Retrieving immune responses stored in the insular cortex

Various findings indicate that the brain can influence peripheral immunity. However, it is not clear whether the brain forms representations of the state of the immune system. Now, Koren et al. show that information about peripheral immune responses can be stored by neurons in the insular cortex, and that reactivation of these neurons can lead to retrieval of peripheral inflammation.

First, the authors examined whether mouse insular cortex neurons increased their activity during a peripheral immune challenge. To do so, they used mice generated by crossing targeted-recombination-in-active populations (TRAP) mice, which express Cre recombinase in active cells in the presence of tamoxifen, with mice expressing a Cre-dependent fluorescent reporter (tdTomato). The authors treated these TRAP–tdTomato mice with dextran sulfate sodium (DSS) to induce colitis (a model of inflammatory bowel disease), and then, 48 h later, with tamoxifen to induce tdTomato expression in active cells. They found increased tdTomato expression in several brain regions, including the insular cortex, in line with studies showing that peripheral immune challenge can increase brain activity.