Daniel: Susan and Joe had a wonderful little boy named Daniel,but he had been having an awful lot of bacterial infections and hewas barely a year old. It seemed that the antibiotics cleared upone bacterial respiratory infection only to have another followshortly. The scary thing was that Daniel had just fought off a caseof pneumonia caused by Pneumocystis carnii, a fungal infection thatwas usually found in people with HIV. Waiting for the test resultsof an HIV test for their little boy was one of the worstexperiences ever. Thank goodness it came back negative. However, itseemed that their troubles were just beginning. After this lastlung infection, the fungal one, and a negative HIV test, theirdoctor had ordered a number of other blood tests, including agenetic test that Susan didn’t fully understand. Apparently thedoctor was worried about Daniel’s immune system functions. Susanhad also met with a genetic counselor who collected a familyhistory of any immune disorders. The details were vague, butSusan’s mother, Helen, knew that one of her three brothers had diedyoung from an unexplained lung infection. Unfortunately, GrandmaRuth had passed away a few years ago, leaving them with numerousunanswered questions. Susan and Joe had an appointment with theirdoctor that afternoon to go over the results. When they arrived Dr.Dresdner led them into an office where Ms. Henchey, the geneticcounselor, waited. This can’t be good, thought Susan. The doctorbegan by explaining that they had analyzed Daniel’s blood and foundthat while he had normal levels of B cells and T cells, hisantibody levels were anything but normal. The levels of IgG, IgA,and IgE were very low, almost undetectable, and Daniel hadabnormally high levels of IgM and IgD. It appears that his immunesystem failed to undergo immunoglobulin isotype switching due to aCD40 ligand mutation in Daniel's DNA. Diagram an antibody responsegraph for a normal 1st and 2nd exposure with the antibodiescorrectly labeled for each exposure. Then diagram whatDaniel's graph would look like, based on his situation. Diagramand/or explain why IgG is low and what CD40's role is? Why is amutation in that gene a problem? (There is no specific diagram I amlooking for here, either diagram it or explain it, depending onwhich you prefer.)
