Presence Of Human Leukocyte Antigen Antibodies Research Articles

Pre-transplant HLA Antibodies and Delayed Graft Function in the Current Era of Kidney Transplantation.

Delayed graft function (DGF) occurs in a significant proportion of deceased donor kidney transplant recipients and was associated with graft injury and inferior clinical outcome. The aim of the present multi-center study was to identify the immunological and non-immunological predictors of DGF and to determine its influence on outcome in the presence and absence of human leukocyte antigen (HLA) antibodies. 1,724 patients who received a deceased donor kidney transplant during 2008–2017 and on whom a pre-transplant serum sample was available were studied. Graft survival during the first 3 post-transplant years was analyzed by multivariable Cox regression. Pre-transplant predictors of DGF and influence of DGF and pre-transplant HLA antibodies on biopsy-proven rejections in the first 3 post-transplant months were determined by multivariable logistic regression. Donor age ≥50 years, simultaneous pre-transplant presence of HLA class I and II antibodies, diabetes mellitus as cause of end-stage renal disease, cold ischemia time ≥18 h, and time on dialysis >5 years were associated with increased risk of DGF, while the risk was reduced if gender of donor or recipient was female or the reason for death of donor was trauma. DGF alone doubled the risk for graft loss, more due to impaired death-censored graft than patient survival. In DGF patients, the risk of death-censored graft loss increased further if HLA antibodies (hazard ratio HR=4.75, P < 0.001) or donor-specific HLA antibodies (DSA, HR=7.39, P < 0.001) were present pre-transplant. In the presence of HLA antibodies or DSA, the incidence of biopsy-proven rejections, including antibody-mediated rejections, increased significantly in patients with as well as without DGF. Recipients without DGF and without biopsy-proven rejections during the first 3 months had the highest fraction of patients with good kidney function at year 1, whereas patients with both DGF and rejection showed the lowest rate of good kidney function, especially when organs from ≥65-year-old donors were used. In this new era of transplantation, besides non-immunological factors, also the pre-transplant presence of HLA class I and II antibodies increase the risk of DGF. Measures to prevent the strong negative impact of DGF on outcome are necessary, especially during organ allocation for presensitized patients.

Posttransplant Major Histocompatibility Complex Class I Chain-Related Gene A Antibodies and Long-Term Graft Outcomes in a Multicenter Cohort of 779 Kidney Transplant Recipients

The impact of major histocompatibility class I chain-related A (MICA) antibodies on renal graft outcomes is unclear. The goal of this work was to assess the impact of posttransplant MICA antibodies, assayed at 1 year, with two commercially available kits, on long-term renal graft outcomes. We retrospectively tested sera from 779 kidney transplant recipients with two single-antigen flow bead assays 1 year after transplantation. Samples were considered positive for MICA if they were positive in both tests or positive for MICA specificities that were present in one kit only. The main outcome was 4-year death-censored graft survival. The prevalence of MICA antibodies was 5.4% at 1 year. MICA+ patients were more frequently human leukocyte antigen (HLA) sensitized and regrafted. Four-year death-censored graft survival was not different between MICA+ and MICA- patients (97% vs. 94%, P=0.28). By Cox multivariate analysis, independent risk factors for graft loss were as follows: number of HLA DR mismatches, acute rejection within the first year posttransplantation, 1-year serum creatinine, and the presence of HLA antibodies at 1 year, but not the presence of MICA antibodies. These data do not support an independent pathogenic role for MICA in long-term renal graft injury and question the interest of posttransplant monitoring of MICA antibodies with single-antigen flow bead assays currently available.

The Presence of Donor-Specific Human Leukocyte Antigen Antibodies Does Not Preclude Successful Withdrawal of Tacrolimus in Stable Renal Transplant Recipients

Because of the adverse events associated with the administration of immunosuppressive drugs, reduction of immunosuppression after solid-organ transplantation is highly desirable provided that graft rejection is prevented. In our transplant center, we used an immunosuppression reduction regimen in stable renal transplant patients. The presence of human leukocyte antigen (HLA) antibodies has been negatively associated with transplant outcome. Therefore, we evaluated the impact of HLA antibodies on the occurrence of acute rejection after immunosuppression reduction. The presence and antigen specificity of HLA immunoglobulin G antibodies in serum samples were detected using enzyme-linked immunosorbent assay and single-antigen bead assays. Donor-specific cytotoxic potential was tested by standard CDC cross-match analysis. The presence of donor-specific or total HLA antibodies was not predictive for the occurrence of acute rejection after the reduction of immunosuppression. In addition, the presence of HLA antibodies did not preclude successful reduction of immunosuppression. After reduction of immunosuppression, newly formed HLA antibodies were seldom detected. Interestingly, evaluation of the cytotoxic potential of the detected HLA antibodies revealed that the one patient who developed donor-specific HLA antibodies and experienced a subsequent rejection episode was the only patient who carried cytotoxic HLA antibodies. This finding fueled the notion that the functional capacity, rather than the mere presence of donor-specific HLA antibodies, is indicative for transplant outcome. The presence of HLA antibodies does not preclude the successful reduction of immunosuppression in renal transplant patients with stable graft function.

Antibodies Against Donor Human Leukocyte Antigens and the Outcome of Cardiac Allografts in Adults and Children

Mismatched histocompatibility antigens between donor organ and host stimulate the immune response that causes allograft rejection. Antibodies against human leukocyte antigen (HLA) are known to appear in the serum of heart transplant recipients. We have tested stored sera with HLA bound to polystyrene microbeads in a retrospective analysis of heart recipients transplanted in our center to better understand the impact of antibodies against HLA on the posttransplant course. Our analysis included two groups of patients: 113 adults and 31 children who received consecutive heart transplants performed between 1996 and 2003. Presence of HLA antibodies, especially when donor-specific, as determined with single HLA class I or class II beads, was associated with more frequent occurrence of acute rejection, development of transplant-related coronary artery disease and decreased graft survival. Recipients having antibodies only to HLA not in the transplant and those without any HLA antibodies had similar outcomes, suggesting that antibodies against antigens not present on the donor organ did not harm the graft. The results showed that presence of antibodies against HLA of the donor correlated with graft loss and suggested that testing for these antibodies may help in the management of heart transplant patients.

Relevance of Posttransplant Flow Cytometric T- and B-cell Crossmatches in Tacrolimus-Treated Renal Transplant Patients

De novo development of anti-human leukocyte antigen (HLA) antibodies after transplantation is associated with increased rejection and decreased graft survival. In this study, the effect of posttransplant HLA antibodies on clinical outcome was evaluated in patients treated with tacrolimus by means of flow cytometric crossmatches (FCXm). T- and B-cell FCXm were performed retrospectively on posttransplant sera of patients who received a graft between 1997 and 1999. Ninety-four kidney-only recipients were tested and all FCXm positive sera were investigated for the presence of HLA class I and II antibodies by Flow panel reactive antibodies. From 94 patients with a negative pretransplant complement-dependent cytotoxicity crossmatch, seven (7%) showed a positive pretransplant FCXm. After transplantation the FCXm became positive in five patients (6%). The predictive value of a positive FCXm after transplantation, and the log-transformed relative change in fluorescence ratio between pretransplant and posttransplant serum, were not significant to rejection within six months, nor to graft survival censored for death. The presence of HLA antibodies before rejection or graft failure could only be shown in a minority of patients; most antibodies were detected after graft failure, especially after transplantectomy. Monitoring through antibody testing after transplantation on the basis of our results has no added value with tacrolimus-based immunosuppression.

Effect of HLA mismatching and antibody status on “homovital” aortic valve homograft performance

Background. Recipients of “homovital” aortic valve homografts are known to produce specific antibodies to human leukocyte antigen (HLA) determinants present on the cellular compartment of the valve tissue; however, the clinical significance of these antibodies is unknown. Data from 182 patients receiving homovital aortic valve homografts has been analyzed to determine the impact of HLA disparity and HLA antibody production on survival and function of the homograft. Methods. Human leukocyte antigen mismatch data were available for 127 patients (mean follow-up, 6.02 ± 0.26 years). Two patients were considered well matched for HLA A+B antigens (zero or one mismatch) compared with 125 poorly matched (two to four mismatches). Nine patients had a zero HLA-DR mismatch compared with 52 with one mismatch and 59 patients completely mismatched for DR antigens. Results. There was no significant association between the degree of HLA mismatch for either class I or class II antigens whether the loci were considered alone or in combination (ie, A, B, DR, AB, or ABDR mismatching) with markers of long-term valve function including patient mortality, reoperation, valve degeneration, valve stenosis, presence of regurgitation, and postoperative New York Heart Association class. One hundred thirty-six of 167 (82%) were found to have produced antibodies after operation (mean time after operation, 6.42 ± 0.58 years). In 61 cases both antibody specificity and donor HLA typing was available. In 92% of these, the antibodies were of the IgG subclass and were specific for the HLA class I molecules of the donor. The presence of HLA antibodies was associated with an increase in the frequency of mild valve stenosis (not significant) compared with those patients who did not develop HLA antibodies (antibody negative = 9.7%; panel reactive antibodies <50% = 29.1%; and panel reactive antibodies >50% = 22.2%; not significant). There was also an increased prevalence of valve degeneration associated with HLA antibodies. The actuarial freedom from valve degeneration for the 35 HLA antibody-negative patients was 100% at 1, 5, and 10 years compared with 100% at 1 year, 97% at 5 years, and 92% at 10 years for 55 patients with panel reactivity less than 50%, and 98% at 1 year, 94% at 5 years, and 88% at 10 years for the 77 patients who were highly sensitized (not significant). There was no correlation with other markers of long-term valve function. Conclusions. The influence of the immune response on valve function requires further studies involving large numbers of patients followed for a longer period of time. We believe prospective matching for HLA antigens is warranted to produce a well-matched cohort of patients for analysis and to reduce antibody sensitization, which would help to clarify this issue.