Histologic Evaluation
The biopsy specimens were processed for light microscopy,
immunofluorescence and electron microscopy. Paraffin sections for light
microscopy were stained with hematoxylin and eosin, periodic
acid-Schiff, and Masson’s trichrome stain for pathologic analysis.
Direct immunofluorescence for IgA, IgG, IgM, and C3 was performed in
frozen sections. Clinical renal pathologists performed qualitative
assessment of the degree of immunofluorescent staining. The degree of
glomerular C3 immunofluorescent stain intensity was reported on a scale
of 1+ to 3+, with 1+ representing low-intensity staining; 2+,
medium-intensity staining; or 3+, high-intensity staining. Glomerular
IgG and IgM deposition were graded by absent (score, 0), mild (score,
1), marked (score, 2), respectively. Glomerular IgA deposition were
graded by IgA=2+ and IgA>2+. Pathological features were
scored using the existing literature [14, 15]. In particular,
mesangial hypercellularity, segmental glomerulosclerosis, endocapillary
hypercellularity, tubular atrophy/interstitial fibrosis were graded by
Oxford classification. For each biopsy, we determined the fraction of
glomeruli with cellular or fibrocellular or fibrous crescents. A crescent
was defined as extracapillary proliferation of more than two cell layers
of any size; this definition was uniform in all studies. The severity of
global glomerulosclerosis and arterial wall thickening was graded in
three groups: absent (score, 0), mild (score, 0), and marked (score, 0).
Crescents and arterial hyalinosis were scored as either absent or
present.