Patterns of IgG subclass deposits in membranous glomerulonephritis in renal allografts

Membranous glomerulonephritis (MGN) may develop in the renal allograft either de novo or as a recurrence. These 2 forms of MGN may have different pathogenic mechanisms, with different IgG subclass profiles in the immune deposits. This study examined IgG subclass distributions in recurrent and de novo MGN in allograft kidneys. We identified allograft kidneys with MGN, including 7 with recurrent MGN, 2 with de novo MGN, and 2 atypical/ indeterminate, and determined the relative intensity of IgG1, IgG2, IgG3, and IgG4 staining in capillary wall deposits by immunofluorescence microscopy. IgG4 was the dominant or codominant IgG subclass in capillary loop deposits in all 7 cases of recurrent MGN. IgG1 staining was dominant in 3 of 4 de novo or atypical MGN cases and codominant with IgG4 in the fourth. Although pretransplantation kidney biopsies were not available for comparisons, these findings suggest that all allograft recurrences represent idiopathic MGN and that de novo MGN cases had a different pathogenic mechanism.