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C4b-binding protein, a regulatory component of the classical pathway of complement, is an acute-phase protein and is

S R Barnum1, B Dahlbäck

  • 1Department of Microbiology, University of Alabama, Birmingham.

Complement and Inflammation
|January 1, 1990
PubMed

Insights

Human complement factor C4b-binding protein (C4BP) levels are significantly elevated in systemic lupus erythematosus (SLE) and acute-phase patients. C4BP is an acute-phase reactant, regulated differently from C-reactive protein (CRP).

Area of Science:

  • Immunology
  • Biochemistry
  • Clinical Chemistry

Background:

  • Complement factor C4b-binding protein (C4BP) plays a crucial role in regulating the complement system.
  • Understanding C4BP levels in autoimmune diseases and acute-phase responses is important for diagnostic and prognostic purposes.

Purpose of the Study:

  • To develop a radioimmunoassay for quantifying human C4BP in serum.
  • To determine C4BP levels in healthy individuals, patients with systemic lupus erythematosus (SLE), and individuals in an acute-phase response.
  • To investigate the relationship between C4BP and C-reactive protein (CRP) during the acute-phase response and in SLE.

Main Methods:

  • Development of a radioimmunoassay utilizing monoclonal and polyclonal antihuman C4BP antibodies.
  • Quantification of serum C4BP levels in different patient cohorts.
  • Assessment of serum C-reactive protein (CRP) levels to confirm acute-phase response and evaluate correlation with C4BP.

Main Results:

  • Serum C4BP levels were significantly elevated in SLE patients (186% increase, p=0.0001) and even higher in acute-phase individuals (286% increase, p=0.0001).
  • In acute-phase individuals, CRP levels were markedly elevated (100-fold) but showed no correlation with C4BP levels (r=-0.031, p=0.899).
  • SLE patients exhibited moderately elevated CRP levels (5-fold increase, p=0.028).

Conclusions:

  • C4b-binding protein (C4BP) is identified as an acute-phase reactant.
  • C4BP exhibits differential regulation compared to C-reactive protein (CRP) during the acute-phase response.
  • The findings suggest C4BP's potential as a biomarker in inflammatory and autoimmune conditions.

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