Currently available useful immunohistochemical markers of renal pathology for the diagnosis of renal allograft rejection

Caveolin-1 in Kidney Chronic Antibody-Mediated Rejection: An Integrated Immunohistochemical and Transcriptomic Analysis Based on the Banff Human Organ Transplant (B-HOT) Gene Panel

Caveolin-1 overexpression has previously been reported as a marker of endothelial injury in kidney chronic antibody-mediated rejection (c-ABMR), but conclusive evidence supporting its use for daily diagnostic practice is missing. This study aims to evaluate if Caveolin-1 can be considered an immunohistochemical surrogate marker of c-ABMR. Caveolin-1 expression was analyzed in a selected series of 22 c-ABMR samples and 11 controls. Caveolin-1 immunohistochemistry proved positive in peritubular and glomerular capillaries of c-ABMR specimens, irrespective of C4d status whereas all controls were negative. Multiplex gene expression profiling in c-ABMR cases confirmed Caveolin-1 overexpression and identified additional genes (n = 220) and pathways, including MHC Class II antigen presentation and Type II interferon signaling. No differences in terms of gene expression (including Caveolin-1 gene) were observed according to C4d status. Conversely, immune cell signatures showed a NK-cell prevalence in C4d-negative samples compared with a B-cell predominance in C4d-positive cases, a finding confirmed by immunohistochemical assessment. Finally, differentially expressed genes were observed between c-ABMR and controls in pathways associated with Caveolin-1 functions (angiogenesis, cell metabolism and cell–ECM interaction). Based on our findings, Caveolin-1 resulted as a key player in c-ABMR, supporting its role as a marker of this condition irrespective of C4d status.

Early postoperative urinary MCP-1 as a potential biomarker predicting acute rejection in living donor kidney transplantation: a prospective cohort study

We investigated the clinical relevance of urinary cytokines/chemokines reflecting intrarenal immunologic micromilieu as prognostic markers and the optimal measurement timing after living donor kidney transplantation (LDKT). This prospective cohort study included 77 LDKT patients who were followed for ≥ 5 years. Patients were divided into control (n = 42) or acute rejection (AR, n = 35) group. Early AR was defined as AR occurring within 3 months. Serum and urine cytokines/chemokines were measured serially as follows: intraoperative, 8/24/72 h, 1 week, 3 months, and 1 year after LDKT. Intrarenal total leukocytes, T cells, and B cells were analyzed with immunohistochemistry followed by tissueFAXS. Urinary MCP-1 and fractalkine were also analyzed in a validation cohort. Urinary MCP-1 after one week was higher in the AR group. Urinary MCP-1, fractalkine, TNF-α, RANTES, and IL-6 after one week were significantly higher in the early AR group. Intrarenal total leukocytes and T cells were elevated in the AR group compared with the control group. Urinary fractalkine, MCP-1, and IL-10 showed positive correlation with intrarenal leukocyte infiltration. Post-KT 1 week urinary MCP-1 showed predictive value in the validation cohort. One-week post-KT urinary MCP-1 may be used as a noninvasive diagnostic marker for predicting AR after LDKT.

The Immune Cell Landscape in Renal Allografts

Immune cell infiltration plays an important role in the pathophysiology of kidney grafts, but the composition of immune cells is ill-defined. Here, we aimed at evaluating the levels and composition of infiltrating immune cells in kidney grafts. We used CIBERSORT, an established algorithm, to estimate the proportions of 22 immune cell types based on gene expression profiles. We found that non-rejecting kidney grafts were characteristic with high rates of M2 macrophages and resting mast cells. The proportion of M1 macrophages and activated NK cells were increased in antibody-mediated rejection (ABMR). In T cell-mediated rejection (TCMR), a significant increase in CD8 T cell and γδT cell infiltration was observed. CD8 positive T cells were dramatically increased in mixed-ABMR/TCMR. Then, the function of ABMR and TCMR prognostic molecular biomarkers were identified. Finally, we described the gene expression of molecular markers for ABMR diagnosis was elevated and related to the ratio of monocytes and M1 macrophages in ABMR biopsies, while the expression of TCMR diagnosis markers was increased too and positively correlated with γδT cells and activated CD4 memory T cells in TCMR biopsies. Our data suggest that CIBERSORT’s deconvolution analysis of gene expression data provides valuable information on the composition of immune cells in renal allografts.

iTRAQ-based quantitative proteomic analysis reveals potential early diagnostic markers in serum of acute cellular rejection after liver transplantation

Liver transplantation (LT) is the most effective treatment method for advanced stage liver disease but acute cellular rejection (ACR) seriously affects the prognosis of LT. To discover novel diagnostic biomarkers of ACR after LT, Isobaric Tags for Relative and Absolute Quantitation (iTRAQ)-based mass spectrometry was performed to characterize alterations of serum proteins among patients validated to be pathologically ACR or pathologically no-ACR after LT and healthy controls. As a result, 10 differentially expressed proteins were found out between the ACR group and the No-ACR group; 88 differentially expressed proteins were found out between the ACR group and the Healthy Control group; 39 differentially expressed proteins were found out between No-ACR group and Healthy Control group. After analysis and ELISA validation, the results showed that CFHR1, CFHR5 and CFH could be candidate protein biomarkers for the early diagnosis of ACR after LT.

Novel non-invasive biomarkers diagnostic of acute rejection in renal transplant recipients: A systematic review

BACKGROUND AND OBJECTIVES

Acute rejection is a significant complication detrimental to kidney transplant function. Current accepted means of diagnosis is percutaneous renal biopsy, a costly and invasive procedure. There is an urgent need to detect and validate non-invasive biomarkers capable of replacing the biopsy.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Comprehensive literature searches of Medline, EMBASE and Cochrane Central Register of Controlled Trials databases were performed. Eligible studies were included as per inclusion criteria and assessed for quality using the GRADE quality of evidence tool. Outcomes evaluated included biomarker diagnostic performance, number of patients/samples, mean age and gender ratio, immunosuppression regime, in addition to clinical applications of the biomarker(s) tested. PRISMA guidelines were followed. Where possible, statistical analysis of comparative performance data was performed.

RESULTS

23 studies were included in this review, including 19 adult, 3 paediatric and 1 mixed studies. A total of 2858 participants and 50 candidate non-invasive tests were identified. Sensitivity, specificity and area under the curve performance values ranged 36%-100%, 30%-100% and 0.55-0.98, respectively.

CONCLUSIONS

Although larger, more robust multi-centre validation studies are needed before non-invasive biomarkers can replace the biopsy, numerous candidate tests have demonstrated significant promise for various facets of postoperative management. Suggested uses include: ruling out patients with a low risk of acute rejection to avoid the need for biopsy, non-invasive testing where the biopsy is contraindicated and a prompt diagnosis is needed, and integration into a serial blood monitoring protocol in conjunction with serum creatinine.

Cell mediated rejection revisited: Past, current, and future directions

The Banff histopathology classification system is the gold standard for assessing the causes of kidney allograft dysfunction triggered by antibody-mediated and T-cell-mediated immune reactions, thereby providing mechanistic insight and guiding therapeutic decisions. The original Banff classification (1993) consisted of four histological categories representing cell-mediated rejection: interstitial inflammation (i), tubulitis (t), endoarteritis (v), and transplant glomerulitis (g). The revised Banff 2007 classification added total inflammation score (ti) from both scarred and unscarred areas based on evolving interpretations of interstitial infiltrates. Further reappraisal of cell-mediated interstitial inflammation led to the introduction of a new inflammation score specific for areas of interstitial fibrosis and tubular atrophy, termed i-IF/TA, in the Banff 2015 scheme, establishment of a new Banff working group on T-cell-mediated rejection (TCMR), and revised criteria of chronic active TCMR in Banff 2017 classification. These Banff scheme updates reflect the general recognition that chronic interstitial inflammation is a common denominator of poor kidney allograft outcome. However, revised theories on the pathogenic importance of interstitial infiltrates have created difficulties in interpretation of chronic tubulointerstitial inflammation, as there are currently no histological criteria to discriminate immune-mediated tissue injury from 'non-specific' injury. Evolving theories on vascular lesions, both active and chronic, have also complicated histological assessment by obscuring the distinction between antibody-mediated and T-cell-mediated tissue injury. This review provides an overview of recent ideas on interstitial inflammation and vascular lesions based on emerging concepts of T-cell-mediated rejection.