Slow Start

There are lots of things newborn babies can’t quite do yet. One of those is to fight off certain types of infections that most adults brush aside with ease. Researchers examined how the neonatal mouse immune system handles cytomegalovirus infection – a virus that can cause serious harm in newborns. They tracked T cell numbers (immune cells, white) in the spleen (pictured at intervals from 0, left, to 28, right, days post birth),and found not only that newborns start life with very few of these cells, but also that the cells fail to mature into effective virus-killing fighters. Adding extra adult T cells didn’t help, unless those cells had already been trained by prior infection, showing that the newborn environment cannot properly prepare them for battle. New therapies could build on this, boosting the signals that help ready T cells for action, or providing a ready-primed supply to give newborns a helping hand.

Written by Anthony Lewis

Anthony Lewis

Writer

Ant was the web editor in the early days of BPoD, and has since worked with the UK’s top science organisations as a writer and multimedia producer. He now splits his time between freelance work and managing multimedia at The Lancet.

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• Image from work by Luís Fonseca Brito and colleagues
• Institute of Immunology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in PLOS Pathogens, April 2026