Regional skull translocator protein elevation in autistic adults detected by PET-MRI

Immune processes have been implicated in the pathophysiology of autism spectrum disorder (ASD). Brain borders, such as the skull, have recently been highlighted as sites where neuro-immune interactions occur with key consequences for brain immunity. Translocator protein (TSPO), a mitochondrial protein involved in immune functions, was measured in the skull using [¹¹C]PBR28 positron emission tomography-magnetic resonance imaging (PET-MRI) in 38 autistic adults (26 males, 12 females) and 29 age-and sex-matched healthy controls (19 males, 10 females). [¹¹C]PBR28 uptake relative to a pseudo-reference region assessed using standardized uptake value ratio (SUVR) revealed elevated TSPO in autistic adults in frontal and temporal skull. We did not observe an association between [¹¹C]PBR28 uptake in total or regional skull areas and autism symptom severity. C-reactive protein levels were positively associated with [¹¹C]PBR28 uptake in the total skull across participants. Lastly, [¹¹C]PBR28 uptake in the total skull was stable across a 4-month period. This work indicates regional TSPO elevations in the skull in autistic adults, which may suggest immune involvement.