While the aetiology of IBD is not known, it is well established that endogenous bacteria, their components and/or antigenic products have a prevailing role in the initiation Seliciclib and perpetuation of the chronic inflammatory response. Indeed, in these genetically susceptible individuals

there is loss of immune tolerance for commensal faecal bacteria and their antigens and a bacteria-specific mucosal and systemic immune response ensues subsequently [4]. In several animal models it has been demonstrated that genetically susceptible animals remain disease-free in a germ-free (axenic) state, but will develop rapid-onset chronic intestinal inflammation when associated with H 89 normal endogenous microflora [5–7]. We have demonstrated previously that the acquisition of commensal faecal bacteria in pre-weaned neonatal wild-type mice caused a transient release of cytokines, which was important subsequently for the establishment of tolerance to the individual endogenous microflora later in life [8]. Nevertheless, the intestinal immune and injury response and the systemic response to faecal bacteria and antigen exposure to a sterile intestinal lumen of a healthy post-weaned animal with a mature immune

system are not understood clearly. Understanding the natural immune and injury response in the normal and immune competent animal can

be key to understanding the disease state. We thus examined the effects of normal faecal bacteria mafosfamide and antigen exposure on the intestinal mucosal and systemic immune system in wild-type axenic mice. Experiments were performed in two different mouse strains. Axenic Swiss Webster mice were purchased initially from Taconic Farm (Germantown, NY, USA) and were bred at the University of Alberta in specific sterile isolator bubbles. Axenic 129/SvEv mice were purchased from the Gnotobiotic Core Facility at North Carolina State University. The mice in this experiment were used at approximately 15 weeks of age. Results from analyses performed in both mouse strains had identical outcomes. Faecal material was collected from 129/SvEv mice housed under conventional conditions. For each preparation, 20 fresh faecal pellets were mashed into 3 ml of sterile distilled water. Axenic mice were removed from the sterile environment and 100 µl of this faecal slurry was given orally to the mice with a blue tip (Fisherbrand® General Purpose Redi-Tip™; Fisher Scientific, Ontario, Canada). Mice were forced to swallow by blocking their nasal airways temporarily, forcing the mice to gulp. An additional 100 µl was spread over their abdominal skin. Mice were held subsequently under conventional housing conditions.