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Membranous glomerulonephritis (MGN) is the most common cause of adulthood nephrotic syndrome. Diagnosis of membranous nephritis is based on light electron immunofluorescence microscopy and clinical signs. Immune complex deposition against podocyte antigens such as phospholipase A2 receptor (PLA2R) activates the complement system. Of this, complement Component C4d (C4d) is involved in the classical and lectin pathways. This marker may be used by immunohistochemistry to diagnose MGN when other methods are not available. In this work, C4d expression was monitored by immunohistochemical analysis in the glomerular capillaries of patients with primary MGN (study group, N=33) versus patients with minimal change disease (MCD, control group, N=20) in a cross-sectional evaluation performed based on the diagnosis confirmed by light microscopy and immunofluorescence. There was no significant demographic difference between the two groups except for age (P=0.002). C4d immune-expression was positive in glomerular capillary (2+ to 4+) in most of the MGN patients, while it was negative in the MCD group. The sensitivity and specificity of C4d immunostaining were 95% and 100%, respectively. The Pearson correlation coefficient was 0.74 between C4d (immunohistochemistry) and immunoglobulins (IgG; immunofluorescence) and 0.65 between C4d (immunohistochemistry) and the C3 complement product (immunofluorescence). Immunohistochemical evaluation of C4d is, therefore, a sensitive and specific method that has a high correlation with IgG immunofluorescence.

Objectives: The present study aimed to examine the expression of CD44 and claudin-1 markers using immunohistochemical methods to differentiate patients with minimal change disease (MCD) from those afflicted with focal segmental glomerulosclerosis (FSGS). Materials and Methods: In this descriptive-analytical study, twenty patients with definite FSGS, twenty patients with FSGS/MCD spectrum, and seven patients with definite MCD were randomly chosen from Imam Reza hospital affiliated with Tabriz University of Medical Sciences. All patients underwent renal biopsy, and then the presence of the immune complex was examined in the obtained samples using immunofluorescence staining. Some renal specimens were paraffin-embedded for the evaluation of the expression levels of CD44 and claudin-1 utilizing the immunohistochemistry method. Results: Among the twenty samples obtained from patients with definite FSGS, 13 samples (65%) were double-positive for CD44 and claudin-1, 3 specimens (15%) were positive only for claudin-1, and 4 samples (20%) were double-negative for CD44 and claudin-1. The percentages of renal specimens expressing claudin-1 in patients with definite FSGS, FSGS/MCD, and MCD were 80%, 85%, and 0%, respectively. Finally, the percentages of renal samples expressing CD44 in patients with definite FSGS, FSGS/MCD, and MCD were 65%, 10%, and 0%, respectively. Conclusions: The results of the present research indicated that the rate of CD44-positive specimens was higher in patients with FSGS while the percentage of claudin-1-positive samples was more frequent in MCD patients compared with FSGS patients. [ABSTRACT FROM AUTHOR]