Measuring humoral immunity — Which laboratory metric detects a humoral response to influenza virus?
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Acytotoxicity of virus-infected cells in tissue culture
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Bdividing T cells in the draining lymph nodes
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Cplasma cytokine levels
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Dserum antibody titer
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ET-cell receptor repertoire sequencing
Answer
Correct Answer: serum antibody titer
Explanation
Introduction:Humoral immunity refers to antibody-mediated protection. This question asks which laboratory measurement best reflects a humoral response after exposure or vaccination against influenza virus.
Given Data / Assumptions:
- Influenza infection or vaccination context.
- Standard clinical and research assays.
- Goal: detect antibody presence/levels.
Concept / Approach:Humoral responses are quantified by measuring antigen-specific antibodies in serum (e.g., ELISA, hemagglutination inhibition titer, neutralization assays). These correlate with protection and vaccine efficacy in many settings.
Step-by-Step Solution:
1) Identify humoral hallmark: antigen-specific antibodies in blood.2) Choose the direct measure: serum antibody titer provides quantitative evidence of humoral response.3) Other listed assays primarily reflect cellular immunity or nonspecific inflammation.Verification / Alternative check:Vaccine trials commonly use hemagglutination inhibition titers against influenza antigens as correlates of protection, confirming their role as humoral markers.
Why Other Options Are Wrong:
- Cytotoxicity assays: measure cell-mediated killing by CTLs or NK cells.
- Dividing T cells: indicates cellular proliferation, not antibodies.
- Plasma cytokines: nonspecific; do not directly quantify antigen-specific antibodies.
- TCR repertoire: characterizes T-cell diversity, not humoral titers.
Common Pitfalls:Assuming any immune assay reflects humoral function; only serum antibody measurements directly quantify the antibody arm.
Final Answer:serum antibody titer.