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A 14-year-old girl ...... - a_antibody
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03-08-2007, 02:23 PM
A 14-year-old girl is admitted to the hospital with dyspnea, tachycardia, and diaphoresis following a bee sting. Which of the following was the first immunoglobulin produced in response to this antigen?
A. IgA B. IgD C. IgE D. IgG E. IgM
03-08-2007, 02:26 PM
IgE....cant b so straightfwd...gotta b sumthin else....hmmm
03-08-2007, 02:57 PM
The correct answer is E. The first immunoglobulin produced in response to any immunogen is always IgM. This is because of the sequential transcription of the DNA coding for the immunoglobulin isotype genes. It is not possible for any other immunoglobulin to be made first.
IgA (choice A), IgE (choice C), and IgG (choice D) can only be produced as a secondary response, i.e., one that follows the primary IgM response. The DNA coding for the IgD (choice B) heavy chain follows that of IgM in the lymphocyte germ-line DNA. Mature, naïve B lymphocytes express both IgM and IgD on their surfaces because of alternative RNA splicing, but the complete IgM molecule is always produced first. |
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