C4d staining in renal allograft biopsies with early acute rejection and subsequent clinical outcome

Histological picture of antibody-mediated rejection without donor-specific anti-HLA antibodies: Clinical presentation and implications for outcome

In this cohort study (n = 935 transplantations), we investigated the phenotype and risk of graft failure in patients with histological criteria for antibody-mediated rejection (ABMR) in the absence of circulating donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA), and compared this to patients with definite ABMR and HLA-DSA-positivity. The histological picture did not differ between HLA-DSA-positive (n = 85) and HLA-DSA-negative (n = 123) cases of ABMR histology, apart from increased complement split product 4d (C4d) deposition in the peritubular capillaries in HLA-DSA-positive cases. Histology of ABMR without HLA-DSA was more transient than DSA-positive ABMR, and patients with ABMR histology without HLA-DSA had graft survival superior to that of HLA-DSA-positive patients, independent of concomitant T cell-mediated rejection (38.2%) or borderline changes (17.9%). Multivariate analysis showed that the risk of graft failure was not higher in patients with histological picture of ABMR (ABMR_h ) in the absence of HLA-DSA, compared to patients without ABMR_h . Despite an association between C4d deposition and HLA-DSA-positivity, using C4d deposition as alternative for the DSA criterion in the diagnosis of ABMR, as proposed in Banff 2017, did not contribute to the prognosis of graft function and graft failure. We concluded that biopsies with ABMR_h but without detectable HLA-DSA represent a distinct, often transient phenotype with superior allograft survival.

The effect of histopathologic and clinical features on allograft survival in renal transplant patients with antibody-mediated rejection

Background: Antibody-mediated rejection is a frequent cause of graft failure; however, prognostic indications of this complication have not been well defined. The aim of this study was to evaluate the association of histopathological and clinical features and to determine the effect of these findings on allograft survival in patients with AMR.

Methods: Fifty-two patients suffered from AMR (30 male; mean age 39 ± 11 years) were included in the study. Data were investigated retrospectively and graft survival was analyzed. All transplant biopsies were evaluated according to Banff 2009 classification.

Results: Of the 52 cases, 45 were transplanted from living-donors. Twenty-one patients were diagnosed in the first 3-months after transplantation. Graft survival was 65% at 12 months and 54% at 36 months. Mean serum creatinine at time of biopsy was 3.8 ± 3.6 mg/dL. Thirty-five of the 52 cases showed diffuse C4d positivity, 12 cases showed focal and 5 remained C4d negative. One of the patients died, 13 experienced graft loss and 38 survived with functioning grafts. Serum creatinine levels at time of biopsy were correlated with graft survival (p = .021: OR = 1.10: 95 % CI = 1.015–1.199). In terms of the impact of pathological findings; tubulitis (p=.007: OR = 2.62: 95 % CI = 1.301–5.276), intimal arteritis (p=.017: OR = 2.85: 95% CI = 1.205–6.744) and interstitial infiltration (p=.004: OR = 3.37: 95% CI = 1.465–7.752) were associated with graft survival.

Conclusions: Serum creatinine at time of biopsy, tubulitis, intimal arteritis and interstitial infiltration were significantly associated with graft survival. Antibody-mediated rejection is associated with reduced long-term graft survival.

Stability and Species Specificity of Renal VEGF-A Splicing Patterns in Kidney Disease

Vascular endothelial growth factor A (VEGF-A) is essential for maintaining the glomerular filtration barrier. Absolute renal levels of VEGF-A change in patients with diabetic nephropathy and inflammatory kidney diseases, but whether changes in the renal splicing patterns of VEGF-A play a role remains unclear. In this study, we investigated mRNA splicing patterns of pro-angiogenic isoforms of VEGF-A in glomeruli and whole kidney samples from human patients with kidney disease and from mouse models of kidney disease. Kidney biopsies were obtained from patients with acute rejection following kidney transplantation, patients with diabetic nephropathy, and control subjects. In addition, kidney samples were obtained from mice with lupus nephritis, mice with diabetes mellitus, and control mice. The relative expression of each VEGF-A splice variant was measured using RT-PCR followed by quantitative fragment analysis. The pattern of renal VEGF-A splice variants was unchanged in diabetic nephropathy and lupus nephritis and was stable throughout disease progression in acute transplant rejection and diabetic nephropathy; these results suggest renal VEGF-A splicing stability during kidney disease. The splicing patterns were species-specific; in the control human kidney samples, VEGF-A 121 was the dominant isoform, whereas VEGF-A 164 was the dominant isoform measured in the mouse kidney samples.

Beneficial Immune Effects of Myeloid-Related Proteins in Kidney Transplant Rejection

Acute rejection is a risk factor for inferior long-term kidney transplant survival. Although T cell immunity is considered the main effector in clinical acute rejection, the role of myeloid cells is less clear. Expression of S100 calcium-binding protein A8 (S100A8) and S100A9 was evaluated in 303 biopsies before and after transplantation from 190 patients. In two independent cohorts of patients with acute rejection (n = 98 and n = 11; mostly cellular rejections), high expression of S100 calcium-binding protein A8 (S100A8) and A9 (S100A9) was related to improved graft outcome. Mechanisms of action of the S100 molecules were investigated. In the graft and peripheral blood cells, S100A8 and S100A9 expression correlated with myeloid-derived suppressor markers. In line with this finding, recombinant S100A8 and S100A9 proteins inhibited maturation and the allogeneic T cell stimulatory capacity of dendritic cells. S100A9 enhanced the production of reactive oxygen species by macrophages, which suppressed T cell activity at low concentrations in the form of hydrogen peroxide. Intragraft S100A8 and S100A9 expression linked to reduced expression of T cell immunity and tissue injury markers and higher expression of immune regulatory molecules. This study sheds new light on the importance of myeloid cell subsets in directing the outcome of T cell-mediated acute rejection.

Pathological diagnosis of antibody-mediated rejection in renal allograft without c4d staining, how much reliable?

Background:

C4d as a part of complement activation process is a marker for detecting antibody-mediated rejection (ABMR) and its positivity accompanied by positive donor specific antibody (DSA), and morphologic view of humoral rejection has been suggested to detect ABMR since 2003.

Materials and Methods:

41 specimens of transplanted kidney biopsies gathered from 2006 to 2008 were evaluated for morphological changes on light microscopy, and nephro-pathologist made distinct diagnosis for all of specimens then c4d staining was done for all of them. The association between primary diagnosis without c4d staining and c4d scoring on peritubular capillaries and glomerular capillaries were evaluated to determine whether morphological changes were enough for distinct diagnosis or not.

Results:

Acute tubular necrosis (ATN) 27%, interstitial fibrosis and tubular atrophy (IF&TA) 17%, and T cell mediated rejection (TCMR) 22% were the commonest diagnosis on light microscopy, and 17% of all biopsies had diffuse positive c4d staining. There was not any report of ABMR in morphological evaluation while c4d positive staining was seen in some specimens (17%). It may result from masking of ABMR by other morphological changes such as TCMR and no specific histologic changes for ABMR on light microscopy.

Conclusion:

We would like to emphasize that c4d staining should be done for all of renal allograft biopsies, and pathologists all over the world should consider the probability of ABMR masked by other morphological changes on light microscopic evaluation.

Quantitative polymerase chain reaction profiling of immunomarkers in rejecting kidney allografts for predicting response to steroid treatment

BACKGROUND

Steroid-resistant acute rejection is a risk factor for inferior renal allograft outcome.

METHODS

From 873 kidney transplant recipients (1995-2005), 108 patients with a first rejection episode were selected for study using strict inclusion criteria and clinical endpoint definition. We aimed to predict response to corticosteroid treatment using gene expression of 65 transcripts. These reflect cytokines, chemokines, and surface and activation markers of various cell types including T cells, macrophages, B cells, and granulocytes. Steroid resistance (40% of the patients) was defined as requirement for antithymocyte globulin treatment within 2 weeks after corticosteroid treatment.

RESULTS

None of the clinical and histomorphologic parameters showed a significant association with response to treatment. Univariate logistic regression analysis resulted in 11 messenger RNA markers, including T-cell-related transcripts CD25, lymphocyte activation gene-3, Granzyme B, and interleukin-10, and macrophage-specific transcripts mannose receptor and S100 calcium-binding protein A9, which significantly discriminated steroid resistant from steroid-responsive rejections (P<0.05). In multivariate logistic regression, the combination of T-cell activation markers CD25:CD3e ratio (odds ratio, 8.7; confidence interval, 2.4-31.2) and lymphocyte activation gene-3 (odds ratio, 3.3; confidence interval, 1.4-7.7) represented the best predictive model for steroid response (P<0.0001). Specificity and sensitivity were 78% and 60%, respectively. After internal stratified 10-fold cross-validation, the model remained significant. Inclusion of clinical variables into the model with molecular variables did not enhance prediction.

CONCLUSIONS

Differences in intragraft expression profiles reflect variability in the response to antirejection treatment. In acute rejection, molecular markers, particularly those reflecting T-cell activation, offer superior prognostic value compared with conventional parameters.

C4d deposits in acute "cell-mediated" rejection: a marker for renal prognosis?

BACKGROUND

Accumulation of C4d along peritubular capillaries (PTC) of renal allografts is normally attributed to antibody-mediated rejection. The prognostic implication of these deposits associated with "cell-mediated" rejection on graft survival remains uncertain. Our study aims to evaluate the impact of C4d deposits along PTC of patients with acute cell- mediated rejection on graft function and survival.

METHODS

We retrospectively analyzed patients transplanted between 2005 and 2010 with histopathologic diagnosis of acute rejection (AR). Eleven patients with "pure" antibody-mediated rejection were excluded. The remaining 79 patients were divided into two groups according to type of AR by Banff 2003 criteria: type I (69.6%) versus type II (30.4%). In each group, comparisons were made between C4d-negative (-) and C4d-positive (+) biopsies.

RESULTS

Fifty-five patients presented with type I AR: 35 (63.6%) C4d- and 20 (36.4%) C4d+. Twenty-four patients presented with type II AR: 13 (54.2%) C4d- and 11 (45.8%) C4d+. In the type I AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (94% and 91% versus 75% and 75%, respectively, log-rank P = .26). No differences were encountered in estimated glomerular filtration rate (eGFR) between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 14.7% of C4d- patients versus 25% in C4d+ patients (P = NS). In the type II AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (85% and 85% versus 72% and 61%, respectively, log-rank P = .50). No differences were encountered in eGFR between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 30.8% of C4d- patients versus 45.5% in C4d+ patients (P = NS).

CONCLUSION

Our results suggest that detection of C4d staining in acute "cell-mediated" rejection does not imply a worse renal prognosis.