Stem cells injected intravenously or intra-arterially can modulate the immune system systemically, potentially improving brain plasticity.

“those cells it turns out don't even get into the brain um and the idea is that uh in some of the better studies that that have been done in animals that they work by modulating the IM immune system systemically those cells get trapped in the lung in the spleen which people describe as bioreactors and modulate the immune system which does make some sense as I say we we think one of the main benefits of these stem cells is that they modulate the immune system uh and that helps with plasticity in the brain”