Antibody Polymers and Antibody Binding to Antigens – Humoral Immunity

by Peter Delves, PhD

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    Two of the five classes of antibody can actually polymerize, form polymers. Those two classes are IgA and IgM. So you can find immunoglobulins as a single unit if you like, what immunologists refer to as a monomer. And IgG, IgD, IgE and IgM when it’s found on the cell surface acting as the B-cell receptor of B-cells. And IgA in the blood circulation. These are all found in this monomeric form. However IgA is also very dominant at mucosal surfaces. And this so called secretory IgA is two individual units of IgA linked together by a molecule called the J chain. There’s also an additional molecule called secretory component that is associated with this dimeric secretory IgA that is present at mucosal surfaces. The IgM that is found in the circulation, in contrast to that found acting as the B-cell receptor on the surface of B-lymphocytes; when IgM is present in the circulation, five units of IgM link together to form a pentamer. And again, this J chain molecule, it’s nothing to do with the J genes that you may have heard about when we were talking about immunoglobulin and T-cell receptor gene rearrangement. This is a completely different thing, it’s a separate, it’s a protein molecule called J chain. It joins together individual units of antibodies when they polymerize. So for both secretory dimeric IgA and for circulating pentameric IgM, J chain facilitates that polymerization. The different antibodies are not all present in the circulation at the same concentration. In fact, far from it. IgM is present in a concentration of around about 45 to 250 milligrams per deciliter (mg/dL) in the adult. IgG is more dominant. We have approximately 620 to 1400 mg/dL. And in fact IgG is the most dominant class of antibody in the circulation....

    About the Lecture

    The lecture Antibody Polymers and Antibody Binding to Antigens – Humoral Immunity by Peter Delves, PhD is from the course Humoral Immunity and Cell-Mediated Immunity. It contains the following chapters:

    • Antibody Polymers
    • Antibody Binding to Antigens

    Included Quiz Questions

    1. 45-250 mg/dL
    2. 620-1,400 mg/dL
    3. 80-350 mg/dL
    4. <8 mg/dL
    5. <0.04 mg/dL
    1. Secretory IgA
    2. Cell surface IgM
    3. IgE
    4. IgD
    5. IgG
    1. A decrease in circulating IgM
    2. A decrease in IgE response
    3. An increase in secretory IgA
    4. A decrease in cell surface IgM
    5. A decrease in circulating IgA
    1. Larger antigens have more epitopes that multiple antibodies can recognize and bind to
    2. Large antigens have less variability in their amino acid sequence, making it easier for antibodies to bind to them
    3. Larger antigens bind with higher intrinsic affinity to antibodies
    4. Larger antigens are recognized by more isotypes of the immunoglobulin heavy chain
    5. Larger antigens can be presented more effectively by dendritic cells

    Author of lecture Antibody Polymers and Antibody Binding to Antigens – Humoral Immunity

     Peter Delves, PhD

    Peter Delves, PhD

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    By Bjarni J. on 20. December 2016 for Antibody Polymers and Antibody Binding to Antigens – Humoral Immunity

    Understood the concepts after not understanding them from reading my curriculum books..