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Related Experiment Video

Updated: Jun 3, 2026

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion

Published on: June 15, 2019

Heme interacts with c1q and inhibits the classical complement pathway.

Lubka T Roumenina¹, Maria Radanova, Boris P Atanasov

¹Centre de Recherche des Cordeliers, Université Pierre et Marie Curie, Paris 6, UMR S 872, Paris, France. lubka.roumenina@crc.jussieu.fr

The Journal of Biological Chemistry

|April 2, 2011

Summary

Heme naturally inhibits C1q, a key component of the complement system. This discovery reveals heme

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Last Updated: Jun 3, 2026

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Published on: June 15, 2019

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Area of Science:

Immunology
Biochemistry

Background:

C1q initiates the classical complement pathway, crucial for pathogen defense and clearance.
Dysregulated complement activation causes tissue damage in various diseases.
Inhibitors of the complement system are needed for therapeutic development.

Purpose of the Study:

To investigate heme as a potential inhibitor of C1q and the classical complement pathway.

Main Methods:

Studied the effect of heme on C1q interactions with C-reactive protein (CRP) and IgG.
Analyzed heme's direct binding to C1q.
Assessed changes in C1q's recognition mechanisms upon heme complex formation.

Main Results:

Heme significantly reduced classical complement pathway activation mediated by CRP and IgG.
Heme directly binds to C1q, inhibiting its interaction with CRP and IgG.
Heme-C1q complex formation alters C1q's recognition of CRP and IgG.

Conclusions:

Heme acts as a natural negative regulator of the classical complement pathway by inhibiting C1q.
Heme may play a physiological role in mitigating complement activation at sites of tissue damage and hemolysis.