Because there are many antigens that enter the body through the gastrointestinal tract, there must be a method by which the immune system is suppressed in order to prevent potentially harmful immune responses resulting from encountering these antigens. It is thought that intraepithelial lymphocytes (IELs) regulate innate and adaptive immune responses, and because there is one IEL per ten intestinal epithelial cells, suppression of the immune system occurs frequently in the gut – in particular, the mesenteric lymph nodes. Microbiota in the gut also induce accumulation of T regulatory cells, which will reduce the immune response to new antigens encountered through oral administration (Wang, 2014). Oral tolerance can be achieved through these means because dendritic cells can move the antigen from the intestinal lamina propria to the mesenteric lymph node, which is a site of Treg cell generation (Chinthrajah, 2016).
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In the intestinal lumen, IgA is able to control the composition of the environment and prevent inflammation that would otherwise be promoted by the oral antigen (Chinthrajah, 2016). Differentiation of B cells that secrete IgA in the intestinal lumen can be induced by TGF-β, which is produced from dendritic cells. The dendritic cells are activated when the antigen is encountered in the lamina propria of the intestine, and also have an important role in generation of Treg
In the intestinal lumen, IgA is able to control the composition of the environment and prevent inflammation that would otherwise be promoted by the oral antigen (Chinthrajah, 2016). Differentiation of B cells that secrete IgA in the intestinal lumen can be induced by TGF-β, which is produced from dendritic cells. The dendritic cells are activated when the antigen is encountered in the lamina propria of the intestine, and also have an important role in generation of Treg