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Question #46518
The Question
A population is exposed to a rapidly mutating RNA virus. Despite having high titers of circulating IgG from a previous infection by the same viral lineage, individuals suffer severe reinfection. Clinical analysis reveals that their immune system is mounting a slow, primary response rather than a rapid anamnestic (secondary) response. Which of the following best explains the molecular basis of this immunological failure?
Options
- A.
The viral paratopes underwent rapid mutation, preventing them from binding to the host's memory B-cell receptors.
- B.
Conformational changes in the viral epitopes disrupted the spatial complementarity with the hypervariable regions of the pre-existing Fab fragments.
- C.
The mutated virus evolved to cleave the disulfide bonds between the heavy and light chains, separating the Fab and Fc regions of the circulating IgG.
- D.
The viral mutation altered the constant region of the host's antibodies, preventing the activation of the complement system and subsequent phagocytosis.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Paratope|Epitope|Antigenic_Shift
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between Epitope (on antigen) and Paratope (on antibody) and understanding that immunological memory relies on strict spatial complementarity at the variable region (Fab).
The trap relies on terminology reversal (Option A) and confusing the target of the mutation (Option D assumes the virus mutates the host's antibody structure, rather than its own surface proteins).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Health and Disease - Class 12 |
| Concept | Antibody Structure Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |