These delicate green branches belong to a Purkinje neuron, one of the largest types of nerve cells in the brain. It's been known for some time that infections in the body have an impact on the brain, but exactly how this happens isn't clear. Now scientists have discovered that immune cells in the blood release tiny molecular packages containing fragments of genetic information, in the form of RNA. These messages get taken up by Purkinje neurons, where they switch particular genes on and off. This cell glows because it has taken up some of these packages that switch on a gene making a green fluorescent protein. In healthy mice, hardly any of the Purkinje cells seem to respond to the packages. But six times as many cells get the messages when the animals have an infection, highlighting the close connection between the brain and the immune system.
Written by Kat Arney
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