VIP Regulates the Development & Proliferation of Treg in vivo in spleen

Using flow cytometric analysis, we examined the relative preponderance of CD25+CD4+ cells and anti-inflammatory Treg cells, in extracts of thymus and spleen from VIP KO mice (5 VIP KO; 5 VIP KO+ VIP; 10 wild-type). This method allowed antibody-based flow cytometric identification of Treg cells using surface markers CD25 and CD4, along with the: 1) intracellular activation marker FoxP3; and 2) Helios, which distinguishes cells of thymic versus splenic derivation.Deletion of the VIP gene results in: 1) CD25+CD4- cell accumulation in the thymus, which is corrected by VIP treatment; 2) more Treg in thymus lacking Foxp3 expression, suggesting VIP is necessary for immune tolerance; and, 3) a tendency towards deficiency of Treg cells in the spleen, which is normalized by VIP treatment. Treg lacking Helios are induced by VIP intrasplenically rather than by migration from the thymus. These results confirm the dual role of VIP as an anti-inflammatory and immune tolerance-promoting agent.We hypothesized: 1) Vasoactive Intestinal Peptide (VIP) may be regulating the development and proliferation of regulatory T lymphocytes (Treg); and 2) VIP can efficiently and quickly induce Treg. Because they promote immune tolerance and are anti-allergic, Treg are important. Current methods of allergy immunotherapy, for tree pollen, for example, reduce seasonal symptoms and medication usage and costs, but are not efficient to induce Treg and require slow protocols, taking years to reach maximal dosage. The underlying immune mechanisms of VIP and Treg interactions are not entirely known. Better understanding of the VIP-Treg system may pave the way to use VIP as an adjunct or replacement for allergy immunotherapy, a treatment for allergic asthma.A defect in current literature is that other investigators have studied in vitro immune responses to VIP but lacked the in vivo VIP knockout mouse model. Knowing that Treg are a critical cell type to engage in order to induce tolerance in allergic indiv