The molecular soldiers of the immune system affect brain development and may contribute to many cases of autism. That’s the emerging hypothesis from five new studies that use different methods — ranging from screening blood samples of pregnant women to mathematical analyses of gene expression in the brain — published in the past few months.
One report shows, for example, that pregnant women whose babies later develop autism tend to carry rare antibodies in their blood. Another finds that they harbor an excess of certain signaling molecules of the immune system, called cytokines, in the amniotic fluid. A third study found that some autism risk genes expressed in the developing brain belong to networks of genes related to cytokine signaling.
“These studies further build the case for the relevance of the immune system in autism using totally different approaches,” says Paul Patterson, professor of biology at the California Institute of Technology. Patterson has made animal models of the immune system’s role in brain development but was not involved in any of the new studies.
Many investigations of older children and adults with autism have uncovered signs of the immune system gone awry. The new studies are finding similar signatures in early brain development, from the womb through the first few years of life.
Still, no one knows much about the biological mechanisms that determine when, how or why immune molecules affect the fetal brain — let alone whether or why they might contribute to autism.
“Obviously the immune changes are there and are prominent. We just have to figure out what they’re doing,” Patterson says.
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