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In a random quality-control test of 73 batches of Hemophilus influenzae vaccines administered nationwide, the FDA discovered two lots in which the capsular polysaccharide of
Hemophilus was not covalently coupled to the Diphtheria toxoid. Which of the following immunologic responses would be predicted in children receiving one of these unusual vaccine lots?
A. They should produce a normal delayed-type hypersensitivity response to Hemophilus
B. They should produce a normal IgA response to Hemophilus
C. They should produce a normal IgG response to Hemophilus
D. They should produce a normal IgM response to Hemophilus
E. They should produce a normal natural killer cell response to Hemophilus
F. They should produce no response to Hemophilus
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D.
this vaccine need the diphtheria toxoid to stimulate TH2 and a T cell response. it helps the inmune response of the vaccine.
right?
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needs a protein carrier..
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u got it right...
The correct answer is D. The function of covalently coupling the capsular polysaccharide of Hemophilus to the Diphtheria toxoid in this common childhood vaccine is to involve T lymphocytes to assist in the production of antibodies against Hemophilus. T lymphocytes
respond to processed peptides presented in the groove of major histocompatibility antigens on antigen-presenting cells, and are necessary for causing class switching in B lymphocytes. Therefore, in the absence of T cell stimulation, B lymphocytes will make only IgM, and will be incapable of switching to other isotypes of immunoglobulin production.
A normal DTH response (choice A) is incorrect because DTH is a T cell mediated immune response, and without covalent coupling to a protein material, T cells will not recognize a polysaccharide antigen.
A normal IgA response (choice B) is incorrect because the production of IgA is dependent on the stimulation of T lymphocytes, which is not possible without covalent coupling between the protein and the polysaccharide.
A normal IgG response (choice C) is incorrect because the production of IgG is dependent on the stimulation of T lymphocytes, which is not possible without covalent coupling between the protein and the polysaccharide.
A normal NK response to Hemophilus (choice E)</B> is not the best answer because NK cells are elicited in response to some tumors and viruses, but not typically to bacterial antigens.
No response to Hemophilus (choice F) is not true, because even a person without T cells will make an IgM response to a polysaccharide antigen. It will not be a large response, but it will be present, simply due to the random recognition of this antigen by naïve B lymphocytes being produced by the bone marrow.
