This was a WOW for me.
An international team of researchers have discovered that, in mice at least, immune cells in the brain react differently to changes in gut bacteria…and on whether or not they are fetuses or adults.[i]
The absence of a maternal microbiome dramatically affects the microglia (the immune cells) of the brain in developing fetuses, and much more so in male offspring than female. Oddly enough this is reversed in adult mice: adult female mice are far more sensitive than males to a depletion of the microbiome.
Says one of the scientists involved in this work, “This was really dramatic…We never thought that a fetus, which is inside a mother, would be affected by her lack of a microbiome. We had previously believed that the brain of a fetus is a closed system, not subject to perturbations, and that it was only when the fetus goes out of the womb, that the environment can influence it.”[ii]
No one yet knows why there is this male/female dichotomy in inflammatory response at different life stages.
This could, of course, explain why male infants are so much more likely to have developmental disorders like autism or early-onset schizophrenia…and why adult women are so much more likely to suffer from depression and autoimmune illnesses.
The researchers are intending to take this to the next step, studying, for example, how different potential treatments like antibiotics and diet modulate the microglia. I’ll definitely keep an eye out for more on this.