The mast cell-nerve functional unit: a key component of physiologic and pathophysiologic responses.

A key characteristic of mast cells appears to be an ability to span the division between nervous and immune system. Indeed, much of our understanding of the bi-directional relationship between the nervous and immune systems has come from the study of mast cell-nerve interaction. Although differences in species have been reported, morphologic as well as functional associations between mast cell and nerves are found in most tissues in many mammalian species, including humans. These interactions are involved in the regulation of physiologic homeostatic processes as well as in disease mechanisms. Here we discuss the influence of cholinergic and sensory neurons on mast cells as well as the importance of mast cell nerve interactions at specific tissue sites, including the brain.