For example, reduction in youth-associated recent thymic emigrant CD103+ CD8 T cells, or in immune-priming CD103+ dendritic cells (22, 64, 65), may effectively promote neurodevelopmental symptoms of ASD and ADHD, while reduction of age-associated TRM or regulatory T cells (30) may protect against age-related cognitive decline in CD103-deficient animals. This evidence concerns the gene CD8A and attention deficit-hyperactivity disorder.