IFI27 Is a Useful Genetic Marker for Diagnosis of Immunoglobulin A Nephropathy and Membranous Nephropathy Using Peripheral Blood

Diagnosis of chronic glomerulonephritis (CGN) depends primarily on renal biopsy, which is expensive and requires hospitalization, creating a demand for noninvasive diagnostic method for this disease. We used DNA microarray analysis to search for genes whose expression levels in peripheral blood mononuclear cells (PBMCs) could distinguish between patients with CGN and healthy volunteers (HVs). We selected immunoglobulin A nephropathy (IgAN) and membranous nephropathy (MN) as typical forms of CGN. The mRNA level of the gene encoding interferon (IFN)-alpha-inducible protein 27, IFI27, which is preferentially expressed in podocytes of glomeruli, was lower in PBMCs of IgAN and MN patients than in those of HVs. This result was confirmed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Moreover, qRT-PCR analysis revealed that the IFI27 mRNA level was reduced in PBMCs of patients with other types of chronic glomerulonephritis. IFI27 immunohistochemical staining of biopsied specimens also confirmed reduced expression of IFI27 protein in IgAN and MN patients. Based on these results, we propose that IFI27 could serve as a noninvasive diagnostic marker for CGNs using peripheral blood.