Mast cells serve to protect the central nervous system. They live on the inside of the blood-brain barrier and interact with the cells of the barrier, namely, the astrocytes, microglia, and blood vessels. This is one of the critical ways the immune system interacts with the central nervous system. And this interaction can lead to vascular inflammation and neuroinflammation.
When mast cells suspect danger, they degranulate, which means they release stored chemicals, as part of the cell danger response. These chemicals include, already formed and ready to be released, transmitters such as histamine, tryptase, serotonin, and dopamine. But they also contain enzymes that can disrupt cellular membranes, blood clotting, and cellular signaling. Furthermore, upon activation, they begin to produce a multitude of inflammatory mediators such as interleukins, cytokines, chemokines, mitokines, and factors that play a role in many of the body's physiological pathways. They may even be tumorigenic, or tumor-forming.