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Class Switch Recombination, Co-Expression and B-Cell Development – Lymphocyte Development

by Peter Delves, PhD
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    B-cells initially start off making the IgM class of antibody. But following antigen stimulation, they will switch to making other classes of antibody - IgG, IgA or IgE. This class switching also takes place at the genetic level. Here we can see the immunoglobulin heavy chain gene locus with the VDJ segment already recombined. This is lying immediately upstream of C mu (Cµ) and C delta (Cδ). So the IgM class of antibody will be produced. However, following antigen stimulation, the antibody going to be produced will be, in this instance, an IgE antibody. This requires signals from helper T-cells, for example CD40 ligand on the surface of the T-cell interacting with CD40 on the surface of the B-cell. And also cytokines produced by the helper T-cells. What will happen in this particular case is that the switch sequence immediately upstream of the Cµ gene is going to be placed next to the switch sequence immediately upstream of the C epsilon (Cε) gene. So there’s a recombination of the switch sequence for mu with the switch sequence for epsilon, and the deletion of the intervening constant region genes. Now there will be transcription and RNA splicing, and the messenger RNA encoding the IgE antibody, in other words, VDJ plus Cε will be translated into protein. And plasma cells will secret the IgE class of antibody. Naïve B-cells co-express IgM and IgD on their cell surface. And when activated, and when they differentiate into plasma cells, those plasma cells also secrete IgM and IgD. Although they produce much, much more IgM than they do IgD. You’ll hardly be surprised to learn that yet again, it is at the genetic level that this co-expression is determined. Here we can see the already recombined VDJ segment in the B-cell immunoglobulin heavy chain DNA....

    About the Lecture

    The lecture Class Switch Recombination, Co-Expression and B-Cell Development – Lymphocyte Development by Peter Delves, PhD is from the course Adaptive Immune System. It contains the following chapters:

    • Class Switch Recombination
    • Co-Expression on Naive B-Cells
    • The B-Cell Receptor
    • B1 and B2 Cells

    Included Quiz Questions

    1. IgM and IgD
    2. IgM and IgG
    3. IgG and IgD
    4. IgA and IgE
    5. IgG and IgE
    1. Signals from Helper T cells
    2. Recombination
    3. Deletion of intervening genes
    4. RNA splicing
    5. Translation
    1. The genes on the constant regions express a switch sequence (except for C delta) which enable it to produce C mu (IgM) or C delta (IgD)
    2. The constant region is attached after VJD class switching to match the appropriate immunoglobulin
    3. C delta has a switch signal which determines the expression of the rest of the genes on the constant region that determine if the immunoglobulin is IgM or IgD
    4. The VJD sequence on the immunoglobulin heavy chain controls translation of the genes required for each immunoglobulin class
    5. Signals from Helper T cells dictate which immunoglobulin will be produced on the B cell
    1. ITAMs and Src family kinases
    2. Heavy chain sequences of antibody
    3. Transmembrane sequence that holds antibody into the B cell membrane
    4. Light chain sequence of antibody
    5. Immunoglobulin class switching

    Author of lecture Class Switch Recombination, Co-Expression and B-Cell Development – Lymphocyte Development

     Peter Delves, PhD

    Peter Delves, PhD


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