When an antigen is detected, B-cells whose receptors bind it (have high affinity) are selected,
clonally expanded, and undergo somatic hypermutation in germinal centers.
Mutant clones with higher affinity are preferentially selected — a Darwinian optimization process
that produces antibodies with picomolar affinity in days.
Affinity is modeled as A = exp(−‖b − ag‖² / σ²) in shape space.
Clones proliferate proportionally to affinity. Mutation adds Gaussian noise to receptor shape.
High-affinity clones suppress low-affinity ones via competition for antigen.