Vasoactive intestinal peptide (VIP) and the structurally related pituitary adenylate cyclase-activating polypeptide (PACAP), two neuropeptides present in the lymphoid microenvironment, elicit a broad spectrum ofBioLogical functions, including the modulation of innate and adaptive immunity. Another important immunoregulatory function of VIP and PACAP is their inhibition effect on AICD in T Cells. They inhibit the TCR-stimulated FasL expression and apoptosis of T cell through specific receptors and induction of intracellular cAMP. VIP down-regulate c-myc synthesis, the NF-AT-dependent Egr2 and Egr3 expression, the NF-AT and nf-kb.