Question

Susan and Joe were worried. Their little boy, Daniel, had been having an awful lot of bacterial infections and he was barely a year old. It seemed that the antibiotics cleared up one bacterial respiratory infection only to have another follow shortly. The scary thing was that Daniel had just fought off a case of pneumonia caused by Pneumocystis carnii, a fungal infection that was usually found in people with HIV. Waiting for the test results of an HIV test for their little boy was one of the worst waits ever. Thank goodness it came back negative.

However, it seemed that their troubles were just beginning. After this last lung infection, the fungal one, and a negative HIV test, their doctor had ordered a number of other blood tests, including a genetic test that Susan didn’t fully understand. Apparently the doctor was worried about Daniel’s immune system functions. Susan had also met with a genetic counselor who collected a family history of any immune disorders. The details were vague, but Susan’s mother, Helen, knew that one of her three brothers had died young from an unexplained lung infection. Unfortunately, Grandma Ruth had passed away a few years ago, leaving them with numerous unanswered questions.

Susan and Joe had an appointment with their doctor that afternoon to go over the results. When they arrived Dr. Dresdner led them into an office where Ms. Henchey, the genetic counselor, waited. This can’t be good, thought Susan. The doctor began by explaining that they had analyzed Daniel’s blood and found that while he had normal levels of B cells and T cells, his antibody levels were anything but normal. The levels of IgG, IgA, and IgE were very low, almost undetectable, and Daniel had abnormally high levels of IgM and IgD. He went on to explain the nature of these different categories of immunoglobulins.

1) Using what you know of the different immunoglobulin isotypes, their location and their function, do Daniel’s recurrent lung infections make sense? Why?

2)Dr. Dresdner went on to explain that it appeared Daniel’s immune system failed to undergo immunoglobulin isotype switching (class switching).How would you explain immunoglobulin isotype switching to Daniel’s parents?

3)Ms. Henchey, the genetic counselor, explained that Daniel had a genetic mutation in the gene for the CD40 ligand.

How does a deficiency in CD40 ligand explain Daniel’s immunological deficiency?

4) Treatment or Cure?

Dr. Dresdner explained that there was treatment for this disease. Daniel would need immunoglobulin infusions every three to four weeks in order to provide him with missing IgG and hopefully lower the abnormally high level of IgM in his bloodstream. Also, although current therapies could result in a happy, healthy adult, Daniel was at risk for an increased rate of liver disease. However, the doctor stated, there was a potential cure. A bone marrow transplant or cord blood stem cell transplantation, particularly from a matching HLA sibling, could provide a permanent cure. Someday, the doctor stated, gene therapy may be an option, but not at the present moment.

How can a bone marrow or cord blood stem cell transplant cure Daniel?

Answer 1

1):

Answer: 0 IgG : Most common immunoglobulin present in the body. It is a vital part in the adaptive immune system because it has a variety of functions including complement activation, neutralization, cytotoxicity, opsonization, and feed back inhibiting of B-cells. IgM re heavy chains. found on the surface of B cells, function as antigen receptors. Involved in the activation pathway of complement and neutralization of the microbe IgA : & heary chains, secreted across mucosal layer in order - to prevent microbes from entering the body. IgD: S heary chains. Found on surface of 'B'cells, can be found in . lymph nodes and spleen. Function as antigen receptors. IgE ; & heary chain. Fight off parasiles, also bind to allergens, can be found on the surface of large poradilte microbes.

. Yes, Daniel's Infections are realistic because IgA, IgE, and IgG are responsible for protecting the body from bactorial and fungal infections, IgA protede mucosal Surface, like the respiratory tract, which explains his numerous respiratory infections. Lange parasiters and fungi can easily infect the body because Daniel's low Ige count. The biggest contributor to Daniel's infections has to be the lack of Ig G because It provides the most antibody - based responses.

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