Intravenous immune globulin treatment inhibits crossmatch positivity and allows for successful transplantation of incompatible organs in living-donor and cadaver recipients

Antibody-mediated rejection in kidney transplantation: a review

Antibody mediated rejection (AMR) poses a significant and continued challenge for long term graft survival in kidney transplantation. However, in the recent years, there has emerged an increased understanding of the varied manifestations of the antibody mediated processes in kidney transplantation. In this article, we briefly discuss the various histopathological and clinical manifestations of AMRs, along with describing the techniques and methods which have made it easier to define and diagnose these rejections. We also review the emerging issues of C4d negative AMR, its significance in long term allograft survival and provide a brief summary of the current management strategies for managing AMRs in kidney transplantation.

The role of therapeutic apheresis in high immunologic risk renal transplantation: a review of current trends

Immunologic sensitization, defined by the presence of antibodies directed against donor human leukocyte antigen (or so called donor-specific antibodies [DSA]), is common among those awaiting kidney transplantation, and is associated with worse outcomes following transplant. Existing DSA have historically been screened for pretransplant using complement-dependent cytotoxic crossmatching and their risk circumnavigated through policies that prohibit transplants between incompatible donor-recipient pairs. This risk avoidance strategy maximizes outcomes following transplant, but at the expense of limiting access to transplant for sensitized individuals. Over the last decade, the field of kidney transplantation has moved to actively modify the risks posed by DSA, rather than to simply avoid them. More sensitive detection methods have provided detailed immunologic risk stratification of potential donor-recipient pairs. Desensitization protocols, in which therapeutic aphaeresis plays a central role, have been used to reduce the potential harms posed by DSA. More recently, desensitization and paired donor exchange programs have been used in combination to expand transplantation to highly sensitized patients with incompatible living donors. It is likely that this combination of risk mitigation and avoidance strategies will be used together more often to both maximize individuals' access to transplant, and optimize patient and graft outcomes.

Pediatric renal transplantation in a highly sensitised child-8 years on

Highly sensitised children have markedly reduced chances of receiving a successful deceased donor renal transplant, increased risk of rejection, and decreased graft survival. There is limited experience with the long-term followup of children who have undergone desensitization. Following 2 failed transplants, our patient was highly sensitised. She had some immunological response to intravenous immunoglobulin (IVIg) but this was not sustained. We developed a protocol involving sequential therapies with rituximab, IVIg, and plasma exchange. Immunosuppressant therapy at transplantation consisted of basiliximab, tacrolimus, mycophenolate mofetil, and steroids. At the time of transplantation, historical crossmatch was ignored. Current CDC crossmatch was negative, but T and B cell flow crossmatch was positive, due to donor-specific HLA Class I antibodies. Further plasma exchange and immunoglobulin therapy were given pre- and postoperatively. Our patient received a deceased donor-kidney-bearing HLA antigens to which she originally had antibodies, which would have precluded transplant. The graft kidney continues to function well 8 years posttransplant.

Humoral immunity and antibody-mediated rejection in solid organ transplantation

The humoral arm of the immune system provides robust protection against extracellular pathogens via the production of antibody molecules that neutralize or facilitate the destruction of microorganisms. However, the humoral immune system also provides a significant barrier to solid organ transplantation due to the antibody-mediated recognition of non-self proteins and carbohydrates expressed on transplanted organs. Historically, the presence of donor-specific antibodies (DSA) that recognize donor HLA molecules, incompatible ABO blood group antigens and other endothelial or xenogeneic antigens was considered a contraindication to transplantation. However, recent advances in antibody testing and immunosuppressive therapies have made it possible to cross certain antibody barriers successfully. In this article, we review our current understanding of antibody-mediated processes in solid organ transplantation and discuss the clinically available treatment options for preventing and treating antibody-mediated rejection.

Treatment options and strategies for antibody mediated rejection after renal transplantation

Antibody mediated rejection is a significant clinical problem encountered in a subset of renal transplant recipients. This type of rejection has a variable pathogenesis from the presence of donor specific antibodies with no overt disease to immediate hyperacute rejection and many variations between. Antibody mediated rejection is more common in human leukocyte antigen sensitized patients. In general, transplant graft survival after antibody mediated rejection is jeopardized, with less than 50% graft survival 5 years after this diagnosis. A variety of agents have been utilized singly and in combinations to treat antibody mediated rejection with differing results and significant research efforts are being placed on developing new targets for intervention. These same agents have been used in desensitization protocols with some success. In this review, we describe the biology of antibody mediated rejection, review the available agents to treat this form of rejection, and highlight areas of ongoing and future research into this difficult clinical problem.

The utility of comprehensive assessment of donor specific anti-HLA antibodies in the clinical management of pediatric kidney transplant recipients

Advances in anti-HLA antibody characterization have had a major impact on kidney transplantation. Comprehensive characterization of DSA has improved protocols for allosensitized transplant candidates, increasing access to acceptable donors. Sensitive and specific solid phase antibody detection assays have given important insight into the clinical characteristics of antibody-mediated allograft injury, resulting in the development of a classification system for acute AMR. In addition, important insights into the nature of chronic antibody-mediated allograft rejection have been achieved as a result of improvements in DSA characterization. Finally, assays initially developed as tools to detect DSA in the clinical setting have been employed in innovative research protocols, allowing the investigation of new therapeutic approaches.

Antibody testing strategies for deceased donor kidney transplantation after immunomodulatory therapy

BACKGROUND

Immunomodulatory protocols including intravenous immunoglobulin/rituximab (IVIG/R) are employed to decrease anti-human leukocyte antigen (HLA) antibody levels for patients broadly sensitized to HLA and increase chances for transplantation with a compatible deceased donor (DD). The aim of our study was to identify the optimal antibody levels allowing for selection of compatible DDs for these sensitized patients.

METHODS

From January 2006 to December 2009, 108 patients broadly sensitized to HLA who had reached the top of the DD waitlist were treated with IVIG/R. Antibody levels were monitored monthly by Luminex-based single-antigen bead assay. The antigens identified to produce positive complement-dependent cytotoxicity crossmatches (XMs; >200,000 standard fluorescence intensity [SFI]/10,000 median fluorescence intensity [MFI]) were determined to be unacceptable and entered into the United Network for Organ Sharing database generating the calculated panel reactive antibody (CPRA). The mean CPRA (mCPRA) for this group was more than 80. DDs were selected based on T-cell flow XMs (FXMs) less than 250 MCS and B-cell FXMs less than 300 mean channel shifts (MCS).

RESULTS

Monthly Luminex-based single-antigen assays showed that the IVIG/R therapy decreased antibody levels for a period of 30 to 120 days. Of the 108 patients treated, 80 (74%) were transplanted and 28 (26%) were not (mCPRA 96 ± 11). Forty-two (53%) patients were transplanted with a positive FXM; 28 (35%) patients (mCPRA 84 ± 25) were transplanted with a negative FXM; and 10 patients (12%; mCPRA 90 ± 19) received zero HLA ABDR mismatched grafts.

CONCLUSIONS

After therapy, careful selection of acceptable DD involves the antibody profiling strength and XM results. These approaches provide patients broadly sensitized to HLA with an opportunity for compatible DD transplantation.

Prevention and treatment of alloantibody-mediated kidney transplant rejection

Antibody-mediated rejection (AMR), which is commonly caused by preformed and/or de novo HLA alloantibodies, has evolved as a leading cause of early and late kidney allograft injury. In recent years, effective treatment strategies have been established to counteract the deleterious effects of humoral alloreactivity. One major therapeutic challenge is the barrier of a positive pretransplant lymphocytotoxic crossmatch. Several apheresis- and/or IVIG-based protocols have been shown to enable successful crossmatch conversion, including a strategy of peritransplant immunoadsorption for rapid crossmatch conversion immediately before deceased donor transplantation. While such protocols may increase transplant rates and allow for acceptable graft survival, at least in the short-term, it has become evident that, despite intense treatment, many patients still experience clinical or subclinical AMR. This reinforces the need for innovative strategies, such as complementary allocation programs to improve transplant outcomes. For acute AMR, various studies have suggested efficiency of plasmapheresis- or immunoadsorption-based protocols. There is, however, no established treatment for chronic AMR and the development of strategies to reverse or at least halt chronic active rejection remains a big challenge. Major improvements can be expected from studies evaluating innovative therapeutic concepts, such as proteasome inhibition or complement blocking agents.

Update and review: state-of-the-art management of cytomegalovirus infection and disease following thoracic organ transplantation

PURPOSE

Cytomegalovirus (CMV) is among the most important viral pathogens affecting solid organ recipients. The direct effects of CMV (eg, infection and its sequela; tissue invasive disease) are responsible for significant morbidity and mortality. In addition, CMV is associated with numerous indirect effects, including immunomodulatory effects, acute and chronic rejection, and opportunistic infections. Due to the potentially devastating effects of CMV, transplant surgeons and physicians have been challenged to fully understand this infectious complication and find the best ways to prevent and treat it to ensure optimal patient outcomes.

SUMMARY

Lung, heart, and heart-lung recipients are at considerably high risk of CMV infection. Both direct and indirect effects of CMV in these populations have potentially lethal consequences. The use of available treatment options depend on the level of risk of each patient population for CMV infection and disease. Those at the highest risk are CMV negative recipients of CMV positive organs (D+/R-), followed by D+/R+, and D-/R+. More than 1 guideline exists delineating prevention and treatment options for CMV, and new guidelines are being developed. It is hoped that new treatment algorithms will provide further guidance to the transplantation community. The first part describes the overall effects of CMV, both direct and indirect; risk factors for CMV infection and disease; methods of diagnosis; and currently available therapies for prevention and treatment. Part 2 similarly addresses antiviral-resistant CMV, summarizing incidence, risk factors, methods of diagnosis, and treatment options. Parts 3 and 4 present cases to illustrate issues surrounding CMV in heart and lung transplantation, respectively. Part 3 discusses the possible mechanisms by which CMV can cause damage to the coronary allograft and potential techniques of avoiding such damage, with emphasis on fostering strong CMV-specific immunity. Part 4 highlights the increased incidence of CMV infection and disease among lung transplant recipients and its detrimental effect on survival. The possible benefits of extended-duration anti-CMV prophylaxis are explored, as are those of combination prophylaxis with valganciclovir and CMVIG.

CONCLUSION

Through improved utilization of information regarding optimized antiviral therapy for heart and lung transplant recipients to prevent and treat CMV infection and disease and through increased understanding of clinical strategies to assess, treat, and monitor patients at high risk for CMV recurrence and resistance, the health care team will be able to provide the coordinated effort needed to improve patient outcomes.

Antibody-mediated rejection--an ounce of prevention is worth a pound of cure

The presence of preformed, donor-specific alloantibodies inpatients undergoing renal transplantation is associated with a high risk of hyperacute and acute antibody-mediated rejection (ABMR), and often limits potential recipients' access to organs from living and deceased donors. Over the last decade, understanding of ABMR has improved markedly and given rise to numerous, diverse strategies for the transplantation of allosensitized recipients. Antibody desensitization programs have been developed to allow renal transplant recipients with a willing but antibody-incompatible living donor to undergo successful transplantation, whereas kidney paired exchange schemes circumvent the antibody incompatibility altogether by finding suitable pairs to donors and recipients. Recognizing the complexity of ABMR and the recent developments that have occurred in this important clinical research field, the Roche Organ Transplantation Research Foundation (ROTRF) organized a symposium during the XXIII Congress of The Transplantation Society in Vancouver, Canada, to discuss current understanding in ABMR and ways to prevent it. This Meeting Report summarizes the presentations of the symposium, which addressed key areas that included the interactions between alloantibodies and the complement system in mediating graft injury, technological advancements for assessing antibody-mediated immune responses to HLA antigens, and the potential benefits and challenges of desensitization and kidney paired donation schemes.

Desensitization: achieving immune detente

Antibodies to donor HLA (human leukocyte antigen) and/or ABO antigens were a contraindication to transplantation of most organs for decades. Desensitization protocols have shown the ability to produce reduction of such antibodies sufficient to achieve a successful transplantation. The two major protocols in use are high-dose IVIg or plasmapheresis with low-dose IVIg. The protocols differ in the basic treatment and, to some degree, in their application, but both use standard immunosuppressive agents as well as more recently developed adjunctive agents such as cell-depleting antibodies. Graft and patient survival with both types of protocol are comparable to that of non-sensitized patients, although desensitized patients do have a higher incidence of antibody-mediated rejection (AMR). Antibodies to donor antigens may persist after transplantation, and while the initial antibody titer represents the level of difficulty for successful desensitization, the strength of antibodies that persist after transplantation reflects the risk of AMR. Current protocols do not eliminate B cell clones specific for donor HLA; therefore, desensitized patients remain at an increased risk of antibody rebound if patients experience pro-inflammatory events. Therefore, ongoing antibody monitoring is crucial for early detection of antibody-mediated graft injury. Importantly, the results of numerous programs show that ABOi- and HLA-positive crossmatch renal transplantation, with proper desensitization, can be performed successfully. Further, in addition to increasing the rate of transplantation among sensitized patients, desensitization is providing insight into immunoregulatory processes and may provide information useful in diseases involving immune dysfunction.

Desensitization protocols and their outcome

In the last decade, transplantation across previously incompatible barriers has increasingly become popular because of organ donor shortage, availability of better methods of detecting and characterizing anti-HLA antibodies, ease of diagnosis, better understanding of antibody-mediated rejection, and the availability of effective regimens. This review summarizes all manuscripts published since the first publication in 2000 on desensitized patients and discusses clinical outcomes including acute and chronic antibody-mediated rejection rate, the new agents available, kidney paired exchange programs, and the future directions in sensitized patients. There were 21 studies published between 2000 and 2010, involving 725 patients with donor-specific anti-HLA antibodies (DSAs) who underwent kidney transplantation with different desensitization protocols. All studies were single center and retrospective. The patient and graft survival were 95% and 86%, respectively, at a 2-year median follow-up. Despite acceptable short-term patient and graft survivals, acute rejection rate was 36% and acute antibody-mediated rejection rate was 28%, which is significantly higher than in nonsensitized patients. Recent studies with longer follow-up of those patients raised concerns about long-term success of desensitization protocols. The studies utilizing protocol biopsies in desensitized patients also reported higher subclinical and chronic antibody-mediated rejection. An association between the strength of DSAs determined by median fluorescence intensity values of Luminex single-antigen beads and risk of rejection was observed. Two new agents, bortezomib, a proteasome inhibitor, and eculizumab, an anti-complement C5 antibody, were recently introduced to desensitization protocols. An alternative intervention is kidney paired exchange, which should be considered first for sensitized patients.

Intravenous immunoglobulin-based immunotherapy: an arsenal of possibilities for patients and science

The use of intravenous immunoglobulin (IVIG) concentrated from pooled healthy donors' plasma has gained increasing popularity. IVIG therapy has become important as a replacement therapy in primary and acquired humoral immunodeficiencies, and it has been extended to autoimmune, neurodegenerative and inflammatory conditions and transplantation therapy. Recurrent pregnancy failure and cancer are rather new platforms, where IVIG has shown its beneficial effects. This manuscript is focused on these two off-labelled usages. The immunomodulatory mechanisms of IVIG therapy appear as a coordinated orchestration of different functions, resulting in a synergistic effect. Treatment monitoring and detailed molecular analyses reveal how such treatments may interfere with disease pathogenesis. These finding may foster the development of novel therapeutic and/or preventive strategies. Studying this field with bidirectional bench-to-bedside and bedside-to-bench approaches fit well into 'the two-way road' paradigm of translational medicine.

Donor exchange programs in kidney transplantation: rationale and operational details from the north central donor exchange cooperative

The increasing need for kidney transplants has led to innovations such as donor exchange programs. These programs offer transplant recipients with incompatible donors an opportunity to receive a compatible kidney. They also provide an alternative to costly desensitization protocols that have unproven long-term outcomes. Donor exchange programs have multiple options, including simple 2-pair exchanges, more complicated domino exchanges, or chain donations. The United States currently is limited by regional programs that provide for kidney donor exchanges. However, with the increasing public interest in and need for kidney transplants, general nephrologists will be approached with questions about these donor exchange programs. The goal of this review is to discuss donor exchange programs, including their role in expanding the donor pool, various types of exchanges, regional centers that provide these programs, and the process involved in patient enrollment. General knowledge of donor exchange programs will help providers in discussing options with patients approaching end-stage kidney disease and transplant.

Effect of the proteasome inhibitor bortezomib on humoral immunity in two presensitized renal transplant candidates

BACKGROUND

Recipient presensitization represents a major hurdle to successful renal transplantation. Previous case series have suggested that the proteasome inhibitor bortezomib directly affects the alloantibody-secreting plasma cells in rejecting allograft recipients. However, the ability of this agent to desensitize nonimmunosuppressed transplant candidates before transplantation is currently unknown.

METHODS

In this analysis, two sensitized hemodialysis patients were selected to receive two subsequent bortezomib cycles. Bortezomib was given at 1.3 mg/m(2) on days 1, 4, 8, and 11. Dexamethasone was added to the second cycle to enhance treatment efficiency. Serial immune monitoring included cytotoxic panel reactive antibody testing, Luminex single antigen testing for anti-human leukocyte antigen (HLA) IgG with or without C4d-fixing capability, and ABO antibody detection.

RESULTS

During a half-year follow-up period, cytotoxic panel reactive antibody decreased from 87% to 80% (patient 1) and 37% to 13% (patient 2). Patient 1 showed a 40% reduction in binding intensities of identified Luminex HLA single antigen reactivities and, in parallel, slight reductions in ABO blood group antibody and total immunoglobulin levels. In patient 2, bortezomib did not affect circulating antibody levels in a meaningful way. Both patients showed a more than 50% reduction in the levels of anti-HLA antibody-triggered C4d deposition to Luminex beads.

CONCLUSION

Our initial experience suggests that, without additional immunosuppressive measures, bortezomib has modest effects on circulating antibodies against HLA or blood group antigens. The reduced levels of antibody-triggered complement fixation, however, imply potential clinical relevance of proteasome inhibition for recipient desensitization.

In vitro effects of everolimus and intravenous immunoglobulin on cell proliferation and apoptosis induction in the mixed lymphocyte reaction

Targeting multiple pathways in the activation of alloimmune responses by multi-drug immunosuppressive regimens with complementary mechanisms of action enhances allograft survival and improves quality of life, owing to the reduction of adverse drug effects. In this report we investigated the effect of the combination of everolimus and intraveneous immunoglobulin (IVIG) on cell proliferation and apoptosis induction in human two-way mixed lymphocyte reaction (MLR). Everolimus alone (0.1-50 ng/ml) and IVIG (1-10 mg/ml) alone inhibited cell proliferation in a dose-dependent manner (16.4-67.2% and 12.1-66.3% inhibition, respectively). The inhibition by everolimus was not enhanced in the presence of 1 mg/ml IVIG. Addition of 10 and 50 ng/ml everolimus increased the inhibitory effect of 5 and 10 mg/ml IVIG, but only by 10-27%. Addition of 0.1 and 1 ng/ml everolimus did not increase IVIG's inhibitory effects. Apoptosis was significantly higher in IVIG (5 mg/ml)-treated CD19+ cells and less so in CD3+ cells as assessed by Annexin V and TUNEL assays. However, everolimus (0.1-50 ng/ml) did not induced apoptosis or alter apoptosis induced by IVIG. These results suggest that everolimus is a potent inhibitor of immune cell proliferation but does not act additively or synergistically with IVIG when analyzed in this in vitro system.

Baseline donor-specific antibody levels and outcomes in positive crossmatch kidney transplantation

Renal transplant candidates with donor-specific alloantibody (DSA) have increased risk of antibody-mediated allograft injury. The goal of this study was to correlate the risk of antibody-mediated rejection (AMR), transplant glomerulopathy (TG) and graft survival with the baseline DSA level (prior to initiation of pretransplant conditioning). These analyses include 119 positive crossmatch (+XM) compared to 70 negative crossmatch (-XM) transplants performed between April 2000 and July 2007. Using a combination of cell-based crossmatch tests, DSA level was stratified into very high +XM, high +XM, low +XM and -XM groups. In +XM transplants, increasing DSA level was associated with increased risk for AMR (HR = 1.76 [1.51, 2.07], p = 0.0001) but not TG (p = 0.18). We found an increased risk for both early and late allograft loss associated with very high DSA (HR = 7.71 [2.95, 20.1], p = 0.0001). Although lower DSA recipients commonly developed AMR and TG, allograft survival was similar to that of -XM patients (p = 0.31). We conclude that the baseline DSA level correlates with risk of early and late alloantibody-mediated allograft injury. With current protocols, very high baseline DSA patients have high rates of AMR and poor long-term allograft survival highlighting the need for improved therapy for these candidates.

The use of immunoglobulin therapy for patients undergoing solid organ transplantation: an evidence-based practice guideline

This guideline for the use of immunoglobulin (IG) for sensitized patients undergoing solid organ transplantation (SOT) is an initiative of the Canadian Blood Services and the National Advisory Committee on Blood and Blood Products of Canada to (1) provide guidance for Canadian practitioners involved in the care of patients undergoing SOT and transfusion medicine specialists on the use of IG and (2) standardize care, limit adverse events, and optimize patient care. A systematic expert and bibliography literature search up to July 2008 was conducted, with 791 literature citations and 45 reports reviewed. To validate the recommendations, the guideline was sent to physicians involved in SOT in Canada and a patient representative. The recommendations identify (1) sensitized patients undergoing SOT that would have a better survival and decreased morbidity by receiving IG preoperatively, postoperatively, and for the treatment of organ rejection; (2) patients who may not have any benefit from receiving IG; and (3) potential adversities to IG.

Highly successful and low-cost desensitization regime for sensitized living donor renal transplant recipients

10-30% of dialysis population awaiting renal transplantation is sensitized. Present desensitization protocols use intravenous immune globulins, rituximab, and plasmapheresis in various combinations; however, these regimens are unaffordable by many in developing countries. We tried desensitization with mycophenolate mofetil and plasmapheresis. Methods. Patients with high PRA titre (> or =50%) or positive crossmatch (>10%) were treated with MMF for a month before proposed transplant and were given five sittings of plasmapheresis. Results. 11 of 12 patients had normalization of PRA/crossmatch with this regimen and were successfully transplanted. One patient lost the graft due to graft vein thrombosis, and two patients died within three months after transplant due to septicemia and pulmonary embolism, respectively, with a functioning graft. No patient, including the two who died, developed clinical rejection over a mean follow-up of 10 months (range 1-16 months). Mean serum creatinine at last follow up was 1.1 mg/dL (range 0.9-1.3 mg/dL). Conclusions. Though the number of patients studied is small, we feel that highly sensitized patients awaiting living donor renal transplant should be tried on this simple and cost-effective regime before transplant. The more aggressive and expensive approaches incorporating IVIg and rituximab should be used only if this relatively low-cost regime is unsuccessful.

Treatment with immunoglobulin improves outcome for pediatric liver transplant recipients

Immunoglobulin mitigates autoimmune disease and facilitates acceptance of ABO-incompatible transplanted organs. To test the hypothesis that treatment with immunoglobulin is associated with improved graft survival and a decreased rate of allograft rejection, a cohort study of primary liver transplant recipients in the Studies of Pediatric Liver Transplantation registry was performed. The outcomes of 336 pediatric liver transplant recipients who received immunoglobulin within 7 days of liver transplantation were compared with the outcomes of 1612 recipients who did not receive immunoglobulin. The outcome measures were patient survival, death-free graft survival, and allograft rejection. The Kaplan-Meier probability of patient survival was not different between patients treated with immunoglobulin and patients who did not receive immunoglobulin. Death-free graft survival was increased in patients treated with immunoglobulin (hazard ratio of death-free survival = 0.57, P = 0.014). The probability of allograft rejection at 3 months was 31% for patients treated with immunoglobulin versus 40% for patients who did not receive immunoglobulin (hazard ratio = 0.81, P = 0.02). The proportion of patients with 2 or more episodes of allograft rejection was lower in patients treated with immunoglobulin (13.1% with immunoglobulin versus 19.2% with no immunoglobulin, P = 0.009). Treatment with immunoglobulin was associated with a decreased risk for allograft rejection, whereas use of cyclosporine as the initial immunosuppression and transplantation before 2002 were independently associated with an increased risk of allograft rejection in pediatric liver transplantation recipients. A trend toward a decreased rate of retransplantation was detected in the population that received treatment with immunoglobulin.

Intravenous immunoglobulin preparations have no direct effect on B cell proliferation and immunoglobulin production

Intravenous immunoglobulin (IVIg) is used for treatment of a variety of immunological disorders and in transplantation. As one of its applications in transplantation is the reduction of donor specific antibodies in the circulation, we examined the direct effect of IVIg on essential parameters of human B cell responses in vitro. Purified human B cells, human B cell hybridomas and T cells were cultured in the presence of graded concentrations of IVIg to test its effect on their proliferative capacity. To address the effect of IVIg on immunoglobulin production, we designed a novel technique making use of quantitative polymerase chain reaction to assess IgM and IgG levels. IVIg failed to inhibit proliferation of human B cells and human B cell hybridomas. In contrast, when IVIg was added to T cell cultures, a dose-dependent reduction of the proliferative capacity was observed. IVIg did not affect the levels of IgM and IgG mRNA of activated B cells. Our data show that IVIg is not capable of directly inhibiting key B cell responses. Direct B cell inhibition by IVIg seems therefore unlikely, implying that alteration in humoral immunity by IVIg is due to indirect effects on T cells and/or interactions with circulating antibodies and complement factors.

Utility of virtual crossmatch in sensitized patients awaiting heart transplantation

BACKGROUND

Organ transplant candidates with serum antibodies directed against human leukocyte antigens (HLA) face longer waiting times and higher mortality while awaiting transplantation. This study examined the accuracy of virtual crossmatch, in which recipient HLA-specific antibodies, identified by solid-phase assays, are compared to the prospective donor HLA-type in heart transplantation.

METHODS

We examined the accuracy of virtual crossmatch in predicting immune compatibility of donors and recipients in heart transplantation and clinical outcomes in immunologically sensitized heart transplant recipients in whom virtual crossmatch was used in allograft allocation.

RESULTS

Based on analysis of 257 T-cell antihuman immunoglobulin complement-dependent cytotoxic (AHG-CDC) crossmatch tests, the positive predictive value of virtual crossmatch (the likelihood of an incompatible virtual crossmatch resulting in an incompatible T-cell CDC-AHG crossmatch) was 79%, and the negative predictive value of virtual crossmatch (the likelihood of a compatible virtual crossmatch resulting in a compatible T-cell CDC-AHG crossmatch) was 92%. When used in a cohort of 28 sensitized patients awaiting heart transplantation, 14 received allografts based on a compatible virtual crossmatch alone from donors in geographically distant locations. Compared with the other 14 sensitized patients who underwent transplant after a compatible prospective serologic crossmatch, the rejection rates and survival were similar.

CONCLUSION

Our findings are evidence of the accuracy of virtual crossmatch and its utility in augmenting the opportunities for transplantation of sensitized patients.

Defining High Risk in Adult Kidney Transplantation

Background

Because identifiable factors contribute to allograft loss, and because no consensus has been reached on the definition of high risk, an interdisciplinary group of nurses, physicians, pharmacists, and social workers was convened in May 2008.

Objective

Participants sought to reach consensus about the current state of science and best practices related to the definition and management of high-risk kidney transplant recipients.

Methods

An expert facilitator with extensive experience in leading consensus teams guided consensus-building activities, which included discussion and small-group work.

Results

This consensus group conceptualized the definition of the “high-risk” kidney transplant recipient and provided information to guide the multidisciplinary team in their assessment of these patients before and after transplant. Three key areas, which were conceptualized as independent scales, had a substantial impact on outcomes: (1) transplant recipient medical factors, (2) donor and recipient immunological factors, and (3) transplant recipient psychosocial factors. Though depicted separately, alteration of a specific risk on one scale could influence some risk factors on another scale. In addition, the kidney allograft itself must be considered in the assessment of high risk.

Conclusions

The continuum of risk described here should be useful to transplant clinicians in their assessment of high-risk adult kidney transplant patients, may aid centers in developing a more complete definition of high risk, and may lead to risk-reduction efforts.

Subclinical rejection in stable positive crossmatch kidney transplant patients: incidence and correlations

We reviewed 116 surveillance biopsies obtained approximately 1, 3, 6 and 12 months posttransplantation from 50 +XM live donor kidney transplant recipients to determine the frequency of subclinical cell-mediated rejection (CMR) and antibody-mediated rejection (AMR). Subclinical CMR was present in 39.7% of the biopsies at 1 month and >20% at all other time points. The presence of diffuse C4d on biopsies obtained at each time interval ranged from 20 to 30%. In every case, where histological and immunohistological findings were diagnostic for AMR, donor-specific antibody was found in the blood, challenging the long-held belief that low-level antibody could evade detection due to absorption on the graft. Among clinical factors, only recipient age was associated with subclinical CMR. Clinical factors associated with subclinical AMR were recipient age, positive cytotoxic crossmatch prior to desensitization and two mismatches of HLA DR 51, 52 and 53 alleles. Surveillance biopsies during the first year post-transplantation for these high-risk patients uncover clinically occult processes and phenotypes, which without intervention diminish allograft survival and function.

Hemoglobinuria and acute kidney injury requiring hemodialysis following intravenous immunoglobulin infusion

Intravenous immunoglobulin (IVIG), a product initially developed for patients with immunodeficiencies, now has multiple other indications and increasing off-label use. IVIG generally is well tolerated, with few adverse effects. Antibody-mediated (Coombs-positive) hemolysis is known to occur after IVIG infusion, but often is subclinical and previously has not been reported to lead to acute kidney injury (AKI). The predominantly known mechanism of AKI after IVIG infusion has been osmotic nephrosis, primarily associated with sucrose-containing formulations. We present a case of a bone marrow transplant recipient who was treated with a sucrose-free IVIG product and subsequently developed Coombs-positive hemolysis leading to AKI requiring hemodialysis, who ultimately died secondary to infectious complications. The severity of this case emphasizes the importance of identifying populations who may be at increased risk of pigment-mediated kidney injury before consideration of IVIG therapy.

Clinical relevance of pretransplant human leukocyte antigen donor-specific antibodies in renal patients waiting for a transplant: a risk factor

The use of highly sensitive solid-phase antibody detection assays, including x-MAP multiple bead-based technology (Luminex), has greatly enhanced our ability to accurately detect and define very low levels of HLA antibodies. These developments have led to patients having increasing lists of antibody specificities (which may not be clinically relevant), resulting in a new "technological barrier" to transplantation in sensitized patients. Alloantibodies play a major role in all types of solid organ rejection; the presence of low-titer donor-specific antigen (DSA) identified pretransplant is associated with an increased risk of antibody-mediated rejection (AMR). However, these low-titer antibodies do not represent an absolute contraindication to transplant. Improvement in the diagnosis and treatment of AMR will allow sensitized patients with DSA to be successfully transplanted in the short term, but extended follow-up is required to ensure acceptable long-term graft survival in this group. These factors must be integrated into the decision algorithms for immunosuppressive treatment in patients at immunologic risk.

Positive cross-match living donor kidney transplantation: longer-term outcomes

The long-term graft outcomes after positive cross-match (PXM) living donor kidney transplantation (LDKT) are unknown and the descriptive published data present short-medium term results. We conducted a retrospective cohort study of LDKT with PXM by flow cytometry performed at our center during February 1999 to October 2006, compared to a control group, matched 1:1 for age, sex, race, retransplantation and transplant year. The PXM group was treated with a course of plasmapheresis/low-dose intravenous immunoglobulin (IVIg) preoperatively, and OKT3 or thymoglobulin induction. Both groups (n = 41 each) were comparable except for duration of end-stage renal disease (ESRD), induction, HLA mismatch and panel-reactive antibody (PRA). During the period of up to 9 years, 14 PXM and 7 controls lost their grafts (p < 0.04). Graft survival rates at 1 and 5 years were 89.9% and 69.4% for PXM group and 97.6% and 80.6% for the controls, respectively. PXM was associated with higher risk of graft loss (HR 2.6, p = 0.04; 95%CI 1.03-6.4) (t(1/2)= 6.8 years), but not with patient survival (HR 1.96, p = 0.29; 95%CI 0.6-7.0) or 1-year serum creatinine (beta= 0.06, p = 0.59 for ln (SCr); 95% CI -0.16 to 0.28). These results suggest that despite the favorable short-term results of PXM LDKT after PP/IVIg conditioning, medium-long-term outcomes are notably worse than expected, perhaps comparable to non-ECD deceased donor kidney transplantation (KT).

Antibody-mediated rejection: treatment alternatives and outcomes

Over the past 10 years, thanks to the development of sensitive methods of antibody detection and markers of antibody injury such as C4d staining, the role of anti-human leukocyte antigen (HLA) and non-HLA alloantibodies as effectors of acute and chronic immune allograft injury has been revisited. Antibody-mediated rejection (AMR) defines all allograft rejection caused by antibodies directed against donor-specific HLA molecules, blood group antigen (ABO)-isoagglutinins, or endothelial cell antigens. Antibody-mediated rejection can be a recalcitrant process, resistant to therapy and carries an ominous prognosis to the graft. In concordance with these views, treatment protocols for AMR use permutations of a multiple-prong approach that include (1) the suppression of the T-cell dependent antibody response, (2) the removal of donor reactive antibody, (3) the blockade of the residual alloantibody, and (4) the depletion of naive and memory B-cells. Although all published protocols report a variable rate of success, a major weakness of all current protocols is the lack of effective anti-plasma cell agents. In comparison to acute AMR, the treatment for chronic AMR (CAMR) is not well characterized. Although in acute AMR large titers of pre-existent alloantibodies result in massive activation of the complement system and lytic injury of the graft endothelium, thereby requiring aggressive and fast removal of the offending agents, in CAMR, complement activation results in sublytic endothelial cell injury and activation. Although this type of injury results in chronic graft failure, its slow progression likely renders it amenable of suppression by heightening of maintenance immunosuppression and anti-idiotypic blockade of the circulating alloantibody without the need of plasma exchange. In this review, we will discuss the rationale behind the design of treatment protocols for acute AMR and CAMR as well as their reported results and complications.

Living donor kidney transplantation across positive crossmatch: the University of Illinois at Chicago experience

BACKGROUND

To increase living donation for kidney transplantation, we investigated desensitization of recipients with positive crossmatch against a potential living donor.

METHODS

Between June 2001 and March 2007, 57 consecutive sensitized candidates for kidney transplantation, with crossmatch positive potential living donors, were treated with various desensitization protocols. All patients received plasmapheresis every other day with intravenous immune globulin 100 mg/kg starting 1 week before the scheduled transplant. Postoperatively, the recipients continued to receive every other day plasmapheresis with intravenous immune globulin for the initial week. Immunosuppression therapy consisted of induction with thymoglobulin and a combination of tacrolimus, mycophenolate, and corticosteroids.

RESULTS

Six patients failed to convert with pretransplant immunomodulation and were not transplanted; 51 underwent live donor kidney transplant. Mean follow-up was 23 months and 36 patients have more than 1-year follow-up. One-year patient and graft survivals were 95% and 93%, respectively. There were 25 episodes of biopsy-proven or clinically presumed rejection in 22 patients in the first year. Of the 17 biopsy-proven episodes, 12 were antibody-mediated rejection and five were acute cellular rejection. Of the patients with antibody-mediated rejection (biopsy proven or empiric), two patients (12%) lost their graft by 1 year. The median modification of diet in renal disease at 6 and 12 months was 55 mL/min (range 9-104 mL/min) and 48 mL/min (range 8-99), respectively.

CONCLUSIONS

Despite increased rejection rates, graft and patient survivals indicate that desensitization of positive crossmatch patients is a reasonable alternative for a sensitized patient who could potentially wait 10 or more years for a suitable cadaveric kidney.

History of immunoglobulin replacement

The provision of antibodies to prevent and treat infection began with the application of "curative serum" in the first years of the last century. After the process of large-scale plasma fractionation was developed in the 1940s, the general use of immunoglobulin expanded. Intravenous immunoglobulin products became available in the 1970s, and their only use for the provision of antibodies governed the opinion of experts over the next decade. Modulation of inflammation and immunosuppression were introduced in treatment of inflammatory and autoimmune diseases and became accepted indications. The history of adverse events of treatment and their management are outlined in this article. Consensus indications and evidence-based off-label uses are discussed.

Acute antibody-mediated rejection after lung transplantation

The role of humoral immunity after lung transplantation remains unclear. In this report, we describe the pathologic findings and clinical course of a case of acute antibody-mediated rejection (AMR) after lung transplantation. After an uncomplicated early course, a 31-year-old man with cystic fibrosis developed acute graft dysfunction 1 month after bilateral lung transplantation. Lung biopsies showed acute pneumonitis with capillary injury, neutrophilic infiltration and nuclear dust. Immunostaining for C4d demonstrated endothelial cell deposition, and circulating donor-specific human leukocyte antigen (HLA) antibodies were identified. Despite severe hypoxemic respiratory failure, he responded well to a regimen consisting of methylprednisolone, plasma exchange, intravenous immunoglobulin and rituximab therapy. He completely recovered clinically although donor-specific HLA antibodies have remained detectable. The incidence of acute AMR after lung transplantation is unknown, but this case fulfills all of the consensus diagnostic criteria, and we suggest that AMR could be an under-recognized cause of acute graft dysfunction.

Successful deceased donor renal transplant in a sensitized pediatric recipient with the use of plasmapheresis

Sensitization following renal transplant is a significant barrier to repeat transplantation in children. We report a successful DD renal transplant, with the use of PP, in an 11-yr-old girl who became highly sensitized following a prior failed transplant. She received PP treatments after failure of high-dose IVIg (Gamimune). We established the effectiveness of PP by attaining a 0% PRA and negative cross-matches after five PP treatments. Subsequently, our patient underwent a second round of scheduled PP. When the PRA was 0%, unacceptable antigens were removed from the UNOS wait list, PP was continued, and a kidney became available within 10 days. The final flow cytometry cross-match with the eventual donor was negative. This success demonstrates that coordination of desensitization by PP and advanced laboratory monitoring techniques with recent policies regarding allocation of organs to pediatric patients provides new opportunities for children awaiting transplantation. Since the transplant, our patient sustained a low-titer increase of anti-HLA antibodies. However, she has had no episodes of acute rejection and has maintained excellent graft function more than 17 months later.

Renal transplantation in patients with positive lymphocytotoxicity crossmatches: one center's experience

BACKGROUND

Sensitization to human leukocyte antigens remains an important barrier to successful renal transplantation.

MATERIALS AND METHODS

Herein we describe our center's experience with a plasmapheresis-based desensitization protocol for highly sensitized patients. Twenty-nine patients had a positive T-cell or positive B-cell lymphocytotoxicity crossmatch against their donors. In some cases, baseline crossmatches were of high titer (e.g., 11 had baseline titers > or =1:32).

RESULTS

Twenty-eight of 29 patients were rendered T-cell crossmatch negative and B-cell crossmatch negative/low positive and transplanted. None had hyperacute rejection but 11 (39%) had acute antibody mediated rejection. Median follow-up is 22 months: 25 of the 28 (89%) of allografts are still functioning with mean plasma creatinine 1.5 mg/dL. There was one death because of the transplant or immunsuppression, one case of cytomegalovirus disease and no cases of lymphoproliferative disease.

CONCLUSION

This series provides further evidence of the high efficacy of plasmapheresis-based desensitization protocols. Even patients with high baseline crossmatch titers can be successfully desensitized and transplanted. Short- and medium-term outcomes are encouraging but longer-term data are needed.