The immune system is like a tireless editor, revising antibody drafts to make them stickier to viruses and bacteria. This process is called antibody maturation: random typos (mutations) arise in the genes, and natural selection keeps those that improve target capture.
The catch is that a mutation's "usefulness" isn't universal. What strengthens one antibody can ruin another. The authors analyzed over 10,000 "public clonotypes"—groups of very similar antibodies that arise independently in different people. By comparing mutations within these groups across 20 healthy donors, they spotted a pattern: frequent mutations usually give a small boost in strength, while rare ones give a large jump. It's a trade-off between reliability and ambition.
The new method requires no prior knowledge of antibody structure and works as a simple population-genetics tool. It was tested on antibodies against SARS-CoV-2 and flu — predictions matched real data. Moreover, popular protein language models mostly "see" neutral mutations, but after a simple renormalization, the same selection signals the method finds emerge.
Antibodies can mutate at a rate a million times higher than ordinary genes: this allows them to quickly adapt to new threats.
In Peter Watts's novel "Blindsight," modified immune cells use directed evolution right inside a patient's body to defeat an unknown pathogen.