Assessing the potential of angiotensin II type 1 receptor and donor specific anti-endothelial cell antibodies to predict long-term kidney graft outcome.

Endothelial cell antigens have been reported as potential targets for antibodies in the context of organ transplantation, leading to increased risk for graft failure. Serum samples from 142 consecutive living donor kidney recipients were tested for the presence of antibodies to angiotensin II - type 1 receptor (AT1R), donor endothelial cells, and donor HLA. Graft survival was monitored for five years post-transplant, and secondary outcomes, including biopsy-proven rejection, proteinuria, biopsy-proven vasculopathy, and renal function based on serum creatinine were also assessed for the first two to three years. AT1R antibody levels were positive (>17U/mL) in 11.3%, 18.8% and 8.1% of patients pre-transplant, post-transplant and at time of indication biopsy, respectively. XM-ONE assay was positive in 17.6% of patients pre-transplant (7 IgG+; 15 IgM+; 3 IgG+/IgM+). Overall, 4 patients experienced antibody-mediated rejection (AMR), 31 borderline cellular rejection (BCR), 19 cellular rejection (CR) and 3 mixed AMR and CR within the first 24months. While pre-existing and de novo donor-specific HLA antibodies were associated with graft failure and many secondary outcomes, no statistical association was found for either anti-endothelial or anti-AT1R antibodies, indicating that these tests may not be the best predictors of graft outcome in living donor renal transplantation.

Real-time qPCR for chimerism assessment in allogeneic hematopoietic stem cell transplants from unrelated adult and double umbilical cord blood.

Allogeneic hematopoietic stem cell transplantation is the standard therapy for patients with various malignant hematologic disorders. A successful treatment results in complete engraftment of donor cells in the absence of the patient's own hematopoietic system. Chimerism analysis, aimed at determining the coexistence of genetically different cell populations, is considered a useful method to measure treatment success. A new, qPCR based, commercially available chimerism assay was recently introduced. Here we report our results of comparing STR with qPCR-based chimerism analysis, and assessment of sensitivity and reproducibility of the qPCR chimerism assay. A specific emphasis is put on analyzing chimerism in recipients of double cord blood transplantation. We conclude that the qPCR chimerism assay for engraftment monitoring is a reliable and sensitive assay. Advantages and limitations of the assay in its current format are summarized.

HLA-DQ barrier: effects on cPRA calculations.

BACKGROUND: Panel-reactive antibody (PRA) testing provides assessment of the breadth of sensitization a patient might have against human leukocyte antigen (HLA) antigens. The evolution of calculated PRA (cPRA) reflects the commitment of the transplant community to increase accessibility and promote equity to all patients awaiting kidney transplantation. Recent data from our center and others, however, suggested that a significant diversity of HLA-DQ antigens is not captured, which may lead to inequity in allocating cPRA points. METHODS: HLA-DRB1-DQA1-DQB1 typing of 2182 individuals was evaluated for this study using Luminex-based sequence-specific oligonucleotide typing. A total of 3182 haplotypes were confirmed to have the level of resolution required for this study. RESULTS: The diversity of HLA-DQαß alleles is greater than what is apparent using the serologic equivalents. The distribution of these alleles within a serologic group varies, with some alleles being more frequent than others; therefore, their representation within the current cPRA system is inaccurate. Three informative examples are given. Haplotypes of DR antigens with DQαß alleles did not always follow the common published linkage disequilibrium, especially in populations where there is greater genetic diversity. CONCLUSIONS: The current cPRA system does not take into account the distribution of molecular equivalents within DQ serologic specificities. This can result is inequitable allocation of sensitization points and disadvantaging the more sensitized patients. To ameliorate this situation, the United Network for Organ Sharing system should allow inputting HLA-DQαß alleles both for donor typing and as antibody specificities, which will lead to better representation of unacceptable DQ alleles and improve organ allocation equity.

A prospective study evaluating the role of donor-specific anti-endothelial crossmatch (XM-ONE assay) in predicting living donor kidney transplant outcome.

Anti-endothelial cell antibodies (AECAs) may play a role in allograft rejection. We prospectively tested 150 consecutive living donor kidney transplant recipients, with transplants performed at Northwestern Memorial Hospital between January and December 2010, using the donor-specific endothelial (XM-ONE) crossmatch. 88/150 Patients received standard of care (SOC) immunosuppression and analyzed separately, in addition to the complete study cohort. Patients were followed for one year and XM-ONE results were analyzed in relation to occurrence of acute rejection, proteinuria, serum creatinine levels, and biopsy proven fibrosis. No correlation was found between XM-ONE results and protocol or "for-cause" biopsy proven acute rejection or vasculopathy at 12 months. When IgG+ and IgM+ results of the XM-ONE assay were combined, a correlation with proteinuria at 12 months was observed (p=0.047). Although IgG+XM-ONE results were associated with significantly higher creatinine at 6 months (p=0.018), significance was lost at 12 months. Conversely, patients with an IgM+XM-ONE crossmatch had significantly lower creatinine at 1 month (p=0.019), 3 months (p=0.0045), and 6 months (p=0.038) post-transplant, but lost statistical significance at 12 months (p=0.67) post-transplant. In summary, the presence of AECAs as determined by a positive XM-ONE result was not predictive of overall poorer graft outcome after one year in our center.

The DQ barrier: improving organ allocation equity using HLA-DQ information.

BACKGROUND: The United Network for Organ Sharing algorithm for deceased-donor kidney allocation considers only the human leukocyte antigen (HLA)-A, HLA-B, and HLA-DR loci. Although HLA-DQ serologic specificities can be entered as unacceptable antigens, they are assigned only by the identity of the DQß chain, disregarding the role of the similarly polymorphic α chain. DQα/ß combinations result in unique antigenic epitopes, which serve as targets to different antibodies. Therefore, the presence of HLA antibodies to one DQα/ß combination should not preclude negative crossmatch (XM) against another combination. In this retrospective analysis, patients were allowed XM against a particular donor if they had antibodies to some, but not all, DQα/ß allele combinations with the donor serologic HLA-DQ antigens. METHODS: HLA antibody signature was obtained using solid-phase Luminex-based antibody analysis. Results were captured at the high-resolution level (as provided by the positive beads). Potential donors were typed to include information on both HLA-DQA and HLA-DQB alleles. RESULTS: Of the 1130 flow XM assays performed, 147 patients had antibodies to donor serologic HLA-DQ antigens. Thirty-five of those patients had antibodies to an allelic DQα/ß combination within the donor serologic DQ specificity that were different from the donor's DQα/ß, leading to negative flow XM results (24%). Virtual XM, accounting for donor DQα/ß combinations, successfully predicts more than 98% of XM outcomes. CONCLUSIONS: In patients with allelic DQα/ß antibodies, denying the opportunity for XM based on serologically defined unacceptable antigens can disadvantage the patient. Larger cohort studies are required to substantiate our observation. Introducing DQα/ß combination information may increase virtual XM accuracy and organ allocation equity.

Role of ELISPOT Assays in Risk Assessment Pre- and Post-Kidney Transplantation.

Immunologic risk in kidney transplantation is typically minimized by avoiding, or at least limiting, the potential of donor specific humoral responses by testing for the presence of donor-specific antibodies (DSA). Additionally, selecting donor and recipient pairs with the least number of human leukocyte antigen (HLA) mismatches has been shown to play a role in transplant outcome. However, numerous other factors may play a role in the success of transplant outcome and patient health. Specifically, the use of T-cell allospecific ELISPOT assays have helped elucidate the role of pre-formed cellular responses as additional factors in post-transplant outcome. In this review, we will evaluate numerous uses of ELISPOT assays to assess the pre- and post-transplant immunologic risk of rejection episodes, graft survival and even viral susceptibility as well as the utility of ELISPOT assays in monitoring tolerance and withdrawal of immunosuppressive medications following kidney transplantation.

Common gamma chain cytokines promote rapid in vitro expansion of allo-specific human CD8+ suppressor T cells.

Human CD8(+) regulatory T cells, particularly the CD8(+)CD28(-) T suppressor cells, have emerged as an important modulator of alloimmunity. Understanding the conditions under which these cells are induced and/or expanded would greatly facilitate their application in future clinical trials. In the current study, we develop a novel strategy that combines common gamma chain (γc) cytokines IL-2, IL-7 and IL-15 and donor antigen presenting cells (APCs) to stimulate full HLA-mismatched allogeneic human CD8(+) T cells which results in significant expansions of donor-specific CD8(+)CD28(-) T suppressor cells in vitro. The expanded CD8(+)CD28(-) T cells exhibit increased expressions of CTLA-4, FoxP3, and CD25, while down-regulate expressions of CD56, CD57, CD127, and perforin. Furthermore, these cells suppress proliferation of CD4(+) T cells in a contact-dependent and cytokine-independent manner. Interestingly, the specificity of suppression is restricted by the donor HLA class I antigens but promiscuous to HLA class II antigens, providing a potential mechanism for linked suppression. Taken together, our results demonstrate a novel role for common γc cytokines in combination with donor APCs in the expansion of donor-specific CD8(+)CD28(-) T suppressor cells, and represent a robust strategy for in vitro generation of such cells for adoptive cellular immunotherapy in transplantation.