FIGURE 3.

Weaning reaction and the intestinal immune system maturation. Neonates have low competence to establish mucosal tolerance due to their immature gut immune system, low levels of vitamin A and maternal breast milk factors such as EGF. Declining levels of EGF in the second and third week of life, increased microbial colonization and exposure to solid foods trigger an intense albeit transient immune activation known as the weaning reaction. The weaning reaction is associated with the formation of food and microbiota induced pTregs. This process is crucial for establishing intestinal homeostasis and creating a tolerogenic environment that prevents food allergies and intestinal inflammation.