Kinetics of neuronal contribution during the development of a contact allergic reaction.

The nervous system contributes to allergic contact dermatitis (ACD). Elucidation of the implication of the nervous system during different stages of ACD could be of therapeutic value. Our aim was to study the kinetics and contribution of the nervous system to ACD by investigating innervation and expression of neuropeptides in skin biopsies obtained at 0, 6, 24, 48 and 72 h post-challenge. Biopsies were stained using antisera against protein gene product (PGP) 9.5, growth associated protein (GAP)-43, substance P and its receptor (R) neurokinin (NK)-1, NKA and NK-2R, and calcitonin gene-related peptide (CGRP). GAP-43-immunoreactive (ir) nerves revealed a time-dependent increase that was more pronounced at 48 and 72 h, while PGP 9.5-ir nerves remained unaltered. Substance P-, NKA- and CGRP-ir nerves at 0 and 6 h were significantly higher compared to later time points, whereas NKA-, NK-1R- and NK-2R-ir cells were lower. A dramatic rise in cell numbers was noted at 24 h. Our findings demonstrate the implication of nerves and sensory neuropeptides during the kinetics of ACD and suggest a possibility to target this system at an early time point for therapy.