Value of Pretransplantation Cytokine Profiles for Predicting Acute Rejection in Renal Transplant Recipients

Transitional immature regulatory B cells and regulatory cytokines can discriminate chronic antibody-mediated rejection from stable graft function

BACKGROUND

The balance between inflammatory and anti-inflammatory responses of the immune system has been demonstrated to determine the fate of transplanted allografts. Here we analyzed CD19⁺CD24^hiCD38^hi immature transitional regulatory B (TRB) cells, as well as the gene and protein levels of interleukin (IL)-10 and transforming growth factor (TGF)-β in the three separate groups, include of stable transplanted subjects, chronic antibody-mediated rejection (cAMR) patients, and healthy individuals.

METHOD

Peripheral blood mononuclear cells (PBMCs) from stable subjects (n = 36), cAMR patients (n = 36) and healthy controls (n = 18) were isolated. Flowcytometry was performed for CD19, CD24, and CD38 surface markers. ELISA and quantitative real-time PCR were performed for IL-10 and TGF-β cytokines.

RESULT

The percentages of immature TRB cells were significantly decrease in cAMR patients (0.98%) versus stable recipients (2.81%) and healthy subjects (4.03%) (P = 0.001 and P < 0.001, respectively). Total lymphocytes, circulating B cells, memory and mature subsets of B cells did not show any significant difference between the groups. TGF-β mRNA was 3-fold upregulated in the cAMR group compared to stable patients (P < 0.001.), but without significant alteration at the protein level. Also, long-term survival renal transplant recipients had a higher protein but not mRNA levels of IL-10 than short-term survival renal transplant recipients.

CONCLUSION

It seems that immature TRB cell subpopulation might be a crucial regulator of immune system response and plays an important role in determining the transplantation outcome. Furthermore, immunosuppressive IL-10 and TGF-β cytokines might act as a double sword and can exhibit either pathogenic or protective effects against allograft.

Pretransplant Immune Interplay Between Donor and Recipient Influences Posttransplant Kidney Allograft Function

BACKGROUND

Renal transplant candidates present immune dysregulation caused by chronic uremia, and deceased kidney donors present immune activation induced by brain death. Pretransplant donor and recipient immune-related gene expression were examined in the search for novel predictive biomarkers crosslinking recipient and donor pretransplant immune status with transplant outcome.

MATERIALS AND METHODS

This study included 33 low-risk consecutive renal transplant recipients and matched deceased donors. The expression of 29 genes linked to tissue injury, T-cell activation, cell migration, and apoptosis were assessed in postreperfusion kidney biopsies, as well as 14 genes in pretransplant peripheral blood of the kidney recipients. Gene expression was analyzed with real-time polymerase chain reaction on custom-designed low-density arrays.

RESULTS

Donor MMP9 expression was related to delayed graft function occurrence (P = .036) and short term kidney allograft function (14th day r_s = -0.44, P = .012; 1st month r_s = -0.46, P = .013). Donor TGFB1 expression was associated with short- and long-term graft function (14th day r_s = -0.47, P = .007; 3rd month r_s = -0.63, P = .001; 6th month r_s = -0.52, P = .010; 12th month r_s = -0.45, P = .028; 24th month r_s = -0.64, P = .003). Donor TGFB1 expression was not related to donor age (r_s = 0.32, P = .081), which was also an independent factor influencing the outcome. Recipient gene expression was not related to graft function but determined the acute rejection risk. Recipient IFNG and, to a lesser extent, IL18 expression were protective against acute rejection (area under the curve [AUC] 0.84, P < .001, and AUC 0.79, P < .001, respectively).

CONCLUSION

Kidney transplant outcome depends on the interplay between donor-related immune factors, which mostly affect allograft function and recipient immune milieu, influencing an alloreactive response.

Pretransplant Immune- and Apoptosis-Related Gene Expression Is Associated with Kidney Allograft Function

Renal transplant candidates present immune dysregulation, caused by chronic uremia. The aim of the study was to investigate whether pretransplant peripheral blood gene expression of immune factors affects clinical outcome of renal allograft recipients. Methods. In a prospective study, we analyzed pretransplant peripheral blood gene expression in87 renal transplant candidates with real-time PCR on custom-designed low density arrays (TaqMan). Results. Immediate posttransplant graft function (14-day GFR) was influenced negatively by TGFB1 (P = 0.039) and positively by IL-2 gene expression (P = 0.040). Pretransplant blood mRNA expression of apoptosis-related genes (CASP3, FAS, and IL-18) and Th1-derived cytokine gene IFNG correlated positively with short- (6-month GFR CASP3: P = 0.027, FAS: P = 0.021, and IFNG: P = 0.029) and long-term graft function (24-month GFR CASP3: P = 0.003, FAS: P = 0.033, IL-18: P = 0.044, and IFNG: P = 0.04). Conclusion. Lowered pretransplant Th1-derived cytokine and apoptosis-related gene expressions were a hallmark of subsequent worse kidney function but not of acute rejection rate. The pretransplant IFNG and CASP3 and FAS and IL-18 genes' expression in the recipients' peripheral blood is the possible candidate for novel biomarker of short- and long-term allograft function.

Serum levels of N-terminal pro-B-type natriuretic peptide are associated with allograft function in recipients of renal transplants

BACKGROUND

B-type natriuretic peptide (BNP) plays a key role in the regulation of volume homeostasis, and elevated blood levels of BNP are associated with end-stage renal disease. Renal transplantation leads to a decrease of elevated BNP levels with established graft function. Assessment of N-terminal pro-BNP (NT-proBNP) is established as reflecting volume homeostasis, and we therefore studied the relationship between NT-proBNP and allograft function in a prospective study.

METHODS

NT-proBNP was assessed in 76 patients with end-stage renal disease undergoing renal transplantation. Patients were grouped according to immediate or delayed graft function. The degree of allograft function was assessed from the estimated glomerular filtration rate according to the MDRD formula.

RESULTS

In patients with immediate graft function (n = 48), median NT-proBNP decreased immediately after transplantation; in patients with delayed function (n = 28), median NT-proBNP first increased and then decreased as function improved. Patients with early acute rejection showed significantly higher NT-proBNP levels prior to transplantation than patients without rejection. NT-proBNP levels measured 2 or 3 weeks post-transplant were significantly correlated with the estimated glomerular filtration rate 1 year after transplantation.

CONCLUSIONS

An association was observed between renal allograft function and post-transplant levels of NT-proBNP. The association was not found to be a useful general predictor for graft function in individual patients in a clinical setting, as the range of NT-proBNP levels measured was too wide.

Urinary connective tissue growth factor increases far earlier than histopathological damage and functional deterioration in early chronic renal allograft injury

OBJECTIVE

To date, serum biochemistry examination and routine biopsy are the most commonly used methods to assess renal function after allogenic kidney transplantation. Connective tissue growth factor (CTGF) has been considered as a biomarker of chronic renal allograft injury characterized by tubular atrophy and interstitial fibrosis (TA/IF). This study explored the potential value of urinary CTGF as an early predictor of TA/IF using a rat model.

MATERIAL AND METHODS

A Fisher to Lewis allogenic rat kidney transplant model was established and the recipients were killed at weeks 4, 8 and 12 post-transplantation. TA/IF was graded based on Banff Schema 1997. The location and expression of CTGF mRNA were detected by oligonucleotide-primed in situ DNA synthesis and quantitative polymerase chain reaction. CTGF protein expression was examined with immunohistochemistry and immunoblotting. Urinary CTGF concentration was measured by enzyme-linked immunosorbent assay. The correlation between urinary CTGF concentration and serum creatinine (SCr) and Banff score was analysed statistically.

RESULTS

Typical morphological changes including TA/IF in allograft appeared at week 8 and became very severe at week 12 post-transplantation. CTGF expression in epithelium was up-regulated early and urinary CTGF was markedly elevated from week 4. SCr in recipients was stable before week 8 but increased tremendously at week 12. Urinary CTGF concentration was positively correlated with SCr and degree of interstitial fibrosis.

CONCLUSION

Urinary CTGF increases earlier than the appearance of biochemical abnormalities and pathological changes. Measurement of urinary CTGF may offer a potential non-invasive strategy to predict the early onset of chronic renal allograft injury.

Granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and other immunomodulatory therapies for the treatment of infectious diseases in solid organ transplant recipients

PURPOSE OF REVIEW

Infections continue to cause significant morbidity and mortality in SOT recipients despite major advances in immunosuppressive and antimicrobial regimens. Immunomodulatory cytokines provide a potential means to augment the host immune response to infection. This review will focus on cytokine therapy for the prophylaxis and treatment of infections in solid organ transplant recipients, and will speculate on the potential for further advances in the field.

RECENT FINDINGS

In kidney and liver transplant recipients, granulocyte colony-stimulating factor (G-CSF) has been used successfully to reverse ganciclovir-induced neutropenia or cytomegalovirus-induced neutropenia. Although G-CSF also reversed corticosteroid-induced suppression of the neutrophil respiratory burst in vitro, prophylactic G-CSF failed to reduce infections or mortality in nonneutropenic solid organ transplant recipients. Published clinical experience with granulocyte-macrophage colony-stimulating factor (GM-CSF) in this population has been limited to case reports and a small case series, whereas the use of macrophage colony-stimulating factor (M-CSF) or interferon-gamma (IFN-gamma) has not been systematically investigated in controlled clinical trials.

SUMMARY

Despite encouraging results in vitro and in preclinical models, immunomodulatory cytokines have not met expectations when administered to SOT recipients. Nonetheless, the principle of selective enhancement of innate immunity for the prevention and treatment of infections in this patient population has promise and warrants further study.

Prolongation of cardiac allograft survival by rapamycin and the invariant natural killer T cell glycolipid agonist OCH

BACKGROUND

Invariant natural killer T (iNKT) cells are glycolipid-responsive cells with potent immunomodulatory properties. Although iNKT cells have been implicated in cardiac allograft tolerance, whether in vivo triggering of iNKT cells with Th2-promoting glycolipids offers a therapeutic benefit in heart transplantation remains unexplored.

METHODS

C3H (H-2k) hearts were transplanted into C57BL/6 (H-2b) mice. The recipients were left untreated or received the Th2-promoting iNKT cell agonist OCH, the antirejection agent rapamycin, or both. Allografts were recovered on postoperative day 8 or at endpoint, stained with hematoxylin-eosin, and analyzed for intragraft transcript levels of effector cytokines and iNKT cells' invariant T-cell receptor segment Valpha14-Jalpha18. The presence of circulating alloantibodies was assessed in recipients' sera at similar time points. A second fully mismatched cardiac allograft model (BALB/c-to-C57BL/6) was used to further validate the efficacy of our treatment regimens.

RESULTS

Combination immunotherapy with OCH and rapamycin significantly enhanced C3H allograft survival and led to nearly normal graft histology with minimal vascular changes and mononuclear cell infiltration, and an almost normal IgG1:IgG2a ratio in recipients' sera. These were accompanied by elevated intragraft mRNA levels of interleukin (IL)-4, and to a lesser extent IL-10 and IL-13, and high transcript levels of Valpha14-Jalpha18 T-cell receptor gene segment. Furthermore, when used alone or together with rapamycin, OCH delayed allograft rejection in our BALB/c-to-C57BL/6 model.

CONCLUSIONS

In vivo administration of OCH may deviate alloimmune responses towards a Th2 phenotype and prolong allograft survival. Select iNKT cell glycolipid agonists can therefore be used in monotherapy or combination immunotherapy of transplant rejection.

T regulatory cells in stable posttransplant bronchiolitis obliterans syndrome

BACKGROUND

Obliterative bronchiolitis (OB), mainly mediated by T cells, remains the major cause of morbidity and death in long-term lung transplant. Acute rejection (AR), also a T-cell mediated process, is strongly linked to OB. For unknown reasons, several patients with OB halt their pulmonary function decline and stabilize their obstructive defect for a long period. Our aim was to assess the T-cell activation in blood, induced sputum, and broncho-alveolar lavage during AR, stable OB (sOB), and evolving OB (eOB).

METHODS

T-cell phenotype and cytokine production were assessed by flow cytometry in these three compartments. Interleukin-4, interferon-gamma and transforming growth factor (TGF)-beta levels were measured by enzyme-linked immunosorbent assay in blood cell culture supernatants. Results were compared between healthy lung transplant recipients and AR (n=7), sOB (n=7), and eOB (n=13).

RESULTS

Stable and evolutive OB were characterized by a Treg, Th1, and Th2 activation, but compared to eOB, Treg and Th2 cells predominated in sOB. A clear Th1 activation was observed in AR. TGF-beta was increased in AR and evolving OB.

CONCLUSION

These preliminary results indicate a contrasted T-cell activation profile depending on the clinical conditions. We speculate that Treg cells could counterbalance the Th0 activation seen in evolving OB and participate in stabilization of airway obstruction.

The Ratio of Interferon-γ and Interleukin-10 Producing Donor-Specific Cells as an In Vitro Monitoring Tool for Renal Transplant Patients

If in vitro tools can be used to predict which renal transplant patients are at risk for rejection and which patients are more predisposed to tolerance, the immunosuppressive regimen can be adjusted to prevent rejection before it becomes clinically apparent or, in case of a tolerant patient, medication can be reduced or even stopped. Peripheral blood mononuclear cells (PBMC) of patients with persistent stable graft function and of patients with (biopsy-confirmed) acute rejection were stimulated with donor cells and tested with Elispot analysis. A significantly higher number of donor-specific interferon (IFN)-gamma producing cells were found in patients with rejection, as determined with Elispot analysis. Furthermore, a trend towards a higher number of interleukin (IL)-10 producing cells was found in patients with stable graft function. The ratio of IFN-gamma/IL-10 producing cells showed to be the best tool to discriminate between nonrejecting patients and rejecting patients.