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B-Cell Immunodeficiencies: Common Variable Immunodeficiency, X-linked Agammaglobulinemia and Selective IgA Deficiency – Primary Immunodeficiency

by Peter Delves, PhD

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    00:01 Examples of primary immunodeficiencies affecting B-cells include common variable immunodeficiency, X-linked agammaglobulinemia, selective IgA deficiency.

    00:21 So looking first at common variable immunodeficiency; in patients with this condition, there is low IgG, and IgA and/or IgM.

    00:42 The gene defects in most patients have yet to be fully defined.

    00:49 But in some patients, mutations have been identified in a number of different molecules important in the B-cell response - TAC1, CD19, ICOS, substance P, MHC Class II, various complement components, mismatch repair protein MSH5, B-cell surface receptor BAFF. And these patients have recurrent infections with a number of different species - S. pneumoniae, Hemophilus influenza, Mycoplasma species and so forth.

    01:32 In X-linked agammaglobulinemia, as the name suggests, the gene is on the X chromosome.

    01:38 And agammaglobulinemia means without gamma globulins.

    01:43 And most of the gamma globulins are the immunoglobulins.

    01:47 This is due to mutations in the Bruton’s tyrosine kinase or Btk gene.

    01:53 There’s a developmental defect at the pre-B stage.

    01:59 Antibody production is grossly compromised.

    02:03 And there are infections with a number of different pyogenic bacteria, and also with the fungus pneumocystis jirovecii. Looking at selective IgA deficiency, both circulating IgA and secretory dimeric IgA are affected.

    02:20 The gene defects in most patients have yet to be discovered.

    02:25 Maybe you’ve got selective IgA deficiency and you don’t even know about it, you’ll be absolutely fine.

    02:30 Most patients, there’s no consequence.

    02:33 And this is because other classes of antibody, including IgM transported to mucosal surfaces by the poly-Ig receptor compensate for the lack of IgA.

    02:45 It’s actually quite a common theme in immunology, that there are lots of different mechanisms that can take over if one is defective.


    About the Lecture

    The lecture B-Cell Immunodeficiencies: Common Variable Immunodeficiency, X-linked Agammaglobulinemia and Selective IgA Deficiency – Primary Immunodeficiency by Peter Delves, PhD is from the course Immunodeficiency and Immune Deficiency Diseases. It contains the following chapters:

    • Examples of Primary Immunodeficiency Affecting B-cells
    • Common Variable Immunodeficiency
    • X-Linked Agammaglobulinemia
    • Selective IgA Deficiency

    Included Quiz Questions

    1. Bruton’s tyrosine kinase
    2. gp91phox
    3. MEFV
    4. TNFRSF13C
    5. Inducible T-cell COStimulator (ICOS)
    1. Most patients are severely immunocompromised.
    2. Circulating IgA and secretory dimeric IgA are affected.
    3. A causative gene defect has not been identified.
    4. Other immune mechanisms may often compensate.
    5. Normal antibody response to vaccinations occurs.

    Author of lecture B-Cell Immunodeficiencies: Common Variable Immunodeficiency, X-linked Agammaglobulinemia and Selective IgA Deficiency – Primary Immunodeficiency

     Peter Delves, PhD

    Peter Delves, PhD


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    Great Lecture
    By Laura P. on 19. March 2019 for B-Cell Immunodeficiencies: Common Variable Immunodeficiency, X-linked Agammaglobulinemia and Selective IgA Deficiency – Primary Immunodeficiency

    The lecture was amazing, it had all the important details that my textbook had, but at the same time it was very punctual and didactic. I was able to visualize all the things that I read with good examples.