Fitness Race

From the moment we’re infected with a virus, the race is on. Our B-lymphocyte cells rush to make intricate antibodies that latch on to proteins called antigens on the pathogen’s surface. Only the best fitting antibody will emerge victorious. B-cells perfect their antibodies inside structures called germinal centres – mutating their DNA, to changing antibody 'designs' and try out different prototypes. Here researchers watch a simplified form of this race in mouse lymph nodes (highlighted in blue). Activating some of the germinal centres (red) with a burst of laser light (turning them green), they follow B-cells using a technique called deep mutational scanning to predict how the antibodies change with each mutation. Similar to evolution, this trial and error eventually finds a champion B-cell with the best fitting antibody to tackle the virus. Such insights might influence vaccines designed to tackle viruses that change their antigens, like HIV.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image from work by William S. DeWitt, Ashni A. Vora and Tatsuya Araki, and colleagues
• Department of Genome Sciences, University of Washington, Seattle, WA; Laboratory of Lymphocyte Dynamics, the Rockefeller University, New York, NY, USA
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in Cell, June 2026