Immunologists sometimes infer that when descendants of memory B cells bind to multiple influenza variants, the cells have broadened their specificity. A recent study measured a precursor population's binding to three strains: 70% of its aggregate binding was directed to the original strain and 15% to each of two variants. A descendant population recognized only those same three strains and showed nearly the same aggregate binding, but the corresponding shares were 45%, 30%, and 25%. The mutations had therefore ______ the binding response.
Which choice completes the text with the most logical and precise word or phrase?
For a demanding words-in-context question, distinguish among every dimension described in the passage before comparing the choices. Here, track target range, total binding, and proportional distribution separately, then select the word that describes only the feature that actually changed.
Hints
Distinguish the dimensions
Consider separately whether the target range, the total amount of binding, and the distribution of binding changed.
Compare the proportions
Determine whether the final percentages are identical or merely less concentrated on one strain than the original percentages were.
Step-by-step Explanation
Separate the measured features
The passage provides information about three distinct features: the number of strains recognized, the aggregate amount of binding, and the proportion of binding directed to each strain.
Identify what changed
The descendant population still recognized the same three strains and had nearly the same aggregate binding. However, the proportions changed from 70%, 15%, and 15% to 45%, 30%, and 25%.
Choose the precise description
The response was rebalanced because binding was apportioned differently among the same targets. The final proportions were not equal, the total was not substantially increased, and no additional strains were recognized.