Immunohistochemical characterization of glomerular and tubulointerstitial infiltrates in renal transplant patients with chronic allograft dysfunction

Characterization of Cytotoxic T Lymphocytes (CTL) by Tissue Microarray

Tissue microarray (TMA) is a smart technical innovation recently imposed in pathology research. This technology provides a high-throughput analysis of multiple tissues at the same time. The technique allows faster analysis and considerably reducing costs for the staining because many small representative tissue samples from hundreds of different cases are assembled on a single histologic slide. This versatile technique may improve conventional microscopic techniques to detect and characterize cytotoxic T lymphocytes (CTL). Immunohistochemistry (IHC) may be effectively employed in CTL characterization to identify the location and distribution of target antigens in tissues by staining with a specific antibody. The antibody may be conjugated to either a fluorescent or enzymatic label, and the location of the label seen through a microscope approximates the position of the target antigen.This article summarizes the technical aspects of tissue microarray construction and sectioning, advantages, application, and limitations associated with immunohistochemistry and immunofluorescence.

Multicolor Flow Cytometry and Cytokine Analysis Provides Enhanced Information on Kidney Transplant Biopsies

Introduction

Current processing of renal biopsy samples provides limited information about immune mechanisms causing kidney injury and disease activity. We used flow cytometry with transplanted kidney biopsy samples to provide more information on the immune status of the kidney.

Methods

To enhance the information available from a biopsy, we developed a technique for reducing a fraction of a renal biopsy sample to single cells for multicolor flow cytometry and quantitation of secreted cytokines present within the biopsy sample. As proof of concept, we used our technique with transplant kidney biopsy samples to provide examples of clinically relevant immune information obtainable with cytometry.

Results

A ratio of CD8⁺ to CD4⁺ lymphocytes greater than or equal to 1.2 in transplanted allografts is associated with rejection, even before it is apparent by microscopy. Elevated numbers of CD45 leukocytes and higher levels of interleukin (IL)−6, IL-8, and IL-10 indicate more severe injury. Antibody binding to renal microvascular endothelial cells can be measured and corresponds to antibody-mediated forms of allograft rejection. Eculizumab binding to endothelial cells suggests complement activation, which may be independent of bound antibody. We compared intrarenal leukocyte subsets and activation states to those of peripheral blood from the same donor at the time of biopsy and found significant differences; thus the need for new techniques to evaluate immune responses within the kidney.

Conclusion

Assessment of leukocyte subsets, renal microvascular endothelial properties, and measurement of cytokines within a renal biopsy by flow cytometry enhance understanding of pathogenesis, indicate disease activity, and identify potential targets for therapy.

Urinary Markers of Fibrosis and Risk of Cardiovascular Events and Death in Kidney Transplant Recipients: The FAVORIT Trial

Cardiovascular risk remains high in kidney transplant recipients (KTRs) despite improved kidney function after transplant. Urinary markers of kidney fibrosis and injury may help to reveal mechanisms of this risk. In a case-cohort study among stable KTRs who participated in the FAVORIT trial, we measured four urinary proteins known to correlate with kidney tubulointerstitial fibrosis on biopsy (urine alpha 1 microglobulin [α1m], monocyte chemoattractant protein-1 [MCP-1], procollagen type I [PINP] and type III [PIIINP] N-terminal amino peptide) and evaluated associations with cardiovascular disease (CVD) events (n = 300) and death (n = 371). In adjusted models, higher urine α1m (hazard ratio [HR] per doubling of biomarker 1.40 [95% confidence interval [CI] 1.21, 1.62]), MCP-1 (HR 1.18 [1.03, 1.36]), and PINP (HR 1.13 [95% CI 1.03, 1.23]) were associated with CVD events. These three markers were also associated with death (HR per doubling α1m 1.51 [95% CI 1.32, 1.72]; MCP-1 1.31 [95% CI 1.13, 1.51]; PINP 1.11 [95% CI 1.03, 1.20]). Higher concentrations of urine α1m, MCP-1, and PINP may identify KTRs at higher risk for CVD events and death. These markers may identify a systemic process of fibrosis involving both the kidney and cardiovascular system, and give new insights into mechanisms linking the kidney with CVD.

The role of renin-angiotensin system in the chronic allograft nephropathy: an immunohistochemical study

BACKGROUND

Evidences suggest a role of renin-angiotensin system (RAS) in the development of chronic allograft injury.

METHODS

We correlated intrarenal angiotensin-converting enzyme, angiotensin II (Angio II) and transforming growth factor β1 (TGFβ1) expression in 58 biopsies-proven chronic allograft nephropathy (CAN) with tissue injury and allograft survival.

RESULTS

The biopsies with CAN were graded according to Banff classification as I (22 cases), II (17) and III (19); 27 biopsies also showed a mononuclear inflammatory infiltrate in scarred areas. There were increased expression of angiotensin converting-enzyme (ACE), Angio II and TGFβ1 mainly in tubulointerstitial compartment in the group with CAN; there was no association of Angio II and TGFβ1 expression with interstitial fibrosis. There were no significant differences of ACE, Angio II and TGFβ1 expression between the patients treated and untreated with RAS blockade, and with the graft outcome. Interstitial inflammatory infiltrate had positive correlation with interstitial fibrosis and significant impact on graft survival at 8 years.

CONCLUSIONS

Our study showed in a group of cases with CAN a high percentage of inflammatory infiltrate that correlated with interstitial fibrosis and graft outcome. The chronic inflammatory changes in these cases did not show significant association with local RAS expression.

Characterization of CTL by microscopy

Conventional microscopic techniques may be easily employed to detect and characterize cytotoxic T lymphocytes (CTL). Immunohistochemistry (IHC) may be effectively performed in CTL characterization to identify the location and distribution of target antigens in suspension cells or in tissues by staining with a specific antibody. The antibody may be conjugated to either a fluorescent or an enzymatic label, and the location of the label seen through a microscope approximates the position of the target antigen. Here, immunohistochemistry and immunofluorescence for both paraffin-embedded and frozen tissues and for suspended cell are described. Moreover, specific recommendations for analysis of suspension of cells are provided.

Expression of hypoxia-inducible factor-1α (HIF-1α) in infiltrating inflammatory cells is associated with chronic allograft dysfunction and predicts long-term graft survival

BACKGROUND

In chronic kidney failure, a hypoxic state, infiltrating inflammatory cells play a crucial role in the progression to end-stage renal disease. No studies have evaluated the influence of hypoxia and infiltrating inflammatory cells on chronic allograft dysfunction.

METHODS

Renal transplant recipients who underwent renal allograft biopsy with interstitial fibrosis/tubular atrophy (IF/TA) were enrolled and renal allograft tissue sections were processed for immunohistochemical staining including hypoxia-inducible factor-1α (HIF-1α), nitrotyrosine, α-smooth muscle actin and e-cadherin. Patients with total renal tissue HIF score ≥1 were defined as positive for HIF-1α. To assess the phenotype of the infiltrating cells, dual staining of HIF-1α with CD45, CD68 and CD3 was performed. The correlation between HIF-1α score and Banff's score was analysed. Clinical parameters including renal survival among patients with or without an expression of HIF-1α were compared.

RESULTS

Out of 55 patients enrolled, 23 patients (41.8%) had an HIF-1α score ≥1 (Group B). Compared with Group A (total renal HIF score <1), Group B had a significantly higher Banff score of interstitial infiltrates (i) (P = 0.029), vascular fibrous intimal thickening (cv) (P = 0.007) and arteriolar hyaline thickening (ah) (P = 0.026). Clinically, patients with an HIF-1α score were associated with a poor graft survival. Significantly inferior allograft survival was noted in Group B. HIF scores had an adjusted hazard ratio of 3.25 (95% confidence inteval: 1.71-6.16, P = 0.0003) in allograft failure.

CONCLUSIONS

We first demonstrated the expression of HIF-1α protein among infiltrating inflammatory cells in areas with IF/TA in patients with chronic allograft dysfunction.

Accompanying renal injuries did not impact graft survival in patients with transplant glomerulopathy

Transplant glomerulopathy (TG) a morphological feature of chronic active antibody-mediated rejection, is associated with donor-specific antibody, peritubular capillary deposition of C4d, and multilayering of peritubular capillary basement membranes. To evaluate the significance of accompanying nonimmunologic injuries in TG, we retrospectively reviewed 2839 renal allograft cases at our institute among which TG was diagnosed in 81 patients (2.9%). Among TG cases, 48 samples showed accompanying diseases such as chronic calcineurin inhibitor toxicity, hepatitis viral infection, posttransplant diabetes, and glomerulonephritis. Comparing the pure form of TG with TG-mixed diseases, there was no difference in patient demography, serum creatinine values, and proteinuria. Among histological parameters, severe hyalinosis was more frequently observed among the TG plus other diseases group. The two groups did not show significant difference in graft survival (P = .216).