C1q Antibody ELISA Kit (Complement C1q)


Human C1q antibody ELISA kit is a method for determining in vitro quantitative amounts of IgG class auto-antibodies against complement C1q antibody (C1q Ab, C1q IgG, C1q-Ab) in human serum and plasma samples. This assay has a minimum analytical sensitivity limit of 0.5 U/ml.


Complement C1q is a vital first step of the complement activation pathway, in fact it is one of the central molecules involved. This process involves the globular heads of C1q binding to the Fc regions of immunoglobulins IgG or IgM antibodies which can lead the subsequent induced activation of other sub-components of C1, C1r or C1s. It is multivalent for attaching to the complement fixation sites of immunoglobulin and these sites are present on the CH4 domain of IgM or on the CH2 domain of IgG. It contains 18 peptide chains in total (3 subunits of 6 peptides) forming a 400 kDa protein. Each subunits is made up of a Y-shaped pair of triple peptide helices that are joined at the stem and end with a globular non-helical head.

Autoantibodies against C1q have also been instrumental in the diagnosis of hypocomplementaemic urticarial vasculitis. It have been identified in nearly 95% patients having lupus nephritis and over 50% patients having SLE. It has also provided a useful tool in assessing the risk of renal flares, along with monitoring the effectiveness of various immunosuppressive treatments carried out in active lupus nephritis.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • Divisible Microplate: Consisting of 12 modules of 8 wells, highly purified Complement C1q is bound to microwells.
  • Calibrator A-F: Concentration 0-100 U/ml.
  • Control Positive And Control Negative.
  • Sample Buffer (5x).
  • Enzyme Conjugate: Contains anti-human IgG antibodies, HRP labelled.
  • TMB Substrate.
  • Stop Solution: Contains acid.
  • Wash Buffer (50x).
  • Instruction for Use.
  • Certificate of Analysis.


The minimum detection sensitivity level of IgG antibody to complement C1q antibody (C1q Ab, C1q-Ab, C1q-IgG) using current C1q antibody ELISA kit was 0.5 U/ml. The dynamic range for this assay is 6.3 – 100.0 U/ml.


– Limit Of Detection (LOD): Functional sensitivity 0.5 U/ml.
– Measuring Range: 0 – 100 U/ml.
– Results Interpretation: Negative: < 10 U/ml, Positive: ≥ 10 U/ml.
– Expected Values: Samples from healthy blood donors display a cut-off 10 U/ml.
– Linearity: 91 – 104%
– Intra Assay: 2.9 – 3.7%
– Inter Assay: 1.9 – 4.8%
– Interfering Substances: None
– Clinical Diagnosis: Sensitivity (66.3%), Specificity (89.7%), Overall agreement (80.7%).


  1. C1q, antibodies and anti-C1q autoantibodies. Mol Immunol. (2015) 68 (1): 6-13. Review. Beurskens F.J., et al.
  2. How antibodies use complement to regulate antibody responses. Mol Immunol. (2014) 61 (2): 79-88. Review. Sörman A., et al.
  3. New approaches for detecting complement-fixing antibodies. Curr Opin Organ Transplant. (2012) 17 (4): 409-15. Review. Tyan D.B.
  4. The classical and regulatory functions of C1q in immunity and autoimmunity. Cell Mol Immunol. (2008) 5 (1): 9-21. Review. Lu J.H., et al.


  • Full Name: C1q Antibody ELISA Kit (Complement C1q)
  • Reactivity: Human
  • Sample Type: Serum, Plasma
  • Sensitivity: 0.5 U/ml


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