HLA-DP Antibodies Research Articles

The new kidney allocation system-who are we penalizing?

The new kidney allocation system implemented at the end of 2014 attributes additional allocation points to sensitized patients using a sliding cPRA scale. In addition patients with > 98% cPRA receive regional/national allocation priority due to their high level of sensitization. Unfortunately,the new allocation system does not allow for the input of HLA-DQA and HLA-DP unacceptable antigens for the computation of cPRA. To assess the number of patients affected by the lack of programming for HLA-DQA and -DP, we reviewed the antibody data of our adult kidney waitlist population composed of 485 patients. We found that 7.6% of our patients had HLA-DP and/or HLA-DQA antibodies with MFI values > 3000 for which they were not receiving additional allocation points due to our inability to enter HLA-DQA and -DP specificities as unacceptable antigens. The vast majority of the affected patients (86.5%) had HLA-DP antibodies and cPRA of 98%. In fact 75.7% of patients with HLA-DQA or HLA-DP antibodies had cPRA of 98% while 24.3% had cPRA > 98% and thus were eligible for regional/national priority. Our gathered data strongly advocates the implementation of new allocation software allowing for the listing of HLA-DQA and HLA-DP unacceptable antigens and for computation of these unacceptable antigens in the cPRA. Per OPTN data as of 4/22/15 there were 123,193 people waiting for a kidney transplant in the US. Using our center specific data on a national scale, it means that 9300 people are not receiving allocation points for unacceptable antigens against HLA-DP and/or -DQA. Our data also supports the implementation of mandatory typing of donors for HLA-DP and DQA since 24.3% of patients with HLA-DQA and -DP antibodies have cPRA > 98%. Mandatory typing of donors for HLA-DP and -DQA would allow for faster organ allocation and unnecessary shipment of organ for regional/national share to patient having unacceptable HLA-DQA or -DP antibodies.

Prevalence of HLA-DP antibodies in patients awaiting renal transplantation

Aim To determine the prevalence of HLA-DP IgG antibodies in patients on Renal Transplant waitlist at Rush University Medical Center, Chicago, IL. Introduction: Role of HLA-DP antibodies in solid organ and stem cell transplantation is evolving. Isolated reports on possible involvement of only HLA-DP DSA in acute rejection episodes (cases where the Donor/Recipient pairs are matched at HLA-Class , DR and DQ)] show the importance of this issue. In the light of HLA molecular typing and antigen specific HLA antibody assays there is an opportunity to evaluate the role of HLA-DP in allograft rejection. As part of this goal we investigated the prevalence of DP antibodies in our renal transplant candidates. Patients: A total of 532 patients with multiple serum samples tested. Methods HLA-specific antibodies were determined by solid phase assay (One Lambda, Inc. ®). HLA- specific antibody was scored as strong, moderate, or weak depending on their mean fluorescent index (MFI) value of > 5000, 2000–5000, 700–2000, respectively. Results Of the 532 patients, 143 (26.9%) had antibodies against Class II HLA-DP. The number of specific HLA-DP antibodies per patient ranged from 1 to 17 antibodies (Strong, Moderate, Weak), but could also be found entirely in one category as in the case with one patient in which all 16 of the anti-DP antibodies were in the strong MFI category. Conclusions Quarter of renal transplant candidates on waiting at Rush University Medical center have detectable HLA-DP antibodies with varying MFIs. While 36.5% of those antibodies express a low MFI, 31.4% of the patients had strong MFI. Multiple case studies from various centers have shown that transplant patients perfectly matched per UNOS requirements to their donor may still have antibody mediated rejection due to a mismatched at HLA-DP. Hence donor typing for HLA-DP and monitoring of patients for HLA-DP antibodies seems to be important

Allelic antibodies and their impact on organ allocation to highly sensitized patients

Aim Based largely on the success of virtual crossmatching (vXM), the OPTN implemented a new kidney allocation process. Specifically, transplant candidates with cPRA values of 9899% and 100% now have priority for deceased donor (DD) kidneys. Recent studies revealed that the majority of these highly sensitized patients (HSPs) had HLA-DP antibodies, meaning that vXM was not possible unless the corresponding donor HLA-DP type was provided. A similar situation occurs if patients possess allele specific HLA antibodies and donors with the corresponding antigen are not allele level typed. Here again, vXM is not possible. In this study, we evaluated the distribution and frequency of allele specific HLA antibodies among HSPs. The allelic antibodies represented on SAB products are shown in the table below. Methods Luminex SAB assays were performed with sera from all listed kidney candidates with cPRA > 98% (n = 242). An antibody was considered positive when the MFI was > 2000. Results Of 189 black, 44 white and 9 Hispanic HSPs, 85% (n = 160), 89%(n = 39) and 78% (n = 11), respectively, had at least one allele specific antibody.The average number of allele specific antibodies per patient was 1.28 ± 0.71 (Class I) and 2.6 ± 1.59 (Class II). The most prominent allele specific antibodies are shown below (shaded). MFI values for the allele specific antibodies ranged from 2000– > 25000. Conclusions These data clearly show that allele specific HLA antibodies are common in HSPs. They are likely the tip of the iceberg since the only detectable allelic antibodies are those represented on the SAB panel. The “real” number of allelic antibodies is likely much greater. High resolution typing of DDs, at least for those alleles to which antibodies are commonly detected, needs to be provided in a timely fashion in order to perform accurate vXM for HSPs with allele specific antibodies. Download : Download full-size image

OR30 HLA-DPB1* antigen frequencies in deceased donors: Mining the data

Aim The OPTN recently implemented a new process wherein renal transplant candidates with cPRA values of 99% and 100% are given regional and national priority, respectively, for deceased donor (DD) kidneys. While the majority of these highly sensitized patients have HLA-DP antibodies, allocation offers frequently occur without donor HLA-DP typing. Furthermore, information regarding the frequency and distribution of HLA-DP antigens is not readily available. Herein we report the frequency and distribution of HLA-DP antigens in 1168 DDs typed over the past three years. Methods HLA-DPB1* typing was performed by SSO, SSP (One Lambda, Thermal-Fisher) or RT-PCR (Linkage Biosciences). Results Donors were 58.9% white, 32.4% black, 7.3% Hispanic and 1.4% API. As shown below, the frequency and distribution of HLA-DPB1 antigens varied significantly by race. For example, HLA-DPB1*04:01 is seen in 64.6% of whites and 16.2% of blacks while HLA-DPB1*01:01 is in 53.4% of black donors and only 9.1% of whites. Some HLA-DPB1* alleles appear racially restricted; e.g., HLA-DPB1*10:01 was observed in white and Hispanic but not black donors, while HLA-DPB1*85:01 was seen only in black donors. Multiple HLA-DPB1* alleles with a frequency of ⩾1% are not represented on any single antigen bead (SAB) products used to detect HLA antibodies. In contrast, SAB manufacturers allotted up to three beads for HLA-DPB1* 28:01, an allele not observed in any of the 1168 donors in this study. Conclusions OPO laboratories do not yet uniformly perform HLA-DP typing of deceased donors. In the absence of HLA-DP typing information, frequency tables as presented here can aid in the decision process of whether to accept/reject offers for patients with HLA-DPB1* antibodies. Hopefully, these data will stimulate bead manufacturers to provide SAB targets that more accurately reflect donor antigen distribution. Download full-size image

LBP30: THE SPECIFICITY OF HLA-DP ANTIBODIES ARE DEFINED BY TWO DIMORPHIC EPITOPES

Aim The presence of HLA-DP antibodies may cause AMR. It has been reported that serologic epitopes of HLA-DP are defined by two sequence dimorphisms based on a small cohort of patients. Our aim was to determine whether the specificity of DP antibodies we identified in a much larger study were explained by these two serologic epitopes, and to characterize their reactivity patterns. Methods Among 2821 renal patients who were analyzed by SAB class II testing, 486 patients displayed HLA-DP antibodies. The association between DP antibody specificities was analyzed by hierarchical clustering to identify potential epitope patterns. 4 Sera displaying strong DP antibodies were then adsorbed by cells carrying the related epitope, the bound antibodies were eluted with acid, placed in a buffered solution and reanalyzed by SAB testing to identify which antigens remained reactive. Results Based on hierarchical clustering analysis, HLA-DP antibodies were categorized into 4 clusters (Fig. 1). These 4 clusters are largely consistent with the serologic groups as described by Cano et al. dependent on the presence of epitopes GPM or EAV at positions 85–87 or the presence of A or E at position 56. Antibodies against cluster 3 (DP6, 3, 14, 9, 17) are most common and were found in 160 patients. In contrast, antibodies against cluster 2 (DP401, 402, 2, 18, 28) are least common. Only 44 patients developed antibodies against cluster 2. This is likely due to the high frequency of this cluster (>60%) in the population. To confirm whether antibodies within each group recognize the same epitope, we performed the cell adsorption-elution assay. For example, we found cells carrying homologous HLA-DP2 can bind antibodies that are against cluster 2 and 4 antigens which share the epitope GPM 85–87 with HLA-DP2. Conclusion DP antibodies recognize two major dimorphic epitopes. HLA-DP epitope matching between the donor and recipient at these two critical epitopes should reduce post-transplant sensitization and improve transplant outcome.

P123 : GRAFT REJECTION IN A KIDNEY TRANSPLANT RECIPIENT WITH NEGATIVE CROSSMATCHES AND A SINGLE HLA-DP DONOR SPECIFIC ANTIBODY

Among prospective kidney transplant recipients, antibodies to HLA-DP are most frequently identified in re-transplant candidates. The significance of these antibodies and their ability to cause rejection is subject to an ongoing debate. The following is a case study of a kidney re-transplant recipient with many HLA-DP antibodies. The patient is a 27 year-old female who had received one prior transplant. Anti-HLA antibodies were determined by Luminex® single antigen beads. Crossmatching was performed by complement-dependent cytotoxicity (CDC) with and without Dithiothreitol (DTT), and flow cytometry (FXM) with and without Pronase®. The patient exhibited only Class II antibodies, including 16 HLA-DP specificities with MFI >10,000. The recipient had a single donor-specific antibody to HLA-DP11 (21,000 MFI) to the potential living donor. The preliminary crossmatch was negative by both CDC and FXM and was reconfirmed with subsequent crossmatches. Post-transplant, the recipient demonstrated good kidney function and a steady decrease in serum creatinine (sCr) to 1.1 mg/dL until developing pyelonephritis two weeks later. The infection was resolved with antibiotics, but the patient’s sCr increased a week later to 3.1 mg/dL, and a kidney biopsy was performed. The biopsy was positive for vasculitis and cellular rejection, with equivocal C4d staining. Following treatment with steroids, IVIG, and thymoglobulin, the patient stabilized with a sCr of 1.6 mg/dL, and the single HLA-DP11 donor-specific antibody persists. Crossmatches performed with current serum and freshly drawn cells from the living donor remained negative. In the presence of negative crossmatches, the recipient experienced cellular and antibody-mediated rejection associated with a donor specific antibody against HLA-DP. The findings suggest that donor-specific HLA-DP antibodies present a risk to kidney transplantation.

P126 : A CASE STUDY: ACUTE HUMORAL REJECTION DUE TO ANTI-HLA DP ANTIBODIES IN A RENAL TRANSPLANT RECIPIENT

We report the case of a highly sensitized 37 year old male who suffered an acute humoral rejection due to donor specific anti-HLA DP (DP) following a second kidney transplant. A previous living donor kidney graft failed in 2005 due to noncompliance with immunosuppression and he returned to hemodialysis. Past history included two blood transfusions. On evaluation for retransplant in 2010, his cPRA using microarray single antigen beads (One Lambda) was 100% including anti-DP1 (MFI 4221). On 2/17/14, he received a deceased donor kidney (KDPI 17%). T and B cell crossmatches by CDC-AHG/CDC long incubation and by the rosette method (Life Technologies) were compatible. There were no donor specific antibodies (DSA) to HLA A B Cw DR or DQ. DP typing of deceased donors was not performed. Retrospective DP typing indicated that the donor was DP1. The clinical staff was advised. He received Thymoglobulin induction and was placed on Mycophenolate Mofetil (MMF), prednisone and Tacrolimus. By post op day (POD) 10, his creatinine decreased to 1.6 mg/dL. On POD 18, his creatinine increased to 2.5 mg/dL. Biopsy results showed acute glomerulitis and acute tubular necrosis. C4d staining was positive. A biopsy day serum showed anti-DP1 (MFI 7627) by microarray single antigen beads and (MFI 26038) using the C1q binding assay (One Lambda). C1q testing of archived crossmatch serum did not show anti-DP1. After treatment with plasmapheresis and 1 g/kg IVIg, his creatinine stabilized at 1.8–2 mg/dL. He is currently maintained on MMF, Tacrolimus and prednisone. A survey of 1069 renal transplant candidates revealed that 13% had DP antibodies. Two of three transplanted patients with DP antibodies retrospectively determined to be DSA had humoral rejections. Another patient with no pre-transplant DSA received a crossmatch compatible kidney and had a rejection due to de novo anti-DP. These 3 cases were regrafts. Our experience is consistent with recent literature. With increasing evidence that DP antibodies can cause graft rejection and with technology available to perform HLA DP typing and antibody monitoring, the transplant community should take action to recognize the potential risk of DP antibodies in renal transplant, require DP typing of all donors prior to transplant and consider incompatible donor DP antigens unacceptable for regrafts.

Donor Specific Anti-HLA Antibodies Towards HLA Cw and HLA DP Should Be Considered as Pathogenic in Kidney Transplantation.

It is widely accepted that HLA donor-specific antibodies (DSA) have a deleterious impact in kidney transplantation. However, non-classical preformed anti-HLA Cw and anti-HLA DP DSA are not considered in organ allocation policies and their clinical relevance is uncertain. Here we wondered whether anti-Cw/DP DSA should be considered as pathogenic through a retrospective study, comparing 48 patients transplanted with isolated preformed anti-Cw/DP DSA (Anti-Cw/DP DSA group) with (i) 104 matched HLA-sensitized kidney transplant recipients (KTR) with no DSA at D0 (No DSA group)and with (ii) 58 KTR with at least one identified preformed DSA other than anti HLA-Cw or HLA-DP antibodies (anti-A, -B, -DR, -DQ group or Classical DSA group). A positive flow cytometry XM in the anti Cw/DP DSA group was more frequent than in the No DSA group and as frequent as in the Classical DSA group. Two years after transplantation, graft survival and renal function were significantly lower in the anti-Cw/DP group than in the No DSA group, but not different from the Classical DSA group. Similarly, the biopsy-proven acute rejection-free survival was worse in the anti-Cw/DP and Classical DSA groups (with more inflammatory microcirculations lesions g+ptc) compared to No DSA group. Taken together, our results suggest that preformed anti-Cw and anti-DP DSA can exert the same deleterious effects that classical anti-A, -B, -DR, -DQ DSA. This might justify the systematic typing of HLA Cw and DP donor antigens and the detection of anti-Cw and anti-DP recipient antibodies as well as their inclusion in the kidney allocation algorithms.

173-P: A SINGLE DONOR SPECIFIC HLA-DP ANTIBODY IN A KIDNEY TRANSPLANT RECIPIENT RESULTING IN ANTIBODY MEDIATED REJECTION

Aim Among prospective kidney transplant recipients, antibodies to HLA-DP are most frequently identified in re-transplant candidates. The significance of these antibodies and their ability to cause AMR is subject to an ongoing debate. We report here a case study of a kidney transplant recipient with many HLA-DP antibodies. Methods The patient is a 27 year-old female with one prior transplant. Anti-HLA antibodies were determined by the Luminex single antigen bead assay. Crossmatching was performed by CDC and flow cytometry (FXM), with and without pronase. Results The patient had many antibodies against both HLA Class I and II, including 10 DPB1 specificities with MFI >10,000. The patient had 7 DD XM before being transplanted ( Table 1 ). The final XM (Table 1, bottom row) was negative by CDC and regular FXM, weakly B positive with pronase, and no DSA was identified at the time. Her sCr decreased for 2 months before beginning to rise. A biopsy was deemed suspicious of CMR, and she was treated with steroids. Her sCr continued to rise, and a second biopsy showed positive C4d staining. The DD was typed for HLA-DP, which identified a DSA against HLA-DPB1∗02 (7000 MFI), and the patient was treated with IVIG and C1 esterase inhibitor. A follow-up biopsy was negative for C4d, the patient’s sCr is currently stable, and the DSA persists. [table1] Conclusions A single HLA-DP DSA caused AMR in a renal transplant recipient. The DSA was not identified at the time of transplant, because prospective HLA-DP typing of DD is not a standard practice. In the absence of HLA-DP typing, FXM with pronase can enhance the detection of HLA-DP DSA.

40-OR: The Impact of Pre-Formed HLA-DP Antibody on Kidney Graft Survival – The Tulane Experience

40-OR: The Impact of Pre-Formed HLA-DP Antibody on Kidney Graft Survival – The Tulane Experience

HLA-DP antibodies before and after renal transplantation

Human leukocyte antigen (HLA)-DP is considered a target for humoral immune response in clinical transplantation. This study analyses the incidence of HLA-DP antibodies in renal patients. Development and epitope specificity of donor-specific antibodies (DSA) and non-DSA (NDSA) were examined. Pre- and posttransplant sera of 338 patients were screened for HLA-DP antibodies using the luminex single antigen assay. Positive patients, partners and/or kidney donors were HLA-DP typed by sequence-specific oligonucleotides. Potential epitopes were mapped by comparing the amino acid sequences of HLA-DP hypervariable regions (HVR) A-F of recipient, partner and/or donor. Specificities in the sera were aligned to deduce the HVR motif responsible for the antibodies. HLA-DP antibodies were detected in 14% of the patients (48/338). Before transplantation, the antibodies were shown in 23% (10 females and 1 male) and 77% were found after transplantation (30 in patients after the first, 7 after the second graft). Specificities were never restricted to individual mismatched antigens; broad HLA-DP sensitization was found as a rule. A single HVR mismatch was present in 80% of the DSA and in 79% of the NDSA. No HLA-DPA specific antibodies were found. Our findings confirm that HLA-DP antibodies are specific for epitopes shared by different HLA-DP antigens, indicating that only a restricted number of mismatched epitopes are recognized by the recipients immune system. Matching for immunogenic HLA-DP epitopes for renal transplantation seems to be functionally more relevant than classical matching at the allelic level.

255-P: HLA DP antibodies – are they relevant?

255-P: HLA DP antibodies – are they relevant?

269-P: Acute antibody mediated rejection (AAMR) due to HLA-DP and MICA antibodies against foreign and “shared” antigens

269-P: Acute antibody mediated rejection (AAMR) due to HLA-DP and MICA antibodies against foreign and “shared” antigens

79-P: HLA-DP antibody formation in renal transplantation

79-P: HLA-DP antibody formation in renal transplantation

Chronic humoral rejection mediated by anti-HLA-DP alloantibodies: Insights into the role of epitope sharing in donor-specific and non-donor specific alloantibodies generation

We report the case of a renal transplanted patient, in whom the detection of a unique anti HLA-DP antibody response preceded the development of chronic humoral rejection. In addition to donor-specific anti-DP alloantibodies, the patient displayed reactions against several non-donor-specific DP antigens (NDSA). Interestingly, we found that all the DP molecules recognized by the alloantibodies displayed the same amino-acid sequence suggesting that epitope sharing between unrelated HLA molecules was the mechanism underlying NDSA generation. This case highlights the pathogenicity of anti-DP alloantibodies and suggests that it could be more meaningful to match the epitopes than the HLA antigens for the prevention of rejection.

The Detection of Donor-Directed, HLA-Specific Alloantibodies in Recipients of Unrelated Hematopoietic Cell Transplantation Is Predictive of Graft Failure.

Animal studies point to a strong role for MHC-specific antibody as a cause for failed donor hematopoietic cell engraftment, but the role of donor-directed HLA-specific allo-antibodies in human transplants has been controversial. To investigate such a role, we used a retrospective case-control design and studied unrelated donor:recipient pairs whose transplants were facilitated through the NMDP. A total of 37 cases with graft failure and 78 matched control pairs were evaluated. The 37 graft failure cases were selected based on survival beyond 28 days of transplant with no sustained engraftment, and available cryopreserved recipient serum to test for HLA-specific alloantibodies. Up to 3 controls were selected for each case, and matched for disease, disease status, graft type, patient age and year of transplant. Patients had AML, ALL, CML or MDS, 98% received myeloablative conditioning regimens, 100% received T replete grafts, 97% received marrow, and 97% received calcineurin-based GVHD prophylaxis. Patients and donors were retrospectively typed for HLA-A,B,Cw,DRB1,DQB1,DQA1,DPB1,and DPA1 by sequencing or other high resolution typing methods. Stored pre-transplant serum samples (patients and controls) were retrieved from the NMDP Research Repository, and assayed for HLA antibodies by solid-phase FlowPRA (One Lambda, Inc). All positive samples were evaluated for HLA specificity by single-antigen microparticles (LabScreen, One Lambda, Inc). Among the 37 failed transplants, 11 (30%) recipients possessed alloantibodies specific for donor HLA Class I or Class II, compared to only 3 (4%) of 78 controls. HLA-DR or DQ specific antibodies were not detected; hence, all HLA Class II-specific antibodies were directed to DP. Recipients with anti-DP antibodies against the donor mismatched DP were at increased risk of graft failure, indicating the importance of recipient antibodies directed against mismatched donor DP antigens. Exact conditional logistic regression analysis for the presence of either Class I HLA-A,B,Cw or Class II HLA-DP antibodies showed similar findings (Class I alone: OR. 6.31: 95% CI 1.17–62.9; p=0.03, Class II alone: OR 12.00; 95% CI 1.46–551.97; p=0.01, Class I and II combined: OR 19.08; 95% CI 2.72–828.49; p=0.0003). Further analyses were conducted to evaluate a limited set of covariates not accounted for in the case:control study, i.e. patient CMV status, cell dose and HLA-C match. Cell dose and CMV status were independently predictive of engraftment, p=0.01 and 0.03, respectively. No effect was observed for HLA-Cw match (p=0.84). The presence of anti-donor HLA Class I or II antibodies was predictive of engraftment when adjustment was made for either cell dose (OR 15.49; 95% CI 2.06–697.83; p=0.002) or CMV status (OR 7.94; 95% CI 0.97–367.84; p=0.05). In summary, these results indicate that donor-specific HLA Class I or Class II antibodies in recipients of unrelated donor hematopoietic cell transplants are associated with failed engraftment. We recommend that, as a “Standard-of-Practice”, all potential recipients be screened for the presence of HLA class I and class II antibodies including HLA DP. Donors should be excluded if they carry mismatched HLA types against which the patient has specific antibodies.

Detection of Antibodies to HLA-DP in Renal Transplant Recipients Using Single Antigen Beads

With the development of single DP-antigen beads, antibodies to DP could clearly be segregated from other HLA antibodies. We studied 323 sera of patients from four different centers with functioning or rejected kidney grafts. DP antibodies were found in 5.1% of 138 patients with functioning grafts, and 19.5 % of 185 patients with rejected grafts (P<0.001)). 42.9% and 63.9% of the DP antibody positive patients had DR/DQ antibodies among the functioning and rejected group. Among patients who did not have Class I and DR/DQ antibodies, 13% of those who rejected a graft had DP antibodies, compared to 3.5% of patients with functioning grafts (P<0.05). DP 0301 had the highest specificity frequency in the rejected group. In conclusion, HLA-DP antibodies were detected at a higher frequency in patients who have rejected their grafts than those with functioning grafts. For regrafts, DP tissue typing is recommended to avoid presensitized DP alleles.

The relevance of HLA-DP antibodies in kindey allograft outcome

The relevance of HLA-DP antibodies in kindey allograft outcome

HLA-DP antibodies in patients awaiting renal transplantation

Abstract Sera from 505 patients awaiting renal transplantation with known panel-reactive cytotoxic antibody (PRA) status were tested for HLA-DP antibodies of the IgG class by means of the monoclonal antibody immobilization of leukocyte antigens (MAILA) technique. The overall incidence of HLA-DP antibodies was 7.3 %. A positive HLA-DP antibody status correlated only weakly (r= 0.23) with a positive cytotoxic antibody status. After retrospective analysis, patients with HLA-DP antibodies prior to retransplantation revealed a significantly (P < 0.025) higher graft function rate than HLA-DP-negative patients. One patient was found to possess IgG HLA-DP autoantibodies prior to transplantation; thus far, his graft has been functioning for more than 2 years.

HLA-DP antibodies in patients awaiting renal transplantation.

Sera from 505 patients awaiting renal transplantation with known panel-reactive cytotoxic antibody (PRA) status were tested for HLA-DP antibodies of the IgG class by means of the monoclonal antibody immobilization of leukocyte antigens (MAILA) technique. The overall incidence of HLA-DP antibodies was 7.3%. A positive HLA-DP antibody status correlated only weakly (r = 0.23) with a positive cytotoxic antibody status. After retrospective analysis, patients with HLA-DP antibodies prior to retransplantation revealed a significantly (P < 0.025) higher graft function rate than HLA-DP-negative patients. One patient was found to possess IgG HLA-DP autoantibodies prior to transplantation; thus far, his graft has been functioning for more than 2 years.