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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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    Examples of primary immunodeficiencies affecting B-cells include common variable immunodeficiency, X-linked agammaglobulinemia, selective IgA deficiency. So looking first at common variable immunodeficiency; in patients with this condition, there is low IgG, and IgA and/or IgM. The gene defects in most patients have yet to be fully defined. 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. In X-linked agammaglobulinemia, as the name suggests, the gene is on the X chromosome. And agammaglobulinemia means without gamma globulins. And most of the gamma globulins are the immunoglobulins. This is due to mutations in the Bruton’s tyrosine kinase or Btk gene. There’s a developmental defect at the pre-B stage. Antibody production is grossly compromised. 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. The gene defects in most patients have yet to be discovered. Maybe you’ve got selective IgA deficiency and you don’t even know about it, you’ll be absolutely fine. Most patients, there’s no consequence. 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. 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. MHC class II
    3. CD19
    4. BAFF
    5. ICOS
    1. Most patients are severely immunocompromised
    2. Circulating IgA and secretory dimeric IgA are affected
    3. Sources of genetic defect are largely unknown
    4. IgM can be transported to mucosal surfaces
    5. Other classes of antibodies compensate for IgA

    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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