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Related Experiment Video

Updated: Jun 10, 2026

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion
06:54

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Published on: June 15, 2019

Direct interaction between CD91 and C1q.

Karen Duus1, Erik W Hansen, Pascale Tacnet

  • 1Department of Clinical Biochemistry and Immunology, Statens Serum Institut, Copenhagen, Denmark.

The FEBS Journal
|August 19, 2010
PubMed
Summary

The complement C1q protein directly binds to CD91 (alpha-2-macroglobulin receptor), a scavenger receptor on monocytes. This interaction suggests CD91 acts as a direct receptor for C1q, aiding in the clearance of immune complexes and apoptotic cells.

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Last Updated: Jun 10, 2026

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Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation
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Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation

Published on: February 28, 2019

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • The complement system's C1q protein is crucial for removing immune complexes and apoptotic cells, maintaining tissue homeostasis and preventing autoimmunity.
  • Previous research suggested C1q facilitates apoptotic cell clearance via a receptor complex involving CD91 and calreticulin.

Purpose of the Study:

  • To investigate the direct interaction between C1q and CD91.
  • To determine if CD91 functions as a direct receptor for C1q on monocytic cells.

Main Methods:

  • ELISA and surface plasmon resonance assays to detect direct binding between purified C1q and CD91.
  • Experiments using monocytic cell lines and human blood monocytes to assess C1q binding and its correlation with CD91 expression.
  • Inhibition studies using receptor-associated protein and known CD91/C1q ligands.

Main Results:

  • C1q directly binds to CD91 expressed on monocytic cells and human monocytes.
  • C1q binding to monocytes correlates with CD91 expression and can be inhibited by receptor-associated protein.
  • Direct, specific, time-dependent, and saturable interactions between purified C1q and CD91 were confirmed by ELISA and surface plasmon resonance.

Conclusions:

  • CD91 directly recognizes and binds C1q.
  • CD91 functions as a direct receptor for C1q.
  • This interaction facilitates the clearance of C1q and C1q-bound material by the multifunctional scavenger receptor CD91.