The immune system begins to develop on the day you are born when your mother’s bacteria reach the colon and stimulate the immune cells in the wall of the colon. Subsequently, up to 70% of a person’s immune system resides in the wall of the colon. This immune organ is intimately tied to the type of bacteria within the colon. The following medical articles provide a good overview of the gut and immunity.

Role of the Microbiota in Immunity and Inflammation.

Mucosal immunity and the microbiome.

Along with this new knowledge of where immunity develops and how it is stimulated has come investigations of how prebiotic plant fibers can have a beneficial effect on this development.

The Role of Probiotics and Prebiotics in Inducing Gut Immunity.