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Related Concept Videos

Humoral Immune Responses01:36

Humoral Immune Responses

Overview
Antibody Structure01:10

Antibody Structure

Overview
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.
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Antibodies consist of four polypeptide chains: two identical heavy...
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Immunoglobulin-like cell adhesion molecules or Ig-CAMs are a versatile group of cell surface glycoproteins belonging to the immunoglobulin protein superfamily. Ig-CAMs possess the characteristic immunoglobulin protein domains and other domains such as the fibronectin type III domain. The Ig domains are glycosylated to varying degrees in different Ig-CAMs.
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Antibody Structure and Classes

Antibodies, also known as immunoglobulins, are produced by B cells in response to foreign substances, such as bacteria and viruses. These proteins are critical for recognizing and neutralizing these substances, protecting the body from potential harm.
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Antibody Actions01:26

Antibody Actions

Antibodies, or immunoglobulins, are critical players in the immune system's arsenal against invading pathogens. Produced by B cells and plasma cells, their primary role is to detect and bind to specific antigens, molecules found on the surface of pathogens like bacteria or viruses. Beyond antigen recognition, antibodies perform several vital functions that contribute to immune defense.
Neutralization
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Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a membrane...

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Related Experiment Video

Updated: Jun 9, 2026

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
06:29

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

Published on: January 29, 2014

Defining the Features of Complement-Active IgM.

Michael J Watson1, Charlie C Mundorff1, Eric M Lynch2

  • 1Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, United States.

Journal of Molecular Biology
|March 28, 2025
PubMed
Summary
This summary is machine-generated.

Immunoglobulin M (IgM) antibodies activate complement when bound to antigens. This study reveals the specific structural changes in IgM's Fc domains that trigger this crucial immune response.

Keywords:
HDX-MSIgMcomplement activationdeuteriumimmunoglobulin

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Last Updated: Jun 9, 2026

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
06:29

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

Published on: January 29, 2014

A Protein Microarray Assay for Serological Determination of Antigen-specific Antibody Responses Following Clostridium difficile Infection
09:12

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07:35

Double Labeling Immunofluorescence using Antibodies from the Same Species to Study Host-Pathogen Interactions

Published on: July 10, 2021

Area of Science:

  • Immunology
  • Structural Biology
  • Biochemistry

Background:

  • Immunoglobulin M (IgM) is vital for early adaptive immunity and potent complement activation.
  • The structural basis for IgM-mediated complement activation upon antigen binding is not fully understood.

Purpose of the Study:

  • To investigate the structural transitions of IgM upon antigen binding that lead to complement component C1 activation.
  • To elucidate the functional and structural characteristics of the complement-active IgM conformation.

Main Methods:

  • In vitro complement activation assays.
  • Biolayer interferometry for C1 binding kinetics.
  • Hydrogen/Deuterium exchange with mass spectrometry for conformational analysis.

Main Results:

  • IgM initiated complement activation only when forming a multivalent complex with surface-displayed antigens.
  • Key structural changes in the Fc domains were identified during the transition to the active conformation.

Conclusions:

  • Multivalent antigen binding is essential for IgM-initiated complement activation.
  • Specific conformational changes in IgM's Fc domains define its complement-active state, clarifying a critical immune mechanism.