Immunological Monitoring of Renal Transplant Recipients to Predict Acute Allograft Rejection Following the Discontinuation of Tacrolimus

Contains fulltext : 69863.pdf (publisher's version ) (Open Access)BACKGROUND: Transplant patients would benefit from reduction of immunosuppression providing that graft rejection is prevented. We have evaluated a number of immunological markers in blood of patients in whom tacrolimus was withdrawn after renal transplantation. The alloreactive precursor frequency of CD4+ and CD8+ T cells, the frequency of T cell subsets and the functional capacity of CD4+CD25+FoxP3+ regulatory T cells (Treg) were analyzed before transplantation and before tacrolimus reduction. In a case-control design, the results were compared between patients with (n = 15) and without (n = 28) acute rejection after tacrolimus withdrawal. PRINCIPAL FINDINGS: Prior to tacrolimus reduction, the ratio between memory CD8+ T cells and Treg was higher in rejectors compared to non-rejectors. Rejectors also had a higher ratio between memory CD4+ T cells and Treg, and ratios <20 were only observed in non-rejectors. Between the time of transplantation and the start of tacrolimus withdrawal, an increase in naive T cell frequencies and a reciprocal decrease of effector T cell percentages was observed in rejectors. The proportion of Treg within the CD4+ T cells decreased after transplantation, but anti-donor regulatory capacity of Treg remained unaltered in rejectors and non-rejectors. CONCLUSIONS: Immunological monitoring revealed an association between acute rejection following the withdrawal of tacrolimus and 1) the ratio of memory T cells and Treg prior to the start of tacrolimus reduction, and 2) changes in the distribution of naive, effector and memory T cells over time. Combination of these two biomarkers allowed highly specific identification of patients in whom immunosuppression could be safely reduced

Detailed Kinetics of the Direct Allo-Response in Human Liver Transplant Recipients: New Insights from an Optimized Assay

Conventional assays for quantification of allo-reactive T-cell precursor frequencies (PF) are relatively insensitive. We present a robust assay for quantification of PF of T-cells with direct donor-specificity, and establish the kinetics of circulating donor-specific T cells after liver transplantation (LTx). B cells from donor splenocytes were differentiated into professional antigen-presenting cells by CD40-engagement (CD40-B cells). CFSE-labelled PBMC from LTx-recipients obtained before and at several time points after LTx, were stimulated with donor-derived or 3rd party CD40-B cells. PF of donor-specific T cells were calculated from CFSE-dilution patterns, and intracellular IFN-γ was determined after re-stimulation with CD40-B cells. Compared to splenocytes, stimulations with CD40-B cells resulted in 3 to 5-fold higher responding T-cell PF. Memory and naïve T-cell subsets responded equally to allogeneic CD40-B cell stimulation. Donor-specific CD4+ and CD8+ T-cell PF ranged from 0.5 to 19% (median: 5.2%). One week after LTx, PF of circulating donor-specific CD4+ and CD8+ T cells increased significantly, while only a minor increase in numbers of T cells reacting to 3rd party allo-antigens was observed. One year after LTx numbers of CD4+ and CD8+ T cells reacting to donor antigens, as well as those reacting to 3rd party allo-antigens, were slightly lower compared to pre-transplant values. Moreover, CD4+ and CD8+ T cells responding to donor-derived, as well as those reacting to 3rd party CD40-B cells, produced less IFN-γ. In conclusion, our alternative approach enables detection of allo-reactive human T cells at high frequencies, and after application we conclude that donor-specific T-cell PF increase immediately after LTx. However, no evidence for a specific loss of circulating T-cells recognizing donor allo-antigens via the direct pathway up to 1 year after LTx was obtained, underscoring the relative insensitiveness of previous assays

Mycophenolate mofetil versus cyclosporine for remission maintenance in nephrotic syndrome

We performed a multi-centre randomized controlled trial to compare the efficacy of mycophenolate mofetil (MMF) to that of cyclosporine A (CsA) in treating children with frequently relapsing nephrotic syndrome and biopsy-proven minimal change disease. Of the 31 randomized initially selected patients, seven were excluded. The remaining 24 children received either MMF 1200 mg/m2per day (n = 12) or CsA 4-5 mg/kg per day (n = 12) during a 12-month period. Of the 12 patients in the MMF group, two discontinued the study medication. Evaluation of the changes from the baseline glomerular filtration rate showed an overall significant difference in favour of MMF over the treatment period (p = 0.03). Seven of the 12 patients in the MMF group and 11 of the 12 patients in the CsA group remained in complete remission during the entire study period. Relapse rate in the MMF group was 0.83/year compared to 0.08/year in the CsA group (p = 0.08). None of the patients reported diarrhea. Pharmacokinetic profiles of mycophenolic acid were performed in seven patients. The patient with the lowest area under the curve had three relapses within 6 months. In children with frequently relapsing minimal change nephrotic syndrome, MMF has a favourable side effect profile compared to CsA; however, there is a tendency towards a higher relapse risk in patients treated with MMF

Pin1 Modulates the Type 1 Immune Response

BACKGROUND/ABSTRACT: Immune responses initiated by T cell receptor (TCR) and costimulatory molecule mediated signaling culminate in maximal cytokine mRNA production and stability. The transcriptional responses to co-stimulatory T cell signalling involve calcineurin and NF-AT, which can be antagonized by interference with the cis-trans peptidyl-prolyl isomerases (PPIase), cyclophilin A and FKBP. Signalling molecules downstream of CD28 which are essential for the stabilization of cytokine mRNAs are largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: We now show that Pin1, a third member of the PPIase family mediates the post-transcriptional regulation of Th1 cytokines by activated T cells. Blockade of Pin1 by pharmacologic or genetic means greatly attenuated IFN-γ, IL-2 and CXCL-10 mRNA stability, accumulation and protein expression after cell activation. In vivo, Pin1 blockade prevented both the acute and chronic rejection of MHC mismatched, orthotopic rat lung transplants by reducing the expression of IFN-γ and CXCL-10. Combined transcriptional and post-transcriptional blockade with cyclosporine A and the Pin1 inhibitor, juglone, was synergistic. CONCLUSIONS/SIGNIFICANCE: These data suggest Pin1 inhibitors should be explored for use as immunosuppressants and employed with available calcineurin inhibitors to reduce toxicity and enhance effectiveness

Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis

Selenium-binding protein 1 (SELENBP1) has been associated with several cancers, although its exact role is unknown. We show that SELENBP1 is a methanethiol oxidase (MTO), related to the MTO in methylotrophic bacteria, that converts methanethiol to H2O2, formaldehyde, and H2S, an activity not previously known to exist in humans. We identified mutations in SELENBP1 in five patients with cabbage-like breath odor. The malodor was attributable to high levels of methanethiol and dimethylsulfide, the main odorous compounds in their breath. Elevated urinary excretion of dimethylsulfoxide was associated with MTO deficiency. Patient fibroblasts had low SELENBP1 protein levels and were deficient in MTO enzymatic activity; these effects were reversed by lentivirus-mediated expression of wild-type SELENBP1. Selenbp1-knockout mice showed biochemical characteristics similar to those in humans. Our data reveal a potentially frequent inborn error of metabolism that results from MTO deficiency and leads to a malodor syndrome.info:eu-repo/semantics/publishedVersio

The direct and indirect allogeneic presentation pathway during acute rejection after human cardiac transplantation

Alloreactive T cells may be activated via a direct or an indirect antigen presentation pathway. We questioned whether the frequency of interferon (IFN)-γ producing cells determined by enzyme-linked immunospot (ELISPOT) assay is an effective tool to monitor the direct and/or indirect presentation pathway. Secondly, we wondered whether early and late acute rejection (AR) are associated with both pathways. Before (n = 15), during (n = 18) and after (n = 16) a period of AR, peripheral blood mononuclear cell (PBMC) samples were tested from 13 heart transplant recipients. The direct presentation pathway was always present. The number of IFN-γ producing cells reactive to this pathway increased significantly (P = 0·04) during AR and the number decreased (P = 0·005) after AR therapy. In contrast, the indirect allogeneic presentation pathway was present in only eight of 18 AR samples. When the indirect presentation pathway was detectable, it increased significantly during AR. Five of eight of these AR occurred more than 6 months after transplantation. The ELISPOT assay, enumerating alloreactive IFN-γ producing cells, is a valuable tool to determine the reactivity via both the direct and the indirect presentation pathway. The direct presentation pathway always plays a role in AR, while the indirect pathway contributes especially to late AR

Mutual tolerance after liver and not after heart transplantation? Evaluation of patient-anti-donor and donor-anti-patient responses by mixed lymphocyte culture

The ultimate goal in organ transplantation is the induction of donor-specific transplantation tolerance. The fact that in some patients it is possible to withdraw immunosuppressive therapy completely, suggests that immunological adaptation or donor-specific nonresponsiveness can occur following transplantation. In earlier studies we have shown that after blood transfusion, the mixed lymphocyte reactivity of the donor against patient peripheral blood mononuclear lymphocytes taken after blood transfusion gradually decreased with time. This may reflect the induction of an immunoregulatory mechanism, which protects the recipient against an immune reaction of the donor, enhancing a state of mixed chimerism. A similar phenomenon might also play a role in the immunological mechanism leading to transplantation tolerance. Therefore, we studied responses in patients with a well-functioning liver and heart transplant using a primed lymphocyte test (PLT) and a mixed lymphocyte culture (MLC). Two years after liver transplantation the PLT and MLC responses of patient against donor were decreased significantly compared to the situation before transplantation The response of donor against patient was also lower two years after transplantation The decreased responses were donor-specific since responses to third-party cells generally remained unchanged. Tn heart transplant recipients we could not detect a donor-specific downregulation. The reversed response, of donor against patient, was not different from responses of third-party against patient cells. Therefore, we conclude that donor-specific nonresponsiveness is not induced in patients with well-functioning heart transplants. In contrast, after a successful liver transplantation the response of patient against donor is decreased, as is the reversed response. It may be valuable to test whether in liver transplant patients withdrawing or reducing of maintenance immunosuppression is permitted for patients who appear to have developed two-way donor-specific hyporeactivity

Mutual tolerance after liver and not after heart transplantation? Evaluation of patient-anti-donor and donor-anti-patient responses by mixed lymphocyte culture

The ultimate goal in organ transplantation is the induction of donor-specific transplantation tolerance. The fact that in some patients it is possible to withdraw immunosuppressive therapy completely, suggests that immunological adaptation or donor-specific nonresponsiveness can occur following transplantation. In earlier studies we have shown that after blood transfusion, the mixed lymphocyte reactivity of the donor against patient peripheral blood mononuclear lymphocytes taken after blood transfusion gradually decreased with time. This may reflect the induction of an immunoregulatory mechanism, which protects the recipient against an immune reaction of the donor, enhancing a state of mixed chimerism. A similar phenomenon might also play a role in the immunological mechanism leading to transplantation tolerance. Therefore, we studied responses in patients with a well-functioning liver and heart transplant using a primed lymphocyte test (PLT) and a mixed lymphocyte culture (MLC). Two years after liver transplantation the PLT and MLC responses of patient against donor were decreased significantly compared to the situation before transplantation The response of donor against patient was also lower two years after transplantation The decreased responses were donor-specific since responses to third-party cells generally remained unchanged. Tn heart transplant recipients we could not detect a donor-specific downregulation. The reversed response, of donor against patient, was not different from responses of third-party against patient cells. Therefore, we conclude that donor-specific nonresponsiveness is not induced in patients with well-functioning heart transplants. In contrast, after a successful liver transplantation the response of patient against donor is decreased, as is the reversed response. It may be valuable to test whether in liver transplant patients withdrawing or reducing of maintenance immunosuppression is permitted for patients who appear to have developed two-way donor-specific hyporeactivity