IL17A and Crohn disease: Biopsies from Crohn disease patients show increased expression of cytokines like TNFα, IL-1β IL-6, IL-12p70, IL-23 [7,8] and in particular the IL-12/IL-23 subunit p40 seems to be important for disease development since monoclonal antibodies towards this subunit is able to reduce symptoms and expression of both IL-12p70 and IL-23, but also IL-6 and IL-17 [23].