IgA nephropathy: association of C4d with clinical and histopathological findings and possible role of IgM.
BACKGROUND
In patients with IgA nephropathy (IgAN) lectin and alternative pathways of the complement can be activated. Our aim was to analyze the association of glomerular and extraglomerular C4d staining--the representative of lectin pathway-with demographic, clinical and histopathological findings in primary IgAN patients.


METHODS
Seventy-three patients were enrolled and after re-evaluation 37 of them were included in this study. Biopsies were analyzed for staining with anti-C4d primary monoclonal antibody by immunohistochemistry. Patients were classified as positive and negative groups based on their glomerular C4d deposition. Groups were compared for their baseline clinical and histopathological findings.


RESULTS
Sixteen (43.2%) of 37 patients were C4d-positive. Glomerular C4d-staining was associated with more severe proteinuria (2906 mg/day vs. 1091 mg/day; p = 0.002), lower GFR (54.87 mL/min vs. 95 mL/min; p = 0.023), higher blood pressure (p = 0.022), more severe endocapillary hypercellularity (p < 0.001) and more severe tubular atrophy (p < 0.01). Mesangial IgM deposition was found to be associated with glomerular C4d staining and nephrotic range proteinuria.


CONCLUSIONS
Glomerular C4d deposition was found to be associated with more unfavorable histopathological and clinical findings at the time of diagnosis. Association of mesangial IgM deposition with the activation of lectin pathway is a novel finding. Mesangial IgM deposition in our patients may reflect the genetic heterology of IgAN between diverse populations. However, since these data are about association, a cause-and-effect about IgM and IgAN cannot be proven solely with these findings.
a Department of Internal Medicine , Dokuz Eylul University School of Medicine , İzmir , Turkey .
Cihan
C
Heybeli
b Department of Pathology , Dokuz Eylul University School of Medicine , İzmir , Turkey , and.
Mehtat
M
Unlu
c Department of Nephrology , Dokuz Eylul University School of Medicine , İzmir , Turkey.
Serkan
S
Yildiz
c Department of Nephrology , Dokuz Eylul University School of Medicine , İzmir , Turkey.
Caner
C
Çavdar
b Department of Pathology , Dokuz Eylul University School of Medicine , İzmir , Turkey , and.
Sulen
S
Sarioglu
c Department of Nephrology , Dokuz Eylul University School of Medicine , İzmir , Turkey.
Taner
T
Camsari
D000328:Adult; D000368:Aged; D001706:Biopsy; D015935:Complement C4b / Q000032:analysis*; D037582:Complement Pathway, Mannose-Binding Lectin; D018450:Disease Progression; D005260:Female; D005922:Glomerulonephritis, IGA / Q000150:complications / Q000473:pathology*; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D007678:Kidney Glomerulus / Q000473:pathology*; D037102:Lectins / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000175:diagnosis; D012189:Retrospective Studies; D055815:Young Adult
D007075:Immunoglobulin M; D037102:Lectins; D015935:Complement C4b
C4d; IgA nephropathy; IgM; complement; lectin pathway