Immunotech and Molecular Biology Quiz

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Antibody-antigen interactions rely mainly on non-covalent forces. If you wanted to experimentally disrupt hydrogen bonds specifically during an antigen-antibody binding assay, which treatment would most likely affect the binding affinity?

• Increasing ionic strength with NaCl

• Altering the pH of the buffer

• Adding a mild detergent like Triton X-100

• Reducing the temperature

You are designing a diagnostic test to detect an early infection when the antigen is present in very low amounts. Which assay would provide the highest sensitivity?

• Direct ELISA

• Radioimmunoassay (RIA)

• Western blot

• Sandwich ELISA

In a Western blot, an unexpected band is observed in a patient sample at a lower molecular weight than the target protein. Which of the following most plausibly explains this observation?

• Cross-reactivity of the antibody with a degradation product

• Incomplete transfer of the protein onto the membrane

• Over-saturation of the substrate in the detection step

• Failure of blocking step leading to non-specific binding

You are comparing two techniques for cytokine quantification: ELISPOT and ELISA. Which of the following statements is correct?

• ELISPOT provides information about total cytokine concentration, while ELISA shows cytokine-secreting cell frequency

• ELISA is more sensitive than ELISPOT in detecting rare cytokine-producing cells

• ELISPOT can quantify cytokine production at the single-cell level, while ELISA measures cumulative secretion in a bulk population

• Both techniques provide identical information but use different detection labels

Which of the following best explains why maternal antibodies transferred to a newborn provide only temporary protection?

• They are rapidly degraded by lysosomal enzymes

• They do not stimulate memory cell formation in the infant

• They compete with infant antibodies for Fc receptors

• They enhance tolerance rather than protection

A vaccine is developed using a recombinant protein antigen that is poorly immunogenic by itself. To enhance the immune response, researchers conjugate it with a carrier protein. This is conceptually similar to which of the following?

• Hapten-carrier effect

• Antigenic mimicry

• Epitope spreading

• Affinity maturation

A scientist is testing different antigen preparations for immunogenicity. Which of the following is most likely to be least immunogenic?

• A large, complex polysaccharide with repeating units

• A stable, highly conserved bacterial protein

• A small, non-protein chemical without a carrier

• A recombinant viral surface glycoprotein

In biosensor-based immunoassays (e.g., Surface Plasmon Resonance), what key advantage is gained compared to ELISA?

• Detection of antigen in complex mixtures without antibodies

• Real-time monitoring of binding kinetics without the need for labeling

• Higher specificity due to use of fluorescent reporters

• Ability to detect single antigen molecules at sub-femtomolar levels