In an Oct 9 post, I cited a fascinating talk by Jonathan Kipnis that I heard at a meeting. His paper came out in March, showing that the autism-like behavioral abnormalities in a mouse model of Rett syndrome could be prevented by giving these mice a bone marrow transplant from a normal mouse. By using several manipulations, these experiments indicated that the transplant worked by replacing the Rett microglia with normal microglia in the brain. I noted the potential importance of these cells in a post on June 7.
Now, a very talented graduate student in my laboratory, Elaine Hsiao, in collaboration with the group of Sarkis Mazmanian here at Caltech, has just published results of manipulating the immune system in our mouse model of the autism risk factor, maternal infection. Elaine finds that transplanting bone marrow into this mouse model, even after these mice have developed the autism-like behaviors, can correct several of them. These results provide a further suggestion that the immune system can interact with the brain to regulate behavior – the primary topic of my book!
We emphasize that because the work was conducted in mice, the results cannot be readily extrapolated to humans, and we are not suggesting that bone-marrow transplants should be considered as a treatment for autism. We have yet to establish whether it was the infusion of stem cells or the bone-marrow transplant procedure itself—complete with irradiation—that corrected the behaviors. However, the results do suggest that immune irregularities in children could be an important target for innovative immune manipulations in addressing the behaviors associated with autism spectrum disorder. By correcting these immune problems, it might be possible to ameliorate some of the classic developmental delays seen in autism.