Neuroimmune Interactions in Acute and Chronic Itch
Itch is a sensory experience of the skin that is familiar to all humans. Recent studies have established that the immune system and central and peripheral nervous systems engage in extensive interactions termed “crosstalk,” which gives rise to both acute and chronic itch pathologies. Peripheral sensory neurons detect itch-triggering stimuli from the environment to transduce pruritic signals. Itch signals travel from nerve fibers in the skin and peripheral nervous system to the spinal cord and brain, eliciting scratch behavior as a response to relieve the irritation caused by itch. The mechanisms underlying itch have also been shown to overlap with molecular circuits involved in pain, suggesting a relationship between the two sensations. We discuss various types of pruritogens, released from immune cells, keratinocytes, neurons, glial cells, and cancer cells, as well as the pruritogen receptors expressed by primary sensory neurons (pruriceptors) and spinal cord neurons. Understanding how neuroimmune interactions modulate acute and chronic itch will be necessary to develop more effective treatments for these pathologies.
