Significance of Glomerular Deposition of C3c and C3d in IgA Nephropathy

<i>Background:</i> Complement activation plays an important role in the pathogenesis of IgA nephropathy. The clinico-pathological significance of the glomerular deposition of complement breakdown products, C3c and C3d in IgA nephropathy remains to be clarified. <i>Methods:</i> We examined the relationship between glomerular staining patterns of C3c and C3d and clinico-pathological findings with 163 patients with IgA nephropathy. Renal biopsy specimens were stained with C3c and C3d by immunofluorescence, and patients were divided into the following two groups: the intensity of C3c deposition stronger than C3d deposition, or equal to it (group A); the intensity of C3d deposition stronger than C3c deposition (group B). <i>Results:</i> In group A, the incidence of severe hematuria (over 20 urinary red blood cells in high-power field microscope (×400)) or of higher urinary fibrinogen degenerated products (over 0.1 μg/ml) was significantly higher than that in group B. In addition, group A showed a significant decrease in the glomerular filtration rate. Group A also showed a significantly higher incidence of glomerular endocapillary proliferation than in group B. <i>Conclusion:</i> These findings suggest that the glomerular deposition of C3c is associated with the inflammatory active phase of glomeruli in IgA nephropathy.