CD4+CD25+ T regulatory cells in renal transplantation.

The immune response to an allograft activates lymphocytes with the capacity to cause rejection. Activation of CD4+CD25+Foxp3+T regulatory cells (Treg) can down-regulate allograft rejection and can induce immune tolerance to the allograft. Treg represent <10% of peripheral CD4+T cells and do not markedly increase in tolerant hosts. CD4+CD25+Foxp3+T cells include both resting and activated Treg that can be distinguished by several markers, many of which are also expressed by effector T cells. More detailed characterization of Treg to identify increased activated antigen-specific Treg may allow reduction of non-specific immunosuppression. Natural thymus derived resting Treg (tTreg) are CD4+CD25+Foxp3+T cells and only partially inhibit alloantigen presenting cell activation of effector cells. Cytokines produced by activated effector cells activate these tTreg to more potent alloantigen-activated Treg that may promote a state of operational tolerance. Activated Treg can be distinguished by several molecules they are induced to express, or whose expression they have suppressed. These include CD45RA/RO, cytokine receptors, chemokine receptors that alter pathways of migration and transcription factors, cytokines and suppression mediating molecules. As the total Treg population does not increase in operational tolerance, it is the activated Treg which may be the most informative to monitor. Here we review the methods used to monitor peripheral Treg, the effect of immunosuppressive regimens on Treg, and correlations with clinical outcomes such as graft survival and rejection. Experimental therapies involving ex vivo Treg expansion and administration in renal transplantation are not reviewed.

Association between islet xenograft rejection mediated by activated macrophages and upregulated chemokines.

OBJECTIVE: Our previous study has shown that porcine antigen-primed and CD4+ T cells activated macrophages are capable of the Recognition and rejection of porcine xenografts but not mouse allografts, and therefore suggested the involvement of signaling between the graft and macrophages in this specific graft recognition and destruction. METHODS: NOD-SCID mice were transplanted with fetal pig pancreatic fragment (FPP) before adoptive transfer with exogenous macrophages isolated from rejecting FPP xenografts of BALB/c recipient mice. The exogenous macrophages were tracked by Ly5.1 surface antigen or via CSFE staining. Gene expression of CCR2 and CCR5 and their chemokines in transplanted FPP xenografts was evaluated by real-time PCR. RESULTS: After the adoptive transfer, recently transplanted but not established FPP xenografts were rejected by exogenous activated macrophages. In the meantime, greater level of chemokine gene expression was detected in recently-transplanted compared with the established xenografts. Furthermore, expression of both CCR2 and CCR5 genes was enhanced significantly in activated macrophages when compared with non-activated macrophages. CONCLUSION: Upregulated chemokines were associated with macrophage recruitment and destruction of islet xenografts.

The Utility of Sonographic Assessment in Selecting Patients for Percutaneous Insertion of Peritoneal Dialysis Catheter.

BACKGROUND: Percutaneous insertion of peritoneal dialysis (PD) catheters by nephrologists is a safe and effective alternative to open surgical techniques. These patients are usually carefully selected due to anatomical considerations and medical comorbidities, with the current literature suggesting exclusion of patients with prior abdominal surgery. METHOD: We conducted a retrospective cohort study of pre-dialysis patients who attended a preprocedural clinic in a tertiary center over 6 years. Procedural complications and catheter survival were assessed. Chi-squared test and Kaplan-Meier survival analysis were undertaken. Inpatient assessments were excluded. RESULTS: A total of 217 patients were assessed, of whom 171 (78.8%) were accepted for percutaneous PD catheter insertion by a nephrologist. The key exclusion criteria were: (1) the clinical presence of abdominal hernia (p < 0.001), (2) ultrasound findings of skin to peritoneum depth of > 5.5 cm (p < 0.001) and (3) ultrasound findings of impaired visceral slide test (p < 0.001). Prior abdominal surgery was not a default exclusion criterion (p = 0.1), as 63 patients (37%) with prior abdominal surgery, average of 1.3 prior surgeries per patient, were assessed as appropriate for the percutaneous procedure. There was no difference in the procedural complication rate and catheter survival between patients with and without prior abdominal surgery. CONCLUSION: A comprehensive preprocedural assessment utilizing ultrasound permits an objective selection of patients for percutaneous insertion of PD catheters by nephrologists. This allowed for successful and safe percutaneous insertion of PD catheters in patients who may have otherwise been excluded, e.g., prior abdominal surgery, patients with large bilateral polycystic kidneys, and central obesity.

The impact of tunnelled vascular catheters on time to arteriovenous fistula creation.

PURPOSE: The purpose of this study is to examine the effect of the presence of tunnelled vascular catheter (TVC) on physician referral and surgeon review and operating patterns and ultimately time of creation of permanent haemodialysis (HD) access. METHODS: A retrospective analysis of TVC and arteriovenous fistulae (AVF) databases in 2010. Physician referral time and surgical time to operation were compared between patients commencing HD with TVC and a control group who commenced HD with AVF. RESULTS: The AVF group (n = 27) commenced HD with an AVF and TVC group (n = 49) commenced HD via a TVC. Time from physician referral to surgeon review in the AVF vs. TVC group was 29 vs. 35 days (p = 0.6). Time from surgeon review to access creation was 43 vs. 50 days (p = 0.4). However, in the TVC group, the time from TVC insertion to physician referral to a surgeon was an additional 109 ± 20 days. Subgroup analysis of 11 TVC patients (23%) presenting at end stage without AVF (crash starters) had a TVC to physician referral time of 103 ± 75 days, physician referral to surgeon review of 14.4 ± 4 days and surgeon review to AVF of 67 ± 23 days. CONCLUSIONS: The presence of a TVC is associated with a significant delay (>3 months) before physicians make a referral for surgeon review. There was no surgeon-related delay to access creation related to the presence of a TVC.

Adverse impact of hepatitis C virus infection on renal replacement therapy and renal transplant patients in Australia and New Zealand.

BACKGROUND: Understanding the impact of hepatitis C virus (HCV) infection in patients with end-stage renal disease before and after renal transplantation requires more data. We examined the outcomes of HCV antibody positive (HCVAb+) dialysis and renal transplant patients using the Australian and New Zealand Dialysis and Transplant registry. METHODS: Two cohorts of dialysis (n=23,046) and transplant (n=7572) patients were identified. Survival outcomes, causes of mortality, and causes of graft failure were examined. RESULTS: Dialysis Cohort: 362 (1.6%) were HCVAb+ve. The cause of end-stage renal disease in the HCVAb+ve group was more likely to be glomerulonephritis or diabetes. Survival figures were similar at 5 years (48% vs. 47%) and 10 years (22% and 20%) for HCVAb+ve and HCVAb negative (HCVAb-ve) groups; however, the adjusted hazard ratio (aHR) for mortality was increased, 1.25 (95% confidence interval [CI], 1.07-1.46), for the HCVAb+ve cohort. Liver failure was more likely. Renal Transplantation Cohort: 140 (1.8%) were HCVAb+ve. Patient survival among HCVAb+ve and HCVAb-ve groups was 77% vs. 90% and 50% vs. 79% at 5 and 10 years, respectively. The aHR for patient death was 2.38 (95%CI, 1.69-3.37). Higher rates of death due to cardiovascular disease (aHR=2.74), malignancy (aHR=2.52), and hepatic failure (aHR=22.1) were observed. The aHR for graft loss was 1.71 (95%CI, 1.28-2.29) for HCVAb+ve patients; and glomerulonephritis, chronic allograft neuropathy, and death were more frequent causes of graft failure. CONCLUSION: On dialysis, HCVAb+ve patients had a slightly worse outcome. After renal transplantation, the HCVAb+ve cohort had a markedly worse patient and graft outcome. The impact of viral eradication on these outcomes is unknown.

Chemokine and toll-like receptor signaling in macrophage mediated islet xenograft rejection.

BACKGROUND: Adoptive transfer of antigen-primed T-cell-activated macrophages into NOD-SCID mice within 14 days of foetal porcine pancreatic fragment (FPP) or foetal porcine skin (FPS) transplantation had been shown to cause xenograft rejection. In the present study, it was proposed that signaling between the graft and macrophages promoted specific graft recognition and destruction in this setting. METHODS: Exogenous macrophages isolated from rejecting FPP xenografts were transferred to NOD-SCID FPP recipients and tracked by Ly5.1 surface antigen or via CSFE staining. Monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha), macrophage inflammatory protein-1beta (MIP-1beta), regulated upon activation, normal T-cell expressed and secreted (RANTES), chemokine (C-C motif) receptor 2 (CCR2), chemokine (C-C motif) receptor 5 (CCR5), toll-like receptors (TLRs) (1-9) and gene expression in transplanted FPP xenografts was evaluated by real-time polymerase chain reaction. Gene expression of CCR2, CCR5 and TLRs was also analyzed in pooled samples of activated and non-activated macrophages. RESULTS: Exogenous macrophages were shown to track to and reject recently transplanted but not established FPP xenografts. Gene expression for MCP-1, RANTES, MIP-1alpha and MIP-1beta was at least 3-fold greater in recently transplanted compared with established xenografts (P < 0.05), and CCR2 and CCR5 gene expression was 10-fold greater in activated compared non-activated macrophages, suggesting that graft-mediated pro-inflammatory signals were important for macrophage recruitment. Specific graft recognition by macrophages may involve TLR signaling as macrophages exposed to porcine islets had higher levels of TLR gene expression compared with those exposed to allografts regardless of the level of activation. CONCLUSION: Xenografts provide additional activation signals to macrophages that are not seen following allotransplantation. This study identifies chemokines and TLR as important signals in macrophage-mediated recognition and rejection of islet xenografts.

Fate of alphaGal +/+ pancreatic islet grafts after transplantation into alphaGal knockout mice.

BACKGROUND: Important phylogenetic differences between pig and human tissues prevent xenotransplantation from becoming a clinically feasible option. Humans lack the galactose-alpha1,3-galactose (alphaGal) epitope on endothelial cell surfaces and therefore have preformed anti-alphaGal antibodies. The role of these antibodies in rejection of non-vascular xenografts remains controversial. This study investigated the role of anti-alphaGal antibodies in rejection of non-vascularized alphaGal+/+ grafts in alphaGal -/- mice. METHODS: alphaGal +/+ and alphaGal -/- pancreatic islets were transplanted under the renal capsule of streptozotocin-induced diabetic (1) alphaGal -/- mice and (2) alphaGal +/+ mice. alphaGal -/- recepients were immunized with rabbit red blood cell membranes (RRBCs) to produce elevated anti-alphaGal antibody levels. RESULTS: Six of the 18 alphaGal -/- mice rejected the alphaGal +/+ grafts within 68 days whereas indefinite graft survival was achieved in the control groups. Animals with surviving islet grafts were challenged with alphaGal +/+ skin grafts. Although all alphaGal +/+ skin grafts were rejected within 58 days, the islet grafts remained intact. This observation correlated with the level of alphaGal expression (which was very low on islets compared to skin) rather than the actual titre of anti-alphaGal antibody. DISCUSSION: The results suggest that the level of alphaGal expression plays an important role in graft survival. Therefore, its removal is important in the development of a pig islet donor for future clinical therapy.