. 2020 Mar;20(2):156–160. doi: 10.7861/clinmed.2019-0452

Table 2.

Evidence of complement activation in systemic and renal-limited kidney diseases, typical changes seen in renal disease

Disease	Serum C3	Serum C4	Staining on renal biopsy
Complement-mediated aHUS	Low	Normal	Evidence of TMA, no specific staining
Dense deposit disease	Low	Normal	Dominant C3 in glomerulus (dense deposits in GBM on EM)^a
C3 glomerulonephritis	Low	Normal	Dominant C3 in glomerulus (ill-defined deposits on EM)^a
Lupus nephritis	Low	Low	‘Full house’ of complement components (including C1q), as well as IgG, IgA and IgM
Cryoglobulinaemia	Normal	Low	C1q and C4 staining, immune complexes in capillary loops and subendothelial space on LM
IgA nephropathy	Normal	Normal	Predominant IgA deposition, C3 also commonly seen^a
Anti-GBM disease (Goodpasture's)	Normal	Normal	Linear GBM IgG staining, frequent linear C3 and C1q staining observed
ANCA-associated vasculitis	Normal	Normal	Majority have positive but weak staining for complement or immunoglobulin
Bacterial endocarditis	Low	Low/Normal	C3 deposition, crescentic or endocapillary proliferative glomerulonephritis on LM^a
Post-infectious glomerulonephritis	Low	Normal	Predominant C3 staining, proliferative glomerular injury^a
Antibody-mediated rejection of renal transplant	Normal	Normal	Peritubular capillary and glomerular C4d deposition
Membranous nephropathy	Normal	Normal	C3 and IgG deposition in sub-epithelial immune complexes^a

a = staining for C3 will detect mainly activated C3 (C3b) and the fragments produced by factor I-mediated proteolytic breakdown (iC3b, C3dg and C3d); aHUS = atypical haemolytic uraemic syndrome; EM = electron microscopy; GBM = glomerular basement membrane; Ig = immunoglobulin; LM = light microscopy; TMA = thrombotic microangiopathy.