A flu vaccine is needed seasonally to be effective but a polio vaccine is only needed once. The best explanation of this is
the flu has several strains that change seasonally
exposure to flu vaccine produces no memory cells from proliferating B- lymphocytes
the polio virus is substantially weaker than the flu virus
the flu vaccine is substantially weaker than the polio vaccine
The Correct Answer is A
A. The flu has several strains that change seasonally: Influenza viruses undergo frequent mutations, leading to new strains each season. Because memory cells from previous vaccinations may not recognize these new strains, annual vaccination is required to provide effective immunity against the current circulating strains.
B. Exposure to flu vaccine produces no memory cells from proliferating B-lymphocytes: The flu vaccine does stimulate memory B cells, but its effectiveness can be reduced due to antigenic variation in the virus. The need for seasonal vaccination is not because memory cells fail to form, but because the virus changes frequently.
C. The polio virus is substantially weaker than the flu virus: The strength or virulence of the virus is not the reason for the difference in vaccination schedules. Polio vaccines induce long-lasting immunity because the virus does not mutate rapidly like influenza.
D. The flu vaccine is substantially weaker than the polio vaccine: Vaccine potency does not explain the need for annual flu shots. The primary reason is the frequent mutation of influenza viruses, not the inherent strength or weakness of the vaccine itself.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. The subcapsular sinus:The subcapsular sinus is the space just beneath the capsule of a lymph node where lymph first enters from the afferent vessels. It does not serve as an exit pathway.
B. The cortical sinus:The cortical sinuses are channels within the cortex that allow lymph to percolate through the lymph node, facilitating interaction with lymphocytes and macrophages. They are internal pathways, not exit points.
C. Afferent lymphatic vessels:Afferent lymphatic vessels bring lymph intothe lymph node from peripheral tissues. They are entry vessels, not exit vessels.
D. Efferent lymphatic vessels:Efferent lymphatic vessels carry lymph out ofthe lymph node at the hilum after it has been filtered and exposed to immune cells. They are the correct exit pathway for lymph leaving the node.
Correct Answer is D
Explanation
A. The two main types are T cells and macrophages:Macrophages are phagocytic cells, not lymphocytes. The main lymphocyte types are T cells and B cells, which have distinct roles in adaptive immunity.
B. T cells are the only form of lymphocyte found in lymphoid tissue:Both T cells and B cells are present in lymphoid tissues. Lymphoid organs support the activation, proliferation, and differentiation of multiple lymphocyte types.
C. T cells are the precursors of B cells:T cells and B cells develop separately from hematopoietic stem cells. T cells do not differentiate into B cells; they have distinct lineages and functions in immunity.
D. B cells produce plasma cells, which secrete antibodies into the blood:B cells differentiate into plasma cells upon activation. Plasma cells are specialized for antibody production, releasing large amounts of antigen-specific antibodies into the circulation, making this statement correct.
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