Retrospective Study of Phospholipase A2 Receptor and IgG Subclasses in Glomerular Deposits in Chinese Patients with Membranous Nephropathy

Abstract

Background and objectives: The research work in the past years showed that detection of phospholipase A2 receptor (PLA2R) antigen and its dominant IgG4 autoantibody in glomerular deposits of patients with membranous nephropathy (MN) was useful for the differentiation between primary MN (PMN) and secondary MN (SMN), but so far such research data from large Chinese patient series is little. Here, we are going to report a research work in a Chinese cohort.

Design, setting, participants, & measurements: This study enrolled 179 patients with PMN, 40 patients with membranous lupus nephritis (LN-MN), 26 patients with hepatitis B virus-associated MN (HBV-MN), 2 patients with malignancy-associated MN (M-MN) and one patient with IgG4-related MN (IgG4-MN). PLA2R and IgG subclasses in glomerular deposits of these patients were examined by immunofluorescence and/or immunohistochemical staining, and the potential value of the above examinations for differential diagnosis of PMN and SMN was evaluated.

Results: Glomerular PLA2R deposition was present in 92.2% patients with PMN and 7.7% patients with HBV-MN, but none of the patients with LN-MN. Predominant/codominant IgG4 deposition was found in 93.3% patients with PMN and 11.5% patients with HBV-MN, but none of the patients with LN-MN. The two M-MN patients both had glomerular PLA2R and predominant/codominant IgG4 deposition. The one IgG4-MN patient had deeply staining IgG4 but no PLA2R in glomeruli.

Conclusions: The glomerular PLA2R and predominant/codominant IgG4 deposition is frequently observed in Chinese patients with PMN. Immunofluorescence and immunohistochemical staining of renal biopsy tissue for detection of glomerular PLA2R and IgG subclasses deposition can help to distinguish PMN from LN-MN and most of HBV-MN.

Fig 1. Immunofluorescence and immunohistochemical staining of HBsAg and HBcAg in glomerular deposits.

HBsAg (A and C) and HBcAg (B and D) are distributed along the glomerular capillary walls in a fine granular pattern. immunofluorescence (A and B, ×200) and immunohistochemical assays (C and D, HRP×400).

Fig 2. Immunohistochemical staining of PLA2R in glomerular deposits (ALP ×400).

(A) In patients with minimal change disease there is very weak expression of PLA2R on the glomerular potocytes and it is recognized as negative result in this study. (B) In patients with PMN there is strongly stained PLA2R distributed along the glomerular capillary walls in a fine granular pattern.

Fig 3. Immunofluorescence assay of IgG and IgG4 in glomerular deposits (×400).

In patients with PMN IgG (A) and IgG4 (B) are distributed along the glomerular capillary walls in a fine granular pattern.