What is the role of C3 activation in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN)?

Updated: Dec 05, 2018
  • Author: Rajendra Bhimma, MBChB, MD, PhD, DCH (SA), FCP(Paeds)(SA), MMed(Natal); Chief Editor: Craig B Langman, MD  more...
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Answer

Complement activation from both serum profiles and immunofluorescence patterns for glomerular deposits indicates that C3 activation in APSGN is predominantly via the alternative pathway. [23, 24, 25] The immune deposits consist of immunoglobulin G (IgG), C3, properdin, and C5. [25] These deposits rarely contain C1q or C4, both components of the classic complement pathway. A recent study also showed evidence for activation of the lectin-binding pathway from deposition of membrane-bound lipoprotein in some patients with APSGN. [26]

During the early phase of the diseases (first 2 wk), evidence of classical pathway activation is seen, as demonstrated by transient depression of serum C1q, C2, and/or C4 concentrations. [27, 28, 29] and the presence of circulating C1-inhibitor-C1r-C1s complexes or C4d fragments. It is proposed that the circulating immune complexes in the acute stage of the disease due to classic complement pathway activation is distinct from that seen in the glomerular immune deposits. APSGN with typical findings on histopathology may occur in patients with no evidence of complement activation, as manifested by depression of serum C3 concentrations. [30, 31]


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