THE SIGNIFICANCE OF HLA-DRB1 MATCHING IN CLINICAL RENAL TRANSPLANTATION

Assessment of differences in HLA-A, -B, and -DRB1 allele mismatches among African-American and non-African-American recipients of deceased kidney transplants

Among recipients of deceased donor kidney transplants, African-Americans experience a more rapid rate of kidney allograft loss than non-African-Americans. The purpose of this study was to characterize and quantify the HLA-A, -B, and -DRB1 allele mismatches and amino acid substitutions at antigen recognition sites among African-American and non-African-American recipients of deceased donor kidney transplants matched at the antigen level. In recipients with zero HLA antigen mismatches, the degree of one or two HLA allele mismatches for both racial groups combined was 47%, 29%, and 11% at HLA-DRB1, HLA-B, and HLA-A, respectively. There was a greater number of allele mismatches in African-Americans than non-African-Americans at HLA-A (P < .0001), -B (P = .096), and -DRB1 loci (P < .0001). For both racial groups, the HLA allele mismatches were predominantly at A2 for HLA-A; B35 and B44 for HLA-B; but multiple specificities for HLA-DRB1. The observed amino acid mismatches were concentrated at a few functional positions in the antigen binding site of HLA-A and -B and -DRB1 molecules. Future studies are ongoing to assess the impact of these HLA mismatches on kidney allograft loss.

Early acute rejection does not affect chronic allograft nephropathy and death censored graft failure

BACKGROUND

Even with the development of modern immunosuppression, an acute rejection episode is a major complication after renal transplantation. Acute rejection episodes have been used as clinical indicators for chronic allograft nephropathy and graft loss. We investigated the timing and frequency of acute rejection episodes in relation to long-term graft survival and chronic allograft nephropathy.

METHODS

The Long Term Efficacy and Safety Surveillance study of transplant patients receiving cyclosporin (Neoral) included 1706 adult renal transplants (1995 to 2003) with a functioning graft for at least 1 year. The impact on death-censored long-term graft survival was evaluated for acute rejection episodes (single or multiple) within 3 months, at 3 to 6 months, at 6 to 12 months, or at over 1 year posttransplant. A stepwise binary logistic regression was employed to identify independent risk factors for the time to occurrence of an acute rejection episode.

RESULTS

An acute rejection episode occurring within 3 months posttransplantation had no effect on either death-censored long-term graft failure (P=.2157) or chronic allograft nephropathy (P=.9331). However, an acute rejection episode occurring at 1 year or later posttransplantation was significantly associated with death censored long-term graft failure (P <.0001) and chronic allograft nephropathy (P <.0001). The numbers of HLA-DR mismatches and younger recipient ages were independent risk factors for early acute rejection.

CONCLUSION

Among patients whose graft survives at least 12 months, an early acute rejection episode within 3 months posttransplant was not associated with either death-censored long-term graft survival or chronic allograft nephropathy among adults treated with cyclosporin. However, an acute rejection episode occurring at 1 year or later posttransplantation showed a positive association with death-censored long-term graft survival or chronic allograft nephropathy. Lower numbers of HLA-DR mismatches sum to reduce the occurrence of acute rejection and the hospitalization time.

The effect of HLA-C matching on acute renal transplant rejection

BACKGROUND

The acute immunological rejection and long time survival of kidney allografts are correlated with the human leukocyte antigen (HLA) match status between donor and recipient. HLA-A, -B and -DR have all turned out to be relevant HLA loci in several studies. The role of HLA-C has not been studied before now.

METHODS

In 104 consecutive patient/donor pairs from our transplantation unit, we retrospectively analysed whether acute graft rejection is influenced by HLA-C match status between donor and recipient. For typing HLA-C alleles, we used an allele-specific PCR protocol in combination with serology.

RESULTS

By analysing groups of donor/recipient pairs with a homogeneous distribution of HLA-B mismatches in order to exclude an effect of the linkage disequilibrium between HLA-B/C, HLA-C mismatch turned out to be significantly correlated with acute transplant rejection in pairs with one additional mismatch on the B locus (P=0.004). Additional parameters that may hypothetically influence acute rejection episodes (HLA-A or DR mismatch, time of cold and warm ischaemia, previous transplantations, pre-existing HLA antibodies) were also analysed but cannot explain this finding.

CONCLUSION

HLA-C matching of all kidney donors and recipients seems to be an option to reduce the probability of acute rejection episodes. Further studies of greater patient cohorts analysing organ rejection and organ survival are warranted.

Significance of transporter associated with antigen processing gene polymorphism in living related renal transplantation

The HLA class I and class II mediated antigen presentation plays a major role in the initiation of immune response and the development of acute rejection after transplantation. The purpose of this study was to examine whether MHC-encoded antigen processing (TAP1, TAP2, LMP2, DMA and DMB) gene polymorphisms were associated with the incidence and the severity of acute rejection after renal transplantation. We studied a selected population of 112 pairs of donors and recipients who underwent living-related renal transplantation. They were divided into 3 groups: rejection-free (Group A, n = 51), steroid-sensitive rejection (Group B, n = 31) and steroid-resistant rejection (Group C, n = 30). The frequency of TAP2*0103 (41.2%) was significantly higher in the donors of Group A than that of Group B (12.9%, p = 0.0070, pc = 0.0280) or Group C (16. 7%, p = 0.0225, pc = 0.0900). No significant difference was observed in the allelic frequencies of the TAP1, LMP2, DMA, and DMB genes in the donors or recipients among Groups A, B, and C. This result supported the idea that the TAP2 gene polymorphism might be functionally related to antigen presentation. It also suggested that donor's antigen presenting cells with the TAP2*0103 allele would have the attenuated efficacy in the presentation of allospecific antigens to recipient's T cells.

Matching for private or public HLA epitopes reduces acute rejection episodes and improves two-year renal allograft function

BACKGROUND

The current role of HLA matching in renal transplantation is controversial. Public HLA epitope matching has been suggested to be as advantageous as private HLA matching, with the added benefit of increasing recipients' access to well-matched grafts.

METHODS

In this single-center study of 105 renal transplant recipients, we examined the association of HLA matching with early (0-3 months) and late (4-6 months) rejection episodes (RE), as well as renal allograft function up to 2 years after transplant.

RESULTS

Poor HLA-DR, but not HLA-A or -B, matching was associated with early RE (0 DR matches, RE=2.7+/-0.19, 1 DR match, RE=2.37+/-0.18, vs. 2 DR matches, RE=1.5+/-0.38; P < 0.01). In contrast, poor HLA-B, but not HLA-A or -DR, matching was associated with late rejections (0 HLA-B matches, RE=1.1+/-0.51 vs. 1-2 HLA-B matches, RE=0.51+/-0.1; P < 0.004). HLA-B matching was also associated with a significantly lower serum creatinine (SCr) level at 24 months (0 HLA-B matches, SCr=178+/-20 micromol/L vs. SCr=132+/-6 micromol/L for 1-2 HLA-B matches; P < 0.025). Matching for 10 supertypic HLA-A and -B cross-reactive groups was associated with reduced late graft rejection (0-2 residue matches, RE=1.15+/-0.18 vs. RE=0.62+/-0.12 for 3 to 7 residue matches; P < 0.013) as well as a significantly lower SCr level at 24 months (0-2 residue matches, SCr=205+/-29 micromol/L vs SCr=131+/-6 micromol/L for 3 to 7 residue matches; P < 0.001) after transplantation.

CONCLUSIONS

HLA-DR matching was associated with a reduced frequency of early rejection episodes, whereas HLA-B or residue/cross-reactive group matching was associated with a reduced frequency of late rejection episodes and improved graft function at 2 years.

Significance of tumor necrosis factor microsatellite polymorphism in renal transplantation

Plasma levels of tumor necrosis factor (TNF) alpha are raised during acute rejection following organ transplantation. Variations in TNF alpha production have been found to be associated with the polymorphism of TNF microsatellite. Therefore, there is a possibility that a transplant recipient with some type of TNF microsatellite can be a high-risk patient of graft rejection. The purpose of this study was to examine whether TNF microsatellite polymorphism is related to acute allograft rejection. We investigated the relation of two microsatellites, TNFa and TNFd, to acute rejection after renal transplantation. Among 189 primary living-related renal transplantations from one haplotype-mismatched and one DRB1-mismatched donor, we analyzed TNF microsatellites of 163 patients whose DNA were available to this study. The frequency of the TNFa9 microsatellite allele was significantly higher in the rejection group compared to the rejection-free group. In contrast, the frequency of TNFd4 was significantly lower in the rejection group compared to the rejection-free group. TNFa9 and TNFd4 showed strong associations with HLA-B35 and B44, respectively. However, the TNF microsatellite locus was more closely related to acute rejection than HLA-B. It was suggested that the analysis of TNF microsatellite polymorphism can provide useful information in predicting prognosis after transplantation.

HLA-DRB4 genotyping by PCR-RFLP: diversity in the associations between HLA-DRB4 and DRB1 alleles

The serologically defined HLA-DR53 antigen is associated with HLA-DR4, -DR7, and -DR9 antigens, and these haplotypes contain two functional genes, DRB1 and DRB4, and two pseudogenes, DRB7 and DRB8. The DRB4 gene encodes the DR53 antigen, and has been officially recognized to contain three allelic variants (DRB4*0101, 0102, and 0103). In this study, we have established the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for DRB4 genotyping and analyzed genetic polymorphism of the DRB4 gene in Japanese population. DRB4*0101, DRB4*0102, and DRB4*0103 could be observed at the frequencies of 0.5%, 1.1% and 32.7%, respectively. The same DRB1 allele does not necessarily share an identical DRB4 allele. Further, a tight linkage disequilibrium was found between DRB4*0102 and DRB1*0401 in Japanese population, whereas DRB1*0401 was associated with DRB4*0101 or *0103 in Caucasian population. These findings reveal extensive diversity of the HLA-DRB1 and -DRB4 haplotypes and may have important implications for HLA-disease associations and donor selection in unrelated transplantation.

A single center evaluation of the Collaborative Transplant Study (CTS) DNA project

Historical HLA class II serological typing results of transplantations performed in "The Leuven Collaborative Group for Transplantation" were subjected to retrospective Restriction Fragment Length Polymorfism (RFLP) DNA control typing by the Collaborative Transplant Study (CTS) DNA project using Polymerase Chain Reaction (PCR)-based DNA methods. We re-evaluated the serology/ RFLP-discrepant CTS DNA data for our local patients transplanted during a historical period (January 1988 until May 1992) before any class II DNA typing was performed in our tissue typing laboratory. These retyping results confirm both the CTS data for patient typing and the Eurotransplant data for donor typing. A confirmed high discrepancy rate of 19.0% (after exclusion of 2.2% transcription errors) was found in the patient population. A low discrepancy rate of 6.8% (after exclusion of 2.2% transcription errors) for the donor population is concordant with the Eurotransplant donor data. Only 4 of the 588 individuals were found to be incorrectly typed by the RFLP method; all involving the specificities DRB1*1102. This indicates that RFLP typing, as performed by the CTS DNA project, can be considered a valid, retrospective DNA typing system for the accurate interpretation of class II matching in organ transplantation. A second conclusion to be drawn from this study is the need for prospective DNA typing for kidney transplant recipients, as the discrepancy rate in this cohort is high. Our results suggest that with good quality serological HLA-DR typing, prospective donor DNA typing is not urgently needed.

The significant effect of HLA-DRB1 matching on acute rejection in kidney transplants

The object of the present study was to confirm the HLA-DRB1 matching effect on rejection crisis, its severity, and kidney graft survival based on genotyping. Ninety-four renal allografts were included in this study. DNA typing of HLA-DRB1 was performed by the polymerase chain reaction sequence-specific oligonucleotide method. The incidence of acute rejection within 6 months following transplantation, the frequency of OKT3 administration for steroid-resistant rejection, histopathological findings, and graft survival rate were compared between the DRB1-matched (n = 23) and DRB1-mismatched (n = 71) groups. Four acute rejections occurred in the DRB1-matched group (incidence; 17%) and 40 in the DRB1-mismatched group (56%). In the DRB1-matched group, the incidence of acute rejection was significantly less frequent than that of the DRB1-mismatched group (P < 0.005). In the DRB1-matched group, only one patient received OKT3 administration (4%), in contrast to 16 of 71 patients in the DRB1-mismatched group (23%). The use of OKT3 was significantly less frequent in the DRB1-matched group (P < 0.05). Histopathological findings from biopsy specimens showed no constant distribution of pathological grades of acute rejection according to DRB1 matching in the present study. The graft survival rate in the two groups did not differ significantly, but the graft survival rate in the DRB1-mismatched group had a tendency to decrease as the grafts survived longer. In conclusion, the results of the present study confirm that HLA-DRB1 matching has marked beneficial effects on kidney transplants through reduction of the acute rejection rate and decrease of the severity of rejection, and suggest that improvement of graft survival will be obtained through kidney allocation to a DRB1-matched recipient.