Diagnosis – Primary Immunodeficiency

by Peter Delves, PhD

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    00:01 So very typically in an infant with primary immunodeficiency, the child will be getting recurrent infections that’ll be quite severe.

    00:09 Of course all children get infections but usually one or two days later they’re fit and well and they’re running around again, perfectly healthy.

    00:16 But in children with primary immunodeficiencies, they will not recover very well from these infections and the parents maybe will be a bit concerned and they’ll take them along to the doctor’s clinic and eventually they may get investigated if primary immunodeficiency is suspected.

    00:35 And there are a number of different tests that can be carried out to try and help in the diagnosis of primary immunodeficiency.

    00:42 For example, the number of cells of the immune system can be counted.

    00:46 One can look for the number of CD3+ lymphocytes.

    00:50 CD3 is a molecule that’s found on the surface of all T-cells, so this will tell you whether there is a T-cell deficiency or not.

    00:57 Then one can look a little bit deeper and look at individual subsets of T-cells, for example look at the number of CD4+ cells, the number of CD8+ cells.

    01:08 One can also assess the function of cells in vitro.

    01:12 For example, you can stimulate T-cells with a mitogenic substance called phytohemagglutinin (PHA), or one can stimulate with specific antigens, one can look for the production of cytokines such as interleukin-2 in vitro in the laboratory.

    01:32 One can also look at the function of the immune system within the individual child using delayed hypersensitivity reactions to purified protein derivative (PPD) of Mycobacterium tuberculosis.

    01:50 Regarding investigation of B-cell primary immunodeficiencies, again one can enumerate cells.

    01:57 There are various molecules that are pretty much restricted to being expressed on B-cells but not other cells of the immune response.

    02:05 CD20 is a good example of that.

    02:07 One can look at cell surface membrane immunoglobulin, again very characteristic of a B-lymphocyte.

    02:14 One can also look at the levels of immunoglobulin that are being secreted into the body of that particular individual.

    02:23 Regarding the in vivo functioning, one can look at specific antibody levels.

    02:29 So as well as measuring total immunoglobulin levels, you can look at levels of antibody against particular antigens.

    02:37 For example, isohemagglutinins, antibodies against E-coli, against tetanus and so forth.

    02:43 And one may want to immunize those individuals with non-live vaccines.

    02:49 It’s very important that anybody suspected of immunodeficiency is never ever given a live vaccine, but using bacterial toxins; for example tetanus toxin or diphtheria toxin.

    02:59 One can look and see whether the response is adequate to help identify if there is a B-cell immunodeficiency.

    03:06 Regarding phagocytic cells, one can count the number of circulating neutrophils for example.

    03:11 And there’s also a test that one can carry out in vitro called the nitroblue tetrazolium test, which essentially looks at the ability of neutrophils to mount a respiratory burst.

    03:22 And in chronic granulomatous disease, there is an inability to mount a respiratory burst, so this test would pick that up.

    03:31 And finally, looking at complement deficiencies, one can use a hemolysis assay to look at the ability of serum from the individual to lyse red blood cells, using the membrane attack complex.

    03:46 If the membrane attack complex is not able to be produced, that would suggest a complement deficiency.

    About the Lecture

    The lecture Diagnosis – Primary Immunodeficiency by Peter Delves, PhD is from the course Immunodeficiency and Immune Deficiency Diseases.

    Included Quiz Questions

    1. Nitro blue tetrazolium
    2. Phytohemagglutinin
    3. Delayed hypersensitivity
    4. Isohemagglutinins
    5. Enumeration of neutrophils
    1. The Mantoux test
    2. Hemolysis assay
    3. Enumeration of neutrophils
    4. Nitro blue tetrazolium score
    5. Antibody levels of isohemagglutinins
    1. Isohemogglutinin levels
    2. Nitro blue tetrazolium test
    3. Hemolysis assay
    4. The Mantoux test
    5. Enumeration of neutrophils

    Author of lecture Diagnosis – Primary Immunodeficiency

     Peter Delves, PhD

    Peter Delves, PhD

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    By Pierrot P. on 07. August 2019 for Diagnosis – Primary Immunodeficiency

    Really clear, really good explanations. Thank you professor. Have a good day.