Peptides encoded by the calcitonin gene inhibit macrophage function.

Neuropeptides are considered to play an important role in the modulation of a number of immune functions. Calcitonin gene-related peptide (CGRP), one of the neuropeptides, was found to profoundly inhibit the ability of macrophages to produce H2O2 in response to IFN-gamma or to act as APC. For the inhibition of H2O2 production to occur, preincubation of the macrophages with CGRP was required. Among neuropeptides that are similar in size, calcitonin also prevented macrophage activation but adrenocorticotropic hormone did not. These findings suggest that CGRP and calcitonin play an important role in modulating the ability of macrophages to present Ag and to respond to activating factors.