Mast cell

Mast cells are present in most tissues surrounding blood vessels and nerves, and are play an important role in the mucosal immune system and allergic response.

Central nervous system
Mast cells play an important role in the gut-brain axis. They are found throughout the gastrointestinal tract near sensory nerve fibers. In the nervous system, they are found on the blood-brain barrier, in the dural layer of the meninges, and in areas of the brain responsible for pain or neuroendocrine functions including the pituitary stalk, pineal gland, thalamus, and hypothalamus.

They are the main effector cells though which intestinal pathogens can affect the brain.

Mast cell activation disorder
Mast cell activation disorder (MCAD) is a disorder where mast cells are over-responsive and release excess histamine and other signaling molecules. It is often found in patients with Ehlers-Danlos syndrome (EDS) and postural orthostatic tachycardia syndrome (POTS).