B-Cell crossmatching and kidney allograft outcome in 9031 United States transplant recipients

Refractory CD20 Positive Cellular Rejection in Living Kidney Transplant: A Case Report and Review of Literature

Transplant is the optimal therapy for patients with end-stage renal disease. Acute cellular rejection refractory to treatment remains a major risk factor for graft loss and poor outcomes. In this study, we describe a 39-year-old man who received a living-related kidney transplant. Two days after transplant, the patient displayed acute deterioration of graft function. Conventional anti-rejection therapy was initiated, but graft function did not improve. Biopsy revealed acute cellular rejection (grade IIA), and C4d and HLA antibodies were negative. Immunohistochemistry phenotyping revealed clusters of CD20-positive lymphocytes, with 80% being CD3 positive. Rituximab was prescribed, and graft function improved dramatically. After 1 week, a second graft biopsy was done due to lagging of graft function, shown by serum creatinine of 2.1 mg/dL. Biopsy revealed regenerating acute tubular necrosis with disappearance of the CD20-positive lymphocyte cluster infiltrates. Two year, after transplant, the patient's graft function maintained stable. Phenotyping of the cellular infiltrate is important as it may lead to a proper selection of immunosuppression and consequent improvement of graft outcome.

An update on the impact of pre-transplant transfusions and allosensitization on time to renal transplant and on allograft survival

Background

Blood transfusions have the potential to improve graft survival, induce sensitization, and transmit infections. Current clinical practice is to minimize transfusions in renal transplantation candidates, but it is unclear if the evidence continues to support pre-transplant transfusion avoidance. Changes in the Medicare prospective payment system may increase transfusion rates. Thus there is a need to re-evaluate the literature to improve the management options for renal transplant candidates.

Methods

A review applying a systematic approach and conducted using MEDLINE^®, Embase^®, and the Cochrane Library for English-language publications (timeframe: 01/1984–03/2011) captured 180 studies and data from publically available registries and assessed the impact of transfusions on allosensitization and graft survival, and the impact of allosensitization on graft survival and wait time.

Results

Blood transfusions continued to be a major cause of allosensitization, with allosensitization associated with increased rejection and graft loss, and longer wait times to transplantation. Although older studies showed a beneficial effect of transfusion on graft survival, this benefit has largely disappeared in the post-cyclosporine era due to improved graft outcomes with current practice. Recent data suggested that it may be the donor-specific antibody component of allosensitization that carried the risk to graft outcomes.

Conclusions

Results of this review indicated that avoiding transfusions whenever possible is a sound management option that could prevent detrimental effects in patients awaiting kidney transplantation.

Poor kidney allograft survival associated with positive B cell - Only flow cytometry cross matches: a ten year single center study

The presence of donor specific antibody (DSA) to class 1 or class 2 HLA as detected respectively in T cell or B cell - only flow cytometry cross matches (FCXMs) are risk factors for renal allograft survival, though the comparative risk of these XMs has not been definitively established. Allograft survival and FCXM data in 624 microcytotoxicity (CDC) XM negative kidney transplants were evaluated. Short and long term allograft survival was significantly less in recipients with T(-) B(+) FCXMs (1 year, 74%, 10 year, 58%) compared to T(+) B(+) FCXMs (1 year, 84%, 10 year, 68%) and to T(-) B(-) FCXM (1 year, 90%, 10 year, 85%). Risk factors were positive FCXM, deceased donor (DD) transplantation and donor age, but not race, gender, recipient age or previous transplant. Recipients with T(-) B(+) and T(+) B(+) FCXMs were at 4.5 and 2.5 fold greater risk, respectively, of DD allograft failure compared to patients with T(-) B(-) FCXMs. The quantitative value of FCXM did not correlate with the duration of graft survival. We conclude that patients with DSA to class 2 HLA have a greater risk of early and late allograft failure compared to patients with DSA to class 1 HLA.

Combined liver-kidney transplants: allosensitization and recipient outcomes

BACKGROUND

A pretransplant positive crossmatch in combined liver kidney transplants (CLK) is not considered a contraindication based on the reported immunoprotection conferred by the liver allograft. However, antibody-mediated rejection of the kidney in CLK has been reported recently. This prompted our study to investigate the impact of presensitization on CLK recipient outcomes.

METHODS

We examined kidney allograft and patient survival by indication of sensitization using Scientific Registry of Transplant Recipients data on CLK performed from 1995 to 2008. We defined sensitization as panel reactive antibody (PRA) more than 10% or a positive T-cell crossmatch (TXM).

RESULTS

Among 2484 CLK recipients with available PRA or TXM information, 30% had positive TXM or PRA more than 10%. Among those with TXM information, 12% had a positive crossmatch (n=234). In univariate analyses, patient (P=0.002) and overall kidney graft survival (P=0.015) were significantly diminished among sensitized patients. Differences in patient survival translated to estimated half-lives of 10.3 years among nonsensitized recipients versus 7.8 years among sensitized recipients, In multivariable Cox models, allosensitization was independently associated with patient death (adjusted hazard ratio=1.22, 95% CI, 1.04-1.43) and overall kidney graft loss (adjusted hazard ratio=1.16, 95% CI, 1.00-1.36).

CONCLUSIONS

These results suggest a negative impact of presensitization on patient and overall renal allograft survival in CLK. Accordingly, presensitization may need to be considered in risk stratification and clinical management of CLK.

Desensitization for renal transplantation: depletion of donor-specific anti-HLA antibodies, preservation of memory antibodies, and clinical risks

Desensitization protocols reduce donor-specific anti-HLA antibodies (DSA) and enable renal transplantation in patients with a positive complement-dependent cytotoxic cross-match (CDC-CXM). The effect of this treatment on protective antibody and immunoglobulin levels is unknown. Thirteen patients with end-stage renal disease, DSA and positive CDC-CXM underwent desensitization. Sera collected pre- and post-transplantation were analysed for anti-tetanus and anti-pneumococcal antibodies, total immunoglobulin (Ig) levels and IgG subclasses and were compared to healthy controls and contemporaneous renal transplant recipients treated with standard immunosuppression alone. Ten patients developed negative CDC-CXM and enzyme-linked immunosorbent assay (ELISA) and underwent successful transplantation. Eight recipients achieved good graft function without antibody-mediated or late rejection, BK virus or cytomegalovirus infection. One patient had primary non-function due to recurrent oxalosis, and one patient with immediate graft function died from septicaemia. Seven recipients required post-operative transfusion and three developed septicaemia. DSA remained negative by ELISA at 12 months, but were detectable by Luminex(®) . Anti-tetanus and anti-pneumococcal antibodies, total Ig and IgG subclasses were below the normal range but comparable to levels in renal transplant recipients who had not undergone desensitization. Desensitization protocols effectively reduce DSA and allow successful transplantation. Post-operative bleeding and short-term infectious risk is increased. Protective antibody and serum immunoglobulin levels are relatively preserved.

Clinical significance of anti-HLA antibodies detected by Luminex: enhancing the interpretation of CDC-BXM and important post-transplantation monitoring tools

B-cell crossmatch (BXM) was originally introduced to increase the sensitivity to detect anti-HLA antibodies of conventional CDC crossmatch in renal transplantation. Newer techniques such as Luminex((R)) have greater sensitivity in detecting anti-HLA antibodies but have not been directly evaluated versus BXM. We discuss our experience with Luminex testing and the significance of donor-specific antibodies (DSA) defined by Luminex in three populations, as compared with the CDC crossmatch. In the general transplant population, Luminex-defined DSA were found in only one third of positive CDC-BXM and were associated with graft rejection. Luminex testing enhanced the interpretation of CDC-BXM and identified patients with clinically relevant BXM. In the highly sensitized transplant population, Luminex-defined DSA were found in two thirds of positive BXM and were a better predictor of graft rejection. Therefore, Luminex assays rather than CDC-BXM should be used to facilitate kidney allocation in highly sensitized patients. In the post-transplantation population, Luminex antibody monitoring for DSA was shown to be important, as it defined low-level de novo DSA that were associated with development of transplant glomerulopathy and a significant predictor of graft loss in those patients. Thus Luminex testing facilitated the interpretation of CDC-BXM and provided a useful predictive tool for the detection of clinically significant DSA in post-transplantation antibody monitoring.

Back to the future: application of contemporary technology to long-standing questions about the clinical relevance of human leukocyte antigen-specific alloantibodies in renal transplantation

Luminex technology allows the accurate identification of human leukocyte antigen (HLA) class I and class II-specific antibodies at levels below the threshold detectable by either conventional complement-dependent lymphocytotoxicity or flow cytometry. The technology enables the analysis of complex antibody profiles in sensitized patients and gives improved definition of acceptable and unacceptable HLA specificities to guide donor kidney allocation. This helps to facilitate virtual cross-matching and avoid inappropriate shipping of kidneys for incompatible patients in distant centers. Luminex allows the cause of a positive cross-match test to be determined in a clinically relevant time scale and, when used in conjunction with lymphocytotoxic and flow cytometric cross-matching, it provides an assessment of the level of immunological risk in patients being considered as potential recipients for a particular donor kidney. Information is now emerging to enable the full clinical potential of Luminex to be realized.

Analysis of positive kidney, heart, and liver transplant crossmatches reported to the Collaborative Transplant Study

The relationship of positive lymphocytotoxic T-cell and B-cell crossmatches as well as that of flow-cytometric crossmatches with transplant survival was analyzed in kidney, heart, and liver transplants from deceased donors reported to the international Collaborative Transplant Study. High rates of hyperacute rejection were not observed with any type of crossmatch test or type of organ transplant, probably because immunosuppressive treatment has improved. Positive lymphocytotoxic T-cell crossmatches were associated with significantly decreased graft survival in first kidney transplants performed from 1990 to 1999, but not from 2000 to 2007, in kidney retransplants regardless of transplant period and in heart and liver transplants. Positive B-cell crossmatches were associated with significantly decreased kidney and heart transplant survival. It is concluded that a positive lymphocytotoxic crossmatch continues to indicate an increased risk of graft loss and that pretransplantation crossmatches should be performed regardless of type of organ transplanted.

[Transplantation strategies in immunized and hyperimmunized patients]

The rate of access to transplantation of hyperimmunized patients has improved thanks to a modification of the organ allocation rule in 2002 and the initiation of the Acceptable Mismatch program. Transplantation of immunized patients must be now preceded by a fine description of the characteristics of pretransplantation immunization using sensitive techniques and by an indispensable clinical and biological discussion to choose the best transplantation strategy, taking into account the risk/benefit balance for the patient of each strategy. Whichever transplantation strategy is adopted, immunosuppression should be adapted to the immunological status of the patient, often using the new therapeutic strategies (IVIg, rituximab, plasma exchange) with a specific follow-up, notably for anti-HLA antibodies, checking their evolution post treatment.

Anti-HLA donor-specific antibodies detected in positive B-cell crossmatches by Luminex predict late graft loss

The significance of B-cell crossmatching in kidney transplantation is controversial. Recipients (n = 471) transplanted in a single centre from 1987 to 2005 with complete T- and B-cell crossmatch records were studied. Sera from 83 patients transplanted across a positive B-cell crossmatch, with concomitant negative T-cell crossmatch (T-B+) on either current and/or peak sera were studied using Luminex to determine presence of donor-specific antibodies (DSA). Clinical outcomes of T-B+ patients were compared with 386 T-B- patients. T-B+ predicted vascular (p = 0.01), but not cellular (p = 0.82) or glomerular (p = 0.14) rejection. IgG HLA DSA were found in 33% (n = 27) of the T-B+ patients and were associated with higher risk of any (p = 0.047), vascular (p = 0.01) or glomerular (p < 0.001) rejection at 6 months. Of 27 patients with DSA, 18/21 (86%) were the complement-fixing IgG(1) and/or IgG(3) subclass antibodies. DSA imposed a statistically significant higher risk of graft loss 5 years posttransplant (1.8 [1.0-3.3], p = 0.045). This study showed that only one-third of positive B-cell crossmatch (BXM) was caused by DSA and was associated with late graft loss. Thus, using BXM to preclude kidney transplantation may potentially disadvantage >60% of patients in whom BXM is not indicative of the presence of DSA.

Retransplant candidates have donor-specific antibodies that react with structurally defined HLA-DR,DQ,DP epitopes

This report describes a detailed analysis how donor-specific HLA class II epitope mismatching affects antibody reactivity patterns in 75 solid organ transplant recipients with an in situ allograft and who were considered for retransplantation. Sera were tested for antibodies in a sensitive antigen-binding assay (Luminex) with single class II alleles. Their reactivity was analyzed with HLAMatchmaker, a structural matching algorithm that considers so-called eplets to define epitopes recognized by antibodies. Only 24% of the patients showed donor-specific anti-DRB1 antibodies and there was a significant correlation with a low number of mismatched DRB1 eplets. This low detection rate of anti-DRB1 antibodies may also be due to allograft absorption. In contrast, antibodies to DRB3/4/5 mismatches were more common. Especially, 83% of the DRB4 (DR53) mismatches resulted in detectable antibodies against an eplet uniquely found on DR53 antigens. Donor-specific DQB mismatches led to detectable anti-DQB antibodies with a frequency of 87%. Their specificity correlated with eplets uniquely found on DQ1-4. The incidence of antibodies induced by 2-digit DQA mismatches was 64% and several eplets appeared to play a dominant role. These findings suggest that both alpha and beta chains of HLA-DQ heterodimers have immunogenic epitopes that can elicit specific antibodies. About one-third of the sera had anti-DP antibodies; they reacted primarily with two DPB eplets and an allelic pair of DPA eplets. These data demonstrate that HLA class II reactive sera display distinct specificity patterns associated with structurally defined epitopes on different HLA-D alleles.

Re-exposure to mismatched HLA class I is a significant risk factor for graft loss: multivariable analysis of 259 kidney retransplants

BACKGROUND

Kidney retransplants carry increased immunologic risk. One possible contributor to this risk may be re-exposure to human leukocyte antigens (HLA) common to a previous donor but foreign to the recipient. Conflicting publications have assessed this risk, so to examine our experience 259 kidney retransplants were analyzed.

METHODS

A retrospective cohort of retransplant patients from 1973 to 2005 with minimum 12 months follow up was examined. Using multivariable modeling, important confounders were controlled for identifying factors significantly affecting graft survival.

RESULTS

Re-exposure to HLA class I (HLA-A or B) antigens, peak panel reactive antibodies and donor source were the most important determinants of allograft survival, despite a negative conventional or anti-human globulin-augmented T cell crossmatch. We failed to demonstrate that recipient re-exposure to HLA class II (HLA-DR) or positive B cell crossmatch were associated with adverse outcomes. Sample size and molecular versus serologic methods may have influenced the former, while inability to determine antibody specificities may have influenced the latter. Controlling for other variables, the adjusted risk of graft loss associated with re-exposure to HLA class I increased by 71% (P=0.006) and occurred early, consistent with recall of memory cytotoxic T lymphocyte or antibody responses.

CONCLUSIONS

Kidney recipients re-exposed to mismatched HLA class I antigens appear to be at heightened risk of early graft loss. Such patients may benefit from pretransplant identification of donor specific antibodies using solid phase methods and heightened vigilance for acute rejection. Future studies may indicate whether more intensive immunosuppression for these patients is warranted.

Options for immunologic support of renal transplantation through the HLA and immunology laboratories

HLA and immunology laboratories are an integral part of clinical kidney transplant programs. They assist transplant clinicians with evaluating the immunological suitability of potential recipients for transplantation and selecting donor-recipient combinations with a low risk of immunological failure. With sophisticated new techniques becoming available for posttransplant immunological monitoring, laboratories play an increasing supporting role during posttransplant follow up. The level of precision at which immunological testing predicts clinical outcome, however, leaves room for improvement. In this article, we summarize the current state of diagnostics, discuss problems, and point out promising developments.

Kidney transplantation in patients with antibodies against donor HLA class II

The immunologic risk associated with donor-specific antibodies (DSA) against Class II human leukocyte antigens (HLA) in kidney transplant (KTx) recipients is unclear. The aim of this study was to determine the outcome of KTx when DSA was detected only against HLA Class II. To isolate the impact of anti-Class II DSA, we retrospectively analyzed 12 KTx recipients who at baseline had a positive B-cell flow cytometric crossmatch (FXM) and a negative T-cell FXM. Using alloantibody specification analysis, 58.3% (7/12) had DSA against donor Class II and 41.7% had no demonstrable DSA. Biopsy-proven AMR occurred in 57% (4/7) in the Class II(+) group and 0% in the Class II(-) group (p > 0.05). Peritubular capillaries stained positive for C4d in 86% (6/7) of the Class II(+) patients and in 40% (2/5) of the Class II(-) patients (p > 0.05). One patient in the Class II(+) group lost their graft at 3 months to accelerated transplant glomerulopathy, while all other grafts were functioning 3-37 months posttransplant despite the persistence of anti-Class II DSA. We conclude that KTx recipients with clearly defined anti-Class II DSA are at risk for humoral rejection suggesting that desensitization and/or close posttransplant monitoring may be needed to prevent AMR.

Renal graft survival is not influenced by a positive flow B-cell crossmatch

INTRODUCTION

The influence of a positive B-cell crossmatch on graft outcome in renal transplantation is controversial.

METHODS

We analyzed graft survival using Kaplan-Meier estimates for recipients of deceased donor kidneys who were either regraft transplant patients (n = 198) from 1990 to August 20, 2004, or primary transplant patients (n = 361) from December 15, 2000 to August 8, 2004, each of whom had a flow T- and B-cell IgG crossmatch performed before transplantation. The flow B-cell crossmatch (FBXM) was not used to decide whether or not to transplant. Graft survival was analyzed by whether the patient's FBXM was positive or negative. We also evaluated creatinine levels and graft survival of 131 transplant patients (June 1, 2004 to July 1, 2005) by their FBXM result and by their HLA class II flow-defined IgG PRA.

RESULTS

One- and three-yr graft survival for the primary transplant patient group with a positive FBXM (98% and 84%) was not significantly different from the group with a negative FBXM (96% and 93%) (log-rank = 0.9). Similarly, graft survival at one, five, and 10 yr for the regraft transplant group whose FBXM was positive (91%, 76%, and 61%) was not significantly different from the group whose FBXM was negative (91%, 79%, and 77%) (log-rank = 0.4). Creatinine levels in the group of patients whose FBXM was positive (1.4 +/- 0.4 mg/dL; n = 76) were not significantly different from the group with a negative FBXM (1.4 +/- 0.4 mg/dL; n = 42). Even in the presence of class II PRA, a positive FBXM did not impact a patient's creatinine levels or graft outcome.

CONCLUSION

Neither short nor long-term graft survival of deceased donor kidneys is influenced by a positive flow B-cell IgG crossmatch, even when caused by HLA class II antibody.

HLAMatchmaker: a molecularly based algorithm for histocompatibility determination. V. Eplet matching for HLA-DR, HLA-DQ, and HLA-DP

This report describes the design of the eplet version of HLAMatchmaker to determine class II compatibility at the structural level. This matching algorithm is based on the hypothesis, developed from molecular modeling of crystallized antigen-antibody complexes, that functional epitopes are represented by patches of surface-exposed nonself-amino acid residues surrounded by residues within a 3-A radius. Patch determinations with a molecular viewer of crystalline structural models downloaded from the Entrez Molecular Modeling Database Web site led to the identification of 44 DRB, 33DQB, 29 DQA, 20 DPB, and 9 DPA unique combinations of polymorphic positions. The residue compositions of these patches were then determined from amino acid sequences. This analysis resulted in a repertoire of 146 DRB, 74 DQB, 58 DQA, 45 DPB, and 19 DPA eplets. In many eplets, the residues are in short linear sequences, but many other eplets have discontinuous sequences of residues that cluster on or near the molecular surface. This analysis has also shown that all serologically defined DR and DQ antigens detectable by monospecific antibodies have unique eplets. Other eplets are present in groups of class II antigens, many of which appear as cross-reacting. The eplet version of HLAMatchmaker should be considered as a hypothetical model for the structural assessment of donor-recipient compatibility and the determination of mismatch acceptability for sensitized patients. This computer algorithm can be downloaded from the HLA Matchmaker Webside at http://tpis.upmc.edu.

A significant role for histocompatibility in human islet transplantation

BACKGROUND

In recent years, transplantation of islets and pancreas has become a viable option for patients debilitated with type I diabetes. The success of islet transplantation has been attributed to the ability to isolate high quality islets for transplantation and capacity to maintain the recipient's immunosuppressive levels within a specific target range following transplantation. The purpose of this study was to determine the role of pretransplant sensitization to human leukocyte antigen (HLA) in islet transplantation.

METHODS

We retrospectively analyzed seven patients that were transplanted with islets under the auspices of the Juvenile Diabetes Research Foundation and Islet Cell Resource Center/National Institutes of Health. Humoral sensitization towards donor antigens both prior to and following islet transplantation was detected by FLOW panel reactive antibodies (PRA) and donor-specific cellular sensitization was detected by performing enzyme-linked immunospot assay analysis for cytokines interferon-gamma and interleukin-2.

RESULTS

Our analysis demonstrates that humoral and cellular sensitization to histocompatibility antigens prior to and after islet transplantation are associated with the failure of transplanted islets

CONCLUSION

Patient selection based on sensitization to donor HLA may be one of the factors crucial for the success of islet transplant. Further, in some patients, rejection of islets can be associated with sensitization to mismatched donor histocompatibility antigens.

Alloantibodies and the outcome of cadaver kidney allografts

The role of humoral immunity in causing antibody-mediated rejection (AMR) of organ allografts has been extensively documented. For this reason, negative complement-dependent cytotoxicity (CDC) cross-matches between recipient sera and donor T and B lymphocytes have become a mandatory requirement for cadaveric kidney transplantation. However, the significance of donor-specific antibodies (DSAs) detectable only by flow cytometry (FC) or solid phase assays (SPA) but not CDC is still controversial. We have performed a retrospective analysis of FC cross-matching results in 80 consecutive cadaver kidney allograft recipients. Antibodies against HLA class I and class II antigens were measured by CDC and SPA in sequential samples of sera obtained prior to transplantation. The preoperative cross-match was performed by CDC using magnetically sorted T and B cells from donor spleen. Sera obtained from each patient before and at the time of transplantation were included in the final cross-match. The sample of serum obtained at the time of transplantation was cross-matched retrospectively by FC and analyzed for anti-HLA antibody specificity on high resolution SPA. The actuarial kidney allograft survival at one year was 98%. Two of these eighty patients lost the graft, one due to AMR, the other for reasons unrelated to DSAs. Donor-specific antibodies were detected by FC in 17 of 80 patients, yet only 6 of 17 had an early episode of AMR. This episode was successfully reversed by desensitization therapy using intravenous immunoglobin (IVIG) and plasmapheresis. Flow cytomery cross-matching showed 95% specificity but only 35% sensitivity for prediction of AMR (p = 0.002). There was a significant correlation between high panel reactive antibodies (PRA) and positive FC cross-matching (p = 0 .0001), as well as high PRA and AMR (p = 0.0004 by CDC and 0.0011 by Luminex). Reversible AMR occurred 12-30 days post-transplantation in 8 patients. Of these 8 patients, 3 had no detectable DSAs in spite of C4d positivity, 4 had C4d deposition in conjunction with anti-HLA antibodies, and 1 patient had DSAs (anti-MICA) yet no C4d deposition. We conclude that early initiation of desensitization protocols can prevent transplant failure and that retrospective FC cross-matches may facilitate the diagnosis of AMR. Extensive analysis of patients' sera using a comprehensive set of tests may contribute to early treatment and better understanding of the mechanism underlying humoral rejection.

Transplantation across previously incompatible immunological barriers

This article reviews recent advances, which allow the transplantation across or around previously incompatible immunological barriers such as a positive crossmatch or ABO blood group incompatibility.

Immunoglobulin G–Positive in B-Cell Cross-Match Decreases Kidney Allograft Survival

We retrospectively studied all 1149 transplants performed at our center between 1993 and 2003 to determine the incidence and clinical effect of pretransplant B-positive cross-match on kidney graft survival. The patients were divided in two groups: B-negative (n = 1102) and B-positive in current sera (n = 47; 4.1%). AB-positive test was more frequent among regrafted patients (14% vs 3%; P = .00). Demographic data were not different between the groups. The overall rate of graft loss was similar (26% vs 24%, respectively; P = .86). However, early nonsurgical graft losses were more frequent among B-positive patients (46% vs 20%, respectively; P = .04). IgM was the most frequent immunoglobulin in the B-positive group (76% IgM and 24% IgG). There was no significant difference between B-negative and B-positive groups in the 1-, 5-, and 10-year graft survival rates (87% vs 83%, 73% vs 78%, 64% vs 66%, respectively; P = .87). The graft survival was significantly reduced comparing an IgG anti-B cell to the B-negative group (P = .03) as well as IgG compared to IgM (P = .004). In conclusion, only B-positive cross-match due to IgG decreased graft survival. Even though it is an uncommon situation (0.9%), this study stressed the clinical value of the B-cell cross-match as a tool to identify patients with a higher immunological risk.

Intravenous Immunoglobulin Induction Treatment in Flow Cytometry Cross-Match—Positive Kidney Transplant Recipients

Many recent studies have demonstrated increased acute humoral, cellular, subclinical, or chronic rejection, and decreased allograft survival in flow cytometry cross-match-positive kidney transplant recipients. The use of newer techniques and more sensitive of enzyme-linked immunosorbent assay (ELISA) or Flow Beads (microparticle based methods), donor-specific anti-human leukocyte antigen (HLA) antibodies have been detected in these immunologically high-risk patients. Intravenous immunoglobulin (IVIG) has immunomodulatory effects and has been demonstrated to downregulate anti-HLA antibodies in highly sensitized dialysis patients awaiting transplantation. Our initial studies demonstrate that IVIG induction treatment is promising in flow cytometry cross-match-positive kidney transplant recipients, and thus, those patients should not be excluded from receiving transplantation despite a positive flow cytometry cross match. Further studies with long-term follow-up are required to determine the effective dose and duration of IVIG treatment, and additional studies are needed to determine the most accurate tests for risk stratification.

A prospective 3-yr evaluation of tacrolimus-based immunosuppressive therapy in immunological high risk renal allograft recipients

BACKGROUND

There have been no published data on use of the the newer immunosuppressants tacrolimus and mycophenolate mofetil (MMF) in high immunological risk renal transplantation. We therefore undertook a prospective study to systematically assess outcomes using these agents as part of an aggressive immunosuppressive regimen.

METHODS

Fifty-nine high-risk renal allograft recipients were enrolled at 10 Canadian sites and given a regimen of: a biological induction agent, tacrolimus, MMF, and corticosteroids. Patients included 10 (17%) who had lost a previous graft to rejection <1 yr, 31 (53%) with a current panel reactive antibody (PRA) >30%, 47 (80%) with a historic PRA >50%, four (7%) who had a positive historical T-cell crossmatch with the current donor, and six (10%) with a current positive B-cell crossmatch. The mean peak PRA was 76 +/- 33%.

RESULTS

The estimated 3-yr Kaplan-Meier patient and graft survival estimates were 89% and 75%, respectively. There were nine graft losses other than deaths with a functioning graft, of which six were preceded by delayed graft function (p = 0.01, chi2). Sixteen (27%) recipients experienced at least one episode of biopsy-confirmed acute rejection. Infections included cytomegalovirus in 16 patients, eight of whom had tissue-invasive disease. Only one malignancy occurred.

CONCLUSIONS

The immunosuppressive strategy investigated is effective and displays a satisfactory safety profile in high immunological risk renal allograft recipients.

Refractory acute kidney transplant rejection with CD20 graft infiltrates and successful therapy with rituximab

Acute rejection is an expected event after transplantation and has been associated with poor long-term kidney transplant outcome. The presence of B cells in the kidney graft with acute rejection is thought to be an omnious sign, as it has been associated with poor graft outcome. There is no definitive treatment for acute rejection with B cells in the graft. Rituximab, a humanized monoclonal antibody against CD20, has been used in the treatment of B cell lymphoma. We present the case of a 49-yr-old Caucasian male with early acute kidney allograft rejection that was refractory to high doses of steroids and rabbit anti-thymocyte globulin (thymoglobulin). Repeat renal biopsy revealed T cell and B cells in the kidney graft and responded to the combination of rituximab and muromonab (a mouse monoclonal antibody to CD3 receptor). Over 9 months post-transplant, the patient remains rejection free with a serum creatinine of 1.7 mg/dL.

Transplanting patients with a positive donor-specific crossmatch: a single center's perspective

An increasing number of individuals with end-stage renal disease have become sensitized to human leukocyte antigens (HLA). Sensitization can have a profound impact on the likelihood of obtaining a requisite negative crossmatch (-XM) with a potential donor. Technologic breakthroughs in our ability to diagnose antibody-mediated rejection (AMR) and monitor anti-HLA antibodies has set the stage for a renascence in the understanding and treatment of individuals who harbor donor-specific antibody (DSA). Promising early results from single institutions that have developed preconditioning protocols allowing successful transplantation of XM (+) patients have encouraged other centers to adopt these protocols. Sensitized patients represent a great challenge for the clinician and there is much that remains unknown about the assessment and treatment of these patients. We have successfully preconditioned and transplanted more than 80 patients over a 5-yr period. As our understanding of these patients has increased, we have progressed from a 'one size fits all' approach to therapy to more rational, individualized treatment plans that take into account the varying immunologic risk that each patient possesses. In this article we have summarized our evolving experience with the assessment, treatment, transplantation, and monitoring of patients who undergo preconditioning for a (+) XM with a live donor.

ATG induction is associated with an increase in anti-HLA antibodies after kidney transplantation

Anti-human histocompatibility antigen antibodies (HLA-Ab) are deleterious after kidney transplant and may be increased after T-cell depleting agents are given. A retrospective case control study was conducted to evaluate increase in HLA-Ab in 27 kidney transplant recipients who had received antithymocyte globulin (ATG) induction compared with 27 control subjects. A greater than 10% increase in class I or class II HLA-Ab was found in 6 (22.2%) of ATG subjects versus only 1 (3.7%) of non-ATG subjects (p = 0.05). In females, 6/14 ATG subjects developed increased HLA-Ab > or =10% compared with none of the control subjects (p = 0.016). In sensitized subjects, 4/10 in the ATG group developed increased HLA-Ab > or =10% versus none of the controls (p = 0.043). There was no difference in number or severity of acute rejection episodes or estimated glomerular filtration rate 6 months after transplant between the two treatment groups. We conclude that ATG induction may result in increased posttransplant HLA-Ab, particularly in subjects at higher immunologic risk. Further studies are necessary to determine the natural history, clinical consequences, appropriate therapy, and mechanisms responsible for HLA-Ab in this setting.

Weak humoral posttransplant alloresponse after a well-HLA-matched cadaveric kidney transplantation

BACKGROUND

Screening of donor-specific antibodies or alloantibodies after kidney transplantation has not been performed routinely. The aim of this study was to evaluate the humoral antidonor and alloresponse of immunologically low-risk recipients of cadaveric renal allografts during the first posttransplant year.

METHODS

Alloresponse against the donor was analyzed by means of T-cell immunoglobulin (Ig)G and IgM and B cell IgG flow cytometric crossmatch (FCXM) tests with sera from days 0, 21, 90, and 365 posttransplant. In addition, panel reactive anti-human leukocyte antigen (HLA) class I and class II antibodies (PRA I and PRA II) were analyzed using flow cytometric methods. The recipients were treated either with a low initial cyclosporine regimen with single-bolus antithymocyte globulin (ATG) or basiliximab induction or conventional cyclosporine triple therapy.

RESULTS

No significant posttransplant anti-HLA class I or class II sensitization was found in the recipients as a whole. Recipients receiving a single-bolus ATG showed significantly higher proportion of PRA I positivity in the day 21 sample compared with the other groups. Flow cytometric donor-specific T- and B-cell IgG alloresponses remained low, but the proportion of T-cell IgM crossmatch-positive recipients increased during the study. Positive T-cell IgM FCXM was found to be associated with acute rejection episodes and cytomegalovirus (CMV) infections.

CONCLUSIONS

In immunologically low-risk kidney-graft recipients, positive T-cell IgM FCXM at transplantation was found to be a risk factor for rejection episodes. Conversion of T-cell IgM FCXM to positive was found to be associated with CMV infections.

Intravenous immunoglobulin and thymoglobulin facilitate kidney transplantation in complement-dependent cytotoxicity B-cell and flow cytometry T- or B-cell crossmatch-positive patients

BACKGROUND

The aim of this study was to investigate the effect of Thymoglobulin and intravenous immunoglobulin (i.v.IG) therapy on the clinical outcome of a putatively high-risk group of kidney transplant recipients who have positive B-cell complement-dependent cytotoxicity (CDC) along with positive T- or B-cell flow cytometry (FC) crossmatch results.

METHODS

We prospectively studied the effects of i.v.IG and Thymoglobulin induction treatment in B-cell CDC, and T- or B-cell FC crossmatch-positive kidney transplant recipients (seven women and one man; mean age, 43+/-12 years).

RESULTS

Mean peak panel-reactive antibody (PRA) was 47+/-32. Three patients had donor-specific antibody by flow PRA (two anti-DR4 and one anti-A2). Each recipient received induction treatment with i.v.IG 100 mg/kg for 3 days and Thymoglobulin 1.5 mg/kg for 5 days after transplantation. No acute cellular rejections occurred during a median follow-up of 15 months (range, 12-17 months). Only one acute humoral rejection occurred 8 days after transplantation, which responded to plasmapheresis, i.v.IG, and rituximab. One allograft was lost because of polyoma nephritis. Patient survival was 100% and allograft survival was 88%.

CONCLUSION

Our results indicate that i.v.IG and Thymoglobulin induction treatment may facilitate kidney transplantation in B-cell CDC and T- or B-cell FC crossmatch-positive patients.

Humoral theory of transplantation

According to the humoral theory of transplantation, antibodies cause allograft rejection. Publications are cited showing that antibodies: (1). cause hyperacute kidney rejection, (2). lead to C4d deposits associated with early kidney graft failures, (3). are a good indicator of presensitization leading to early acute rejections, (4). were present in 96% of 826 patients who rejected a kidney graft, (5). are associated with chronic rejection in 33 studies of kidney, heart, lung and liver grafts, and (6). in three studies, appeared in the circulation BEFORE evidence of bronchiolitis obliterans in lung transplants, and BEFORE kidney rejection. In addition, a prospective cooperative study of 1629 patients in 24 centers demonstrated that antibodies foretold subsequent failures after a follow-up period of 6 months (p = 0.05). The specificity of antibodies detected in the serum of rejecting patients were often not donor specific, presumably because they were absorbed by the rejecting organ. If the humoral theory is accepted, even provisionally, transplanted patients who have antibodies could be treated with immunosuppression until the antibodies disappear to determine whether chronic rejection can be blocked. If successful, in patients who do not have antibodies, immunosuppression could be reduced until antibodies appear.