A new study entitled “Normal gut microbiota modulates brain development and behavior”, published in the Proceedings of the National Academy of Sciences, requires that we reconsider the notion that the brain is an immune‐privileged site. The authors demonstrate that intestinal microbiota must be present within a set time‐frame for normal synaptogenesis to occur in the brain. In the absence of intestinal microbiota, histopathological and behavioral abnormalities arise. These observations necessitate a new look at the many interconnections of the immune system (...) and the brain, suggesting new frontiers for research and new therapeutic strategies for neurodevelopmental diseases. (shrink)