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Related Concept Videos

B Cell Activation and Differentiation01:24

B Cell Activation and Differentiation

The adaptive immune response, a sophisticated defense mechanism, relies on the activation and differentiation of B lymphocytes, or B cells. These processes enable our bodies to mount a tailored response against specific pathogens such as bacteria, free virus particles, toxins, and parasites.
When naive B cells encounter a specific antigen that can bind to the B cell receptor (BCR) on their surface, they undergo sensitization to respond to the antigen's presence. Sensitization begins with...
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.
The Y-Shaped Structure of Antibodies Consists of Four Polypeptide Chains
Antibodies consist of four polypeptide chains: two identical heavy...
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.
The Y-Shaped Structure of Antibodies Consists of Four Polypeptide Chains
Antibodies consist of four polypeptide chains: two identical heavy...
Immunoglobulin-like Cell Adhesion Molecules01:31

Immunoglobulin-like Cell Adhesion Molecules

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.
Ig-CAMs exhibit either homophilic binding (to other Ig-CAMs) or heterophilic binding (to other ligands such as integrins). While most Ig-CAMs...
T Cell Activation and Clonal Selection01:22

T Cell Activation and Clonal Selection

T cells are integral to our adaptive immune system, recognizing and effectively responding to foreign antigens. T cell activation and clonal selection are pivotal in orchestrating this immune response. This article elucidates these mechanisms, detailing the roles of cluster of differentiation (CD) markers, major histocompatibility complex (MHC) molecules, costimulatory signals, and the process of clonal selection.
Naive T cells that have not yet encountered an antigen express two primary CD...
Antibody Structure and Classes01:25

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.
The basic structure of an antibody consists of four protein chains: two identical heavy chains and two identical light chains. These chains are held together by disulfide bonds and other non-covalent interactions, forming a Y-shaped structure.

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Characterization of Glycoproteins with the Immunoglobulin Fold by X-Ray Crystallography and Biophysical Techniques
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Characterization of Glycoproteins with the Immunoglobulin Fold by X-Ray Crystallography and Biophysical Techniques

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Ca2+-dependent structural changes in the B-cell receptor CD23 increase its affinity for human immunoglobulin E.

Daopeng Yuan1, Anthony H Keeble, Richard G Hibbert

  • 1King's College London and the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, Randall Division of Cell and Molecular Biophysics, Guy's Campus, London, SE1 1UL, United Kingdom.

The Journal of Biological Chemistry
|June 19, 2013
PubMed
Summary
This summary is machine-generated.

Calcium ions significantly enhance the binding affinity of CD23 (FcεRII) to Immunoglobulin E (IgE) antibodies. This study reveals the structural basis for calcium

Keywords:
AllergyCD23CalciumFC ReceptorsImmunoglobulin EImmunologyX-ray Crystallography

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Area of Science:

  • Structural biology
  • Immunology
  • Biochemistry

Background:

  • Immunoglobulin E (IgE) antibodies are central to allergic diseases.
  • IgE interacts with receptors FcεRI and CD23 (FcεRII) on various cells.
  • CD23 regulates IgE synthesis on B-cells and is a calcium-dependent lectin.

Purpose of the Study:

  • To elucidate the structural basis for calcium's effect on CD23-IgE interaction.
  • To understand how calcium binding modulates CD23's affinity for IgE.

Main Methods:

  • Determined crystal structures of CD23 head domain (Ca(2+)-free and Ca(2+)-bound) and CD23-IgE complex.
  • Employed site-directed mutagenesis, isothermal titration calorimetry, surface plasmon resonance, and stopped-flow analysis.
  • Investigated Ca(2+) ligand mutants to confirm binding site and functional impact.

Main Results:

  • Calcium binds to a conserved site on CD23, inducing a conformational change in an IgE-binding loop.
  • This Ca(2+)-induced change enhances interactions with IgE, increasing binding affinity by 30-fold.
  • The structural changes promote a more entropically favorable binding interaction.

Conclusions:

  • Calcium binding is a key modulator of CD23's interaction with IgE.
  • The structural insights explain the calcium-dependent increase in CD23-IgE affinity.
  • Findings suggest a mechanism for fine-tuning IgE regulation via calcium.