonal antibody. This process occurs in mass tissue culture or by intraperitoneal injection into immunodeficient mice, producing an ascites tumor that generates large amounts of monoclonal antibodies after 2 to 4 weeks. The monoclonal antibody produced is of a single predetermined specificity. In contrast to polyclonal antibodies, monoclonal antibodies are homogenous, have greater potency at lower doses, and have a more predictable and consistent effect. Fusion technology has led to the development of monoclonal antibody immunoconjugates, so that cytotoxic therapy may be delivered with specificity to cells that carry epitopes reactive with the antibody portion of the conjugate. This allows for delivery of the immunotoxin to the cell type

Monoclonal antibodies in organ transplantation

Monoclonal antibody (mAb) technology has made possible the production of designer proteins, specifically reactive with almost any conceivable biological molecule. Using these reagents, the surface molecules on cells crucial for allograft rejection have been identified and described in detail. These structures can now be selectively targeted by mAb-based therapy in order to prevent rejection. For instance, the CD3 molecule, expressed on all mature T lymphocytes, triggers T cell activation, a key event in rejection. OKT3, an anti-CD3 mAb, disrupts T cell function and is now the agent of choice for the treatment of severe rejection episodes. MAbs targeting other T cell molecules are currently being investigated. Some of the most promising, the anti-CD4, anti-ICAM-1, and anti-interleukin 2 receptor mAbs, have already induced donor-specific tolerance in rodent models. These hosts accept permanently a genetically incompatible graft after only a limited period of mAb therapy. Interestingly, anti-ICAM-1 also diminishes the ischemic injury of preservation. The development of these new molecular agents, effectively directed to specific cellular targets, will likely play an increasingly important role in future clinical protocols, and perhaps finally provide a means to achieve long-term tolerance in human allograft recipients.

Use of Monoclonal Antibodies in Organ Transplantation

Use of Monoclonal Antibodies in Organ Transplantation