The Intestine: Development, Functions, and Its Impact on Disease Risk across the Lifespan

The intestine plays a central role in the immune system, continuously interacting with antigens, dietary components, and the microbiota. Intestinal immune processes are increasingly recognized for their influence on the development of both local and systemic diseases, with long-term effects on health and disease progression. This review provides an overview of intestinal development, encompassing its maturation from conception, temporal changes, regenerative capacity, interactions with the microbiota, and involvement in disease. Early life, particularly critical periods such as pregnancy and lactation, may represent a "window of opportunity," establishing lasting conditions that either increase disease risk or confer protection in adulthood. Understanding the regulatory factors, regional and temporal variations, and existing knowledge gaps is essential for guiding clinical practice, as well as for the prevention and treatment of diseases.