The prevalence of autism spectrum disorder (ASD) is roughly one in 36 people, with a male-to-female ratio of 4:1. The disorder is known to be influenced by multiple factors, both genetic (gene mutations and copy number variations) and environmental, such as infections during pregnancy. However, the role of immunity in genetic ASD remains unclear.
One area of interest lies in lymphocytes—cells that are known to shape neurodevelopment and behavior. But their roles in neurodevelopmental disorders are not well defined.
Now, new research shows that a subset of T cells—γδ T cells—can infiltrate the brain and contribute to changes in social behavior in a genetic mouse model that mimics behavioral features of ASD. Depleting these cells from the brain increased sociability, suggesting that targeting abnormal immune function during neurodevelopment may offer interventions for ASD.
This work is published in Science Immunology in the paper, “CXCL16-mediated recruitment of γδ T cells to the brain reduces sociability in mice.”
Infections during pregnancy can induce the release of interleukin-17A (IL-17A) from T helper 17 cells and γδ T cells. Prior research has linked this type of maternal immune activation to neurodevelopmental disorders, but there is a lack of evidence connecting IL-17A and social behaviors in genetic mouse models.
To investigate this further, a team of researchers from the Division of Allergy and Immunology in the Medical Institute of Bioregulation at Kyushu University, in Fukuoka, Japan, studied 15q11-13 duplication (15q dup) mice—a mouse model that mimics a chromosome duplication found in some humans with ASD. These mice also demonstrate reduced social interactions, behavioral inflexibility, and increased anxiety-like behaviors.
The team analyzed immune cell populations in the brains of the 15q dup mice. Their findings suggest an increase in γδ T cells in the developing brains when compared with wild-type mice.
Using single-cell RNA sequencing (scRNA-seq), the team uncovered that this was most likely due to microglia in the brain expressing the chemokine CXCL16, which promotes immune cell migration. CXCL16 was highly expressed in the brains of 15q dup mice and contributed to increased infiltration of γδ T cells.
In addition, experiments revealed that deleting IL-17A–producing γδ T cells or blocking them with antibodies after birth increased sociability and reduced anxiety-like behaviors in the 15q dup mice.
Taken together, the authors note that these findings suggest that “immune dysregulation contributes to social behavior deficits in 15q dup mice, consistent with observations in maternal immune activation models, and may represent a potential target for interventions for ASD-associated differences in social behavior.”
