ADCYAP1 and Crohn ileitis: In our study, the better outcome following prophylactic PACAP treatment was due to a dampened small intestinal Th1-type immunopathology as indicated by a reduced accumulation of T lymphocytes, the major driving forces of T. gondii induced ileitis, in the ileal mucosa and lower local expression of the key regulator IL-23p19 and pro-inflammatory mediators such as IFN-γ, nitric oxide, and the chemokine MCP-1.