List the different immunoglobulin types and explain where they are found and what their functions are. IgM – found on B cell surfaces and functions as antigen receptor IgD – also found on B-cell surfaces and functions as antigen receptor IgA – antibodies that are secreted across mucus layer to prevent microbes from penetrating cell bodies IgE – defend body from parasites and binds to allergens to initiate destruction. IgG – funtions in neutralizing, opsonation, compliment activation, antibody dependent cell-mediated cytocity, neonatal immunity, and feedback inhibition of B-cells and found in the blood. Looking over this list, do Daniel’s recurrent lung infections make sense? Why? Yes because he is lacking these antibodies to protect his body from these reoccurring lung infections. What is an antigen?
A foreign object that induces an immune response in the body. What is immunoglobulin isotope switching? It is a biological mechanism that changes a B-cell’s production of immunoglobulin or antibodies from one class to another. How does the failure of immunological isotope switching explain the lack of IgG, IgA, and IgE in Daniel’s blood? Since IgM and IgD are the most prevalent, there aren’t enough of other antibodies to undergo isotope switching. Is this the only explanation for the lack of IgG, IgA, and IgE in Daniel’s blood? No.
Why do you think the doctor suspected the need for genetic testing? There could be genome defects that is causing something in the immune system no to produce these antibodies or the cells. What is the role of a genetic counselor?
To closely look at Daniels genes and see if this immunodeficiency has been passed down from the parents. Draw out the family pedigree that the counselor is presenting and show how this X-linked genetic disorder has passed through Susan’s family tree.
Why is the genetic counselor suggesting genetic testing for Susan’s sisters? Because the disorder is X-linked, which means Daniel inherited from his mother. If the genetic counselor examines the genes of her sisters she could possible find out if they carry the disorder as well. Which cells have the CD’, ligand? Which cells have the CD’, receptor? T-cells have the CD40 ligand and B-cells carry CD40 receptor on their respective surfaces. What does their interaction cause? How does this explain Daniel’s immunological deficiency? There interaction creates the signal transduction that is needed for immunoglobulin isotope switching which explains his immunological deficiency. Since this event does not happen he lacks the antibodies necessary to fight these infections. What is immunoglobulin therapy?
It is when immunoglobulins from a donor are injected into the blood stream. Why will Daniel need a transfusion every three to four weeks? Because white blood cells in the body do not last very long because they will be constantly used up fighting his already present infections and because his body does not create these antibodies he will need these transfusion to place them back into his body. Why do you think it will it lower his IgM levels?
It will lower because with increased antibodies present in his bloodstream they will constantly bind to the receptor that trigger IgM antibody production. How can a bone marrow or cord blood stem cell transplant cure Daniel? The cells that Daniel need for isotope switching is produced in the bone marrow. If he gets the transplant that cause increase the chances for him to produce these cells needed. What is HLA? Why is a matched sibling the best possible donor? It stands for Human Leukocyte Antigen and it is the major histocompatibility complex. A matched sibling could decrease the chances for the body to fight off the foreign bone marrow. What is prenatal testing?
It is the testing of disease in an embryo or fetus before it is born. How would Susan and Joe be able to select a child with matching HLA? They would have to do prenatal testing of embryos in order to get that matching HLA.
Courtney from Study Moose
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