C1q, antibodies and anti-C1q autoantibodies

Mol Immunol. 2015 Nov;68(1):6-13. doi: 10.1016/j.molimm.2015.05.010. Epub 2015 May 29.


The complement system has long been known for its role in combating infections. More recently the complement system is becoming increasingly appreciated for its role in processes that range from waste transport, immune tolerance and shaping of the adaptive immune response. Antibodies represent the humoral part of the adaptive immune response and the complement system interacts with antibodies in several ways. Activated complement fragments impact on the production of antibodies, the complement system gets activated by antibodies and complement proteins can be the target of (auto)antibodies. In this review, written to celebrate the contributions of Prof. Dr. M.R. Daha to the field of immunology and especially complement, we will focus on C1q and its various interactions with antibodies. We will specifically focus on the mechanisms by which C1q will interact with monomeric IgG versus polymerized IgG and fluid-phase IgM versus solid-phase IgM. In addition in this review we will discuss in detail how C1q itself is targeted by autoantibodies and how these autoantibodies are currently considered to play a role in human disease.

Keywords: Antibodies; C1q; Complement.

Publication types

  • Review

MeSH terms

  • Adaptive Immunity
  • Antigen-Antibody Complex / chemistry
  • Antigen-Antibody Complex / genetics*
  • Autoantibodies / genetics*
  • Autoimmune Diseases / genetics
  • Autoimmune Diseases / immunology*
  • Autoimmune Diseases / pathology
  • Complement Activation
  • Complement C1q / genetics*
  • Complement C1q / immunology
  • Dendritic Cells / immunology
  • Dendritic Cells / pathology
  • Gene Expression Regulation
  • Humans
  • Immune Tolerance
  • Immunoglobulin G / genetics
  • Immunoglobulin G / immunology
  • Immunoglobulin M / genetics
  • Immunoglobulin M / immunology
  • Macrophages / immunology
  • Macrophages / pathology
  • Protein Multimerization
  • Signal Transduction


  • Antigen-Antibody Complex
  • Autoantibodies
  • Immunoglobulin G
  • Immunoglobulin M
  • Complement C1q