Separate risk factors for the development of transplant glomerulopathy vs chronic tubulointerstitial rejection

Immune responses to collagen-IV and fibronectin in renal transplant recipients with transplant glomerulopathy

Antibodies (Abs) to donor HLA (donor-specific antibodies [DSA]) have been associated with transplant glomerulopathy (TG) following kidney transplantation (KTx). Immune responses to tissue-restricted self-antigens (self-Ags) have been proposed to play a role in chronic rejection. We determined whether KTx with TG have immune responses to self-Ags, Collagen-IV (Col-IV) and fibronectin (FN). DSA were determined by solid phase assay, Abs against Col-IV and FN by enzyme-linked immunosorbent assay and CD4+ T cells secreting interferon gamma (IFN-γ), IL-17 or IL-10 by ELISPOT. Development of Abs to self-Ags following KTx increased the risk for TG with an odds ratio of 22 (p-value = 0.001). Abs to self-Ags were IgG and IgM isotypes. Pretransplant Abs to self-Ags increased the risk of TG (22% vs. 10%, p < 0.05). Abs to self-Ags were identified frequently in KTx with DSA. TG patients demonstrated increased Col-IV and FN specific CD4+ T cells secreting IFN-γ and IL-17 with reduction in IL-10. We conclude that development of Abs to self-Ags is a risk factor and having both DSA and Abs to self-Ags increases the risk for TG. The increased frequency of self-Ag-specific IFN-γ and IL-17 cells with reduction in IL-10 demonstrate tolerance breakdown to self-Ags which we propose play a role in the pathogenesis of TG.

Intragraft tubular vimentin and CD44 expression correlate with long-term renal allograft function and interstitial fibrosis and tubular atrophy

BACKGROUND

Development of interstitial fibrosis and tubular atrophy (IF/TA) is the main histologic feature involved in renal allograft deterioration. The aim of this study was to validate whether de novo tubular expression of CD44 (transmembrane glycoprotein) and vimentin (mesenchymal cell marker), both involved in renal fibrosis, can operate as surrogate markers for late IF/TA and renal function. Furthermore, we wanted to establish the interrater reproducibility for the scoring system, which can be a problem in histologic assessments.

METHODS

Six-month protocol renal allograft biopsies (n=30 for matching 12 months estimated glomerular filtration rate (eGFR) from which 20 matched the 12-month protocol biopsy) were immunostained for CD44 and vimentin, semiquantitatively scored by three observers of two centers, and correlated with IF/TA and eGFR at 12 months.

RESULTS

The interobserver agreement was excellent for CD44 (Kendall's W-coefficient: 0.69; P<0.001) and vimentin (Kendall's W-coefficient: 0.79; P<0.001). CD44 and vimentin expression at 6 months were significantly correlated with IF/TA (rho=0.481 for CD44 and rho=0.619 for vimentin) and eGFR (rho=-0.569 for CD44 and rho=-0.376 for vimentin) at 12 months.

CONCLUSIONS

Summarizing, de novo tubular expression of CD44 and vimentin can function as surrogate marker for IF/TA and eGFR at 12 months. Further area under receiver operator characteristic curve analysis has to establish the predictive value for both biomarkers.

The clinical impact of chronic transplant glomerulopathy in cyclosporine era

BACKGROUND

The clinical impact of chronic transplant glomerulopathy (CTG) on the outcome of kidney allograft receiving calcineurin inhibitors (CNIs) remains uncertain. A retrospective study of renal transplant recipients at Ospedale Maggiore of Milan was undertaken to evaluate the clinical outcome of patients with CTG.

METHODS

Among 666 biopsies taken at least 6 months after transplantation (Tx) in 498 transplant patients treated with CNIs, 28 cases (5.6%) of chronic transplant glomerulopathy (CTG) were identified and their clinical features at Tx, at follow-up and graft survival were compared with those of 56 controls transplanted in the same period and with kidney functioning 12 months after Tx. Clinical characteristics at biopsy and at 1 year after Tx were similar in the two groups.

RESULTS

After diagnosis graft function deteriorated in 22 patients (78.5%), while it remained stable in 6. Graft loss developed in 92 % of patients with proteinuria >2.5 g/day and in 33 % of those with lower proteinuria (P<0.005). In cases with more severe CTG the rate of graft loss was higher, though not significantly. Graft survival at 10 years was 48% in patients with CTG and 88% in controls (P<0.0001).

CONCLUSIONS

The incidence and clinical course of CTG do not seem to be modified by CNI-based immunosuppression. The evolution is unpredictable but the severity of glomerulopathy and proteinuria at follow-up are associated with progression to graft failure. Patients with CTG have a graft survival significantly worse than that of the general population of transplanted patients.

Antibody response against perlecan and collagen types IV and VI in chronic renal allograft rejection in the rat

Chronic rejection is the leading cause of late renal transplant failure. Various structural lesions are observed in grafts undergoing chronic rejection including glomerular basement membrane (GBM) duplications. The well-established Fisher (F344) to Lewis (LEW) rat renal transplant model for chronic rejection was used to assess the presence and role of the humoral immune response against graft antigens during chronic rejection. LEW recipients of F344 allografts develop transplant glomerulopathy and produce IgG1 antibodies directed against F344 GBM preparations that are detectable 3 weeks after transplantation. Glomerular IgG1 deposition was observed that in vitro co-localized with a rabbit anti-rat GBM antiserum in rejecting F344 grafts; elution experiments of isolated glomeruli yielded IgG1 antibodies reactive in vitro with F344 GBM, but not LEW GBM. Prevention of acute rejection by transient treatment of the recipients with cyclosporin A completely abrogated the production of anti-GBM antibodies. Using proteomic techniques we identified the antigens recognized by the LEW posttransplant sera as being the heparan sulfate proteoglycan perlecan and the alpha1 chain of collagen type VI in association with the alpha5 chain of collagen type IV. In conclusion, LEW recipients of F344 kidney grafts produce IgG1 antibodies against donor type perlecan and alpha1(VI)/alpha5(IV) collagen and develop transplant glomerulopathy. These data implicate an important role for the humoral immune response in the development of glomerulopathy during chronic rejection.

Serial protocol biopsies to quantify the progression of chronic transplant nephropathy in stable renal allografts

AIM

To evaluate the utility of intimal thickness and interstitial width as a primary efficacy variable in the design of clinical trials aimed to modify the natural history of chronic allograft nephropathy.

METHODS

A donor and a 4-month protocol biopsy were evaluated in 40 stable grafts according to the Banff schema. In 27 patients, a second protocol biopsy was done at 1 yr. Arterial intimal volume fraction (Vvintima/artery) and cortical interstitial volume fraction (Vvinterstitium/cortex) were estimated with a point counting technique.

RESULTS

Chronic Banff scores increased during follow-up, while acute scores reached its peak at 4 months. Vvintima/artery and Vvinterstitium/cortex significantly increased at 4 months, but not at 1 yr. Vvintima/artery at 4 months correlated with donor Vvintima/artery (r = 0.57, p < 0.001), histocompatibility (r = 0.38, p = 0.01) and serum cholesterol (r = 0.31, p = 0.047). Vvinterstitium/cortex at 4 months correlated with recipient body surface area (r = 0.44, p = 0.004) and delayed graft function (p = 0.016). Power calculations showed that Vvintima/artery and Vvinterstitium/cortex allow an important reduction in minimum sample size of a hypothetical trial aimed to prevent chronic allograft nephropathy.

CONCLUSIONS

Intimal thickening and interstitial widening progresses rapidly during the first 4 months after transplantation and slowly thereafter. These parameters can be considered as a primary efficacy variable in trials aimed to prevent chronic allograft nephropathy.

Switch from cyclosporine A to tacrolimus in renal transplant recipients: impact on Th1, Th2, and monokine responses

We showed previously that pretransplant CD4 helper defects and low in-vitro IL-10 responses predict a low risk of acute kidney graft rejection. To compare the effect of tacrolimus (Tacr) and cyclosporine A (CsA) on the humoral immune response we assessed T helper function, B cell/monocyte responses and in-vitro cytokine responses (TNF-alpha, GM-CSF, IL-1 beta, IL-2, IL-4, IL-6, IL-10) in 20 renal transplant recipients before and 3 months after they were switched from CsA to Tacr because of hyperlipoproteinemia, hirsutism, or gum hyperplasia. T helper function was assessed using a PWM-driven allogeneic coculture system of patient T cells together with control B cells. B cell/monocyte responses were determined using a PWM-stimulated allogeneic coculture system, SAC I-stimulated B-cell cultures and LPS-stimulated monocyte cultures. Immunoglobulin-secreting cell (ISC) responses were assessed in a reverse hemolytic plaque assay, and ELISA were used to determine cytokine secretion. Treatment with Tacr resulted in a decreased expression of costimulatory ligands and adhesion molecules (T cells: CD40L, p < 0.05; CD28 and CD54, p < or = 0.01; B cells: CD25, p = 0.05; CD40, p < 0.001; monocytes: CD40, p < 0.05), which coincided with decreased PHA-stimulated T cell IL-2 responses (398 +/- 153 versus 43 +/- 15 pg/ml, p < 0.05), impaired CD4 helper activity (117% +/- 22% versus 73% +/- 19%, p < 0.05) and increased CD4 suppressor activity (-120% +/- 28% versus -18% +/- 27%, p = 0.02). We observed enhanced CD4 IL-10 responses (p < 0.01) and LPS-stimulated monocyte responses (TNF-alpha, IL-1 beta, and IL-6, p < 0.005; IL-10, p < 0.05), indicating an increased humoral immune responsiveness under treatment with tacrolimus. Our data show that switching of immunosuppressive therapy from CsA to tacrolimus results in suppression of costimulatory ligands, adhesion molecules, Th1 responses and CD4 helper activity. However, enhanced humoral immune responses, Th2 and monokine responses, might have a negative impact on long-term graft function.

Chronic allograft nephropathy: An update

Chronic allograft nephropathy is the most prevalent cause of renal transplant failure in the first post-transplant decade, but its pathogenesis has remained elusive. Clinically, it is characterized by a slow but variable loss of function, often in combination with proteinuria and hypertension. The histopathology is also not specific, but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified, such as advanced donor age, delayed graft function, repeated acute rejection episodes, vascular rejection episodes, and rejections that occur late after transplantation. A common feature of chronic allograft nephropathy is that it develops in grafts that have undergone previous damage, although the mechanism(s) responsible for the progressive fibrosis and tissue remodeling has not yet been defined. Hypotheses to explain chronic allograft nephropathy include the immunolymphatic theory, the cytokine excess theory, the loss of supporting architecture theory, and the premature senescence theory. The most effective option to prevent chronic allograft nephropathy is to avoid graft injury from both immune and nonimmune mechanisms.