Immune cells (in green) on the mouse choroid plexus, with blood vessels in red. Credit: Shipley et al., Neuron 2020, 10.1016/j.neuron.2020.08.024

Floating in fluid deep in the brain are small, little understood fronds of tissue. Two new studies reveal that these miniature organs are a hotbed of immune system activity. This activity may protect the developing brain from infections and other insults—but may also contribute to neurodevelopmental disorders like autism.

“There is a correlation between maternal illness during pregnancy and autism, and we wanted to investigate how this is happening,” says Maria Lehtinen, Ph.D., a neurobiologist at Boston Children’s Hospital