I will talk about barriers in autism. Normally, the brain is protected. The ability of each molecule to reach the brain is regulated and prevented by various control mechanisms. In this context, two barrier systems have been planned in front of the brain;

1. Intestinal barrier (Gut-Brain Barrier, GBB)

2. Blood-brain barrier (BBB)

Both barriers are maintained by intercellular proteins, known as tight junction (TJ) proteins. As for the maintenance of the blood-brain barrier, glial cells known as astrocytes are responsible, which are concentrated in the perivascular regions around the blood vessels within the brain.

In the event of a disruption in barrier function (integrity), permeability increases, allowing unwanted/harmful molecules (bacterial lipopolysaccharides, LPS, peptidoglycans, toxins, etc.) to first pass through the intestinal barrier; into the bloodstream; into circulation, and then, with the increased permeability of the blood-brain barrier, they can reach deep into the brain.