Regulatory T cells in kidney transplant recipients: the effect of induction immunosuppression therapy

Background. Regulatory T cells have been suggested to down-regulate the alloimmune response. The aim of this prospective open study was to evaluate the effects of different inductive agents on peripheral blood regulatory T cells in kidney transplant patients and to analyse their association with short-term graft outcome.
Methods. Regulatory and effector T cell numbers in peripheral blood were determined by flow cytometry in 71 prospectively followed kidney transplant recipients at postoperative day 0, 7, 14, 21, 28, 60 and 90. Patients were treated with a calcineurin inhibitor-based triple immunosuppression with polyclonal rabbit anti-thymocyte globulin (rATG, n = 28), basiliximab, the anti-CD25 monoclonal antibody (n = 18) or without induction (controls, n = 25). Flow cytometry data were correlated to rejection incidence.
Results. Compared to controls, CD4⁺CD25⁺FoxP3⁺ regulatory T-cell expansion among CD4⁺ T cells was noticed in the rATG group at all post-transplant time-points by Day 14 (P < 0.001). A significant decrease in Treg frequency (P < 0.001) and concurrently a transient increase of CD4⁺CD25^low/–FoxP3⁺ population were observed in basiliximab-treated patients 7–60 days post-transplantation. Biopsy-proven acute rejection occurred in 16.7% of controls, 10.7% of the rATG group and in 11.1% of the basiliximab group. Higher CD4⁺FoxP3⁺/CD8⁺CD45RA⁺CD62L^– ratios were observed repeatedly in those patients after basiliximab induction who were rejection free (P < 0.01).
Conclusions. In this study, the rATG induction therapy was associated with an expansion of regulatory cells. Sustained high CD4⁺FoxP3⁺/Teff ratios were associated with the absence of rejection after basiliximab induction (read more).

Trends in immune function assay (ImmuKnow; Cylex™) results in the first year post-transplant and relationship to BK virus infection

Background. The ImmuKnow assay is a functional T-cell assay (TCA) that may quantify cellular immune responsiveness following renal transplantation. Using a standard protocol of TCA sampling in the first year post-transplant, we examined changes in TCA values over time and tested for an association between TCA and BK virus (BKV) infection as a marker of over-immunosuppression.
Methods. We performed a single-center retrospective analysis of 897 TCA results in 414 renal transplant recipients obtained at 0 (N = 122), 1 (N = 316), 6 (N = 258) and 12 (N = 201) months post-transplant from May 2005 to July 2009 with concurrent urine and blood BKV polymerase chain reaction measurements.
Results. Nearly 40% of patients experienced a decrease in TCA of >150 ng/mL from 1 to 6 months (mean 466–356 ng/mL, P < 0.0001) and remained stable from 6 to 12 months (mean 357 versus 370 ng/mL, P = 0.33). Neither a change in TCA of >150 ng/mL nor a TCA value of ≤225 ng/mL were associated with a diagnosis of BKV infection at 1 or 6 months, while TCA ≤225 ng/mL was associated with BKV infection at 12 months (P = 0.005).
Conclusions. A reduction in TCA from 1 to 6 months post-transplant is common and is not associated with conditions of over-immunosuppression, rendering the interpretation of changes in TCA during this time period difficult. BKV infection is associated with low TCA values at 12 months, suggesting that patients with low TCA values after 6 months may benefit from potential tailoring of immunosuppression or more aggressive monitoring to prevent subsequent BKV infection (read more).

Localization of Mesenchymal Stromal Cells Dictates Their Immune or Proinflammatory Effects in Kidney Transplantation

Multipotent mesenchymal stromal cells (MSC) have recently emerged as promising candidates for cell-based immunotherapy in solid-organ transplantation. However, optimal conditions and settings for fully harnessing MSC tolerogenic properties need to be defined. We recently reported that autologous MSC given posttransplant in kidney transplant patients was associated with transient renal insufficiency associated with intragraft recruitment of neutrophils and complement C3 deposition. Here, we moved back to a murine kidney transplant model with the aim to define the best timing of MSC infusion capable of promoting immune tolerance without negative effects on early graft function. We also investigated the mechanisms of the immunomodulatory and/or proinflammatory activities of MSC according to whether cells were given before or after transplant. Posttransplant MSC infusion in mice caused premature graft dysfunction and failed to prolong graft survival. In this setting, infused MSC localized mainly into the graft and associated with neutrophils and complement C3 deposition. By contrast, pretransplant MSC infusion induced a significant prolongation of kidney graft survival by a Treg-dependent mechanism. MSC-infused pretransplant localized into lymphoid organs where they promoted early expansion of Tregs. Thus, pretransplant MSC infusion may be a useful approach to fully exploit their immunomodulatory properties in kidney transplantation (read more).

Graft invariant natural killer T-cell dose predicts risk of acute graft-versus-host disease in allogeneic hematopoietic stem cell transplantation

Invariant natural killer T (iNKT) cells are powerful immunomodulatory cells that in mice regulate a variety of immune responses, including acute GVHD (aGVHD). However, their clinical relevance and in particular their role in clinical aGVHD are not known. We studied whether peripheral blood stem cell (PBSC) graft iNKT-cell dose affects on the occurrence of clinically significant grade II-IV aGVHD in patients (n = 57) undergoing sibling, HLA-identical allogeneic HSCT. In multivariate analysis, CD4^– iNKT-cell dose was the only graft parameter to predict clinically significant aGVHD. The cumulative incidence of grade II-IV aGVHD in patients receiving CD4^– iNKT-cell doses above and below the median were 24.2% and 71.4%, respectively (P = .0008); low CD4^– iNKT-cell dose was associated with a relative risk of grade II-IV aGVHD of 4.27 (P = .0023; 95% CI, 1.68-10.85). Consistent with a role of iNKT cells in regulating aGVHD, in mixed lymphocyte reaction assays, CD4^– iNKT cells effectively suppressed T-cell proliferation and IFN- secretion in a contact-dependent manner. In conclusion, higher doses of CD4^– iNKT cells in PBSC grafts are associated with protection from aGVHD. This effect could be harnessed for prevention of aGVHD (read more).

Proteinuria after kidney transplantation

The prevalence of proteinuria at 1 year after renal transplantation ranges between 11% and 45% and is even higher in patients treated with inhibitors of the mammalian target of rapamycin (mTOR). Two main mechanisms can lead to proteinuria: an inadequate reabsorption of small proteins from proximal tubular cells damaged by ischemia-reperfusion injury, rejection, or toxic agents (tubular proteinuria) or an increased passage of albumin and/or protein with higher molecular weight (MW) because of a disruption of glomerular barrier caused by recurrent or de novo glomerulonephritis, transplant glomerulopathy, chronic rejection, or CNI toxicity (glomerular proteinuria). Proteinuric patients have worse patient and graft survival rates in comparison to non proteinuric patients. The amount of proteinuria is a reliable predictor of the allograft outcome. However, even microalbuminuria may be associated with a poor outcome. Treatment of proteinuria mainly rests on the management of the etiologic cause. Inhibitors of renin-angiotensin system (RAS) are useful in reversing microalbuminuria and can reduce proteinuria, but their efficacy in interfering with patient or graft survival is not demonstrated (read more).

HHV-6B is frequently found in the gastrointestinal tract in kidney transplantation patients

In immunosuppressed patients human herpesvirus 6 (HHV-6) reactivations are common. The aim of the study was to determine to which extent HHV-6 can be found in the gastrointestinal tract in kidney transplant recipients and in patients on chronic dialysis. The HHV-6 and cytomegalovirus (CMV) examinations were performed on gastro duodenal and colon biopsy specimens obtained from 81 kidney transplant recipients and on 46 chronic dialysis patients. The HHV-6 and CMV were demonstrated by immunohistochemistry detecting both HHV-6A and HHV-6B, and CMV-specific antigens. The HHV-6B-positive cells, were found in gastroduodenal biopsy specimens from 34% of the transplant recipients and 28% of the patients on chronic dialysis, CMV-positive cells were found in specimens from 53% of the transplant recipients and 28% of the patients on chronic dialysis. The HHV-6B positive cells were found in the colonic mucosa specimens from 36% of the transplant recipients and 22% of the patients on chronic dialysis, CMV-positive cells were found in specimens from 36% of the transplant recipients and 17% of the patients on chronic dialysis. The HHV-6B positive cells were found equally often in the gastroduodenal as in the colorectal mucosa. The HHV-6B positive cells as well as CMV positive cells were simultaneously found in every fifth of transplant recipients (read more).

Human leukocyte antigen epitope analysis to assess complement- and non-complement-binding donor-specific antibody repertoire in a pediatric heart transplant recipient.

This case report summarizes the spectrum of anti-human leukocyte antigen (HLA) antibody reactivity determined by single-allele Luminex immunoglobulin G and C1q binding assays before transplant, during an episode of antibody-mediated rejection (AMR), and following treatment in a sensitized pediatric heart transplant (Tx) recipient. We were able to discriminate between complement- and non-complement-binding epitope-specific antibodies present against a single donor antigen (HLA-A2) during the progression of AMR and its resolution. Our findings illustrate the usefulness of determining antibody specificities against epitopes using various Luminex-based assays (read more)