War Games

Bacteria that inhabit and colonise the human body have an ever-changing array of cunning strategies to avoid detection by the immune system. But, like any counterintelligence operation, the human immune system is also constantly adapting to deal with the latest threats. For example, human phagocytes (one of which is shown coloured purple) express a particular receptor protein called CEACAM3 that helps these cells detect and destroy certain human-specific bacteria (turquoise). And, by examining the genetic sequence of CEACAM3 in humans and our close cousins chimpanzees, it’s clear that the protein has been rapidly evolving to adapt to the bacteria that have been simultaneously adapting to us. Moreover, the identification of naturally occurring variants of the receptor that are capable of recognising a wider range of bacterial species than others highlights the unrelenting outmanoeuvring in which host and pathogens partake.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image by the Electron Microscopy Centre, Department of Biology, University of Konstanz, Dr. M. Laumann and Prof. Dr. C. R. Hauck
• Lehrstuhl für Zellbiologie, Fachbereich Biologie, Universität Konstanz, Konstanz, Germany
• Image copyright held by the original authors
• Research published in Current Biology, February 2019