In children with autism, certain immune cells known as granulocytes have only one-third the capacity to fight infection and protect the body from illness compared to these same cells in children without autism, according to a new study published in the journal Pediatrics.
Because of a dysfunction in their mitochondria (tiny energy generators), the granulocytes in children with autism are less able to fight off bacteria and other intruders.
The cells in children with autism also produce more free radicals and are less able to repair the damage. As a result, they experience more oxidative stress. The free radical levels in the blood cells of children with autism are one half times greater than those without the disorder.
“Granulocytes fight cellular invaders like bacteria and viruses by producing highly reactive oxidants, toxic chemicals that kill microorganisms. Our findings show that in children with severe autism the level of that response was both lower and slower,” said Eleonora Napoli, lead study author and project scientist in the Department of Molecular Biosciences in the UC Davis School of Veterinary Medicine.
“The granulocytes generated less highly reactive oxidants and took longer to produce them.”
The findings also showed that the mitochondria in the granulocytes of children with autism used much less oxygen than those of children without the disorder — another sign of weaker mitochondrial function.
For the study, researchers collected blood samples of children enrolled in the Childhood Risk of Autism and the Environment (CHARGE) Study. This included 10 children with severe autism (ages two to five) and 10 controls.
In a previous study, researchers found impaired mitochondrial function in another type of immune cell, the lymphocytes. These findings show that impairments in the cells’ ability to fuel brain neurons might lead to some of the cognitive problems found in autism. Higher levels of free radicals also might contribute to autism severity.
“The response found among granulocytes mirrors earlier results obtained with lymphocytes from children with severe autism, underscoring the cross-talk between energy metabolism and response to oxidative damage,” said Cecilia Giulivi, professor in the Department of Molecular Biosciences in the University of California Davis School of Veterinary Medicine and the study’s senior author.