The neuro-immuno-cutaneous system and ultraviolet radiation.

Numerous cells are closely associated with cutaneous nerve fibers, which through the action of neuropeptides are able to modulate cellular function. Anatomical and physiological links between immune cells and nerves and other cells in skin are so close that we propose the concept of a neuro-immuno-cutaneous system (NICS). Under the impact of ultraviolet radiation (UVR) virtually all properties of the NICS are modified. UVR induces melanin synthesis and immunosuppression, events in which neuropeptides, especially melanocyte stimulating hormone (MSH) and the calcitonin gene-related peptide CGRP, play a role.