Pathogenesis Of Transplant Glomerulopathy Research Articles

B-cell Deficiency Attenuates Transplant Glomerulopathy in a Rat Model of Chronic Active Antibody-mediated Rejection.

Transplant glomerulopathy (TG) is a pathological feature of chronic active antibody-mediated rejection (cAMR) and is associated with renal allograft failure. The specific role of B cells in the pathogenesis of TG is unclear. We used a minor mismatched rat kidney transplant model with B cell-deficient recipients, generated by clustered regularly interspaced short palindromic repeats/Cas9 technology, to investigate the impact of B-cell depletion on the pathogenesis of TG. We hypothesized that B-cell deficiency would prevent TG in the rat kidney transplant model of cAMR. Treatment groups included syngeneic, allogeneic, sensitized allogeneic, and B cell-deficient allogeneic transplant recipients. B cell-deficient recipients demonstrated reduced TG lesions, decreased microvascular inflammation, reduced allograft infiltrating macrophages, and reduced interferon gamma transcripts within the allograft. Allograft transcript levels of interferon gamma, monocyte chemoattractant protein-1, and interleukin-1β correlated with numbers of intragraft macrophages. B cell-deficient recipients lacked circulating donor-specific antibodies and had an increased splenic regulatory T-cell population. In this model of cAMR, B-cell depletion attenuated the development of TG with effects on T cell and innate immunity.

Chronic transplant glomerulopathy: New insights into pathogenesis

There have been recent significant advances in short-term outcomes in renal transplantation, however, long-term allograft survival remains a challenge. With reported incidences as high of 74.5% of chronic graft loss in patients with biopsies showing transplant glomerulopathy (TG), this syndrome represents an important factor for chronic allograft complications. In this review we show an overview of the novel mechanistic insights into pathogenesis of TG, as well as a brief description of the pathology, diagnosis and newer prognostic indices within TG diagnosis. These data raise intriguing roles for cell-mediated immunity and podocyte stress in TG as well as reinforce previous associations of TG with ABMR. We also delve into management strategies for TG and report the paucity of existing clinical trial data for this prevalent condition in renal transplants.

1029-LBP: Immune responses to Collagen IV and Fibronectin in Renal Transplant Recipients with Transplant Glomerulopathy

Antibodies (Abs) to donor HLA (DSA) has 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. In this study we determined the role of kidney restricted self tissue antigens collagen-IV (Col-IV) and fibronectin (FN) in the development of chronic rejection following KTx in TG patients. Biopsy proven 26 KTx TG patients, 10 stable KTx and 14 normal controls were enrolled in this study. Antibodies to self-Ags, Col-IV and FN were determined by ELISA. DSA was determined by solid phase assay and frequency of CD4+ T cells secreting 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 < 0.01). Abs to self-Ags were IgG and IgM isotypes. Pre-transplant Abs to self-Ags increased the risk of TG (22% vs 10%, p < 0.5). 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 (TG: 867 ± 241 pg/mL, stable: 407 ± 178 pg/mL, p = 0.02) and IL-17 (TG: 918 ± 197 pg/mL, stable: 327 ± 142 pg/mL, p = 0.009) with reduction in IL-10 (TG: 184 ± 78 pg/mL, stable: 668 ± 184 pg/mL, p = 0.001). In conclusion, the development of Abs to self-Ags is an independent 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.

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.

Donor human leukocyte antigen specific antibodies predict development and define prognosis in transplant glomerulopathy

The pathogenesis of transplant glomerulopathy (TG) remains unclear, with evidence of human leukocyte antigen (HLA) antibodies as important contributors to the disease. We studied the risk factors and the associations of HLA antibodies in the development of TG. Sixty-one cases with morphologic features of TG were identified and compared with contemporaneous matched patients (without TG) from a 17-year period, all undergoing renal biopsy in a single center. Univariate risk factors for TG were previous glomerulitis [odds ratio (OR) 3.3, 95% confidence interval (95% CI) [1.2–9.4], p = 0.025), delayed graft function (OR 2.3 [1.0–5.1], p = 0.042), HLA class I presensitization defined by Luminex solid-phase immunoassays (OR 5.0 [2.3–11.0]. p < 0.001), and de novo posttransplant development of donor HLA specific antibody (DSA) (OR 4.7 [1.7–13.2], p = 0.002). Only DSA remained significantly associated with TG after adjustment (OR 3.8 [1.1–12.9], p = 0.032). DSA was detected in >50% of TG patients, suggesting HLA antibodies play a critical role in TG pathogenesis. TG patients with DSA had increased risk of graft loss (median graft survival 4.4–5.2 years), whereas patients with morphologic features of TG without DSA had similar graft survival compared with the non-TG group (median graft survival 15 years). Thus, DSA is a useful predictor for graft failure in TG patients.

Predominant Th1 and Cytotoxic Phenotype in Biopsies from Renal Transplant Recipients with Transplant Glomerulopathy

Transplant glomerulopathy (TGP) appears to be a pathogenic feature of chronic antibody-mediated rejection, but the pathogenesis of this histologic entity is still poorly understood. Previous studies suggest the involvement of lymphocytes but the phenotypes of these cells have never been analyzed. Here, we report the first study of mRNAs for specific markers of CD4+ T cells including Th1 (T-bet and INFgamma), Th2 (IL4 and GATA3), Treg (Foxp3) and Th17 (IL-17 and RORgammat) subsets, cytotoxic CD8 T cells (Granzyme B) and B-cell markers (CD20) in renal biopsies from renal transplant recipients suffering interstitial fibrosis and tubular atrophy (IF/TA) with or without TGP but with a similar inflammatory score and controls including transplant recipients with normal renal function. Only INFgamma, T-bet (both functionally defined markers of Th1 CD4 T cells) and granzyme B (a CD8 cytotoxic marker) were significantly more strongly expressed in patients with TGP than in patients without TGP and normal controls. These results indicate a role of an active T-mediated inflammatory and cytotoxic process in the pathogenesis of TGP.

Antibody Response Against the Glomerular Basement Membrane Protein Agrin in Patients with Transplant Glomerulopathy

Chronic allograft nephropathy (CAN) of renal allografts is still the most important cause of graft loss. A subset of these patients have transplant glomerulopathy (TGP), characterized by glomerular basement membrane (GBM) duplications, but of unknown etiology. Recently, a role for the immune system in the pathogenesis of TGP has been suggested. In 11 of 16 patients with TGP and in 3 of 16 controls with CAN in the absence of TGP we demonstrate circulating antibodies reactive with GBM isolates. The presence of anti-GBM antibodies was associated with the number of rejection episodes prior to diagnosis of TGP. Sera from the TGP patients also reacted with highly purified GBM heparan sulphate proteoglycans (HSPG). Indirect immunofluorescence with patient IgG showed a GBM-like staining pattern and colocalization with the HSPGs perlecan and especially agrin. Using patient IgG, we affinity purified the antigen and identified it as agrin. Reactivity with agrin was found in 7 of 16 (44%) of patients with TGP and in 7 of 11 (64%) patients with anti-GBM reactivity. In conclusion, we have identified a humoral response against the GBM-HSPG agrin in patients with TGP, which may play a role in the pathogenesis of TGP.

C4d deposition in the glomeruli and peritubular capillaries associated with transplant glomerulopathy.

Transplant glomerulopathy (TGP) is a unique disease entity with characteristic pathological findings. Although ultrastructural studies for TGP have been performed, histogenesis of TGP is not fully understood. The present study was designed to investigate the relation of complement fragment C4d to the histogenesis of TGP. Nine cases of isolated TGP were randomly selected. A commercially available monoclonal antibody against complement fragment C4d was used in allograft biopsies. To evaluate the extent and severity of deposition of the C4d complement in the glomerular and peritubular capillaries, indirect immunofluoresce method was performed on frozen sections. Intense deposition of C4d in the glomerular basement membrane and peritubular capillaries was found in association with morphological appearance of TGP. Peritubular capillaries were affected in all the patients, showing splitting and multilayering of peritubular capillary basement membrane. These changes, which diffusely affect most capillaries, and their severity pattern were quite similar in each patient. In early stages of all patients with cellular rejection, C4d was not detected in the glomerular and peritubular capillaries. In addition, no C4d deposition was detected in all zero-hour biopsies without diagnostic abnormality. These findings suggest that C4d deposition in the glomerular and peritubular capillaries might be associated with the pathogenesis of TGP in renal transplantation.