The epithelial barrier of the intestine and the gut-associated lymphoid tissue (GALT) protects the host against luminal pathogenic micro-organisms. This is important at weaning, when animals are exposed to infectious agents and stresses. We have developed a rat model of intestinal inflammation post weaning, based on the systemic administration of Staphylococcus aureus enterotoxin B (SEB). Since the inflammatory response obtained is mild, the food intake pattern is not affected, which makes this model useful for studies of nutritional therapies for intestinal inflammatory disease. SEB increased T-lymphocytes in Peyer's patches and the number of activated T-lymphocytes in mesenteric lymph nodes (organized GALT). In the lamina propria, SEB increased activated T-lymphocytes as well as cytotoxic and natural killer-cell populations of the diffuse GALT. It also increased pro-inflammatory cytokines and inflammatory mediators in both Peyer's patches and mucosa. Rats given SEB had higher paracellular permeability to macromolecules, which was associated with a reduction in epithelial tightness. This model was used to examine whether dietary supplementation with spray-dried animal plasma proteins affects intestinal inflammation. Results showed that dietary plasma proteins can attenuate the mucosal immune response in both organized and diffuse GALT and that these effects are mediated by a reduction in the production of pro-inflammatory cytokines.

Bioactive peptides have proven to be active in several conditions, including inflammatory bowel disease (IBD). This is a chronic and relapsing condition of unknown aetiology that comprises chiefly ulcerative colitis and Crohn's disease. Although there are treatments for IBD, they have frequent side effects and they are not always effective; therefore there is a need for new therapies that could alleviate this condition. Two bioactive peptides present in milk (transforming growth factor-β (TGF-β) and casein macropeptide, also named glycomacropeptide) have been shown to have intestinal anti-inflammatory activities. In fact, TGF-β is currently added to formulas intended for patients with IBD, and several studies indicate that these formulas could induce clinical remission. In this paper, evidence supporting the anti-inflammatory effect of TGF-β and bovine glycomacropeptide, as well as their mechanisms of action, is reviewed, focusing on the evidence obtained in animal models.