**Abstract**

Autoimmune diseases (AD) have emerged as a pandemic in our modern societies, especially after the World War II. In part I, we have reviewed five main diseases and shed light on different aspects from introducing the concept of autoimmunity, the description of the disease's pathogenesis and the diagnosis, the role of antibodies as markers for the prediction of the disease, the link between the gut and brain through what is known as the gut–brain axis, and the relationship of this axis in GI autoimmune diseases. In this chapter, we review the role of antibodies as markers for the prediction of the disease, artificial intelligence in GI autoimmune diseases, the nutritional role and implications in the five GI autoimmune diseases, and finally the treatment of those diseases.

**Keywords:** achalasia, atrophic autoimmune Gastritis, celiac disease, eosinophilic esophagitis, inflammatory bowel diseases, Crohn disease, ulcerative colitis, autoantibodies, artificial intelligence, machine learning, immunological nutrition
