Immunostaining findings in IgA nephropathy: correlation with histology and clinical outcome in the Oxford Classification patient cohort

Vitamin D-Binding Protein Is a Potential Urinary Biomarker of Irbesartan Treatment Response in Patients with IgA Nephropathy

AIMS

The purpose of this study was to identify predictive markers of irbesartan (an angiotensin receptor blocker) treatment response in immunoglobulin A nephropathy (IgAN) patients.

METHODS

Urine samples were collected both before and after irbesartan treatment in IgAN patients and compared with urine from healthy volunteers. The total urinary protein produced in 24 h was measured to determine therapeutic response. The urinary proteome was evaluated by two-dimensional gel electrophoresis coupled with MALDI-TOF-MS/MS analysis. Western blotting was used to verify protein expression. A receiver operating characteristic curve was used to evaluate the sensitivity and specificity of candidate biomarkers.

RESULTS

Four differentially expressed proteins were identified as vitamin D-binding proteins (VDPs). Western blot showed that urinary VDPs were significantly elevated in nonresponsive versus responsive IgAN patients. The sensitivity, specificity, and accuracy of urinary VDP as a predictive biomarker of irbesartan nonresponsiveness in IgAN were 65%, 85%, and 75%, respectively.

CONCLUSION

Our results revealed that urinary VDP might be a useful biomarker for predicting irbesartan treatment response.

Association of glomerular C4d deposition with various demographic data in IgA nephropathy patients; a preliminary study

BACKGROUND

IgA nephropathy (IgAN) is the most prevalent primary chronic glomerulopathy worldwide. Thus, it is of vital importance to search for factors aggravating the disease progress, monitor disease activity and predict disease-specific therapy. C4d is a well-known biomarker of the complement cascade with a potential to meet the above needs.

OBJECTIVES

The aim of our study was, therefore, to determine whether C4d staining at the time of kidney biopsy had any correlation with the demographic, clinical and biochemical variables in IgAN.

PATIENTS AND METHODS

The definition of IgAN requires the presence of diffuse and global IgA deposits which were graded ≥2+ and weak C1q deposition. C4d immunohistochemical staining was conducted retrospectively on 29 renal biopsies of patients with IgAN, which were selected randomly from all biopsies. C4d immunohistochemical staining was performed on 3-μm deparaffinized and rehydrated sections of formaldehyde-fixed, paraffin-embedded renal tissues.

RESULTS

Of 29 selected patients, 68% were male. In this study, 54.2±25 percent of glomeruli in all biopsies were positive for C4d. The mean and standard deviation (SD) of serum creatinine and the magnitude of proteinuria were 1.72±1.2 mg/dl and 1582±1214 mg/day, respectively. In this study, we observed statistically significant correlations of percent C4d positivity with the serum creatinine (r=0.61, p=0.0005), magnitude of proteinuria (r=0.72, p=0.0001), the proportion of globally sclerotic glomeruli (r=0.43, p=0.02) and the proportion of tubulointerstitial fibrosis (r=0.54, p=0.0023).

CONCLUSIONS

The results from our investigation on C4d positivity in biopsy-proven cases of IgAN are in accord with some of the previous studies. These findings, however, require further validation in larger samples.

New insights into the pathogenesis of IgA nephropathy

IgA nephropathy (IgAN) is the most common diagnosis amongst primary glomerular diseases in most countries where renal biopsies are regularly performed. Only a fraction of these patients is at high risk of losing glomerular filtration rate (GFR) in particular those with high grade proteinuria, uncontrolled hypertension or already impaired GFR at diagnosis, and those with renal scars in the renal biopsy. Genetic modifiers of IgAN onset and/or course are emerging. Spontaneous animal models of IgAN are problematic given considerable species differences between the rodent and human IgA system. However, new transgenic models help to better understand the pathogenesis. A key pathogenetic role appears to be played by underglycated IgA1 as well as autoantibodies to these IgA glycoforms and IgA receptors such as CD89 and transferrin receptor 1. Once IgA and/or IgA-containing immune complexes are deposited or formed in the mesangium, secondary effector mechanisms become important including complement activation, release of mesangial growth factors (in particular platelet-derived growth factor), and finally non-IgAN-specific events that culminate in glomerular and subsequently renal tubulointerstitial scaring. Here, we review these processes and describe potential novel therapeutic targets in IgAN.

Significance of immunohistochemical findings in Oxford classification of IgA nephropathy: The need for more validation studies

Implication for health policy/practice/research/medical education: Oxford classification of IgA nephropathy (IgAN) has been validated as clinically useful tool for prognostication of individual patients with IgAN. The original classification did not address the significance of immunostaining pattern in IgAN. A subsequent study by the same authors found immunostaining data to be potentially useful in predicting some of the morphological variables of Oxford classification. The study under discussion also addresses the potential significance of these ancillary data in refining the individual prognostication in this disease. Please cite this paper as: Mubarak M. Significance of immunohistochemical findings in Oxford classification of IgA nephropathy: The need for more validation studies. J Nephropathology. 2013; 2(3): 210-213. DOI: 10.5812/nephropathol.11089.

Correlation of immunostaining findings with demographic data and variables of Oxford classification in IgA nephropathy

BACKGROUND

Oxford classification for IgA nephropathy (IgAN) did not include pattern of immunostaining in the analysis.

OBJECTIVE

The aim of this study is to determine the potential correlation between the immunostaining data and morphologic variables of Oxford classification (MEST) and various clinical and demographic data of patients with IgAN.

PATIENTS AND METHODS

The pathologic diagnosis of IgAN requires the demonstration of IgA-dominant mesangial or mesangio-capillary immune deposits through immunofluorescence (IF) microscopy. The immune deposits were semiquantitatively assessed as 0 to 3+ positive bright. These were correlated with various clinical, demographic and histological variables of Oxford classification.

RESULTS

A total of 114 biopsies were enrolled to the study (70.2% were male).  Mean age of the patients was 37.7 ± 13.6 years. This study showed that, only C3 deposits had a significant correlation with serum creatinine. Other antibodies (IgA, IgM and IgG) had no significant association with serum creatinine. This study also showed that IgA deposition score had significant positive association with endocapillary proliferation (E) and segmental glomerulosclerosis (S) variables of Oxford classification. Moreover, IgM deposition score had positive association with S variable. There was no significant association of IgG deposition score with four morphologic variables of Oxford classification. There was significant association of C3 deposition score with S and E variables too.

CONCLUSIONS

The significant relationships of IgA and C3 deposits with some of the Oxford variables need more attention. We propose to further investigate this aspect of IgAN disease.

IgG deposition in IgA nephropathy patients

IgA nephropathy is the most common form of glomerular disease among young adults. The aim of this study is to determine the correlation of IgG deposition with morphologic variables of Oxford classification and some clinical data of patients with IgA nephropathy (IgAN).A total of 114 biopsies were enrolled to the study (70.2% were male). Mean age of the patients was 37.7±13.6 years. This study showed that, IgG deposition intensity had not significant correlation with serum creatinine. No significant association of sex with IgG was found. There was not significant association of IgG deposits with age below and more that 40 years. There was not significant association of IgG deposit intensity with four morphologic variables of Oxford classification. Less studied published regarding the immunostaining findings in IgA nephropathy patients. Location of deposited immunoglobulin (mesangial versus mesangial-capillary) or the type of immunoglobulin (IgG or IgM) may have prognostic significant. More studies needs to find the clinical significance of immunostaining data.