Significance of mast cell renal infiltration in patients with anti-GBM nephritis

Disease activity prediction and prognosis of anti-GBM nephritis based on T lymphocyte subset ratios

Introduction

Cell-mediated autoimmunity, especially the autoreactivity of T cells, is known to underlie the initiation of anti-glomerular basement membrane disease. However, the T lymphocyte subsets that determine the disease activity, renal fibrosis, and prognosis of anti-GBM disease have not been clearly elucidated.

Methods

The T lymphocyte subsets (CD4+ and CD8+) were examined on peripheral blood and renal biopsy tissues from 65 patients with biopsy proven anti-GBM disease. Patients were divided into the high ratio group and low ratio group according to the cutoff values in the receiver operating characteristic curve analysis. The correlations of T lymphocyte subsets with clinical, pathological data, and renal outcome were analyzed.

Results

By the end of follow-up, 45 patients (69.2%) developed end-stage renal disease (ESRD). In peripheral blood, the CD4+/CD8+ ratio showed a predictive ability with a sensitivity and specificity of 91.3% and 52.9%, respectively, which gave rise to a cutoff value of 0.89. There was a significant difference in the activity index between these two groups (3.91 ± 1.38 vs. 2.89 ± 1.13, p = 0.007). In the renal tissues, the CD4+/CD8+ ratio had the optimal cutoff point of 0.82 with a sensitivity of 57.8% and specificity of 85%. The renal activity index was higher for the renal tissues with high CD4+/CD8+ ratios than that of tissues with low CD4+/CD8+ ratios (4.32 ± 1.55 vs. 3.37 ± 1.41, p = 0.016). Peripheral blood CD4+/CD8+ ratios of ≥0.89 or renal tissue CD4+/CD8+ ratios of < 0.82 positively correlated with poor renal prognosis in patients with anti-GBM nephritis.

Conclusions

The CD4+/CD8+ ratio was associated with renal activity index both in peripheral blood and renal tissue and predicts the renal prognosis of patients with anti-GBM nephritis.

Critical Role of Neprilysin in Kidney Angiotensin Metabolism

RATIONALE

Kidney homeostasis is critically determined by the coordinated activity of the renin-angiotensin system (RAS), including the balanced synthesis of its main effector peptides Ang (angiotensin) II and Ang (1-7). The condition of enzymatic overproduction of Ang II relative to Ang (1-7) is termed RAS dysregulation and leads to cellular signals, which promote hypertension and organ damage, and ultimately progressive kidney failure. ACE2 (angiotensin-converting enzyme 2) and NEP (neprilysin) induce the alternative, and potentially reno-protective axis by enhancing Ang (1-7) production. However, their individual contribution to baseline RAS balance and whether their activities change in chronic kidney disease (CKD) has not yet been elucidated.

OBJECTIVE

To examine whether NEP-mediated Ang (1-7) generation exceeds Ang II formation in the healthy kidney compared with diseased kidney.

METHODS AND RESULTS

In this exploratory study, we used liquid chromatography-tandem mass spectrometry to measure Ang II and Ang (1-7) synthesis rates of ACE, chymase and NEP, ACE2, PEP (prolyl-endopeptidase), PCP (prolyl-carboxypeptidase) in kidney biopsy homogenates in 11 healthy living kidney donors, and 12 patients with CKD. The spatial expression of RAS enzymes was determined by immunohistochemistry. Healthy kidneys showed higher NEP-mediated Ang (1-7) synthesis than Ang II formation, thus displaying a strong preference towards the reno-protective alternative RAS axis. In contrast, in CKD kidneys higher levels of Ang II were recorded, which originated from mast cell chymase activity.

CONCLUSIONS

Ang (1-7) is the dominant RAS peptide in healthy human kidneys with NEP rather than ACE2 being essential for its generation. Severe RAS dysregulation is present in CKD dictated by high chymase-mediated Ang II formation. Kidney RAS enzyme analysis might lead to novel therapeutic approaches for CKD.

Mast cells in the kidney biopsies of pediatric patients with lupus nephritis

Introduction:

Mast cells may be involved in inflammation and contribute to the onset of fibrosis in lupus nephritis (LN).

Objective:

This study aimed to correlate the presence of mast cells in kidney biopsy specimens of pediatric patients with LN with activity (AI) and chronicity (CI) indices and assess how effectively mast cells may be used as a prognostic factor.

Method:

The study included 40 patients aged 6-18 years diagnosed with LN at the Renal Disease Service of the Federal University of Triângulo Mineiro between 1996 and 2015. Workup and epidemiological data were evaluated vis-à-vis AI, CI, and mast cell counts (MCC).

Results:

Significant positive correlations were found between mast cell counts (MCC) and AI (p = 0.003; r: 0.66) and MCC and CI (p = 0.048; r: 0.48). The ROC curve showed that mast cells were highly sensitive and specific in the differentiation of patients with an AI > 12 from individuals with an AI ≤ 12. Serum creatinine levels were higher in individuals with class IV LN than in patients with class V disease [1.50 (0.40-20.90) vs. 0.70 (0.62-0.90), p = 0.04]. Blood urea nitrogen had a positive significant correlation with MCC (p = 0.002; r: 0.75). A trend toward a negative correlation was observed between MCC and serum albumin (p = 0.06; r: -0.5459). Kidney biopsies of patients with nephrotic syndrome had higher MCC [2.12 (0.41-5.140) vs. 0.53 (0.0-3.94), p = 0.07].

Conclusion:

Inflammatory cell infiltration and morphological differences between cell types in the inflammatory infiltrate are relevant factors in the assessment of the LN. Mast cell analysis and AI/CI assessment may be relevant prognostic indicators for pediatric patients with LN.