Glomerular IgG subclasses in idiopathic and malignancy-associated membranous nephropathy

Area of Science:

• Nephrology
• Immunology
• Oncology

Background:

• Idiopathic membranous nephropathy (MN) is often associated with IgG4 subclass antibodies against the glomerular phospholipase A2 receptor (PLA2R).
• The role of different immunoglobulin G (IgG) subclasses in MN pathogenesis, including secondary forms, remains unclear.
• This study investigates whether the absence of glomerular IgG4 and PLA2R indicates underlying malignancy in MN patients.

Purpose of the Study:

• To determine if the absence of glomerular IgG4 and PLA2R is a marker for malignancy-associated membranous nephropathy (MN).
• To compare the distribution patterns of IgG subclasses and PLA2R in idiopathic MN versus malignancy-associated MN.

Main Methods:

• Retrospective analysis of kidney biopsies from 69 patients with idiopathic MN and 16 with malignancy-associated MN.
• Immunohistochemical staining for IgG subclasses (IgG1, IgG2, IgG3, IgG4) and PLA2R in glomeruli.
• Follow-up data collected for a mean of 83 months.

Main Results:

• Absence of IgG4 and PLA2R showed a significant correlation with malignancy-associated MN.
• IgG4 was present in 65% of idiopathic MN cases versus 31% of malignancy-associated MN cases.
• PLA2R deposits were found in 56% of idiopathic MN cases compared to 19% of malignancy-associated MN cases. IgG2 positivity exceeded 94% in both groups.

Conclusions:

• The absence of glomerular IgG4 and PLA2R is frequently observed in malignancy-associated MN.
• IgG2, IgG1, and IgG3 are not reliable markers for identifying underlying malignancy in MN.
• These findings aid in differentiating MN subtypes and identifying potential associated cancers.