VIP modulation of immune cell functions.

Neuropeptides have recently been shown to modulate the immune response. Vasoactive intestinal peptide (VIP) released from nerve endings and from immune cells modulates the mobility and adherence of lymphocytes and macrophages, phagocytic cell functions (phagocytosis and free radical production), the lymphocyte proliferative response, lymphokine and immunoglobulin production and the natural killer cell activity, with opposite effects in vitro on these immune cell functions. The VIP receptor heterogeneity and the different action mechanisms of VIP-mediated immunoregulation could explain, at least in part, the different VIP effects observed on lymphoid and phagocytic cells. The evidence supports the theory that VIP acts not as an inhibitor, but as a modulator of immune functions, as previously thought, and that this neuropeptide may play a relevant role in vivo.