NCLEX : Immunoglobulins
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Example Questions
Example Question #1 : Immunoglobulins
Which of the following is the primary immunoglobulin secreted into the intestinal lining and mucus membranes of the respiratory tract?
IgG
IgE
IgA
IgM
IgA
IgA, primarily in its secretory form (sIgA), is the most abundant immunoglobulin in the lining of the gastrointestinal tract and in the mucus membranes of the respiratory tract. It is also present in the urogenital tract, in tears, in saliva, and in breast milk. All of the other immunoglobulins may be present in mucus membranes, depending on the presence of active infection or allergy, but none is as abundant in secretions as IgA. IgE is primarily involved in binding allergens and inducing the allergic response via release of histamine. IgM is expressed on the surface of B cells and is the first immunoglobulin to fight pathogens at the site of infection/injury. IgG are the most abundant antibody throughout the body and play the largest role in fighting pathogens. IgG can cross the placenta and thus confer passive immunity to the fetus.
Example Question #1 : Immunoglobulins
The presence of which of the following cytomegalovirus (CMV) antibodies would suggest an active CMV infection?
CMV IgM
CMV IgE
CMV IgG
CMV IgD
CMV IgM
The presence of CMV IgM would suggest an active cytomegalovirus infection, as IgM is the immunoglobulin released during the initial, active infection with a pathogen. The presence of IgG would suggest a past infection, where IgG specific to the virus would be present as part of adaptive immunity (ready to respond to the virus should the host ever be re-exposed). IgE is not formed when an individual contracts CMV, as IgE is produced in response to allergens rather than pathogens (except parasites). The function of IgD is thought to be related to the allergic response by regulating basophils and mast cells.
Example Question #2 : Immunoglobulins
Which of the following is the only immunoglobulin capable of crossing the placenta and conferring passive immunity to a fetus?
IgM
IgG
IgA
IgE
IgG
The only immunoglobulin that has been shown to be able to cross the placenta is IgG. This is important in that it confers short term immunity to the fetus that continues into the first few months of the infant's life. Note that it is common to give Rh-negative anti-Rh IgG injections at about 28 weeks gestation; a booster may also be given at about 34 weeks gestation.
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