Relationship of donor-specific class-I anti-HLA antibodies detected by ELISA after kidney transplantation on the development of acute rejection and graft survival

TNF-α -308A/G SNP association with kidney allograft rejection in Algerian population: A retrospective case-control study

No consensus has been reached regarding the association beween the -308A/G single nucleotide polymorphism (SNP) in the tumor necrosis factor-α gene (TNFA) and kidney allograft rejection (KAR). Our retrospective case-control study aimed to assess the association of the SNP with KAR in Algerian patients who underwent kidney transplantation. The study enrolled 313 Algerian patients: 58 kidney-transplant recipients without rejection events (PWoR); 58 kidney-transplant recipients with at least one rejection event, with or without graft loss (PWR); and 197 healthy individuals (HI). The TNFA -308A/G SNP was genotyped using a real-time polymerase chain reaction. The results demonstrated that, the frequencies of TNFA -308A allele and AA genotype were higher in the PWR than in the HI groups (p = 0.001, OR = 2.26, CI = 1.33-3.77 and p = 0.0004, OR = 5.53, CI-1.89-16.6, respectively). Furthermore, the frequencies were higher among the PWR than among the PWoR groups (p = 0.001, OR = 3.29, CI = 1.56-7.21 and p = 0.0006, OR = 28.26, CI = 1.62-493.2, respectively), particularly among PWR patients with de novo anti-human leukocyte antigens (HLA) antibodies (PG-a-HLA-Ab). However, the frequency of TNFA -308G allele was lower in the PWR group than in the PWoR group (p = 0.001, OR = 0.3, CI = 0.1-0.64) and the HI group (p = 0.001, OR = 0.44, CI = 0.27-0.44). Our results suggest an association of the TNFA -308A/G alleles with KAR in Algerian patients who underwent kidney transplantation. Carriers of TNFA -308A allele who have PG-a-HLA-Ab might have a higher risk, whereas TNFA -308G allele carriers could have a lower risk of KAR. Thus, therapeutic strategies can be adapted to minimize KAR risk in patients who have a genetic proclivity for increased pro-inflammatory TNF-α activity.

Association Between HLA Antibodies and Different Sensitization Events in Renal Transplant Candidates

BACKGROUND

Human leukocyte antigen (HLA) allo-immunization is caused by various events such as blood transfusions, pregnancies, or organ transplantations, which can lead to sensitization. In this retrospective study, we evaluated different sensitization models and their effects on panel-reactive antibody (PRA) profiles of renal transplantation candidates.

METHODS

Anti-HLA class I/II antibody screening tests were performed in 906 renal transplantation candidates with the use of a microbead-based assay (Luminex).

RESULTS

Two hundred ninety-seven (32.8%) of the patients were determined as positive in terms of PRA, and 609 (67.2%) were negative. Sensitized and non-sensitized patients were compared separately in terms of each sensitization type. The anti-HLA class I, II, and I+II positivity rates in patients sensitized only by blood transfusion were 13.1%, 6.3%, and 14.1%, the rates with pregnancy sensitization were 35.5%, 29%, and 45.2%, and rates with previous transplantation sensitization were 15.6%, 34.4%, and 38.9%, respectively. Prevalence of PRA positivity was significantly higher in patients with previous pregnancy than with transplantation and transfusion (odds ratio, 1.003; 95% confidence interval, 0.441-2.281; P = .031). The risk of developing HLA class I antibodies was higher in pregnancies (P < .001), and the risk of developing anti-HLA class II antibodies was higher in patients who had undergone a previous transplantation (P < .001). The rate of developing HLA-B antibodies in patients sensitized by pregnancy were significantly higher compared with sensitization after transfusion (P = .015), as was the rate of developing HLA-DQ antibodies in patients sensitized by previous transplantation compared with sensitization through pregnancy (P = .042).

CONCLUSIONS

In patients who are waiting for kidney transplantation, sensitization by pregnancy and transplantation have a significant impact on development of HLA class I and class II antibodies.

Detection of HLA Antibodies in Organ Transplant Recipients - Triumphs and Challenges of the Solid Phase Bead Assay

This review outlines the development of human leukocyte antigen (HLA) antibody detection assays and their use in organ transplantation in both antibody screening and crossmatching. The development of sensitive solid phase assays such as the enzyme-linked immunosorbent assay technique, and in particular the bead-based technology has revolutionized this field over the last 10-15 years. This revolution however has created a new paradigm in clinical decision making with respect to the detection of low level pretransplant HLA sensitization and its clinical relevance. The relative sensitivities of the assays used are discussed and the relevance of conflicting inter-assay results. Each assay has its advantages and disadvantages and these are discussed. Over the last decade, the bead-based assay utilizing the Luminex® fluorocytometer instrument has become established as the "gold standard" for HLA antibody testing. However, there are still unresolved issues surrounding this technique, such as the presence of denatured HLA molecules on the beads which reveal cryptic epitopes and the issue of appropriate fluorescence cut off values for positivity. The assay has been modified to detect complement binding (CB) in addition to non-complement binding (NCB) HLA antibodies although the clinical relevance of the CB and NCB IgG isotypes is not fully resolved. The increase sensitivity of the Luminex® bead assay over the complement-dependent cytotoxicity crossmatch has permitted the concept of the "virtual crossmatch" whereby the crossmatch is predicted to a high degree of accuracy based on the HLA antibody specificities detected by the solid phase assay. Dialog between clinicians and laboratory staff on an individual patient basis is essential for correct clinical decision making based on HLA antibody results obtained by the various techniques.

Enhanced de novo alloantibody and antibody-mediated injury in rhesus macaques

Chronic allograft rejection is a major impediment to long-term transplant success. Humoral immune responses to alloantigens are a growing clinical problem in transplantation, with mounting evidence associating alloantibodies with the development of chronic rejection. Nearly a third of transplant recipients develop de novo antibodies, for which no established therapies are effective at preventing or eliminating, highlighting the need for a nonhuman primate model of antibody-mediated rejection. In this report, we demonstrate that depletion using anti-CD3 immunotoxin (IT) combined with maintenance immunosuppression that included tacrolimus with or without alefacept reliably prolonged renal allograft survival in rhesus monkeys. In these animals, a preferential skewing toward CD4 repopulation and proliferation was observed, particularly with the addition of alefacept. Furthermore, alefacept-treated animals demonstrated increased alloantibody production (100%) and morphologic features of antibody-mediated injury. In vitro, alefacept was found to enhance CD4 effector memory T cell proliferation. In conclusion, alefacept administration after depletion and with tacrolimus promotes a CD4+memory T cell and alloantibody response, with morphologic changes reflecting antibody-mediated allograft injury. Early and consistent de novo alloantibody production with associated histological changes makes this nonhuman primate model an attractive candidate for evaluating targeted therapeutics.

The role of B cells in solid organ transplantation

The role of antibodies in chronic injury to organ transplants has been suggested for many years, but recently emphasized by new data. We have observed that when immunosuppressive potency decreases either by intentional weaning of maintenance agents or due to homeostatic repopulation after immune cell depletion, the threshold of B cell activation may be lowered. In human transplant recipients the result may be donor-specific antibody, C4d+ injury, and chronic rejection. This scenario has precise parallels in a rhesus monkey renal allograft model in which T cells are depleted with CD3 immunotoxin, or in a CD52-T cell transgenic mouse model using alemtuzumab to deplete T cells. Such animal models may be useful for the testing of therapeutic strategies to prevent DSA. We agree with others who suggest that weaning of immunosuppression may place transplant recipients at risk of chronic antibody-mediated rejection, and that strategies to prevent this scenario are needed if we are to improve long-term graft and patient outcomes in transplantation. We believe that animal models will play a crucial role in defining the pathophysiology of antibody-mediated rejection and in developing effective therapies to prevent graft injury. Two such animal models are described herein.

Donor-directed MHC class I antibody is preferentially cleared from sensitized recipients of combined liver/kidney transplants

For patients with chronic renal and liver diseases, simultaneous liver and kidney transplantation (SLKT) is the best therapeutic option. The role of a pretransplant donor-specific antibody (DSA) in SLKT is unclear. We report the results of a retrospective review from 7/08 to 10/09 of SLKT at our institution. Monitoring of DSA was performed using single antigen bead assay. Between 7/08 and 10/09, there were six SLKT who had preformed DSA and positive XM (four class I and II DSA, one class I DSA only, one class II only). One-year patient and renal graft survival was 83%. Death-censored liver allograft survival was 100%. Acute humoral rejection (AHR) of the kidney occurred in 66% (three with both class I and II DSA and one with only class II DSA) of patients. In those with AHR, class I antibodies were rapidly cleared (p < 0.01) while class II antibodies persisted (p = 0.25). All patients who had humoral rejection of their kidney had preformed anticlass II antibodies. Liver allografts may not be fully protective of the renal allograft, especially with pre-existing MHC class II DSA. Long-term and careful follow-up will be critical to determine the impact of DSA on both allografts.

Sirolimus is not always responsible for new-onset proteinuria after conversion for chronic allograft nephropathy

An eight-yr-old combined liver and kidney transplant recipient for hyperoxaluria type I developed significant proteinuria and hypertension after conversion of a Tacrolimus, MMF, and corticosteroids-based immunosuppression to Sirolimus, low-dose Tacrolimus, and corticosteroids six and a half yr after the transplant for chronic allograft nephropathy. There was only one class I HLA match and the recipient had multiple blood exposures prior to transplantation. The patient was treated with combined hemodialysis and peritoneal dialysis while awaiting transplantation to reduce the oxalate load. A renal biopsy revealed a de novo transplant glomerulopathy that was associated with specific HLA antibodies unrelated to the donor (HLA DR 17 and 18). After reintroduction of MMF, these antibodies became undetectable and the proteinuria completely resolved. We hypothesize that HLA antibodies may cause transplant glomerulopathy even if they are not donor-specific. Their production appears more susceptible to MMF therapy. A thorough work-up of new-onset proteinuria after conversion to Sirolimus should be performed, including an immunological work-up and a renal biopsy.

Detection and analysis of HLA class I and class II specific alloantibodies in the sera of dialysis recipients waiting for a renal retransplantation

The objective of this study was to evaluate the specificities of HLA class I (-A,-B) and class II (-DR,-DQ) antibodies (Ab) detected in the sera of alloimmunized patients waiting for a subsequent renal transplantation. The study group consisted of 62 dialysis patients (42 men and 20 women, mean age: 43 +/- 18 yr) on waiting list for a subsequent kidney transplant (52 for a second and 10 for a third transplant) at S. Martino Hospital Transplant Centre in Genoa/Italy, who were enrolled from 2002 to 2004 for HLA antibody screening. Complement dependent cytotoxicity (CDC) technique was used firstly to select anti-HLA class I sensitized patients; indeed sera from 50 individuals out of 62 (80.6%) were found to display persistent HLA class I PRA (panel reactive antibody) values >4% (range: 20-100). ELISA technique was subsequently adopted to analyze HLA class I Ab positive sera for the presence also of HLA class II Ab and to characterize class I and class II Ab specificities. Anti-class I immunized patients were divided in three groups according to the type of class I Ab specificities, that were classified as private, public, and multispecific. The first group included 35 patients (70% of the total number of positive patients) showing only antibodies directed against private HLA class I specificities, represented in 33 cases by those expressed by graft donors (first or second transplant). In this group anti-class I PRA% values ranged from 20% to 60%. HLA class II Ab, with an heterogeneous specificity pattern (private, public or multispecific), were present in 25 (78.1%) out of the 32 patients, whose sera were also available for this analysis. The second group comprised 12 patients (24%) who displayed antibodies directed against class I public epitopes belonging to CREGs (Cross reactive Groups) or an association of anti-private and anti-public antibodies. In this group PRA values ranged from 25% to 90%. Five patients (46.7%) were positive for HLA class II Ab, whose specificity pattern appeared also heterogeneous (private or multispecific). The third group was represented by three patients (6%) displaying multispecific antibodies with PRA values > or = 90%. No multispecific class II Ab were found in this group, where only two patients had class II Ab showing anti-private or anti-private plus public specificities. Globally, 74% of anti-class I Ab positive patients, having at least one HLA class II antigen mismatch, appeared also positive for class II Ab. These results indicate that: (i) a large proportion of patients, waiting for a kidney retransplantation, display in their sera alloantibodies specific for graft mismatched HLA class I (80.6%) and class II antigens (54.2); (ii) the immunogenic determinants, mainly involved in HLA class I and II specific Ab production, were, in a significant rate, private specificities of mismatched HLA antigens (70% for class I and 59.4% for class II), and in a lesser percentage by public (CREG) epitopes (24% for class I and 34.3% for class II). In a few patients only no HLA class I and class II Ab specificities could be determined, as they displayed multispecific antibodies (6% for class I and 6.2% for class II). These findings may have important implications to improve donor-recipient matching in dialysis recipients waiting for a subsequent renal transplantation.

Detection of Donor-Specific Anti-HLA Class I and II Antibodies Using Antibody Monitoring System

The antibody monitoring system (AMS, GTI Inc) is a solid enzyme-linked immunosorbent assay (ELISA) crossmatch test for the detection of immunoglobulin G (IgG) antibody to donor-specific solubilized HLA class I and class II antigens. The objective of this study was to compare the results of the AMS assay with donor-specific anti-HLA IgG antibodies (DS-HLA Abs), as determined by ELISA panel reactive antibody (PRA) and the flow cytometric crossmatch test (FCXM). A total of 107 sera were screened for the presence of HLA Abs by ELISA PRA (LAT-M, One-Lambda Inc), the DS-HLA Abs were determined in 34 serum samples (31.8%) by an ELISA panel (LAT class I and class II, One-Lambda Inc) and FCXM. The FCXM and AMS assays were performed with matched lymphocytes from 56 donors. There was a significant degree of concordance (89.7%) between the two tests (P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value of AMS assay to detect DS-HLA Abs was 88.2%, 94.5%, 88.2%, and 94.5%, respectively. The AMS is a simple, objective test, which has several advantages over the cell-based crossmatch test, such as elimination of non-HLA antibody reactivity, elimination of non-donor-specific antibody reactivity, no need for viable cells, and preparation of the donor's HLA antigens in advance. In summary, this study suggested that AMS may be useful as a supportive crossmatch test or as a monitoring test after transplantation to detect class I or class II DS-HLA Abs.

Clinical relevance of anti-HLA antibodies detected by flow-cytometry bead-based assays--single-center experience

The purpose of this study was to define the incidence, dynamics, and profiles of anti-human leukocyte antigen antibodies (HLA-Abs) produced after kidney transplantation and their impact on graft outcome. A total of 72 first cadaver donor kidney recipients were prospectively monitored for the development of HLA-Abs using bead-based flow-cytometry assays (One Lambda FlowPRA tests). Sixteen recipients (22.2%) developed HLA-Abs after transplantation (class I, n = 7; class I+II, n = 6; class II, n = 3), in most cases (81.25%) within the first 2 weeks posttransplantation. A strong association between alloantibody presence and delayed graft function (Chi-square = 7.659, p < 0.01), acute rejection (Chi-square = 14.504, p < 0.001), chronic rejection (Chi-square = 12.84, p < 0.001), and graft loss (Chi-square = 20.283, p < 0.001) was found. Patients with higher alloantibody titers experienced acute rejections and even early graft loss, compared with those with lower titers for whom chronic rejections were more common. Immunologic complications occurred in recipients with both donor-specific and cross-reacting groups or non-donor-specific antibodies alone. A positive correlation (Pearson correlation, 0.245; p < 0.05) between HLA class I amino acid triplet incompatibility and alloantibody production was observed, mainly resulting from immunogenic triplotypes. Given the results obtained in this study, an alloantibody testing algorithm has been designed and implemented for routine monitoring and to define optimally the alloantibody reactivity in kidney transplant recipients.

Impact of HLA Antibodies on Transplant Glomerulopathy

The influence of humoral rejection on the development of chronic allograft nephropathy (CAN) is controversial, especially in relation to transplant glomerulopathy. The aim of our study was to analyse the influence of anti-HLA antibodies on the development of transplant glomerulopathy (cg0, cg1, cg2, and cg3; Banff'97). We selected all renal transplants patients from 1975 to 2003 who had a functioning graft for at least 6 months and a clinically indicated graft biopsy with CAN and chronic glomerular changes (case group). We studied the presence of anti-HLA antibodies (Ab) in the last serum taken while the graft was functioning and divided them into three groups according to the severity of glomerular lesions. We also selected 52 contemporary and comparable cases without transplant glomerulopathy (control group). A total of 77 case had transplant glomerulopathy: 39 cg1, 29 cg2, and 9 cg3. Pretransplant Ab titers and number of previous blood transfusions were higher among the subgroup with the most severe glomerulopathy. Patients who developed posttransplant anti-HLA Ab more frequently showed transplant glomerulopathy. Serum creatinine and proteinuria were higher among cases with chronic glomerulopathy, and more grafts were lost in that group. Thus, the presence of HLA-Ab is a key factor in the development of transplant glomerulopathy and chronic allograft rejection.

Prognostic assays for rejection and tolerance in organ transplantation

In this review, I have summarised our understanding of acute rejection of organ transplants, and for convenience I have identified three processes, recognition, rejection and regulation. In stark contrast to this text-book picture of acute rejection, I have drawn attention to some of the clinical realities, where processes are altered by powerful immunosuppressive drugs, and where many transplant recipients are pre-sensitised to transplantation antigens prior to engraftment. The ultimate goal is to encourage the emergence of a utopian immunological state, wherein patients tolerate organ transplants for life after being weaned from all immunosuppressive drugs. Assays that may be used in the future to reliably monitor this process are still at a very exciting stage of development.

Human Leukocyte Antigen Antibodies for Monitoring Transplant Patients

Human leukocyte antigen (HLA) antibody-mediated hyperacute rejection has dramatically decreased since the clinical introduction of crossmatch technology. However, the role of HLA antibody in acute and chronic rejection remains unclear. In this article, we cite publications to show the correlation between HLA antibody and allograft rejection. Potential pathological mechanisms of antibody-mediated rejection are also proposed and the rationale of commonly used HLA antibody detection techniques are introduced. The advantages and disadvantages of these technologies are further discussed in detail. We conclude that owing to the recent availability of improved antibody detection methods, a causal relationship between HLA antibodies and allograft rejection is now considered to exist.

Soluble CD30 and HLA antibodies as potential risk factors for kidney transplant rejection

Recent literary data suggest that high pre- and post-transplant serum levels of the soluble CD30 (sCD30) molecule may be a risk factor for acute rejection and worse prognosis of the transplanted kidney. The aim of our study was to correlate the concentrations of sCD30 and the presence of HLA antibodies as defined by flow cytometry and ELISA with the clinical course and graft prognosis after transplantation. One hundred and seventeen kidney transplant patients were included into the study. The incidence of rejection episodes, graft function and graft survival for up to 1 year post-transplant were evaluated. Soluble CD30 levels before transplantation were virtually the same in patients who experienced rejection and in non-rejecting patients. In both patient groups, a significant decrease of sCD30 was detected 2 weeks after transplantation (104.4 U/ml before vs. 37.0 U/ml post-transplant, P < 0.001). However, there was a substantial difference in the level of decrease of sCD30 between rejecting and non-rejecting patients. Patients without rejection had lower sCD30 values (31.2 U/ml post-transplant) compared to patients who experienced rejection episodes (62.9 U/ml), P < 0.04. Multifactorial analysis showed that antibodies to HLA class II antigens and elevated concentrations of sCD30 shortly after transplantation were associated with increased risk for acute rejection in the first post-transplant year. Measurement of soluble CD30 after transplantation, taken into consideration with the presence of HLA class II antibodies, might be helpful for evaluating the potential risk for acute rejection.

Impact of ELISA-Detected Anti-HLA Antibodies on Pediatric Cardiac Allograft Outcome

In this study, we determine whether the presence of enzyme-linked immunosorbent assay (ELISA) detected anti-human leukocyte antigen (HLA) antibodies correlates with acute and chronic rejection in pediatric heart transplantation (Tx). Forty-five patients, who had serial ELISA pre- and posttransplantation, were studied. Age at Tx was 8.2 +/- 7.2 years. Acute rejection (AR) was defined as International Society for Heart and Lung Transplantation Grade > or =3a. Patients were defined as rejectors (22 cases) if they had recurrent AR or steroid-resistant AR within the first year post-Tx; the other cases (23) were defined as nonrejectors. Overall, 219 samples were analyzed. Twenty-two of the 45 had pre- or post-Tx anti-HLA antibodies: 77% in rejectors (17/22) and only 22% in nonrejectors (5/23), p = 0.0002. Pre-Tx HLA antibodies were present in 12 cases (27%). Presensitization was more frequent in rejectors (11/22, 50%) than in nonrejectors (1/23, 4%, p = 0.0005). Nineteen cases retained (9 cases) or developed (10 cases) anti-HLA antibodies post-Tx: 14 in rejectors (63.6%) and 5 in nonrejectors (21.7%), p = 0.003. Four of eight cases with coronary artery disease (50%) had preformed anti-HLA antibodies compared with 8 of 37 without coronary artery disease (25.6%) (p = 0.09). Preformed, persistent, and de novo ELISA-detected anti-HLA antibodies were correlated with first-year acute rejection profile.

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.

Immunological monitoring of posttransplant allograft sensitization following living related donor renal transplantation

A better understanding of the immunobiological processes and predictors of graft rejection holds promise for development of new therapeutic strategies and also for individualization of immunosuppression. The objective of this study was to analyze the clinical relevance of immune parameters, such as recipient sensitization status, donor-specific antibodies, and anti-HLA antibodies, which are major predictors of graft outcome following renal transplantation. Sera from 264 renal recipients at different posttransplant period were included for detection of anti-donor antibodies (by flowcytometry); anti-HLA, antibody (by ELISA), and panel-reactive antibodies (PRA) by complement-dependent cytotoxicity (CDC) methods. Graft survival was analyzed in relation to posttransplant PRA at 2 years follow-up time: overall survival was significantly compromised in the highly sensitized group (group III) compared to the other two groups (overall chi2 = 24.20, P = 5.5 x 10(-06)). Flow cytometric cross-matches revealed the presence of anti-donor class I antibodies (T+) in 39 patients who had a poor graft survival of 51% compared with 85% survival in 225 antibody-negative patients. (chi2 = 22.260, P = 2.381 x 10(-.06)). Further analysis was performed based on the presence or absence of FCXM and ELISA-detected antibodies. Recipients belonging to group I (ELISA+/FCXM+) showed significantly lower graft survival (43%) compared with that observed in group II, which were essentially nonsensitized individuals (90%; P = 3.1 x 10(-08)). The graft survival in the ELISA-/FCXM+ group was 63%, which was significantly lower than that in group II (P = 5.14 x 10(-03)). Group IV (ELISA+/FCXM-) including 38 (14%) serum samples with nondonor but HLA-specific antibodies was associated with significantly poorer graft survival (63%) compared with group II (P = 6.6 x 10(-05)). Our data also show that while FCXM is the most sensitive test to detect donor-specific antibodies, the ELISA method offers the additional advantage of detecting anti-HLA class-I antibodies, which are detrimental for renal graft survival. Thus the use of multiple parameters to assess recipient immune profile can predict graft outcome more accurately thus helping the individualization and optimization of immunosuppression.

Plasmapheresis as rescue therapy in accelerated acute humoral rejection

Accelerated acute humoral rejection (AHR) continues to occur in renal transplantation despite improved crossmatching, with potentially devastating consequences. Between 1 June 1998 and 31 December 2000, 440 renal transplants were performed in our center. AHR was diagnosed by the demonstration of typical pathological features on renal histology and positive direct immunofluorescence or detection of anti-HLA antibodies in serum. AHR developed in 20 (4.5%) of our renal transplant recipients, nine male and eleven female at an average of 16.3 days post transplantation. All of these patients had a negative current cytotoxic crossmatch prior to transplantation. The median serum creatinine at diagnosis was 5.96 mg/dL, and 83% of these individuals developed oliguric renal failure requiring dialysis after having initially attained good graft function (median of best serum creatinine before AHR was 2.64 mg/dL). The 18 recipients who had not infarcted their grafts at the time of diagnosis of AHR received plasmapheresis in conjunction with intensification of their immunosuppressive regimen. This regimen was successful in reversing AHR in 78% of those treated with apheresis. In the 14 responders, graft survival at 6 months was 100% and at 12 months was 91%. Median serum creatinine at 6 and 12 months was 1.26 and 1.33 mg/dL, respectively. Patients received an average of 8.1 plasma exchanges. However, responders received a significantly higher frequency of plasmapheresis (P =.0053), despite undergoing a similar number of exchanges overall. Plasmapheresis appears to be an effective modality for reversing AHR and maintaining graft function.